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Abstract

Nanoparticles (NPs) are being used or explored for the development of biomedical applications in diagnosis and therapy, including imaging and drug delivery. Therefore, reliable tools are needed to study the behavior of NPs in biological environment, in particular the transport of NPs across biological barriers, including the blood-brain tumor barrier (BBTB), a challenging question. Previous studies have addressed the translocation of NPs of various compositions across cell layers, mostly using only one type of cells. Using a co-culture model of the human BBTB, consisting in human cerebral endothelial cells preloaded with ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) and unloaded human glioblastoma cells grown on each side of newly developed ultrathin permeable silicon nitride supports as a model of the human BBTB, we demonstrate for the first time the transfer of USPIO NPs from human brain-derived endothelial cells to glioblastoma cells. The reduced thickness of the permeable mechanical support compares better than commercially available polymeric supports to the thickness of the basement membrane of the cerebral vascular system. These results are the first report supporting the possibility that USPIO NPs could be directly transferred from endothelial cells to glioblastoma cells across a BBTB. Thus, the use of such ultrathin porous supports provides a new in vitro approach to study the delivery of nanotherapeutics to brain cancers. Our results also suggest a novel possibility for nanoparticles to deliver therapeutics to the brain using endothelial to neural cells transfer.

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... Uptake and subcellular localization of NanoTEST NPs were extensively studied in different cell types Halamoda Kenzaoui et al., 2012a,b,c, 2013aMagdolenova et al., 2015;Poulsen et al., 2015). If toxicity testing gives negative results, toxic effects cannot be excluded unless uptake of NPs has been demonstrated. ...
... The broad range of toxicity assays tested under NanoTEST, including cytotoxicity, oxidative stress, inflammatory stress, immunotoxicity, genotoxicity, uptake and transport assays, are described in more detail in (Aranda et al., 2013;Correia Carreira et al., 2015;Guadagnini et al., 2015aGuadagnini et al., , 2015bHalamoda Kenzaoui et al., 2012a,b,c, 2013aHarris et al., 2015;Kazimirova et al., 2012;Magdolenova et al., 2012aMagdolenova et al., ,b, 2015Poulsen et al., 2015;Tulinska et al., 2015). SOPs for each selected model and assay, detailed culture conditions, exposure to the NPs and experimental protocols are described in a database, available from the project website (www.nanotest-fp7.eu). ...
... We have evaluated statistically the results of experiments comparing cells representing different organs. Cytotoxic effects induced by NPs depend on the test used, exposure conditions and the cell type (Aranda et al., 2013;Correia Carreira et al., 2015;Guadagnini et al., 2015;Halamoda Kenzaoui et al., 2012a,c, 2013aHarris et al., 2015;Kazimirova et al., 2012;Magdolenova et al., 2012aMagdolenova et al., , 2015Poulsen et al., 2015;Tulinska et al., 2015). The data also suggest that while there are differences between the cell lines, the strongest effect is from the NPs as seen with the OC-Fe 3 O 4 NPs results (Figure 2). ...
Article
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In spite of recent advances in describing the health outcomes of exposure to nanoparticles (NPs), it still remains unclear how exactly NPs interact with their cellular targets. Size, surface, mass, geometry, and composition may all play a beneficial role as well as causing toxicity. Concerns of scientists, politicians and the public about potential health hazards associated with NPs need to be answered. With the variety of exposure routes available, there is potential for NPs to reach every organ in the body but we know little about the impact this might have. The main objective of the FP7 NanoTEST project ( www.nanotest-fp7.eu ) was a better understanding of mechanisms of interactions of NPs employed in nanomedicine with cells, tissues and organs and to address critical issues relating to toxicity testing especially with respect to alternatives to tests on animals. Here we describe an approach towards alternative testing strategies for hazard and risk assessment of nanomaterials, highlighting the adaptation of standard methods demanded by the special physicochemical features of nanomaterials and bioavailability studies. The work has assessed a broad range of toxicity tests, cell models and NP types and concentrations taking into account the inherent impact of NP properties and the effects of changes in experimental conditions using well-characterized NPs. The results of the studies have been used to generate recommendations for a suitable and robust testing strategy which can be applied to new medical NPs as they are developed.
... 23 With porous SiN x membranes, complex tissue models of brain and lung have been established. [24][25][26][27] In search for novel, biocompatible materials and simple, inexpensive fabrication techniques for ultrathin membranes, we here present the development of nanoporous aluminum oxide as unique interface for epithelial intestinal cells from rainbow trout. The anodization of aluminum, resulting in a highly ordered, nanoporous structure, is a well-known, low-cost and reproducible process. ...
... 28 This is different from crafting of SiNx thin films with photolithography techniques, which rather 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 12 yield microporous membranes with pore sizes starting from 1 µm upward. [24][25] On the other hand, fabrication of SiNx membranes with nanopores relies on time consuming and cost intensive techniques like e-beam lithography. 35 The choice of nanoporous or microporous membranes is strongly dependent on the final application and has to be considered in advance to experimentation. ...
Article
Permeable membranes are indispensable for in vitro epithelial barrier models. However, currently available polymer-based membranes are low in porosity and relatively thick, resulting in a limited permeability and unrealistic culture conditions. In this study, we developed an ultrathin, nanoporous alumina membrane as novel cell culture interface for vertebrate cells, with focus on the rainbow trout (Onchorynchus mykiss) intestinal cell line RTgutGC. The new type of membrane is framed in a silicon chip for physical support and has a thickness of only 1 µm, with a porosity of 15% and homogeneous nanopores (Ø = 73 ± 21 nm). Permeability rates for small molecules, namely lucifer yellow, dextran 40 and bovine serum albumin, exceeded those of standard polyethylene terephthalate (PET) membranes by up to 27 fold. With the final goal to establish a representative model of the fish intestine for environmental toxicology, we engineered a simple culture set-up, capable to test the cellular response towards chemical exposure. Herein, cells were cultured in a monolayer on the alumina membranes and formed a polarized epithelium with apical expression of the tight junction protein ZO-1 within 14 days. Impedance spectroscopy, a non-invasive and real time electrical measurement, was used to determine cellular resistance during epithelial layer formation and chemical exposure to evaluate barrier functionality. Resistance values during epithelial development revealed different stages of epithelial maturity and were comparable with the in vivo situation. During chemical exposure, cellular resistance changed immediately, when barrier tightness or cell viability was affected. Thus, our study demonstrates nanoporous alumina membranes as promising novel interface for alterative in vitro approaches, capable to allow cell culture in a physiologically realistic manner and to enable high quality microscopy and sensitive measurement of cellular resistance.
... The SPIONs' cores are composed of magnetite (Fe3O4) or maghemite (γ-Fe2O3), and are encapsulated in organic or inorganic shells, to increase their biocompatibility and enhance their in vivo applications ( Figure 4) [35]. In some studies, SPIONs were used naked or their shells were not specified [44,[51][52][53][54][55]. The composition of the shells is important because it influences the interaction between SPIONs and the medium in which they are placed [34,35]. ...
... SPIONs have been mainly used to carry chemotherapy agents aimed at GBM [18,36,43,48,50,51,55,59,61,63,[65][66][67][68]70,72,74,[76][77][78]82,83,90,92,94,95,[98][99][100][101]109,110,117,119,120,125,133,136,138,[140][141][142], but also for cerebral lymphomas [64] and pediatric CNS tumors [40]. DOX and temozolomide often serving as the first-line chemotherapy are the 2 main candidates combined to SPIONs. ...
Article
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Drug delivery and distribution in the central nervous system (CNS) and the inner ear represent a challenge for the medical and scientific world, especially because of the blood–brain and the blood–perilymph barriers. Solutions are being studied to circumvent or to facilitate drug diffusion across these structures. Using superparamagnetic iron oxide nanoparticles (SPIONs), which can be coated to change their properties and ensure biocompatibility, represents a promising tool as a drug carrier. They can act as nanocarriers and can be driven with precision by magnetic forces. The aim of this study was to systematically review the use of SPIONs in the CNS and the inner ear. A systematic PubMed search between 1999 and 2019 yielded 97 studies. In this review, we describe the applications of the SPIONS, their design, their administration, their pharmacokinetic, their toxicity and the methods used for targeted delivery of drugs into the ear and the CNS.
... Second, from a physical point of view, the time taken for any xenobiotic (e.g., a drug/an aerosol) to diffuse over a certain distance increases with the square of the distance, leading in at best to a nonnegligible impact on the translocation kinetics. [17][18][19] Third, the large internal surfaces of the membrane may adsorb xenobiotics, blocking the micropores and preventing translocation of any species. ...
... A permeable support consisting of a silicon network framing an array of 23 silicon nitride (ceramic) freestanding microporous membranes were microfabricated, each having a thickness of 500 nm. 18 The resulting Silicon nitride Microporous Permeable Insert (SIMPLI-well) system has been patented by the CSEM SA. 20 Furthermore, the ceramic chip can be easily flipped, facilitating the culturing of different cell types on opposite sides of the membrane. Quadruple cultures composed of epithelial-endothelial bilayers supplemented with two immune cells, macrophages and dendritic cells, were optimized and characterized with regard to cell growth, morphology, and membrane integrity. ...
