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Cellular response of RAW 264.7 to spray-coated multi-walled carbon nanotube films with various surfactants
Abstract
The increasing role of carbon nanotubes (CNTs) in various biological applications has led to a number of studies on the cytotoxicity of solution-phase CNTs, but few studies are available concerning the cytotoxicity of CNT films. Herein, we studied the potential health effect of CNT films fabricated with three commercial surfactants (sodium cholate, sodium dodecyl sulfate, and triton X-100). Multi-walled carbon nanotube-surfactant dispersions were coated onto substrates through air-spray technique. Cellular morphology, MTT assays, as well as the expression of TNF-α and IL-1β of RAW 264.7 cells cultured on the spray-coated CNT films were evaluated for cytotoxicity. It was found that the cytotoxicity of the CNT films was largely dependent on the type of surfactant used and could be significantly reduced by mild washing steps.
... However, films based on carbon nanotubes or on graphene, or films that contain these nanoparticles, have often shown some cytotoxicity for mammalian cells. [3][4][5] The diamond surface consists of sp 3 hybridized carbon bonds that are chemically and mechanically stable. Nanosized diamond crystals are packed in a compact form as thin films, referred to as nanocrystalline diamond films (NCD), and display a wide range of unique physical and chemical properties, such as mechanical hardness, chemical and thermal resistance, excellent optical transparency, and controllable electrical properties. ...
... However, films based on carbon nanotubes or on graphene, or films that contain these nanoparticles, have often shown some cytotoxicity for mammalian cells. [3][4][5] The diamond surface consists of sp 3 hybridized carbon bonds that are chemically and mechanically stable. Nanosized diamond crystals are packed in a compact form as thin films, referred to as nanocrystalline diamond films (NCD), and display a wide range of unique physical and chemical properties, such as mechanical hardness, chemical and thermal resistance, excellent optical transparency, and controllable electrical properties. ...
Nanocrystalline diamond (NCD) films are promising materials for bone implant coatings because of their biocompatibility, chemical resistance, and mechanical hardness. Moreover, NCD wettability can be tailored by grafting specific atoms. The NCD films used in this study were grown on silicon substrates by microwave plasma-enhanced chemical vapor deposition and grafted by hydrogen atoms (H-termination) or oxygen atoms (O-termination). Human osteoblast-like Saos-2 cells were used for biological studies on H-terminated and O-terminated NCD films. The adhesion, growth, and subsequent differentiation of the osteoblasts on NCD films were examined, and the extracellular matrix production and composition were quantified. The osteoblasts that had been cultivated on the O-terminated NCD films exhibited a higher growth rate than those grown on the H-terminated NCD films. The mature collagen fibers were detected in Saos-2 cells on both the H-terminated and O-terminated NCD films; however, the quantity of total collagen in the extracellular matrix was higher on the O-terminated NCD films, as were the amounts of calcium deposition and alkaline phosphatase activity. Nevertheless, the expression of genes for osteogenic markers - type I collagen, alkaline phosphatase, and osteocalcin - was either comparable on the H-terminated and O-terminated films or even lower on the O-terminated films. In conclusion, the higher wettability of the O-terminated NCD films is promising for adhesion and growth of osteoblasts. In addition, the O-terminated surface also seems to support the deposition of extracellular matrix proteins and extracellular matrix mineralization, and this is promising for better osteoconductivity of potential bone implant coatings.
... Thus, it is reasonable to consider that the PF108 coating is a promising strategy for the safer design of CNTs in nano-applications [98]. It is believed that substances coated on the MWCNT surface bestow the nanotube with particular physicochemical properties [118] and can alter or even cover the original effects of the MWCNT [115], which will be restored after clearing the coating material [119]. Collectively, these findings show that functionalizing or coating MWCNT surfaces with certain chemicals without changing their intrinsic structure may be a secure design strategy for reducing MWCNT toxicity when taking into account their potential usage in biomedical applications. ...
With the rapid development of engineered nanomaterials (ENMs) in biomedical applications, their biocompatibility and cytotoxicity need to be evaluated properly. Recently, it has been demonstrated that inflammasome activation may be a vital contributing factor for the development of biological responses induced by ENMs. Among the inflammasome family, NLRP3 inflammasome has received the most attention because it directly interacts with ENMs to cause the inflammatory effects. However, the pathways that link ENMs to NLRP3 inflammasome have not been thoroughly summarized. Thus, we reviewed recent findings on the role of major ENMs properties in modulating NLRP3 inflammasome activation, both in vitro and in vivo, to provide a better understanding of the underlying mechanisms. In addition, the interactions between ENMs and NLRP3 inflammasome activation are summarized, which may advance our understanding of safer designs of nanomaterials and ENM-induced adverse health effects.
... Up to date, numerous types of scaffolds with surface modification have been suggested via the involvement of various nanomaterials to enhance cellular behaviors [4][5][6]. In particular, nanomaterial-involved substrates can be manufactured using various conventional coating techniques, including spin coating [7,8], dip coating [9][10][11], drop casting [12,13], vacuum filtration [14], and airspraying [15], for biomedical applications. However, some of these coating methods produce relatively non-uniform thin films of nanomaterials due to the lack of controllability. ...
Recently, black phosphorus (BP) has garnered great attention as one of newly emerging two-dimensional nanomaterials. Especially, the degraded platelets of BP in the physiological environment were shown to be nontoxic phosphate anions, which are a component of bone tissue and can be used for mineralization. Here, our study presents the potential of BP as biofunctional and biocompatible nanomaterials for the application to bone tissue engineering and regeneration. An ultrathin layer of BP nanodots (BPNDs) was created on a glass substrate by using a flow-enabled self-assembly process, which yielded a highly uniform deposition of BPNDs in a unique confined geometry. The BPND-coated substrates represented unprecedented favorable topographical microen-vironments and supportive matrices suitable for the growth and survival of MC3T3-E1 preosteoblasts. The prepared substrates promoted the spontaneous osteodifferentiation of preosteoblasts, which had been confirmed by determining alkaline phosphatase activity and extracellular calcium deposition as early-and late-stage markers of osteogenic differentiation, respectively. Furthermore, the BPND-coated substrates upregulated the expression of some specific genes (i.e., RUNX2, OCN, OPN, and Vinculin) and proteins, which are closely related to osteogenesis. Conclusively, our BPND-coating strategy suggests that a biologically inert surface can be readily activated as a cell-favorable nanoplatform enabled with excellent biocompatibility and osteogenic ability.