Article
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Epithelial tissue serves as an interface between biological compartments. Many in vitro epithelial cell models have been developed as an alternative to animal experiments to answer a range of research questions. These in vitro models are grown on permeable two-chamber systems; however, commercially available, polymer-based cell culture inserts are around 10 μm thick. Since the basement membrane found in biological systems is usually less than 1 μm thick, the 10-fold thickness of cell culture inserts is a major limitation in the establishment of realistic models. In this work, an alternative insert, accommodating an ultrathin ceramic membrane with a thickness of only 500 nm (i.e., the Silicon nitride Microporous Permeable Insert [SIMPLI]-well), was produced and used to refine an established human alveolar barrier coculture model by both replacing the conventional inserts with the SIMPLI-well and completing it with endothelial cells. The structural-functional relationship of the model was evaluated, including the translocation of gold nanoparticles across the barrier, revealing a higher translocation if compared to corresponding polyethylene terephthalate (PET) membranes. This study demonstrates the power of the SIMPLI-well system as a scaffold for epithelial tissue cell models on a truly biomimetic scale, allowing construction of more functionally accurate models of human biological barriers.
... Due to very limited nanoparticle translocation observed in vivo in secondary organs after inhalation and possible adsorption of nanobeads in membranes, it seems difficult to quantitatively compare with translocation rates obtained in this in vitro study [3]. A recent study shows that ultrathin porous Si membranes might be an interesting alternative to Transwell ® membranes for the study of nanoparticle translocation [47]. ...
Article
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As the lung is one of the main routes of exposure to manufactured nanoparticles, we developed an in vitro model resembling the alveolo-capillary barrier for the study of nanoparticle translocation. In order to provide a relevant and ethical in vitro model, cost effective and easy-to-implement human cell lines were used. Pulmonary epithelial cells (Calu-3 cell line) and macrophages (THP-1 differentiated cells) were cultivated on the apical side and pulmonary endothelial cells (HPMEC-ST1.6R cell line) on the basal side of a microporous polyester membrane (Transwell®). Translocation of non-functionalized (51 and 110 nm) and aminated (52 nm) fluorescent polystyrene (PS) nanobeads was studied in this system. The use of Calu-3 cells allowed high transepithelial electrical resistance (TEER) values (>1000 Ω.cm2) in co-cultures with or without macrophages. After 24 h of exposure to non-cytotoxic concentrations of non-functionalized PS nanobeads, the relative TEER values (%/t0) were significantly decreased in co-cultures. Epithelial cells and macrophages were able to internalize PS nanobeads. Regarding translocation, Transwell® membranes per se limit the passage of nanoparticles between apical and basal side. However, small non-functionalized PS nanobeads (51 nm) were able to translocate as they were detected in the basal side of co-cultures. Altogether, these results show that this co-culture model present good barrier properties allowing the study of nanoparticle translocation but research effort need to be done to improve the neutrality of the porous membrane delimitating apical and basal sides of the model.
... This iron oxide core is a main feature, enabling movement in a magnetic field. Magnetic nanoparticles are currently being used for a variety of in vivo and in vitro purposes, for example, as contrast agents for MRI [12], treatment in hyperthermia [13], cell labeling and separation [14][15][16], magnetofection [17] and drug delivery by magnetic targeting [18][19][20][21][22][23]. For such purposes the magnetic nanoparticles can be polymer coated, but they can also be encapsulated inside liposomes, hence forming magnetoliposomes [12,24,25] In this review, we cover the perspectives of using magnetic nanoparticles for guided uptake and transport across the BBB by using application of external magnetic force. ...
Article
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Brain capillary endothelial cells denote the blood-brain barrier (BBB), and conjugation of nanoparticles with antibodies that target molecules expressed by these endothelial cells may facilitate their uptake and transport into the brain. Magnetic nanoparticles can be encapsulated in liposomes and carry large molecules with therapeutic potential, for example, siRNA, cDNA and polypeptides. An additional approach to enhance the transport of magnetic nanoparticles across the BBB is the application of extracranially applied magnetic force. Stepwise targeting of magnetic nanoparticles to brain capillary endothelial cells followed by transport through the BBB using magnetic force may prove a novel mechanism for targeted therapy of macromolecules to the brain.
... NanoTEST addressed the main toxicity endpoints -cytotoxicity, oxidative stress, immunotoxicity and genotoxicity -using various in vitro cell culture models representing eight different organs. Results from vascular system, placenta, brain, kidney, gastrointestinal system and (partially) blood have already been published elsewhere (Aranda et al., 2013;Cartwright et al., 2011;Halamoda Kenzaoui et al., 2012a,b,c, 2013aKazimirova et al., 2012;Magdolenova et al., 2012a,b). One of the main routes of exposure to NPs is through the lungs. ...
... Ultra-small superparamagnetic iron oxide nanoparticles (USPIO NPs) are particularly promising since their magnetic properties increase the number of potential applications in the biomedical area, including drug delivery, thermotherapy, imaging and detection of tumor. Their potential to cross biological barriers, including the BBB and the blood−brain tumor barrier (BBTB) have been recently confirmed (Cassano et al., 2017;Halamoda Kenzaoui et al., 2013;Lopalco et al., 2015) using an in vitro model representative of the endothelialglioblastoma tumor barrier. They demonstrated that USPIO NPs can be translocated from endothelial cells to glioblastoma cells. ...
Article
The translocator protein 18 kDa (TSPO) is mainly located in outer membrane of mitochondria and results highly expressed in a variety of tumor including breast, colon, prostate, ovarian and brain (such as glioblastoma). Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain tumor. Although GBM patients had currently available therapies, the median survival is <14 months. Complete surgical resection of GBM is critical to improve GBM treatment. In this study, we performed the one-step synthesis of water-dispersible ultra-small iron oxide nanoparticles (USPIONs) and combine them with an imidazopyridine based TSPO ligand and a fluorescent dye. The optical and structural characteristics of TSPO targeted-USPIONs were properly evaluated at each step of preparation demonstrating the high colloidal stability in physiological media and the ability to preserve the relevant optical properties in the NIR region. The cellular uptake in TSPO expressing cells was assessed by confocal microscopy. The TSPO selectivity was confirmed in vivo by competition studies with the TSPO ligand PK 11195. In vivo fluorescence imaging of U87-MG xenograft models were performed to highlight the great potential of the new NIR imaging nanosystem for diagnosis and successful delineation of GBM.
... Even though commercially available porous membranes are accessible and convenient, in studies intended to evaluate the transport through the epithelial barrier, they can impede the transport of macromolecules or other physical entities such as nanoparticles or particles due to their thickness and pore size. To encompass this limitation, other kind of solid supports such as ultrathin porous silica membranes have been developed and can be used as an alternative [23]. Moreover, the use of inserts alone does not replicate the 3D architecture and the milieu formed by the extracellular matrix observed in vivo. ...
Article
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Due to the increasing concerns regarding the transferability of data from animal studies to potential human health effects, the development of complex in vitro cellular models which could potentially replace the ethically-debatable in vivo studies and fill the existing gap between in vivo and in vitro data has received considerable attention. The current review focuses on pulmonary in vitro cellular models available for studying the biological effects elicited by inhaled chemicals. The advantages and disadvantages of the 2D monoculture system and the more complex 3D models such as co-cultures and organ-on-a-chip platforms are discussed. Moreover, recent advancements in the field of respiratory toxicology such as the development of air-liquid interface systems that better mimic the in vivo respiratory exposure are reviewed. We conclude with future perspectives of the in vitro cellular models in respiratory toxicology. © 2018, Romanian Society for Pharmaceutical Sciences. All rights reserved.
... What discriminates an agglomerate of cells from a tissue is the expression of its specific function. In case of biological barriers such as intestine, lungs, skin, blood-brain barrier, the discrimination can be done by measuring the Trans Epithelial Electric Resistance (TEER) which correlates to tissue integrity and barrier function [3,4]. ...
... What discriminates an agglomerate of cells from a tissue is the expression of its specific function. In case of biological barriers such as intestine, lungs, skin, blood-brain barrier, the discrimination can be done by measuring the Trans Epithelial Electric Resistance (TEER) which correlates to tissue integrity and barrier function [3,4]. ...
... Transport processes can be divided into "transcellular" and "paracellular" and are assessed by sampling the different compartments for the presence and quantity of nanomaterials. In (B), a setup is shown where cells, representing the blood-brain barrier, are cultured on both sides of a novel ultrathin porous membrane (see Kenzaoui et al., 2013). The advantage of this two-cell type system is that it can monitor if particles that are transported through the endothelial cell layer are indeed also taken up by the glioblastoma cells, equalling the crossing of the blood-brain barrier. ...
Article
When nanomaterials reach environmental compartments, such as freshwater or soil, interaction with organisms living in those compartments is likely to occur. It therefore is important to understand how nanomaterials and organisms interact, and to develop mechanism-based frameworks that allow transfer of knowledge across particle types and biota with justifiable effort to provide a sound risk assessment.First encounter of nanomaterials with organisms always takes place at the level of cells, for example, epithelial cells in animals or epidermal cells in plants, which serve as environment-organism barriers. Being evolutionarily exposed to inorganic or organic particles, cells have evolved stress responses to combat particle exposure but if overwhelmed, toxicity on different cellular levels, such as damage to lysosomes, mitochondria, or DNA may ensue. However, even in the absence of toxicity, nanomaterials may surpass environment-organism barriers. In this case, systemic distribution may occur, potentially triggering whole organism responses, such as immune or altered behavioral responses or contorted development. Finally, whole organism responses may impact on population and ecosystem network interactions. Two examples are impacts on symbiotic interactions or on communication within the same and between different species.Taking such a systems-view approach, from the subcellular to the ecosystem level, I here provide an overview of the mechanistic knowledge in environmental nanotoxicology available thus far. Indeed, we are at the verge of moving from description to mechanistic understanding of nanotoxicity in organisms living in different environments. Advancement in this area, however, strongly depends on rigorous nanomaterial characterization and thus on embracing physical and chemical science to provide the best possible link between particle characteristics, concentrations occurring in the environment and mechanisms of stress response and toxicity.