... DCAS was used for dispersion of SWCNT [47], containing encapsulated organometallic molecules for catalytic applications. The use of CAS as a dispersant allowed the fabrication of SWCNT films for biomedical applications [48], which showed reduced cytotoxicity, compared to the SWCNT films, prepared using other commercial dispersants. The investigation of CAS-SWCNT conjugates in suspensions showed that astrocytoma cells were not affected by CAS-SWCNT [49,50]. ...
This review describes new strategies for the non-covalent functionalization and dispersion of CNT using small molecules, such as commercial bile acid salts (BAS) and organic dyes. Efficient CNT dispersion was achieved due to the small size, charge and unique adsorption properties of BAS and dyes, which facilitated the bundle “unzipping” mechanism. The discovery of interesting electrochemical and film-forming properties of BAS and organic dyes allowed electrophoretic deposition (EPD) of CNT films by cathodic or anodic methods. Of particular importance is the efficiency of BAS dispersants in the sorting of CNT by diameter, chirality and length. These studies allowed for the efficient separation of SWCNT by electronic type and size, which addressed the urgent needs for many advanced applications. New dispersants allowed the fabrication of functional polymer coated CNT and development of advanced techniques for the fabrication of composites. Chelating dyes were used as co-dispersants for CNT and inorganic nanoparticles. The use of BAS and organic dyes for CNT dispersion has driven the development of advanced composites, films, aerogels for electrochemical, electronic, energy generation and storage, biomedical, sensor and other applications. Colloidal and interface chemistry of new dispersing agents is emerging as a new area of technological and scientific interest.
... (a) Chemical modification of MWCNTs through thermal oxidation[6]. (b) Molecular structure of Triton X 100[7]. (c) A simplified scheme of the generation of covalently bound surface acidic groups[8] and different functional groups through thermal oxidation and solvothermal synthesis. ...
The present study focuses on the synthesis of nanocomposite gamma alumina (γ-Al2O3), boehmite and multi- walled carbon nanotubes (MWCNTs) via a solvothermal procedure. The method is based on the ex situ filling of opened CNTs by liquid reactants. The microstructure and morphology of the synthesized nanocomposite Al2O3@CNTs/Al2O3 was characterized by high resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and N2 adsorption–desorption analysis.Based on the experimental results, it was determined that the volume ratio of γ-Al2O3/MWCNTs and the surface tension of the solvent both greatly influence the morphology of the nanocomposite. The resultant MWCNTs were coated and filled by homogeneous and uniform boehmite and γ-Al2O3 layers and nanoparticles with thicknesses of 1–3 nm and diameters of 20–40 nm, when the volume ratio of γ-Al2O3/MWCNTS is 1 and the surface tension of the solvent is approximately 26 mN m−1 at 20 °C, far below the maximum value (100–200 mN m−1) for MWCNT filling.
The commercial production of carbon nanotubes (CNTs) and research in their biomedical applications have increased enormously in the past decade. Despite the augmentation in demand and a concomitant increase in commercial supply of CNTs, the feasibility of their biomedical applications has been compounded by reports of adverse effects. This chapter essentially reviews four aspects of CNTs from a biomedical application point of view. The first part focuses on in vitro and in vivo toxicity of carbon nanotubes, while the second part emphasizes the mechanisms of cellular uptake and toxicity. The third part highlights the experimental parameters that influence toxicity and efforts to reduce untoward effects by tweaking these parameters as well as CNTs. The last part concentrates on the regulatory aspects of CNT applications and tries to bring to the fore the regulatory challenges that CNTs are facing and will continue to face in the foreseeable future.KeywordsBiomedical applicationsCarbon nanotubesToxicityNanotoxicology
Multi-walled carbon nanotubes (MWCNTs) have wide application prospects but also exhibit notable biotoxicity that is tightly associated with macrophages. Macrophages simultaneously act as initiators and defenders in MWCNT-induced organ lesions, and targeting macrophages with MWCNTs may be a potential immunotherapy and oncotherapy approach. This review focuses on the impacts of MWCNTs on macrophages and further discusses the influence of MWCNT characteristics on their bioactivity. Based on existing studies, MWCNTs stimulate macrophage migration, induce secretion of various cytokines and activate inflammatory pathways in macrophages, especially NLRP3-mediated IL-1β production. This inflammatory state, together with the oxidative stress and cell membrane lesions induced by MWCNTs, contributes to decreased phagocytic ability and cell viability, which finally results in cell apoptosis and necrosis. A series of intracellular and systemic components, such as toll-like receptor, high-mobility group box 1, Rho-associated kinases, scavenger receptor and complement components, may be involved in the above-mentioned cell-MWCNT interactions. The characteristics of MWCNTs can influence their bioactivity in macrophages both mechanically and chemically. The size (length and/or diameter), functionalization, purification and even the experimental method can affect the influence of MWCNTs on macrophages, and a better understanding of these MWCNT characteristics may benefit utilization of this nanomaterial in associated nanomedical applications.
Due to their exceptional properties, carbon nanotubes (CNT) have aroused a huge interest among in industrial fields such as microelectronics, material science and nanomedicine. Nevertheless, the health impacts of this nanomaterial still remain not well understood. The first toxicological studies pointed out that there is no unique response regarding the healthimpact of the CNT, but different toxicological profiles according to their various physicochemical properties. A safer by design approach is thus proposed to identify the parameters decreasing from their production the CNT biological impacts. In this context, this work aimed at studying the impact on the in vitro response from a macrophage cell line (RAW 264.7) of two post-Production treatments: acid functionalization and high temperature annealing.Surface acid groups from functionalized CNT enhanced the pro-Inflammatory response although the cytotoxicity remained stable. On the other hand, acid functionalization, through the elimination of metallic impurities, significantly decreased the oxidative stress. Annealed CNT increased the pro-Inflammatory response compared to the pristine CNT. It thus confirmed the sensitivity of this response for the changes in surface chemistry. However, the high temperature annealing did not influence the oxidative stress, despite of the CNT purification. It suggested that structural defects are also of importance for this response. Besides, the acid functionalization of nano-Graphite and carbon black displayed trends in the macrophage response similar to the acid functionalization of CNT. The comparison of these three carbon-Based nanomaterials seemed to conform to the fibre and platelets paradigm. Eventually, exploratory studies have also been conducted on the interferences between CNT and the toxicity assays, and on the oxidative stress.