... Previous work by the authors has demonstrated that these ultrathin porous supports are suitable for epithelial cell culture. Moreover, in the absence of cells, NPs translocate through the membrane with significantly less clogging than in transwell inserts, which typically have high pore tortuosity [12]. ...
Article
Permeability studies across biological barriers are of primary importance in drug delivery as well as in toxicology when investigating the absorption and translocation of a substance. The study of nanomaterial interaction with epithelial barriers is of particular interest given their growing use in nanomedicine as well as concerns about their potential hazard. Here we describe the design and fabrication of a new bioreactor with an ultrathin microporous sensing support for the study of nanoparticle toxicity in intestinal epithelial cells in conditions which better recapitulate the physiological environment. Thanks to the integration of 4 electrodes in the microporous membrane, the system allows real-time and continuous sensing of TEER (trans epithelial electrical resistance) during flow without interruption or perturbation of experiments. The TEER bioreactor was tested using Caco-2 cells as an in vitro model of intestinal epithelia. When exposed to silver nanoparticles, which are known to be toxic, the embedded electrodes enabled non-invasive evaluation of barrier impairment over time. This device can be used to study barrier integrity and the kinetics of nanomaterial induced damage to epithelial barriers in physiologically relevant conditions.
Article
The term "nanotechnology" refers to the development of materials and devices that have been designed with specific properties at the nanometer scale (10(-9) m), usually being less than 100 nm in size. Recent advances in nanotechnology have promised to enable visualization and intervention at the subcellular level, and its incorporation to future medical therapeutics is expected to bring new avenues for molecular imaging, targeted drug delivery, and personalized interventions. Although the central nervous system presents unique challenges to the implementation of new therapeutic strategies involving nanotechnology (such as the heterogeneous molecular environment of different CNS regions, the existence of multiple processing centers with different cytoarchitecture, and the presence of the blood-brain barrier), numerous studies have demonstrated that the incorporation of nanotechnology resources into the armamentarium of neurosurgery may lead to breakthrough advances in the near future. In this article, the authors present a critical review on the current 'state-of-the-art' of basic research in nanotechnology with special attention to those issues which present the greatest potential to generate major therapeutic progresses in the neurosurgical field, including nanoelectromechanical systems, nano-scaffolds for neural regeneration, sutureless anastomosis, molecular imaging, targeted drug delivery, and theranostic strategies.
Chapter
This chapter describes the current state of the art for in vitro modeling of the human blood-brain barrier (BBB) and discusses how well these models reflect the idealized attributes listed earlier. A discussion of the many studies that have employed human in vitro BBB models follows as a demonstration of their utility. There are several unexplored areas where the stem cell-derived BBB model could help make further contributions. First, recent success creating patient-specific pluripotent stem cell lines suggests that skin cells can be biopsied from patients, converted into induced pluripotent stem cell (iPSC) lines, and potentially differentiated into human brain microvascular endothelial cells (hBMECs) to conduct central nervous system (CNS) studies in vitro. Second, advances in genetic manipulation of hPSCs using zinc finger nucleases and TAL effector nucleases could allow for the exploration of genetic contributions to disease.
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Targeted drug delivery is a promising approach to overcome the limitations of classical chemotherapy. In this respect, Imatinib‐loaded chitosan‐modified magnetic nanoparticles were prepared as a pH sensitive system for targeted delivery of drug to tumor sites by applying a magnetic field. The proposed magnetic nanoparticles were prepared through modification of magnetic Fe3O4 nanoparticles with chitosan and Imatinib. The structural, morphological and physicochemical properties of the synthesized nanoparticles were determined by different analytical techniques including energy‐dispersive X‐ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), Fourier‐transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HR‐TEM), vibrating sample magnetometry (VSM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). UV/visible spectrophotometry was used to measure the Imatinib contents. Thermal stability of the prepared particles was investigated and their efficiency of drug loading and release profile were evaluated. The results demonstrated that Fe3O4@CS acts as a pH responsive nanocarrier in releasing the loaded Imatinib molecules. Furthermore, the Fe3O4@CS/Imatinib nanoparticles displayed cytotoxic effect against MCF‐7 breast cancer cells. Results of this study can provide new insights in the development of pH responsive targeted drug delivery systems to overcome the side effects of conventional chemotherapy.
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In this study we present the first fish-gut-on-chip model. This model is based on the reconstruction of the intestinal barrier by culturing two intestinal cell lines from rainbow trout, namely epithelial RTgutGC and fibroblastic RTgutF, in an artificial microenvironment. For a realistic mimicry of the interface between the intestinal lumen and the interior of the organism we i) developed ultrathin and highly porous silicon nitride membranes that serve as basement membrane analogues and provide a culture interface for the fish cells; ii) constructed a unique micro-well plate-based microfluidic bioreactor that enables parallelization of experiments and creates realistic fluid flow exposure scenarios for the cells; iii) integrated electrodes in the reactor for non-invasive impedance sensing of cellular well-being. In a first approach, we used this reactor to investigate the response of epithelial fish cells to in vivo-like shear stress rates of 0.002-0.06 dyne per cm2, resulting from fluid flow within the intestinal lumen. Moreover, we investigated the interplay of epithelial and fibroblast cells under optimal flow conditions to carefully evaluate the benefits and drawbacks of the more complex reconstruction of the intestinal architecture. With our fish-gut-on-chip model we open up new strategies for a better understanding of basic fish physiology, for the refinement of fish feed in aquaculture and for predicting chemical uptake and bioaccumulation in fish for environmental risk assessment. The basic principles of our reactor prototype, including the use of ultrathin membranes, an open microfluidic circuit for perfusion and the micro-well plate-based format for simplified handling and avoidance of air-bubbles, will as well be of great value for other barrier-on-chip models.
Chapter
One of the main obstacles for the effective treatment of CNS disorders is the incapability of drug molecules to cross the blood-brain barrier (BBB). Conventional drug delivery systems are having limited adequacy to assess the restrictions posed by the imperative blood-brain barrier. Numerous drugs designed for the treatment of various disorders are unable to permeate the BBB. This hampers their ability to effectively reach in the brain. Most of the drugs are given in high doses to provide adequate concentration in the brain. Complicated dosage regimens along with the systemic side effects reduce patient compliance, leading to the failure for the efficient disease management. A large number of delivery systems and target systems have been investigated to improve drug bioavailability and enhance drug accumulation at the targeted area in order to minimize systemic side effects, as well as to improve compliance. Nanotechnological approaches involve various nano-sized carrier systems, which promotes the brain availability of therapeutic agents for the effective management of neurodegenerative disorders. Over the conventional approaches, nanotechnological approaches have various promising strategies to cross blood-brain barrier and increase the bioavailability of therapeutics in the brain. This chapter elaborates upon the current and future utility of nano-drug delivery systems for the treatment of various CNS disorders.
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The methods for the delivery of theranostic agents across the blood-brain barrier (BBB) are highly required. Superparamagnetic iron oxide nanoparticles (SPIONs) coated with PEG (poly (ethylene glycol)), PEI (poly (ethylene imine)) and Tween 80 (polysorbate 80) (Tween-SPIONs) were prepared. We demonstrate the effective passage of tail-vein injected Tween-SPIONs across normal BBB in rats under an external magnetic field (EMF). The quantitative analyses show significant accumulation of SPIONs in the cortex near the magnet, with progressively lower accumulation in brain tissues far from the magnet. A transmission electron microscopy picture of an ultra-thin section of the rat brain displays Tween-SPIONs crossing the BBB. The comparative study confirms that both the Tween-80 modification and EMF play crucial roles in the effective passage of SPIONs across the intact BBB. Only the magnetic force cannot drag the SPIONs coated with PEI/PEG polymers through the BBB. The results indicate the Tween-SPIONs cross the BBB via an active penetration facilitated by EMF. This work is encouraging for further study on the delivery of drug or diagnostic agents into the parenchyma of the brain for dealing with neurological disorders by using Tween-SPIONs carriers under EMF.
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Background In addition to possessing intracellular vesicles, eukaryotic cells also produce extracellular microvesicles, ranging from 50 to 1000 nm in diameter that are released or shed into the microenvironment under physiological and pathological conditions. These membranous extracellular organelles include both exosomes (originating from internal vesicles of endosomes) and ectosomes (originating from direct budding/shedding of plasma membranes). Extracellular microvesicles contain cell-specific collections of proteins, glycoproteins, lipids, nucleic acids and other molecules. These vesicles play important roles in intercellular communication by acting as carrier for essential cell-specific information to target cells. Endothelial cells in the brain form the blood–brain barrier, a specialized interface between the blood and the brain that tightly controls traffic of nutrients and macromolecules between two compartments and interacts closely with other cells forming the neurovascular unit. Therefore, brain endothelial cell extracellular microvesicles could potentially play important roles in ‘externalizing’ brain-specific biomarkers into the blood stream during pathological conditions, in transcytosis of blood-borne molecules into the brain, and in cell-cell communication within the neurovascular unit. Methods To study cell-specific molecular make-up and functions of brain endothelial cell exosomes, methods for isolation of extracellular microvesicles using mass spectrometry-compatible protocols and the characterization of their signature profiles using mass spectrometry -based proteomics were developed. Results A total of 1179 proteins were identified in the isolated extracellular microvesicles from brain endothelial cells. The microvesicles were validated by identification of almost 60 known markers, including Alix, TSG101 and the tetraspanin proteins CD81 and CD9. The surface proteins on isolated microvesicles could potentially interact with both primary astrocytes and cortical neurons, as cell-cell communication vesicles. Finally, brain endothelial cell extracellular microvesicles were shown to contain several receptors previously shown to carry macromolecules across the blood brain barrier, including transferrin receptor, insulin receptor, LRPs, LDL and TMEM30A. Conclusions The methods described here permit identification of the molecular signatures for brain endothelial cell-specific extracellular microvesicles under various biological conditions. In addition to being a potential source of useful biomarkers, these vesicles contain potentially novel receptors known for delivering molecules across the blood–brain barrier.
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A route of accumulation and elimination of therapeutic engineered nanoparticles (NPs) may be the kidney. Therefore, the interactions of different solid-core inorganic NPs (titanium-, silica-, and iron oxide-based NPs) were studied in vitro with the MDCK and LLC-PK epithelial cells as representative cells of the renal epithelia. Following cell exposure to the NPs, observations include cytotoxicity for oleic acid-coated iron oxide NPs, the production of reactive oxygen species for titanium dioxide NPs, and cell depletion of thiols for uncoated iron oxide NPs, whereas for silica NPs an apparent rapid and short-lived increase of thiol levels in both cell lines was observed. Following cell exposure to metallic NPs, the expression of the tranferrin receptor/CD71 was decreased in both cells by iron oxide NPs, but only in MDCK cells by titanium dioxide NPs. The tight association, then subsequent release of NPs by MDCK and LLC-PK kidney epithelial cells, showed that following exposure to the NPs, only MDCK cells could release iron oxide NPs, whereas both cells released titanium dioxide NPs. No transfer of any solid-core NPs across the cell layers was observed.
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Nanoparticles (NPs) are in clinical use or under development for therapeutic imaging and drug delivery. However, relatively little information exists concerning the uptake and transport of NPs across human colon cell layers, or their potential to invade three-dimensional models of human colon cells that better mimic the tissue structures of normal and tumoral colon. In order to gain such information, the interactions of biocompatible ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) (iron oxide core 9-10 nm) coated with either cationic polyvinylamine (aminoPVA) or anionic oleic acid with human HT-29 and Caco-2 colon cells was determined. The uptake of the cationic USPIO NPs was much higher than the uptake of the anionic USPIO NPs. The intracellular localization of aminoPVA USPIO NPs was confirmed in HT-29 cells by transmission electron microscopy that detected the iron oxide core. AminoPVA USPIO NPs invaded three-dimensional spheroids of both HT-29 and Caco-2 cells, whereas oleic acid-coated USPIO NPs could only invade Caco-2 spheroids. Neither cationic aminoPVA USPIO NPs nor anionic oleic acid-coated USPIO NPs were transported at detectable levels across the tight CacoReady™ intestinal barrier model or the more permeable mucus-secreting CacoGoblet™ model.
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In this study, primary rat alveolar epithelial cell monolayers (RAECM) were used to investigate transalveolar epithelial quantum dot trafficking rates and underlying transport mechanisms. Trafficking rates of quantum dots (PEGylated CdSe/ZnS, core size 5.3 nm, hydrodynamic size 25 nm) in the apical-to-basolateral direction across RAECM were determined. Changes in bioelectric properties (ie, transmonolayer resistance and equivalent active ion transport rate) of RAECM in the presence or absence of quantum dots were measured. Involvement of endocytic pathways in quantum dot trafficking across RAECM was assessed using specific inhibitors (eg, methyl-β-cyclodextrin, chlorpromazine, and dynasore for caveolin-, clathrin-, and dynamin-mediated endocytosis, respectively). The effects of lowering tight junctional resistance on quantum dot trafficking were determined by depleting Ca(2+) in apical and basolateral bathing fluids of RAECM using 2 mM EGTA. Effects of temperature on quantum dot trafficking were studied by lowering temperature from 37°C to 4°C. Apical exposure of RAECM to quantum dots did not elicit changes in transmonolayer resistance or ion transport rate for up to 24 hours; quantum dot trafficking rates were not surface charge-dependent; methyl-β-cyclodextrin, chlorpromazine, and dynasore did not decrease quantum dot trafficking rates; lowering of temperature decreased transmonolayer resistance by approximately 90% with a concomitant increase in quantum dot trafficking by about 80%; and 24 hours of treatment of RAECM with EGTA decreased transmonolayer resistance by about 95%, with increased quantum dot trafficking of up to approximately 130%. These data indicate that quantum dots do not injure RAECM and that quantum dot trafficking does not appear to take place via endocytic pathways involving caveolin, clathrin, or dynamin. We conclude that quantum dot translocation across RAECM takes place via both transcellular and paracellular pathways and, based on comparison with our prior studies, interactions of nanoparticles with RAECM are strongly dependent on nanoparticle composition and surface properties.
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Different types of NPs (nanoparticles) are currently under development for diagnostic and therapeutic applications in the biomedical field, yet our knowledge about their possible effects and fate in living cells is still limited. In the present study, we examined the cellular response of human brain-derived endothelial cells to NPs of different size and structure: uncoated and oleic acid-coated iron oxide NPs (8-9 nm core), fluorescent 25 and 50 nm silica NPs, TiO2 NPs (21 nm mean core diameter) and PLGA [poly(lactic-co-glycolic acid)]-PEO [poly(ethylene oxide)] polymeric NPs (150 nm). We evaluated their uptake by the cells, and their localization, generation of oxidative stress and DNA-damaging effects in exposed cells. We show that NPs are internalized by human brain-derived endothelial cells; however, the extent of their intracellular uptake is dependent on the characteristics of the NPs. After their uptake by human brain-derived endothelial cells NPs are transported into the lysosomes of these cells, where they enhance the activation of lysosomal proteases. In brain-derived endothelial cells, NPs induce the production of an oxidative stress after exposure to iron oxide and TiO2 NPs, which is correlated with an increase in DNA strand breaks and defensive mechanisms that ultimately induce an autophagy process in the cells.
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Gliomas are a group of heterogeneous primary central nervous system (CNS) tumors arising from the glial cells. Malignant gliomas account for a majority of malignant primary CNS tumors and are associated with high morbidity and mortality. Glioblastoma is the most frequent and malignant glioma, and despite the recent advances in diagnosis and new treatment options, its prognosis remains dismal. New opportunities for the development of effective therapies for malignant gliomas are urgently needed. Magnetic hyperthermia (MHT), which consists of heat generation in the region of the tumor through the application of magnetic nanoparticles subjected to an alternating magnetic field (AMF), has shown positive results in both preclinical and clinical assays. The aim of this review is to assess the relevance of hyperthermia induced by magnetic nanoparticles in the treatment of gliomas and to note the possible variations of the technique and its implication on the effectiveness of the treatment. We performed an electronic search in the literature from January 1990 to October 2010, in various databases, and after application of the inclusion criteria we obtained a total of 15 articles. In vitro studies and studies using animal models showed that MHT was effective in the promotion of tumor cell death and reduction of tumor mass or increase in survival. Two clinical studies showed that MHT could be applied safely and with few side effects. Some studies suggested that mechanisms of cell death, such as apoptosis, necrosis, and antitumor immune response were triggered by MHT. Based on these data, we could conclude that MHT proved to be efficient in most of the experiments, and that the improvement of the nanocomposites as well as the AMF equipment might contribute toward establishing MHT as a promising tool in the treatment of malignant gliomas.
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Paclitaxel appears to be a potential substrate of the multidrug resistance protein p-glycoprotein, thus preventing itself from entry into the brain and penetrating blood-brain barrier poorly. In this study, the main objective was to design paclitaxel formulation using PLGA-based nanoparticles with different additives and surface coatings to facilitate the paclitaxel transport through MDCK cell monolayer. PLGA-based nanoparticles of around 200 nm without and with additives and surface coatings were developed by direct dialysis. The transendothelial electrical resistance (TEER) variation of MDCK cell monolayer on the cell inserts imposed by paclitaxel-loaded nanoparticles with and without additives was investigated. (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) (MTT) assay was used to quantify the cell viability of C6 glioma cells after administration of formulations on the topical side. Investigations showed that particles with additives were able to enhance cellular uptake more than surface-coated particles. TEER values dropped upon the introduction of paclitaxel-loaded PLGA nanoparticles to the cell inserts. After incubation for 24 h, the cell viability of C6 glioma cells in the wells treated with nanoparticles was lower than that of the control wells without particles. Taken together, PLGA nanoparticles with vitamin E TPGS and polysorbate 80 as additives were successfully obtained as paclitaxel formulations, demonstrating great potential for the delivery of paclitaxel through MDCK cell monolayer in vitro.
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Magnetic iron oxide nanoparticles have attracted extensive interest as novel contrast agents for biomedical imaging owing to their capability of deep-tissue imaging, non-invasiveness and low toxicity. This mini-review will provide an overview on the recent synthesis methods, influencing factors and potential applications of magentic nanoparticles for cell labeling and imaging.