Here we demonstrate a polysaccharide hydrogel reinforced with finely dispersed single-walled carbon nanotubes (SWNTs) using biocompatible dispersants O-carboxymethylchitosan (OC) and chondroitin sulfate A (CS-A) as a structural support. Both of the dispersants can disperse SWNTs in aqueous solutions and hydrogel matrix as individual tubes or small bundles. Additionally, we have found that compressive modulus and strain of the hydrogels reinforced with SWNTs were enhanced as much as two times by the addition of a few weight percent of SWNTs. Moreover, the SWNT-incorporated hydrogels exhibited lower impedance and higher charge capacity than the alginate/dispersant hydrogel without SWNTs. The OC and the CS-A demonstrated much higher reinforcing enhancement than a commercially available dispersant, sodium dodecyl sulfate. Combined with the experimental data on the mechanical and electrical properties, the biocompatibility of OC and CS-A can provide the possibility of biomedical application of the SWNT-reinforced hydrogels.
Single-wall carbon nanotubes exhibit many properties analogous to quantum dots and wires at very low temperatures: Coulomb blockade and single-electron charging. These and other phenomena may be exploited in constructing active electronic devices of unprecedentedly small size. Bulk material may be chemically doped to yield mass-normalized electrical conductivity higher than that of copper.
Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ∼0.34 nm. The carbon network of the shells is closely related to the honeycomb arrangement of the carbon atoms in the graphite sheets. The amazing mechanical and electronic properties of the nanotubes stem in their quasi-one-dimensional (1D) structure and the graphite-like arrangement of the carbon atoms in the shells. Thus, the nanotubes have high Young’s modulus and tensile strength, which makes them preferable for composite materials with improved mechanical properties. The nanotubes can be metallic or semiconducting depending on their structural parameters. This opens the ways for application of the nanotubes as central elements in electronic devices including field-effect transistors (FET), single-electron transistors and rectifying diodes. Possibilities for using of the nanotubes as high-capacity hydrogen storage media were also considered. This report is intended to summarize some of the major achievements in the field of the carbon nanotube research both experimental and theoretical in connection with the possible industrial applications of the nanotubes.
Phase contrast and epifluorescence microscopy were utilized to monitor morphological changes in human astrocytoma cells during a time-course exposure to single-walled carbon nanotube (SWCNT) conjugates with different surfactants and to investigate sub-cellular distribution of the nanotube conjugates, respectively. Experimental results demonstrate that cytotoxicity of the nanotube/surfactant conjugates is related to the toxicity of surfactant molecules attached on the nanotube surfaces. Both sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) are toxic to cells. Exposure to CNT/SDS conjugates (0.5 mg/mL) for less than 5 min caused changes in cell morphology resulting in a distinctly spherical shape compared to untreated cells. In contrast, sodium cholate (SC) and CNT/SC did not affect cell morphology, proliferation, or growth. These data indicate that SC is an environmentally friendly surfactant for the purification and dispersion of SWCNTs. Epifluorescence microscopy analysis of CNT/DNA conjugates revealed distribution in the cytoplasm of cells and did not show adverse effects on cell morphology, proliferation, or viability during a 72-h incubation. These observations suggest that the SWCNTs could be used as non-viral vectors for diagnostic and therapeutic molecules across the blood-brain barrier to the brain and the central nervous system.
The aim of this study was to evaluate adverse effects of multiwalled carbon nanotubes (MWCNT), produced for industrial purposes, on the human epithelial cell line A549. MWCNT were dispersed in dipalmitoyl lecithin (DPL), a component of pulmonary surfactant, and the effects of dispersion in DPL were compared to those in two other media: ethanol (EtOH) and phosphate-buffered saline (PBS). Effects of MWCNT were also compared to those of two asbestos fibers (chrysotile and crocidolite) and carbon black (CB) nanoparticles, not only in A549 cells but also in mesothelial cells (MeT5A human cell line), used as an asbestos-sensitive cell type. MWCNT formed agglomerates on top of both cell lines (surface area 15-35 microm(2)) that were significantly larger and more numerous in PBS than in EtOH and DPL. Whatever the dispersion media, incubation with 100 microg/ml MWCNT induced a similar decrease in metabolic activity without changing cell membrane permeability or apoptosis. Neither MWCNT cellular internalization nor oxidative stress was observed. In contrast, asbestos fibers penetrated into the cells, decreased metabolic activity but not cell membrane permeability, and increased apoptosis, without decreasing cell number. CB was internalized without any adverse effects. In conclusion, this study demonstrates that MWCNT produced for industrial purposes exert adverse effects without being internalized by human epithelial and mesothelial pulmonary cell lines.
Iron oxide (Fe(3)O(4)) nanoparticles prepared using co-precipitation method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on indium-tin oxide (ITO) glass plate. Glucose oxidase (GOx) has been immobilized onto this CH-Fe(3)O(4) nanocomposite film via physical adsorption. The size of the Fe(3)O(4) nanoparticles estimated using X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) has been found to be approximately 22 nm. The CH-Fe(3)O(4) nanocomposite film and GOx/CH-Fe(3)O(4)/ITO bioelectrode have been characterized using UV-visible and Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopy (SEM) techniques, respectively. This GOx/CH-Fe(3)O(4)/ITO nanocomposite bioelectrode has response time of 5s, linearity as 10-400 mgdL(-1) of glucose, sensitivity as 9.3 microA/(mgdLcm(2)) and shelf life of about 8 weeks under refrigerated conditions. The value of Michaelis-Menten (K(m)) constant obtained as 0.141 mM indicates high affinity of immobilized GOx towards the substrate (glucose).
Fluorescence has been observed directly across the band gap of semiconducting carbon nanotubes. We obtained individual nanotubes,
each encased in a cylindrical micelle, by ultrasonically agitating an aqueous dispersion of raw single-walled carbon nanotubes
in sodium dodecyl sulfate and then centrifuging to remove tube bundles, ropes, and residual catalyst. Aggregation of nanotubes
into bundles otherwise quenches the fluorescence through interactions with metallic tubes and substantially broadens the absorption
spectra. At pH less than 5, the absorption and emission spectra of individual nanotubes show evidence of band gap–selective
protonation of the side walls of the tube. This protonation is readily reversed by treatment with base or ultraviolet light.
Molecular detection using near-infrared light between 0.9 and 1.3 eV has important biomedical applications because of greater tissue penetration and reduced auto-fluorescent background in thick tissue or whole-blood media. Carbon nanotubes have a tunable near-infrared emission that responds to changes in the local dielectric function but remains stable to permanent photobleaching. In this work, we report the synthesis and successful testing of solution-phase, near-infrared sensors, with beta-D-glucose sensing as a model system, using single-walled carbon nanotubes that modulate their emission in response to the adsorption of specific biomolecules. New types of non-covalent functionalization using electron-withdrawing molecules are shown to provide sites for transferring electrons in and out of the nanotube. We also show two distinct mechanisms of signal transduction-fluorescence quenching and charge transfer. The results demonstrate new opportunities for nanoparticle optical sensors that operate in strongly absorbing media of relevance to medicine or biology.