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Magnetic iron oxide nanoparticles (MNP) coated with gum arabic (GA), a biocompatible phytochemical glycoprotein widely used in the food industry, were successfully synthesized and characterized. GA-coated MNP (GA-MNP) displayed a narrow hydrodynamic particle size distribution averaging about 100 nm; a GA content of 15.6% by dry weight; a saturation magnetization of 93.1 emu/g Fe; and a superparamagnetic behavior essential for most magnetic-mediated applications. The GA coating offers two major benefits: it both enhances colloidal stability and provides reactive functional groups suitable for coupling of bioactive compounds. In vitro results showed that GA-MNP possessed a superior stability upon storage in aqueous media when compared to commercial MNP products currently used in magnetic resonance imaging (MRI). In addition, significant cellular uptake of GA-MNP was evaluated in 9L glioma cells by electron spin resonance (ESR) spectroscopy, fluorescence microscopy, and MRI analyses. Based on these findings, it was hypothesized that GA-MNP might be utilized as a MRI-visible drug carrier in achieving both magnetic tumor targeting and intracellular drug delivery. Indeed, preliminary in vivo investigations validate this clinical potential. MRI visually confirmed the accumulation of GA-MNP at the tumor site following intravenous administration to rats harboring 9L glioma tumors under the application of an external magnetic field. ESR spectroscopy quantitatively revealed a 12-fold increase in GA-MNP accumulation in excised tumors when compared to contralateral normal brain. Overall, the results presented show promise that GA-MNP could potentially be employed to achieve simultaneous tumor imaging and targeted intra-tumoral drug delivery.
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Superparamagnetic iron oxide nanoparticles have diverse diagnostic and potential therapeutic applications in the central nervous system (CNS). They are useful as magnetic resonance imaging (MRI) contrast agents to evaluate: areas of blood-brain barrier (BBB) dysfunction related to tumors and other neuroinflammatory pathologies, the cerebrovasculature using perfusion-weighted MRI sequences, and in vivo cellular tracking in CNS disease or injury. Novel, targeted, nanoparticle synthesis strategies will allow for a rapidly expanding range of applications in patients with brain tumors, cerebral ischemia or stroke, carotid atherosclerosis, multiple sclerosis, traumatic brain injury, and epilepsy. These strategies may ultimately improve disease detection, therapeutic monitoring, and treatment efficacy especially in the context of antiangiogenic chemotherapy and antiinflammatory medications. The purpose of this review is to outline the current status of superparamagnetic iron oxide nanoparticles in the context of biomedical nanotechnology as they apply to diagnostic MRI and potential therapeutic applications in neurooncology and other CNS inflammatory conditions.
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Effective transvascular delivery of nanoparticle-based chemotherapeutics across the blood-brain tumor barrier of malignant gliomas remains a challenge. This is due to our limited understanding of nanoparticle properties in relation to the physiologic size of pores within the blood-brain tumor barrier. Polyamidoamine dendrimers are particularly small multigenerational nanoparticles with uniform sizes within each generation. Dendrimer sizes increase by only 1 to 2 nm with each successive generation. Using functionalized polyamidoamine dendrimer generations 1 through 8, we investigated how nanoparticle size influences particle accumulation within malignant glioma cells. Magnetic resonance and fluorescence imaging probes were conjugated to the dendrimer terminal amines. Functionalized dendrimers were administered intravenously to rodents with orthotopically grown malignant gliomas. Transvascular transport and accumulation of the nanoparticles in brain tumor tissue was measured in vivo with dynamic contrast-enhanced magnetic resonance imaging. Localization of the nanoparticles within glioma cells was confirmed ex vivo with fluorescence imaging. We found that the intravenously administered functionalized dendrimers less than approximately 11.7 to 11.9 nm in diameter were able to traverse pores of the blood-brain tumor barrier of RG-2 malignant gliomas, while larger ones could not. Of the permeable functionalized dendrimer generations, those that possessed long blood half-lives could accumulate within glioma cells. The therapeutically relevant upper limit of blood-brain tumor barrier pore size is approximately 11.7 to 11.9 nm. Therefore, effective transvascular drug delivery into malignant glioma cells can be accomplished by using nanoparticles that are smaller than 11.7 to 11.9 nm in diameter and possess long blood half-lives.
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Inorganic microfiltration membranes with a pore size down to 0.1μm have been made using laser interference lithography and silicon micro machining technology. The membranes have an extremely small flow resistance due to a thickness smaller than the pore size, a high porosity and a very narrow pore size distribution. They are relatively insensible to fouling, because they have a smooth surface, short pore channels and because they can be operated in cross flow configuration at very low transmembrane pressures. Experiments with yeast cell filtration of beer show a minimal fouling tendency and a flux that is about 40 times higher than in conventional diatomaceous earth filtration. The uniform pore distribution makes the membranes suitable for many other applications like critical cell to cell separation, particle analysis systems, absolute filtrations and model experiments.
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The blood-brain barrier (BBB) is composed of the brain capillaries, which are lined by endothelial cells displaying extremely tight intercellular junctions. Several attempts at creating anin vitro model of the BBB have been met with moderate success as brain capillary endothelial cells lose their barrier properties when isolated in cell culture. This may be due to a lack of recreation of thein vivo endothelial cellular environment in these models, including nearly constant contact with astrocyte foot processes. This work is motivated by the hypothesis that growing endothelial cells on one side of an ultra-thin, highly porous membrane and differentiating astrocyte or astrogliomal cells on the opposite side will lead to a higher degree of interaction between the two cell types and therefore to an improved model. Here we describe our initial efforts towards testing this hypothesis including a procedure for membrane fabrication and methods for culturing endothelial cells on these membranes. We have fabricated a 1 μm thick, 2.0 μm pore size, and ∼55% porous membrane with a very narrow pore size distribution from low-stress silicon nitride (SiN) utilizing techniques from the microelectronics industry. We have developed a base, acid, autoclave routine that prepares the membranes for cell culture both by cleaning residual fabrication chemicals from the surface and by increasing the hydrophilicity of the membranes (confirmed by contact angle measurements). Gelatin, fibronectin, and a 50/50 mixture of the two proteins were evaluated as potential basement membrane protein treatments prior to membrane cell seeding. All three treatments support adequate attachment and growth on the membranes compared to the control.
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Many therapeutic drugs are excluded from entering the brain due to their lack of transport through the blood-brain barrier (BBB). The development of new strategies for enhancing drug delivery to the brain is of great importance in diagnostics and therapeutics of central nervous diseases. To overcome this problem, a viral fusion peptide (gH625) derived from the glycoprotein gH of Herpes simplex virus type 1 is developed, which possesses several advantages including high cell translocation potency, absence of toxicity of the peptide itself, and the feasibility as an efficient carrier for delivering therapeutics. Therefore, it is hypothesized that brain delivery of nanoparticles conjugated with gH625 should be efficiently enhanced. The surface of fluorescent aminated polystyrene nanoparticles (NPs) is functionalized with gH625 via a covalent binding procedure, and the NP uptake mechanism and permeation across in vitro BBB models are studied. At early incubation times, the uptake of NPs with gH625 by brain endothelial cells is greater than that of the NPs without the peptide, and their intracellular motion is mainly characterized by a random walk behavior. Most importantly, gH625 peptide decreases NP intracellular accumulation as large aggregates and enhances the NP BBB crossing. In summary, these results establish that surface functionalization with gH625 may change NP fate by providing a good strategy for the design of promising carriers to deliver drugs across the BBB for the treatment of brain diseases.
Book
Synopsis Nanotechnology and microengineering are among the top priority research areas in the United States and will continue to be so during the next decade, making Fundamentals of Microfabrication an important and timely work. Written by an internationally recognized expert on sensors and sensor instrumentation who is also a leading authority on nanotechnology and microfabrication, this book will function as both a valuable textbook and a handy reference. Ten chapters discuss in detail topics such as lithography, pattern transfer, wet and dry bulk micromachining, surface micromachining, and LIGA. Alternative micromachining technologies are described and electronics used with micromachined devices are examined. Bonding and packaging issues are defined. The book also presents quantum structures and reviews molecular engineering. Numerous appendices offer valuable information in an easily accessible format.
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Ultrasmall superparamagnetic iron oxide nanoparticles (USPIO-NPs) are under development for imaging and drug delivery; however, their interaction with human blood-brain barrier models is not known. The uptake, reactive oxygen species production and transport of USPIO-NPs across human brain-derived endothelial cells as models of the blood-brain tumor barrier were evaluated for either uncoated, oleic acid-coated or polyvinylamine-coated USPIO-NPs. Reactive oxygen species production was observed for oleic acid-coated and polyvinylamine-coated USPIO-NPs. The uptake and intracellular localization of the iron oxide core of the USPIO-NPs was confirmed by transmission electron microscopy. However, while the uptake of these USPIO-NPs by cells was observed, they were neither released by nor transported across these cells even in the presence of an external dynamic magnetic field. USPIO-NP-loaded filopodia were observed to invade the polyester membrane, suggesting that they can be transported by migrating angiogenic brain-derived endothelial cells.
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In order to evaluate the potential and mechanism of Angiopep-conjugated poly(ethylene glycol)-co-poly(ε-caprolactone)nanoparticles (ANG-PEG-NP) as brain targeting drug delivery system, Rhodamine B isothiocyanate (RBITC) was used as a fluorescent probe molecule to label ANG-PEG-NP through covalent bonding. The brain transcytosis across the blood-brain barrier (BBB) and brain delivery in mice of RBITC labeled ANG-PEG-NP were investigated in this paper. Results showed that ANG-PEG-NP enhanced significantly the uptake by BCECs compared with that of PEG-NP through caveolae- and clathrin-mediated endocytosis, involving a time-dependent, concentration-dependent and energy-dependent mode. The transport of ANG-PEG-NP across the in vitro BBB model was significantly increased than that of PEG-NP. After injection a dose of 100 mg/kg RBITC labeled ANG-PEG-NP or PEG-NP in mouse caudal vein, the brain coronal section showed a higher accumulation of ANG-PEG-NP in the cortical layer, lateral ventricle, third ventricles and hippocampus than that of PEG-NP. By using an excess of free LRP ligand (Angiopep-2 and/or Aprotinin) as a specific receptor inhibitor, it was evidenced that the uptake by BCECs in vitro, transport across in vitro BBB model and penetration into brain tissue in vivo of RBITC labeled ANG-PEG-NP could be inhibited significantly, which demonstrated the brain targeting mechanism of Angiopep-conjugated poly(ethylene glycol)-co-poly(ε-caprolactone)nanoparticles might be a LRP receptor mediated transcytosis process. Understanding these issues is important for the future development of ANG-PEG-NP as a brain targeting drug delivery system for neurodegenerative disorders including glioma and Alzheimer's disease.
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Effective non-invasive treatment of neurological diseases is often limited by the poor access of therapeutic agents into the central nervous system (CNS). The majority of drugs and biotechnological agents do not readily permeate into brain parenchyma due to the presence of two anatomical and biochemical dynamic barriers: the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Therefore, one of the most significant challenges facing CNS drug development is the availability of effective brain targeting technology. Recent advances in nanotechnology have provided promising solutions to this challenge. Several nanocarriers ranging from the more established systems, e.g. polymeric nanoparticles, solid lipid nanoparticles, liposomes, micelles to the newer systems, e.g. dendrimers, nanogels, nanoemulsions and nanosuspensions have been studied for the delivery of CNS therapeutics. Many of these nanomedicines can be effectively transported across various in vitro and in vivo BBB models by endocytosis and/or transcytosis, and demonstrated early preclinical success for the management of CNS conditions such as brain tumors, HIV encephalopathy, Alzheimer's disease and acute ischemic stroke. Future development of CNS nanomedicines need to focus on increasing their drug-trafficking performance and specificity for brain tissue using novel targeting moieties, improving their BBB permeability and reducing their neurotoxicity.
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The central nervous system is well protected by the blood-brain barrier (BBB) which maintains its homeostasis. Due to this barrier many potential drugs for the treatment of diseases of the central nervous system (CNS) cannot reach the brain in sufficient concentrations. One possibility to deliver drugs to the CNS is the employment of polymeric nanoparticles. The ability of these carriers to overcome the BBB and to produce biologic effects on the CNS was shown in a number of studies. Over the past few years, progress in understanding of the mechanism of the nanoparticle uptake into the brain was made. This mechanism appears to be receptor-mediated endocytosis in brain capillary endothelial cells. Modification of the nanoparticle surface with covalently attached targeting ligands or by coating with certain surfactants enabling the adsorption of specific plasma proteins are necessary for this receptor-mediated uptake. The delivery of drugs, which usually are not able to cross the BBB, into the brain was confirmed by the biodistribution studies and pharmacological assays in rodents. Furthermore, the presence of nanoparticles in the brain parenchyma was visualized by electron microscopy. The intravenously administered biodegradable polymeric nanoparticles loaded with doxorubicin were successfully used for the treatment of experimental glioblastoma. These data, together with the possibility to employ nanoparticles for delivery of proteins and other macromolecules across the BBB, suggest that this technology holds great promise for non-invasive therapy of the CNS diseases.
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The blood brain barrier regulates the transport of chemicals from entering and leaving the brain. Brain capillaries establish the barrier and restrict transport into the brain by providing a physical and chemical barrier. The physical barrier is due to tight membrane junctions separating the capillary endothelial cells resulting in limited paracellular transport. The chemical barrier is due to the expression of multidrug transporters that mediate the efflux of a broad range of hydrophobic chemicals. Because of the unusual nutrient demands of the brain, this limited permeability is compensated by the expression of a large number of transporters that are responsive to the metabolic demands of the brain. Consequently, the blood brain barrier indirectly regulates brain function by directly controlling the uptake of nutrients. Two widely used methods for studying the blood brain are a cell culture model using rat, pig, or cow brain endothelial cells and isolated microvessels. The cell culture model is more popular likely because it is easier to use and less costly compared to isolated microvessels. In some laboratories, brain endothelial cells are cocultured with astrocyte- or astroglial-conditioned media. The endothelial cells express many of the transporters displayed in vivo but not all. Although cell culture models vary, none express the tight barrier observed in vivo. Because microvessels are isolated directly from the brain, they express all of the transporters displayed in vivo. Their disadvantage is that the preparation is laborious, requires animals, and has a shorter lifespan in vitro. We present an approach in which transport is first verified in isolated microvessels, and then the mechanism is studied in cell culture.
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Transferrin conjugated biodegradable polymersomes (Tf-PO) were exploited for efficient brain drug delivery, and its cellular internalization mechanisms were investigated. Tf-PO was prepared by a nanoprecipitation method with an average diameter of approximately 100 nm and a surface Tf molecule number per polymersome of approximately 35. It was demonstrated that the uptake of Tf-PO by bEnd.3 was mainly through a clathrin mediated energy-dependent endocytosis. Both the Golgi apparatus and lysosomes are involved in intracellular transport of Tf-PO. Thirty minutes after a 50mg/kg dose of Tf-PO or PO was injected into rats via the tail vein, fluorescent microscopy of brain coronal sections showed a higher accumulation of Tf-PO than PO in the cerebral cortex, the periventricular region of the lateral ventricle and the third ventricle. The brain delivery results proved that the blood-brain barrier (BBB) permeability surface area product (PS) and the percentage of injected dose per gram of brain (%ID/g brain) for Tf-PO were increased to 2.8-fold and 2.3-fold, respectively, as compared with those for PO. These results indicate that Tf-PO is a promising brain delivery carrier.
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Unlabelled: Gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provides a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood-brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, there are currently no studies that systematically examine brain microvasculature permeation of polyethylene glycol (PEG)-functionalized AuNPs. Such studies could pave the way for rationale AuNP design for passive targeting of malignant tumors. In this report we designed and characterized AuNPs with varying core particle sizes (4-24 nm) and PEG chain lengths [molecular weight 1000-10,000]. Using an in-vitro model designed to mimic the transport-permissive brain microvasculature, we demonstrate size-dependent permeation properties with respect to core particle size and PEG chain length. In general short PEG chain length (molecular weight 1000-2000) in combination with smallest core size led to optimum permeation in our model system. From the clinical editor: In this report the authors designed and characterized PEGylated gold NPs with varying core particle sizes and PEG chain lengths and demonstrate that short PEG chain length in combination with smallest core size led to optimum permeation of a blood-brain barrier model system. These findings may pave the way to optimized therapy of malignant brain tumors.
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Nanotechnology provides a flexible platform for the development of effective therapeutic nanomaterials that can interact specifically with a target in a biological system and provoke a desired response. Of the nanomaterials studied, iron oxide nanoparticles have emerged as one of top candidates for cancer therapy. Their intrinsic superparamagnetism enables noninvasive magnetic resonance imaging (MRI), and their biodegradability is advantageous for in vivo applications. A therapeutic superparamagnetic iron oxide nanoparticle (SPION) typically consists of three primary components: an iron oxide nanoparticle core that serves as both a carrier for therapeutics and contrast agent for MRI, a coating on the iron oxide nanoparticle that promotes favorable interactions between the SPION and the biological system, and a therapeutic payload that performs the designated function in vivo. Often, the design may include a targeting ligand that recognizes the receptors over-expressed on the exterior surface of cancer cells.
Article
Significant progress has been made in nanoscale drugs and delivery systems employing diverse chemical formulations to facilitate the rate of drug delivery and release from the human body. The biocompatible nanomaterials have been used in biological markers, contrast agents for biological imaging, healthcare products, pharmaceuticals, drug-delivery systems as well as in detection, diagnosis and treatment of various types of diseases. Nanomedicines offer delivery of potential drugs to human organs which were previously beyond reach of microscale drugs due to specific biological barriers. The nanoscale systems work as nanocarriers for the delivery of drugs. The nanocarriers are made of biocompatible and biodegradable materials such as synthetic proteins, peptides, lipids, polysaccharides, biodegradable polymers and fibers. This review article reports the recent developments in the field of nanomedicine covering biodegradable polymers, nanoparticles, cyclodextrin, dendrimeres, liposomes and lipid-based nanocarriers, nanofibers, nanowires and carbon nanotubes and their chemical functionalization for distribution to different organs, their solubility, surface, chemical and biological properties, stability and release systems. The toxicity and safety of nanomaterials on human health is also briefly discussed.