Biocomposite scaffolds of poly(lactic-co-glycolic acid) (PLGA), multiwalled carbon nanotubes (MWNTs), and hydroxyapatite (HA) nanoparticles were prepared ‘by electrospinning’ for bone tissue engineering. The structure, surface morphology, and some properties of these PLGA/MWNTs/ HA composites were evaluated. Cultured bone marrow-derived mesenchymal stem cells (BMSCs) were seeded on the PLGA/MWNTs/HA scaffolds, and their attachment and proliferation were determined by scanning electron microscopy (SEM) and MTT assay, respectively. The composite scaffolds, a 3D nonwoven fabric construct mimicked the structure of the natural extracellular matrix. The average diameter of the PLGA/MWNTs/HA fibers increased with increasing HA content from 0.5% to 1.5% in the composites. The SEM and MTT results indicated good biocompatibility by the scaffolds, and that the attachment and proliferation of BMSCs were significantly increased in the PLGA/MWNTs/ 1.0%HA and PLGA/MWNTs/1.5%HA scaffolds compared with the PLGA control. These scaffolds, fabricated by electrospinning, indicate good potential for bone tissue engineering applications.
Because mass‐produced carbon nanotubes (CNTs) are strongly aggregated and highly hydrophobic, processes to make them water soluble are required for biological applications. Suspensions in surfactant solutions are often employed. Among these, Pluronic F127 appear to be highly biocompatible if used at low concentrations. Starting from these results, this work involves a systematic study to clarify the dispersion behaviour of CNTs in Pluronic F127. The results suggest a two‐step process: first, the bundles disaggregate, kinetically driven by the energy supplied to the system; second, they disperse (surfactant adsorption), thermodynamically driven by the surfactant concentration. The dispersion reaction data are well fitted by a first‐order kinetics reaction. By performing a pretreatment step, consisting of stirring at 70°C, the achieved concentration of CNTs in solution is twice that of the traditional process. The proposed procedure provides an optimal compromise between a low Pluronic concentration and a high CNT concentration.
The solubility of small diameter single-wall carbon nanotubes
in several organic solvents is described, and characterization in
1,2-dichlorobenzene is reported.
This chapter discusses the heterogeneity in macrophage phagocytosis. It is important to recognize that the formation of the phagosome can be a heterogenous process even when a single cell ingests two identical particles. While all phagocytosis involves actin remodeling around the phagocytic cup, it has been observed that certain cytoskeletal proteins that decorate a particular phagosome are absent from otherwise identical phagosomes in the same cell. These differences are not temporal, but are likely to arise from stochastic, or even chaotic, processes. It is clear that the molecular dissection of phagocytosis represents a daunting task; more than 100 actin-binding proteins have been identified, and many of these are expressed in the same cell. Two common approaches that have been used to establish the role of specific gene products in a particular biological phenomenon have been to express dominant negative forms of the protein, or to delete the gene encoding the protein. However, the interpretation of the results is complicated by the observation that these two approaches do not always yield the same phenotype. Ultimately, phagocytosis, like most other problems in biology, will have to be analyzed as a complex system rather than a linear series of isolated enzymatic reactions. In this guise, phagocytosis provides a window into the coordinate functioning of the actin and tubulin based cytoskeletons, and could serve as a model system for analyzing diverse biological phenomena including synaptic transmission, mitogenesis, and morphogenesis.
Individual single-walled carbon nanotubes (SWNTs) have been suspended in aqueous media using various anionic, cationic, nonionic surfactants and polymers. The surfactants are compared with respect to their ability to suspend individual SWNTs and the quality of the absorption and fluorescence spectra. For the ionic surfactants, sodium dodecylbenzene sulfonate (SDBS) gives the most well resolved spectral features. For the nonionic systems, surfactants with higher molecular weight suspend more SWNT material and have more pronounced spectral features.
The effect of the bile salt sodium cholate on the permeability properties of lipid vesicles (liposomes) to mononucleotides at pH 8.0 (0.1 M Tris-HCl) in the presence of 5 mM MgCl2 was investigated. The vesicles mainly used were unilamellar with diameters of about 100 nm, prepared from POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine). Depending on the total amount of cholate and POPC, the vesicles could be loaded with ADP (adenosine 5‘-diphosphate), UMP (uridine 5‘-monophosphate), UDP (uridine 5‘-diphosphate), or UTP (uridine 5‘-triphosphate), under conditions where bilayer solubilization did not occur, Re Resat, with Re being the molar ratio of cholate in the vesicle bilayer to POPC under conditions of the uptake experiments (Re) or under conditions of bilayer saturation with cholate (Resat), as determined by light scattering (turbidity) measurements. The uptake experiments were preceded by a detailed study of the interaction between cholate and the POPC vesicles. Most importantly, freeze-fracture electron microscopy showed that vesicle solubilization begun at Re values lower than Resat estimated turbidimetrically. This finding indicates that care has to be taken if vesicle solubilization studies are based only on the measurements of changes in turbidity. Although a number of investigations have been devoted in the past to the cholate-induced release of water-soluble molecules from vesicles, the present work is probably the first detailed study on the reverse process. Nucleotide uptake by the vesicles at subsolubilizing cholate concentration was confirmed in the case of ADP by using vesicles containing entrapped Micrococcus luteus polynucleotide phosphorylase, which catalyzed the endovesicular polymerization of exovesicularly added ADP to poly-A. These latter experiments show that enzyme-containing vesicles can be used as nanoreactor systems in which the permeability of the bilayers is selectively altered by a surfactant, allowing the uptake of substrate molecules but not the release of the entrapped enzyme or reaction product.
Centrifugation is applied to purify single-walled carbon nanotubes (SWCNTs) grown from MCM-41 containing cobalt (Co-MCM-41) catalysts by chemical vapor deposition. We demonstrated that an optimized centrifugation force can lead to analytically pure SWCNTs. Four criteria in terms of physical and chemical properties of Co-MCM-41 were proposed for quality control of catalysts. After centrifugation at 120 000 g, SWCNT purity index based on absorption spectra of sodium cholate (SC) dispersed tubes is 0.268, approaching the previously estimated value (0.325) for analytically pure SWCNTs. It is a significant improvement compared to previously reported high-purity samples (e.g., super purified HIPCO (Unidym) with purity index = 0.087, and SWeNT SG 65 (SouthWest NanoTechnologies) with purity index = 0.194). In photoluminance emission spectra of SC dispersed SWCNTs, (1) line width for E11 emission peaks at E22 excitation energy, (2) intensities of three sidebands, and (3) intensities of E11 emission peaks at E33 excitation energy are found to be related to SWCNT purity. Theoretical models predict that SC molecules adsorbed on the surface of SWCNTs account for about 40−60 wt % of tube samples. Thermogravimetric analyses (TGA) confirm that SC cannot be easily washed away by common solvents. However, after removal of metallic residues (0.15 wt % by TGA), absorbed SC molecules can be eliminated by heating in air at 350 °C for 30 min. The purification protocol may prove useful in evaluating health and environmental effects of SWCNT material and improving separation efficiencies of nanotube species according to electronic type, diameter, length, and chiral handedness.
For the continuous monitoring, diagnosis, and treatment of neural tissue, implantable probes are required. However, sometimes such neural probes (usually composed of silicon) become encapsulated with non-conductive, undesirable glial scar tissue. Similarly for orthopaedic implants, biomaterials (usually titanium and/or titanium alloys) often become encapsulated with undesirable soft fibrous, not hard bony, tissue. Although possessing intriguing electrical and mechanical properties for neural and orthopaedic applications, carbon nanofibres/nanotubes have not been widely considered for these applications to date. The present work developed a carbon nanofibre reinforced polycarbonate urethane (PU) composite in an attempt to determine the possibility of using carbon nanofibres (CNs) as either neural or orthopaedic prosthetic devices. Electrical and mechanical characterization studies determined that such composites have properties suitable for neural and orthopaedic applications. More importantly, cell adhesion experiments revealed for the first time the promise these materials have to increase neural (nerve cell) and osteoblast (bone-forming cell) functions. In contrast, functions of cells that contribute to glial scar-tissue formation for neural prostheses (astrocytes) and fibrous-tissue encapsulation events for bone implants (fibroblasts) decreased on PU composites containing increasing amounts of CNs. In this manner, this study provided the first evidence of the future that CN formulations may have towards interacting with neural and bone cells which is important for the design of successful neural probes and orthopaedic implants, respectively.
In this paper, we report a conduction-type-tunable carbon nanotube field effect transistor (CNT-FET) with double-gate structure (DG CNT-FET). In this study, a specially designed narrow top-gate is created to modulate the energy band in the middle region of a single CNT. In the proposed DG device structure, the top-gate and bottom-gate biases exhibit independent modulation behaviors. Depending on whether a positive or negative bias is applied to the top-gate, the CNT-FET can be operated in either n- or p-type conduction. Energy band diagram conducive to the physical mechanisms of the proposed DG CNT-FET device structure is proposed. Based on the proposed hypothesis, ambipolar CNT-FETs can indeed be converted to n- or p-type-like behaviors.
Metal incorporated MCM-41 has proven to be a valuable template for the growth of narrow distributions of single-walled carbon nanotubes (SWNT), producing samples with a wide range of different mean diameters. The ability to obtain narrow diameter distributions at different mean diameters is important for applications that require particular (n,m) nanotubes. Another advantage of this system is the ease of cleaning and low metal content as compared to bimetallic systems. In this Article, we show that Co-MCM-41 allows diameter tuning of SWNT produced over a broad diameter range (from 0.6-0.8 to 1.8-2.0 nm) by changing reaction temperature. The lower temperature reaction provides a robust means to obtain very small diameter SWNT. X-ray absorption experiments show that the change in SWNT diameter correlates with the change in metal particle size.
Dispersion of PZT powder of average particle size 75 nm in commonly used solvent systems for tape casting namely, toluene-ethanol and MEK-ethanol (azeotropic), xylene-ethanol (zeotropic) along with triton x-100, menhaden fish oil and phosphate ester as dispersants has been studied using simple sedimentation experiments. The relative merits of these three solvent systems and dispersants in dispersing PZT powder was analyzed. In all the three solvent systems, phosphate ester was found to be the best dispersant. Xylene-ethanol with phosphate ester gave the excellent dispersion characteristics for nano-PZT powder. The results of initial dispersion studies were confirmed by the formation of defect free, denser and smooth green tapes using xylene-ethanol and phosphate ester, while the other two solvent systems gave defective green tapes. The influence of phosphate ester on dispersion is explained by the dissociation and ionization, and the dominance of electrostatic repulsion even though organic solvent systems were used.
Carbon nanotubes (CNTs) are among the most promising novel nanomaterials and their unique chemical and physical properties suggest an enormous potential for many areas of research and applications. As a consequence, the production of CNT-based material and thus the occupational and public exposure to CNTs will increase steadily. Although there is evidence that nanoparticles (NPs) can enter the nervous system via the blood stream, olfactory nerves or sensory nerves in the skin, there is still only little knowledge about possible toxic effects of CNTs on cells of the nervous system.
Sodium dodecyl sulfate (SDS) is the most widely used surfactant in micellar electrokinetic capillary chromatography (MECC). The separation of highly hydrophobic compounds by MECC can be difficult because they will completely associate with the micelles and will elute at the end of the elution window. The addition of organic solvents to the running buffer may enhance the separation, but they can also inhibit micelle formation. An alternative is the use of different surfactant systems such as bile salts and ionic polymers. In this work, four different surfactants (SDS, sodium cholate, sodium deoxycholate and Elvacite 2669) have been studied by using two organophosphorus pesticides (chlorpyriphos-methyl and -ethyl) as model compounds.
The preparation of a new type of finite carbon structure consisting of
needlelike tubes is reported. Produced using an arc-discharge
evaporation method similar to that used for fullerene sythesis, the
needles grow at the negative end of the electrode used for the arc
discharge. Electron microscopy reveals that each needle comprises
coaxial tubes of graphitic sheets ranging in number from two up to about
50. On each tube the carbon-atom hexagons are arranged in a helical
fashion about the needle axis. The helical pitch varies from needle to
needle and from tube to tube within a single needle. It appears that
this helical structure may aid the growth process. The formation of
these needles, ranging from a few to a few tens of nanometers in
diameter, suggests that engineering of carbon structures should be
possible on scales considerably greater than those relevant to the
fullerenes.