Article
This study describes the creation and characterization of drug carriers prepared using the polymer poly[aniline-co-N-(1-one-butyric acid) aniline] (SPAnH) coated on Fe(3)O(4) cores to form three types of magnetic nanoparticles (MNPs); these particles were used to enhance the therapeutic capacity and improve the thermal stability of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), a compound used to treat brain tumors. The average hydrodynamic diameter of the MNPs was 89.2 ± 8.5 nm and all the MNPs displayed superparamagnetic properties. A maximum effective dose of 379.34 μg BCNU could be immobilized on 1 mg of MNP-3 (bound-BCNU-3). Bound-BCNU-3 was more stable than free-BCNU when stored at 4 °C, 25 °C or 37 °C. Bound-BCNU-3 could be concentrated at targeted sites in vitro and in vivo using an externally applied magnet. When applied to brain tumors, magnetic targeting increased the concentration and retention of bound-BCNU-3. This drug delivery system promises to provide more effective tumor treatment using lower therapeutic doses and potentially reducing the side effects of chemotherapy.
Article
Ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) are currently under development for the intracellular delivery of therapeutics. However, the mechanisms of cellular uptake and the cellular reaction to this uptake, independent of therapeutics, are not well defined. The interactions of biocompatible cationic aminoUSPIONs with human cells was studied in 2D and 3D cultures using biochemical and electron microscopy techniques. AminoUSPIONs were internalized by human melanoma cells in 2D and 3D cultures. Uptake was clathrin mediated and the particles localized in lysosomes, inducing activation of the lysosomal cathepsin D and decreasing the expression of the transferrin receptor in human melanoma cells and/or skin fibroblasts. AminoUSPIONs deeply invaded 3D spheroids of human melanoma cells. Thus, aminoUSPIONs can invade tumors and their uptake by human cells induces cell reaction.
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Glioma accounts for 80% of brain tumors and currently remains one of the most lethal forms of cancers. Gene therapy could potentially improve the dismal prognosis of patients with glioma, but this treatment modality has not yet reached the bedside from the laboratory due to the lack of safe and effective gene delivery vehicles. In this study we investigate targeted gene delivery to C6 glioma cells in a xenograft mouse model using chlorotoxin (CTX) labeled nanoparticles. The developed nanovector consists of an iron oxide nanoparticle core, coated with a copolymer of chitosan, polyethylene glycol (PEG), and polyethylenimine (PEI). Green fluorescent protein (GFP) encoding DNA was bound to these nanoparticles, and CTX was then attached using a short PEG linker. Nanoparticles without CTX were also prepared as a control. Mice bearing C6 xenograft tumors were injected intravenously with the DNA-bound nanoparticles. Nanoparticle accumulation in the tumor site was monitored using magnetic resonance imaging and analyzed by histology, and GFP gene expression was monitored through Xenogen IVIS fluorescence imaging and confocal fluorescence microscopy. Interestingly, the CTX did not affect the accumulation of nanoparticles at the tumor site but specifically enhanced their uptake into cancer cells as evidenced by higher gene expression. These results indicate that this targeted gene delivery system may potentially improve treatment outcome of gene therapy for glioma and other deadly cancers.
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Nanoparticle approaches to drug delivery for cancer offer exciting and potentially "game-changing" ways to improve patient care and quality of life in numerous ways, such as reducing off-target toxicities by more selectively directing drug molecules to intracellular targets of cancer cells. Here, we focus on technologies being investigated clinically and discuss numerous types of therapeutic molecules that have been incorporated within nanostructured entities such as nanoparticles. The impacts of nanostructured therapeutics on efficacy and safety, including parameters like pharmacokinetics and biodistribution, are described for several drug molecules. Additionally, we discuss recent advances in the understanding of ligand-based targeting of nanoparticles, such as on receptor avidity and selectivity.
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The human airway epithelium serves as structural and functional barrier against inhaled particulate antigen. Previously, we demonstrated in an in vitro epithelial barrier model that monocyte derived dendritic cells (MDDC) and monocyte derived macrophages (MDM) take up particulate antigen by building a trans-epithelial interacting network. Although the epithelial tight junction (TJ) belt was penetrated by processes of MDDC and MDM, the integrity of the epithelium was not affected. These results brought up two main questions: (1) Do MDM and MDDC exchange particles? (2) Are those cells expressing TJ proteins, which are believed to interact with the TJ belt of the epithelium to preserve the epithelial integrity? The expression of TJ and adherens junction (AJ) mRNA and proteins in MDM and MDDC monocultures was determined by RT-PCR, and immunofluorescence, respectively. Particle uptake and exchange was quantified by flow cytometry and laser scanning microscopy in co-cultures of MDM and MDDC exposed to polystyrene particles (1 μm in diameter). MDM and MDDC constantly expressed TJ and AJ mRNA and proteins. Flow cytometry analysis of MDM and MDDC co-cultures showed increased particle uptake in MDDC while MDM lost particles over time. Quantitative analysis revealed significantly higher particle uptake by MDDC in co-cultures of epithelial cells with MDM and MDDC present, compared to co-cultures containing only epithelial cells and MDDC. We conclude from these findings that MDM and MDDC express TJ and AJ proteins which could help to preserve the epithelial integrity during particle uptake and exchange across the lung epithelium.
Article
PEGylated PAMAM conjugated fluorescein-doped magnetic silica nanoparticles (PEGylated PFMSNs) have been synthesized for evaluating their ability across the blood-brain barrier (BBB) and distribution in rat brain. The obtained nanoparticles were characterized by transmission electron microscopy (TEM), thermal gravimetry analyses (TGA), zeta potential (zeta-potential) titration, and X-ray photoelectron spectroscopy (XPS). The BBB penetration and distribution of PEGylated PFMSNs and FMSNs in rat brain were investigated not only at the cellular level with Confocal laser scanning microscopy (CLSM), but also at the subcellular level with transmission electron microscopy (TEM). The results provide direct evidence that PEGylated PFMSNs could penetrate the BBB and spread into the brain parenchyma.
Article
Drug–nanoparticle conjugates: The anticancer drug camptothecin (CPT) was covalently linked at the surface of ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) via a linker, allowing drug release by cellular esterases. Nanoparticles were hierarchically built to achieve magnetically-enhanced drug delivery to human cancer cells and antiproliferative activity. The linking of therapeutic drugs to ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) allowing intracellular release of the active drug via cell-specific mechanisms would achieve tumor-selective magnetically-enhanced drug delivery. To validate this concept, we covalently attached the anticancer drug camptothecin (CPT) to biocompatible USPIOs (iron oxide core, 9–10 nm; hydrodynamic diameter, 52 nm) coated with polyvinylalcohol/polyvinylamine (PVA/aminoPVA). A bifunctional, end-differentiated dicarboxylic acid linker allowed the attachment of CPT to the aminoPVA as a biologically labile ester substrate for cellular esterases at one end, and as an amide at the other end. These CPT–USPIO conjugates exhibited antiproliferative activity in vitro against human melanoma cells. The intracellular localization of CPT–USPIOs was confirmed by transmission electron microscopy (iron oxide core), suggesting localization in lipid vesicles, and by fluorescence microscopy (CPT). An external static magnetic field applied during exposure increased melanoma cell uptake of the CPT–USPIOs.
Article
One of the most challenging problems, if not the most challenging, in drug development is not to develop drugs to treat diseases of the central nervous system (CNS), but to manage to distribute them to the CNS across the blood-brain barrier (BBB) using transvascular routes following intravenous administration. The development of BBB targeting technologies is a very active field of research and development. One goal is to develop chemically modified derivatives of drugs or chemically modified nanoparticulate vectors of drugs, capable of crossing biological barriers, in particular the BBB. This manuscript will review the approaches that have been explored to achieve these goals, using chemical functionalization of drugs or of drug vector systems and endogenous transporters at the BBB.
Article
Our goal is to develop, characterize and optimize functionalized super paramagnetic iron oxide nanoparticles (SPION) demonstrating the capacity to be internalized by human cancer cells. SPION (mean diameter 9nm) were coated with various ratios to iron oxide of either polyvinyl alcohol (PVA), carboxylate-functionalized PVA, thiol-functionalized PVA and amino-functionalized PVA (amino-PVA). The interaction with cells and cytotoxicity of the SPION preparations were determined using human melanoma cells. From the four functionalized SPION preparations, only the amino-PVA SPION demonstrated the capacity to interact with, and were not cytotoxic to, human melanoma cells. This interaction with melanoma cells was dependent on the amino-PVA to iron oxide ratio, was an active and saturable mechanism displayed by all cells in a culture. These functionalized SPION were characterized by transmission electron microscopy and electrophoretic mobility. The physical comportment of SPION changed at specific PVAs to iron oxide ratios, and this ratio corresponded to the ratio of optimal interaction with cells. In conclusion, the successful development of functionalized SPION displaying potential cellular uptake by human cancer cells depends both on the presence of amino groups on the coating shell of the nanoparticles and of its ratio to the amount of iron oxide.