The cytotoxicity of single-walled carbon nanotubes (SWCNTs) suspended in various surfactants was investigated by phase contrast light microscopy characterization in combination with an absorbance spectroscopy cytotoxicity analysis. Our data indicate that individual SWCNTs suspended in the surfactants, sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS), were toxic to 1321N1 human astrocytoma cells due to the toxicity of SDS and SDBS on the nanotube surfaces. This toxicity was observed when cells were exposed to an SDS or SDBS solution having a concentration as low as 0.05 mg ml(-1) for 30 min. The proliferation and viability of the cells were not affected by SWCNTs alone or by conjugates of SWCNTs with various concentrations of sodium cholate (SC) or single-stranded DNA. The cells proliferated similarly to untreated cells when surrounded by SWCNTs as they grow, which indicated that the nanotubes did not affect cells adversely. The cytotoxicity of the nanotube-surfactant conjugates was controlled in these experiments by the toxicity of the surfactants. Consequently, when evaluating a surfactant to be used for the dispersion of nanoscale materials in applications such as nanoscale electronics or non-viral biomolecular transporters, the cytotoxicity needs to be evaluated. The methodology proposed in this study can be used to investigate the cytotoxicity of other nanoscale materials suspended in a variety of surfactants.
This research presents a fabrication method of vertically aligned nanowires on substrates using lithography-assisted template bonding (LATB) towards developing highly efficient electrodes for biomedical applications at low cost. A polycarbonate template containing cylindrical nanopores is attached to a substrate and the nanopores are selectively opened with a modified lithography process. Vertically aligned nanowires are grown by electrochemical deposition through these open pores on polyimide film and silicon substrates. The process of opening the nanopores is optimized to yield uniform growth of nanowires. The morphological, crystalline, and electrochemical properties of the resulting vertically aligned nanowires are discussed using scanning electron microscopy (SEM), x-ray diffraction (XRD), and electrochemical analysis tools. The potential application of this simple and inexpensive fabrication technology is discussed in the development of neural probe electrodes.
Several natural and synthetic polymers are now available for bone tissue engineering applications but they may lack mechanical integrity. In recent years, there are reports emphasizing the importance of carbon nanotubes (CNTs) in supporting bone growth. CNTs possess exceptional mechanical, thermal, and electrical properties, facilitating their use as reinforcements or additives in various materials to improve the properties of the materials. Biomaterials containing polymers often are placed adjacent to bone. The use of CNTs is anticipated in these biomaterials applied to bone mainly to improve their overall mechanical properties and expected to act as scaffolds to promote and guide bone tissue regeneration. This review paper provides a current state of knowledge available examining the use of the polymeric composites containing CNTs for promoting bone growth.
The innate ability of carbon nanotubes to breach the cell membrane of various types of mammalian cells has been reported. Here, we present a summary of the various applications of carbon nanotubes as a cellular transport and delivery system for functional biological cargos. The internalization of SWNTs for transport and delivery into cells is mediated via endocytosis and does not appear to have any detrimental effect on either the transported cargo or the breached cell. The emergence of SWNT as a new class of cellular transporters holds many exciting promises for SWNT-based systems for drug delivery, protein delivery, gene therapy and cancer therapy applications. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/55836/1/3561_ftp.pdf
Cytochrome bc(1) isolated from Triton X-100-solubilized mitochondrial membranes contains up to 120 nmol of Triton X-100 bound per nanomole of the enzyme. Purified cytochrome bc(1) is fully active; however, protein-bound Triton X-100 significantly interferes with structural studies of the enzyme. Removal of Triton X-100 bound to bovine cytochrome bc(1) was accomplished by incubation with Bio-Beads SM-2 in the presence of sodium cholate. Sodium cholate is critical because it does not interfere with the adsorption of protein on the hydrophobic surface of the beads. The resulting Triton X-100-free cytochrome bc(1) retained nearly full activity, absorption spectra, subunit, and phospholipid composition.
Although detergents have been widely used in G-protein studies to increase solubility and stability of the protein, we noticed that detergents modulate the nucleotide-binding properties of G-proteins. Hence, we analysed the effects of detergents on guanine nucleotide exchange reactions of Galpha(i1). Lubrol PX, a non-ionic detergent, which has been widely used in nucleotide dissociation/binding assays, was found to accelerate both GDP dissociation and GTPgammaS binding from/to Galpha in parallel at above its critical micelle concentration (cmc). Sodium cholate, an anionic detergent, which have been used to extract G-proteins from animal tissues, decelerated and accelerated GDP dissociation below and above its cmc, respectively. Surprisingly, micellar cholate decelerated GTPgammaS binding, and the binding rate constant was decreased by three orders of magnitude in the presence of 2% cholate. These results demonstrate that the guanine nucleotide exchange reactions of Galpha(i1) are drastically modulated by detergents differently depending on the type and the state (monomeric or micellar) of the detergents and that dissociation of GDP from Galpha(i1) does not necessarily lead to immediate binding of GTP to Galpha(i1) in some cases. These effects of detergents on G-proteins must be taken into account in G-protein experiments.
We present a series of short, multidomain peptides as biocompatible solubilizing agents of single-walled carbon nanotubes (SWCNTs). These peptides are organized into an ABA block motif, where the A block is composed of charged amino acids, such as glutamic acid, and the B block is composed of alternating hydrophilic and hydrophobic residues. The hydrophobic amino acid residues interact with SWCNT sidewalls, while the hydrophilic residues interact primarily with water in an aqueous solution. When many peptides assemble along the length of the nanotube, it becomes effectively encapsulated within a peptide nanofiber. This noncovalent interaction between the peptide and the nanotube solubilizes SWCNTs while keeping the electronic structure of the nanotube intact, thereby preserving the optical and electrical properties that make SWCNTs promising for use in biological applications. To assess the toxicity of these peptide coatings, they were added to cultures of NIH 3T3 mouse fibroblasts and the effect on cell viability was measured. Toxicity was found to be far lower than for ionic surfactants typically used for SWCNT suspension and similar to Pluronics. The near-IR fluorescence intensity of SWCNTs in peptide suspensions was comparable to that in Pluronics. Five surfactants were tested for their effect on the proliferation of NIH 3T3 cells with and without SWCNTs. Although some differences were observed among surfactants, in no case did the presence of SWCNTs make a statistically significant difference. Based on their ability to solubilize SWCNTs, the fluorescence of the suspended tubes, their minimal impact on cell viability, and their potential for easy chemical modification, multidomain peptides have been found to have excellent potential as a biocompatible surfactant for suspension of SWCNTs.
Composite films of poly(lactic-co-glycolic-acid) with multi-walled carbon nanotubes (PLGA-MWCNT) having two different nanotube orientations, namely random and vertically aligned, have been fabricated and characterized. The effect of these nanostructured surfaces on platelet adhesion is evaluated. In particular, the thrombogenicity of the nanostructured composite films is compared with that of pristine graphite (a low thrombogenic material) and PLGA film, in order to determine the influence of surface chemistry and topography on platelet adhesion. The results in this study show that the PLGA-MWCNT composite with vertically aligned nanotubes exhibits very low levels of fibrinogen adsorption and platelet adhesion, which can be attributed to both chemical and topographical effects. Platelet adhesion shows a good correlation with the presence of COOH groups and appears to be sensitive to the topographic features of the composite films. The results in this study suggest that in addition to chemistry, nanotopographical surface modifications could be an effective strategy in the development of low thrombogenic and hemocompatible materials.
Multi-walled carbon nanotubes (MWNTs) have been proposed for use in many applications and concerns about their potential effect on human health have led to the interest in understanding the interactions between MWNTs and human cells. One important technique is the visualisation of the intracellular distribution of MWNTs. We exposed human macrophage cells to unpurified MWNTs and found that a decrease in cell viability was correlated with uptake of MWNTs due to mainly necrosis. Cells treated with purified MWNTs and the main contaminant Fe(2)O(3) itself yielded toxicity only from the nanotubes and not from the Fe(2)O(3). We used 3-D dark-field scanning transmission electron microscopy (DF-STEM) tomography of freeze-dried whole cells as well as confocal and scanning electron microscopy (SEM) to image the cellular uptake and distribution of unpurified MWNTs. We observed that unpurified MWNTs entered the cell both actively and passively frequently inserting through the plasma membrane into the cytoplasm and the nucleus. These suggest that MWNTs may cause incomplete phagocytosis or mechanically pierce through the plasma membrane and result in oxidative stress and cell death.
Unlabelled:
There are conflicting data concerning the safety and biocompatibility of carbon nanotubes (CNTs). In some reports CNTs have been used for gene delivery without significant toxicity, whereas in others various cytotoxic effects were observed, including induction of intracellular reactive oxygen species (ROS), DNA damage, and apoptosis. Although it is clear that CNT production methods, purity, and functionalization treatments impact on biocompatibility, most of the published reports lack detailed characterization of the CNT samples used. We investigated the effect of various physicochemical features of multiwalled carbon nanotubes (MWCNTs) on toxicity and biocompatibility with cultured human neuroblastoma cells by using MTT, WST-1, Hoechst, and oxidative stress assays. In vitro experiments confirm that after 3 days of incubation with three different types of CNTs dispersed in Pluronic F127 solution, 0.01% cell viability is not affected and apoptosis and ROS are not induced in the SH-SY5Y cells. With prolonged cultures and continued propagation in the presence of MWCNTs, the loss of cell viability was minimal for pure MWCNTs (99% purity), but cell proliferation decreased significantly for 97% purity MWCNTs and acid-treated MWCNTs (97% purity, surface oxidation 8%); no intracellular ROS were detected. When the concentration of CNTs increases, purity and surface oxidation seem to affect cell viability (ED(25) is 48, 34.4, and 18.4 mug/mL, respectively, for 99% purity MWCNTs, 97% purity MWCNTs, and acid-treated 97% purity MWCNTs. Our results indicate that concentrations of 5-10 mug/mL MWCNTs seem ideal for studies on the design and development of artificial MWCNT nanovectors for gene and drug therapy against cancer.
From the clinical editor:
With prolonged cultures, loss of cell viability was minimal for preparations with 99% purity, but significant adverse effects were detected with 97% purity and with acid-treated preparations. A concentrations of 5-10 mug/mL of MWCNTs seems ideal for gene and drug therapy against cancer.
This work investigated the biological influence of water-soluble multiwalled carbon nanotubes (wsMWCNTs) on fibroblast cell growth as a function of concentration control in an aqueous solution. The wsMWCNTs were prepared by an optimal procedure of ultrasonication/concentrated acids oxidation. The concentration of wsMWCNT in the solution was quantified by an established calibration line. A stable concentration of 0.3mg/ml was obtained in the surfactant-free water. The physicochemical properties of wsMWCNTs were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV/VIS/NIR spectroscopy, and dynamic light scattering (DLS). Cell proliferation and the cell cycle were examined by MTS assay, flow cytometry and TEM respectively. Experimental results showed that the oxidation degree was a key factor that determined the concentration and stability of wsMWCNTs in the aqueous solution. The wsMWCNTs were able to enter into the cells and mainly accumulated in the cytoplasm. The wsMWCNTs-induced variations in cell proliferation and the cell cycle were concentration dependent. Cells cultivated with wsMWCNTs of 0.3mg/ml underwent a dramatic apoptosis. The proliferation was clearly suppressed when the cells were cultivated with wsMWCNTs of 0.03 mg/ml. There were no obvious influences on cell proliferation and the cell cycle when the concentration of wsMWNTs decreased to 0.01 mg/ml.
We used conductive nanotube films as substrates with which we could systematically vary the conductance to see how this property affects neuronal growth. Here we show that nanotube substrates in a narrow range of conductivity promote the outgrowth of neurites with a decrease in the number of growth cones as well as an increase in cell body area, while at higher conductance these effects disappear.
Malondialdehyde, a product of lipid peroxidation and a by-product of thromboxane synthesis increases in human cataract. Malondialdehyde bound to soluble lens proteins over 4 h of incubation. Pre-incubation of lens proteins with aspirin offered protection against reaction with MDA. Gel chromatography was used to monitor aggregation of the modified protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the reaction with malondialdehyde led to non-disulphide covalent cross-linking of gamma-crystallin, which was decreased by incubation with aspirin. Malondialdehyde has two carbonyl groups which could react with primary amino groups, forming Schiff-base conjugates and covalently cross-link proteins. The modification and cross-linking could initiate the cataractogenic process.
Carbon nanotubes are strong, flexible, conduct electrical current, and can be functionalized with different molecules, properties that may be useful in basic and applied neuroscience research. We report the first application of carbon nanotube technology to neuroscience research. Methods were developed for growing embryonic rat-brain neurons on multiwalled carbon nanotubes. On unmodified nanotubes, neurons extend only one or two neurites, which exhibit very few branches. In contrast, neurons grown on nanotubes coated with the bioactive molecule 4-hydroxynonenal elaborate multiple neurites, which exhibit extensive branching. These findings establish the feasability of using nanotubes as substrates for nerve cell growth and as probes of neuronal function at the nanometer scale.
In the early 1990s, a chance finding in a Japanese laboratory introduced the world to carbon nanotubes. Today, interest in the tubes is still growing. Philip Ball reports on a decade of discovery.