Article
The endothelial cells comprising brain capillaries have extremely tight intercellular junctions which form an essentially impermeable barrier to passive transport of water soluble molecules between the blood and brain. Several in vitro models of the blood-brain barrier (BBB) have been studied, most utilizing commercially available polymer membranes affixed to plastic inserts. There is mounting evidence that direct contact between endothelial cells and astrocytes, another cell type found to have intimate interaction with the brain side of BBB capillaries, is at least partially responsible for the development of the tight intercellular junctions between BBB endothelial cells. However, the membranes commonly used for BBB in vitro models are lacking certain attributes that would permit a high degree of direct contact between astrocytes and endothelial cells cultured on opposing sides. This work is based on the hypothesis that co-culturing endothelial and astrocyte cells on opposite sides of an ultra-thin, highly porous membrane will allow for increased direct interaction between the two cell types and therefore result in a better model of the BBB. We used standard nanofabrication techniques to make membranes from low-stress silicon nitride that are at least an order of magnitude thinner and at least two times more porous than commercial membrane inserts. An experimental survey of pore sizes for the silicon nitride membranes suggested pores approximately 400 nm in diameter are adequate for restricting astrocyte cell bodies to the seeded side while allowing astrocyte processes to pass through the pores and interact with endothelial cells on the opposite side. The inclusion of a spun-on, cross-linked collagen membrane allowed for astrocyte attachment and culture on the membranes for over two weeks. Astrocytes and endothelial cells displayed markers specific to their cell types when grown on the silicon nitride membranes. The transendothelial electrical resistances, a measure of barrier tightness, of endothelial and astrocyte co-cultures on the silicon nitride membranes were comparable to the commercial membranes, but neither system showed synergy between the two cell types in forming a tighter barrier. This lack of synergy may have been due to the loss of ability of commercially available primary bovine brain microvascular endothelial cells to respond to astrocyte differentiating signals.
Article
Super Paramagnetic Iron Oxide Nanoparticles (SPIONs) combined with magnetic resonance imaging (MRI) are under clinical evaluation to enhance detection of neurodegenerative diseases. A major improvement would be to link therapeutic drugs to the SPIONs to achieve targeted drug delivery, either at the cell surface or intracellularly, together with active disease detection, without inducing cell reaction. Our objectives were to define the characteristics of SPIONS able to achieve cell-specific interaction with brain-derived structures. Our system consisted in an iron oxide core (9-10 nm diameter) coated either with dextran (Sinerem and Endorem) or various functionalized polyvinyl alcohols (PVAs) (PVA-SPIONs). We investigated the cellular uptake, cytotoxicity, and interaction of these various nanoparticles with brain-derived endothelial cells, microglial cells, and differentiating three-dimensional aggregates. None of the nanoparticles coated with dextran or the various PVAs was cytotoxic or induced the production of the inflammatory mediator NO used as a reporter for cell activation. AminoPVA-SPIONs were taken up by isolated brain-derived endothelial and microglial cells at a much higher level than the other SPIONs, and no inflammatory activation of these cells was observed. AminoPVA-SPIONs did not invade brain cells aggregates lower than the first cell layer and did not induce inflammatory reaction in the aggregates. Fluorescent aminoPVA-SPIONs derivatized with a fluorescent reporter molecule and confocal microscopy demonstrated intracellular uptake by microglial cells. Fluorescent aminoPVA-SPIONs were well tolerated by mice. Therefore, functionalized aminoPVA-SPIONs represent biocompatible potential vector systems for drug delivery to the brain that may be combined with MRI detection of active lesions in neurodegenerative diseases.
Article
Most therapeutic drugs distribute to the whole body, which results in general toxicity and poor acceptance of the treatments by patients. The targeted delivery of chemotherapeutics to defined cells, either stromal or cancer cells in cancer lesions, or defined inflammatory cells in immunological disorders, is one of the main challenges and a very active field of research in the development of treatment strategies to minimize side-effects of drugs. Disease-associated cells express molecules, including proteases, receptors, or adhesion molecules, that are different or differently expressed than their normal counterparts. Therefore one goal in the field of targeted therapies is to develop chemically derivatized drugs or drug vectors able to target defined cells via specific recognition mechanisms and also able to overcome biological barriers. This article will review the approaches which have been explored to achieve these goals and will discuss in more detail three examples (i) the use of nanostructures to take advantage of increased vascular permeability in some human diseases, (ii) the targeting of therapeutic drugs to an organ, the brain, protected against foreign molecules by the blood-brain barrier, and (iii) the use of the folate receptor to target either tumor cells or activated macrophages.
Article
In recent years biomedical research indicated, that magnetic nanoparticles can be a promising tool for several applications in vitro and in vivo. In medicine many approaches were investigated for diagnosis and therapy and offered a great variety of applications. Magnetic cell separation, magnetic resonance imaging (MRI), magnetic targeted delivery of therapeutics or magnetically induced hyperthermia are approaches of particular clinical relevance. For medical use, especially for in vivo application it is of great importance that these particles do not have any toxic effects or incompatibility with biological organism. Investigations on applicable particles induced a variability of micro- and nanostructures with different materials, sizes, and specific surface chemistry.
Article
Nanotechnology-based tools and techniques are rapidly emerging in the fields of medical imaging and targeted drug delivery. Employing constructs such as dendrimers, liposomes, nanoshells, nanotubes, emulsions and quantum dots, these advances lead toward the concept of personalized medicine and the potential for very early, even pre-symptomatic, diagnoses coupled with highly-effective targeted therapy. Highlighting clinically available and preclinical applications, this review explores the opportunities and issues surrounding nanomedicine.
Article
This study explored the possibility of utilizing iron oxide nanoparticles as a drug delivery vehicle for minimally invasive, MRI-monitored magnetic targeting of brain tumors. In vitro determined hydrodynamic diameter of approximately 100 nm, saturation magnetization of 94 emicro/g Fe and T2 relaxivity of 43 s(-1)mm(-)(1) of the nanoparticles suggested their applicability for this purpose. In vivo effect of magnetic targeting on the extent and selectivity of nanoparticle accumulation in tumors of rats harboring orthotopic 9L-gliosarcomas was quantified with MRI. Animals were intravenously injected with nanoparticles (12 mg Fe/kg) under a magnetic field density of 0 T (control) or 0.4 T (experimental) applied for 30 min. MR images were acquired prior to administration of nanoparticles and immediately after magnetic targeting at 1h intervals for 4h. Image analysis revealed that magnetic targeting induced a 5-fold increase in the total glioma exposure to magnetic nanoparticles over non-targeted tumors (p=0.005) and a 3.6-fold enhancement in the target selectivity index of nanoparticle accumulation in glioma over the normal brain (p=0.025). In conclusion, accumulation of iron oxide nanoparticles in gliosarcomas can be significantly enhanced by magnetic targeting and successfully quantified by MR imaging. Hence, these nanoparticles appear to be a promising vehicle for glioma-targeted drug delivery.
Article
To determine whether glioma cells can be specifically and efficiently targeted by superparamagnetic iron oxide nanoparticle (SPIO)-fluorescein isothiocyanate (FITC)-chlorotoxin (SPIOFC) that is detectable by magnetic resonance imaging (MRI) and optical imaging. SPIOFC was synthesized by conjugating SPIO with FITC and chlorotoxin. Glioma cells (human U251-MG and rat C6) were cultured with SPIOFC and SPIOF (SPIO-FITC), respectively. Neural cells were treated with SPIOFC as the control for SPIOFC-targeted glioma cells. The internalization of SPIOFC by glioma cells was assessed by MRI and was quantified using inductively-coupled plasma emission spectroscopy. The optical imaging ability of SPIOFC was evaluated by confocal laser scanning microscopy. Iron per cell of U251 (72.5+/-1.8 pg) and C6 (74.9+/-2.2 pg) cells cultured with SPIOFC were significantly more than those of U251 (6.6+/-1.0 pg) and C6 (7.1+/-0.8 pg) cells incubated with SPIOF. The T2 signal intensity of U251 and C6 cells cultured with SPIOFC (233.6+/-25.9 and 211.4+/-17.2, respectively) were substantially lower than those of U251 and C6 cells incubated with SPIOF (2275.3+/-268.6 and 2342.7+/-222.4, respectively). Moreover, there were significant differences in iron per cell and T2 signal intensity between SPIOFC-treated neural cells (1.3+/-0.3; 2533.6+/-199.2) and SPIOFC-treated glioma cells. SPIOFC internalized by glioma cells exhibited green fluorescence by confocal laser scanning microscopy. SPIOFC is suitable for the specific and efficient targeting of glioma cells. MRI and optical imaging in conjunction with SPIOFC can differentiate glioma cells from normal brain tissue cells.
Article
Superparamagnetic iron oxide nanoparticles (SPIONs) are in clinical use for disease detection by MRI. A major advancement would be to link therapeutic drugs to SPIONs in order to achieve targeted drug delivery combined with detection. In the present work, we studied the possibility of developing a versatile synthesis protocol to hierarchically construct drug-functionalized-SPIONs as potential anti-cancer agents. Our model biocompatible SPIONs consisted of an iron oxide core (9-10 nm diameter) coated with polyvinylalcohols (PVA/aminoPVA), which can be internalized by cancer cells, depending on the positive charges at their surface. To develop drug-functionalized-aminoPVA-SPIONs as vectors for drug delivery, we first designed and synthesized bifunctional linkers of varied length and chemical composition to which the anti-cancer drugs 5-fluorouridine or doxorubicin were attached as biologically labile esters or peptides, respectively. These functionalized linkers were in turn coupled to aminoPVA by amide linkages before preparing the drug-functionalized-SPIONs that were characterized and evaluated as anti-cancer agents using human melanoma cells in culture. The 5-fluorouridine-SPIONs with an optimized ester linker were taken up by cells and proved to be efficient anti-tumor agents. While the doxorubicin-SPIONs linked with a Gly-Phe-Leu-Gly tetrapeptide were cleaved by lysosomal enzymes, they exhibited poor uptake by human melanoma cells in culture.
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