A very general and versatile method for functionalizing different types of carbon nanotubes is described, using the 1,3-dipolar cycloaddition of azomethine ylides. Approximately one organic group per 100 carbon atoms of the nanotube is introduced, to yield remakably soluble bundles of nanotubes, as seen in transmission electron micrographs. The solubilization of the nanotubes generates a novel, interesting class of materials, which combines the properties of the nanotubes and the organic moiety, thus offering new opportunities for applications in materials science, including the preparation of nanocomposites.
Epstein-Barr virus (EBV) infects and persists for life in the majority of the human population. Persistence is achieved through a combination of strictly regulated programs of latent infection in B-cells and chronic reactivation of virus replication in lymphoid tissue and mucosal surfaces. The resulting multiple patterns of virus-host interaction have selected unique strategies of immune escape. T-cell mediated immunity plays a central role in the control of EBV latency and several immune escape mechanism that protect the virus at this stage of its life circle have been characterized in details. In contrast, the contribution of innate immunity and the immune regulation of productive infection are largely unexplored areas that may yield important clues on the establishment and maintenance of EBV persistence. This review summarizes well known and emerging mechanisms of EBV immune escape that may reveal new strategies of immunoregulation and promote new approaches to the prophylaxis and treatment of EBV associated diseases.
Nanoparticles are being developed for a host of biomedical and biotechnological applications, including drug delivery, enzyme immobilization and DNA transfection. Spherical nanoparticles are typically used for such applications, which reflects the fact that spheres are easier to make than other shapes. Micro- and nanotubes--structures that resemble tiny drinking straws--are alternatives that might offer advantages over spherical nanoparticles for some applications. This article discusses four approaches for making micro- and nanotubes, and reviews the current status of efforts to develop biomedical and biotechnological applications of these tubular structures.
Tumor necrosis factor (TNF) was first identified in 1984 as a cytokine with anti-tumor effects in vitro and in vivo. Extensive research since then has shown that there are at least 18 distinct members of the TNF super family and they exhibit 15-25% amino acid sequence homology with each other. These family members bind to distinct receptors, which are homologous in their extracellular domain. These cytokines have been implicated in a wide variety of diseases including tumorigenesis, septic shock, viral replication, bone resorption, rheumatoid arthritis, diabetes, and other inflammatory diseases. TNF blockers have been approved for human use in treating some of these conditions in the United States and other countries. Various members of the TNF super family mediate either proliferation, survival, or apoptosis of cells. Although distinct receptors, all members share a common cell signaling pathway that mediates the activation of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein kinases (e.g. c-jun N-terminal kinase). Regulation of cell growth and activation of NF-kappaB and of c-jun N-terminal kinase by the TNF super family is mediated through sequential activation/association of a set of cell signaling proteins named TNF receptor-associated factors, Fas-associated death domain and FADD-like ICE, caspases, receptor-interacting protein, NF-kappaB-inducing kinases, and IkappaBalpha kinases. Both apoptotic and antiapoptotic signals are activated simultaneously by the same cytokine in the same cell. Together these cytokines regulate cell growth/survival/apoptosis in a complex dance of changing partners and overlapping steps.
Genetic vaccination and gene therapy research could benefit from the application of carbon nanotubes. Functionalized, positively charged, water-soluble carbon nanotubes are able to penetrate into cells (see figure) and can transport plasmid DNA by formation of noncovalent DNA-nanotube complexes. Such nanotubes can be used as novel nonviral delivery systems for gene transfer.
The cytotoxic response of cells in culture is dependant on the degree of functionalization of the single-walled carbon nanotube (SWNT). After characterizing a set of water-dispersible SWNTs, we performed in vitro cytotoxicity screens on cultured human dermal fibroblasts (HDF). The SWNT samples used in this exposure include SWNT-phenyl-SO(3)H and SWNT-phenyl-SO(3)Na (six samples with carbon/-phenyl-SO(3)X ratios of 18, 41, and 80), SWNT-phenyl-(COOH)(2) (one sample with carbon/-phenyl-(COOH)(2) ratio of 23), and underivatized SWNT stabilized in 1% Pluronic F108. We have found that as the degree of sidewall functionalization increases, the SWNT sample becomes less cytotoxic. Further, sidewall functionalized SWNT samples are substantially less cytotoxic than surfactant stabilized SWNTs. Even though cell death did not exceed 50% for cells dosed with sidewall functionalized SWNTs, optical and atomic force microscopies show direct contact between cellular membranes and water-dispersible SWNTs; i.e. the SWNTs in aqueous suspension precipitate out and selectively deposit on the membrane.
Resonant Raman spectroscopy and transmission electron microscopy were used to characterize the structural changes of three single-walled carbon nanotube samples processed with purification, pelletization, and surfactant-assisted dispersion. A two-stage purification process selectively removes metallic tubes as well as small-diameter ones, enriching large-diameter semiconducting tubes. Pelletizing reduces the intertube distance but greatly increases the intensity ratio of the D band to the G band. Single-walled nanotube (SWNT) bundle size decreases during ultrasonication dispersion aided by a surfactant. SWNT bundles composed of large-diameter tubes are prone to debundling.
Macrophages play a critical role in mediating the host response to biomaterials, perhaps most notably by guiding the host inflammatory response through the release of inflammatory molecules such as the cytokine interleukin-1 (IL-1). The extent of the macrophage response following interaction with the biomaterial surface contributes greatly to device efficacy, yet the molecular mechanisms of this interaction are still unclear. The extracellular matrix (ECM) protein fibronectin (FN) is recognized by macrophages and frequently used in biomaterial modification to elicit greater cellular adhesion and tissue integration. Macrophage interaction with FN and other ECM molecules on the biomaterial surface has been shown to induce a variety of inflammatory responses, thus both FN and IL-1 can be utilized as model molecules to better understand the mechanisms of material-mediated macrophage responses. This literature review presents a comprehensive survey of past and current research on the interrelated role of IL-1, FN, and FN-derivatives in determining biomaterial-modulated macrophage function.
Carbon nanotubes hold great promise for use in biomedical fields. Among numerous potential applications, including DNA and protein sensors, bioseparators, biocatalysts, and tissue scaffolds, this article emphasizes the use of carbon-nanotube-filled polymer composites as medical devices, namely, microcatheters. The currently hot topic of the biocompatibility (e.g., toxic properties) of carbon nanotubes is discussed. In addition, critical issues that must be clarified for the full utilization of current carbon-nanotube science and technology in biomedical fields are discussed.