[Show abstract][Hide abstract] ABSTRACT: We have developed a theranostic nanoparticle, ie, cet-PEG-dexSPIONs, by conjugation of the anti-epidermal growth factor receptor (EGFR) monoclonal antibody, cetuximab, to dextran-coated superparamagnetic iron oxide nanoparticles (SPIONs) via periodate oxidation. Approximately 31 antibody molecules were conjugated to each nanoparticle. Cet-PEG-dexSPIONs specifically bind to EGFR-expressing tumor cells and enhance image contrast on magnetic resonance imaging. Cet-PEG-dexSPION-treated A431 cells showed significant inhibition of epidermal growth factor-induced EGFR phosphorylation and enhancement of EGFR internalization and degradation. In addition, a significant increase in apoptosis was detected in EGFR-overexpressing cell lines, A431 and 32D/EGFR, after 24 hours of incubation at 37°C with cet-PEG-dexSPIONs compared with cetuximab alone. The antibody-dependent cell-mediated cytotoxicity of cetuximab was observed in cet-PEG-dexSPIONs. The results demonstrated that cet-PEG-dexSPIONs retained the therapeutic effect of cetuximab in addition to having the ability to target and image EGFR-expressing tumors. Cet-PEG-dexSPIONs represent a promising targeted magnetic probe for early detection and treatment of EGFR-expressing tumor cells.
Full-text · Article · May 2015 · International Journal of Nanomedicine
[Show abstract][Hide abstract] ABSTRACT: For this study, we cultured chondrocyte pellets in Dulbecco's modified Eagle's medium plus a 2 % fetal bovine serum medium, and treated them with 2- to 8-mer oligosaccharides of chondroitin sulfate A to examine the effects of these oligosaccharides on the differentiation and protection of chondrocytes. We found low-molecular-weight CSAs to increase the ratio of the gene expression levels of collagen II/collagen I of chondrocytes from the first day up to 14 days after culture compared with those under a CSA-free medium. Moreover, low-molecular-weight CSAs inhibited the expression of matrix metalloproteinases and peptidases, and stimulated an endogenous tissue inhibitor of metalloproteinases. The dp-8 (8-mer) CSA yielded the most effective response among promoting collagen type II protein secretions compared with other groups.
[Show abstract][Hide abstract] ABSTRACT: Parkinson's disease is known to result from the loss of dopaminergic neurons. Direct intracerebral injections of high doses of recombinant glial cell line-derived neurotrophic factor (GDNF) have been shown to protect adult nigral dopaminergic neurons. Because GDNF does not cross the blood-brain barrier, intracerebral gene transfer is an ideal option. Chitosan (CHI) is a naturally derived material that has been used for gene transfer. However, the low water solubility often leads to decreased transfection efficiency. Grafting of highly water-soluble polyethylene imines (PEI) and polyethylene glycol onto polymers can increase their solubility. The purpose of this study was to design a non-viral gene carrier with improved water solubility as well as enhanced transfection efficiency for treating Parkinsonism. Two molecular weights (Mw =600 and 1,800 g/mol) of PEI were grafted onto CHI (PEI600-g-CHI and PEI1800-g-CHI, respectively) by opening the epoxide ring of ethylene glycol diglycidyl ether (EX-810). This modification resulted in a non-viral gene carrier with less cytotoxicity. The transfection efficiency of PEI600-g-CHI/deoxyribonucleic acid (DNA) polyplexes was significantly higher than either PEI1800-g-CHI/DNA or CHI/DNA polyplexes. The maximal GDNF expression of PEI600-g-CHI/DNA was at the polymer:DNA weight ratio of 10:1, which was 1.7-fold higher than the maximal GDNF expression of PEI1800-g-CHI/DNA. The low toxicity and high transfection efficiency of PEI600-g-CHI make it ideal for application to GDNF gene therapy, which has potential for the treatment of Parkinson's disease.
Full-text · Article · Jun 2014 · International Journal of Nanomedicine
[Show abstract][Hide abstract] ABSTRACT: Curcumin is a naturally occurring compound that has been shown to have anti-oxidant, anti-inflammatory, and anti-carcinogenic activities. However, its pharmaceutical potential has been limited due to its low solubility in water. The use of amphiphilic nanocarriers is an attractive and simple method to solubilize curcumin. In this study, we modified Pluronic F-127 [poly(ethylene glycol)100-block-poly(propylene glycol)65-block-poly(ethylene glycol)100] (PF-127) with oligomers of alanine, an amino acid, to increase the drug entrapment efficiency of curcumin through core stabilization. Alanine-modified PF-127 exhibited lower critical micelle concentration and decreased molecular motion in both the hydrophilic and hydrophobic segments ((1)H NMR). Nanocarriers in the size range of 54.2-68.4 nm were observed. Entrapment efficiency of curcumin increased by at most 66% (from 25.3 to 91.3%) and the difference in solubility was clearly visualized by increased transparency of the nanocarrier solutions. Curcumin was released continuously up to 120 h from modified carriers, while drug release from unmodified carriers plateaued within 24 h. These modified nanocarriers exhibited no cytotoxicity and more efficiently delivered drugs to HeLa cells as confirmed by fluorescent microscopy. This study demonstrated that alanine modification of FDA-approved PF-127 affects copolymer nanoassembly and has a profound impact on curcumin loading and possibly on other hydrophobic drugs as well.
No preview · Article · Jun 2014 · Journal of Biomaterials Science Polymer Edition
[Show abstract][Hide abstract] ABSTRACT: Hydrogels are of interest as scaffolds for cartilaginous tissue engineering due to their biocompatibility, swelling ratio, mechanical strength, and degradative behavior. This study was conducted to establish the most suitable poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL) triblock copolymer hydrogel for the optimal proliferation and differentiation of encapsulated chondrocytes for cartilage regeneration. PEG was copolymerized with PCL and then acrylated to confer photocrosslinking capacity. Chondrocytes were encapsulated within photocrosslinked triblock PEG-co-PCL hydrogels prepared with varying compositions. The effects of composition on the hydrogel properties and behavior of embedded cells were studied by varying the molecular weights, and thus the segment length, of the PEG and PCL blocks. Hydrogels with high-molecular-weight (10 000 Da) PEG were associated with higher swelling ratios (9.6 +/- 0.2) and a reduced elastic modulus (0.223 +/- 0.007 N mm(-2)). Biochemical analysis indicated a positive correlation between the swelling ratio and expression levels of glycosaminoglycans and total collagen. There was a 1.8-fold increase in glycosaminoglycan and 2.4-fold increase in total collagen content in hydrogels with the highest-molecular-weight (10 000 Da) PEG when compared to hydrogels with the low-molecular-weight (2000 Da) PEG after four weeks of culture. Histological examinations revealed more extensive collagen type II secretion and accumulation around chondrocytes when the molecular weight of the hydrophobic PCL segment increased. The lengths of the hydrophobic (PCL) and hydrophilic (PEG) segments resulted in changes in the properties of hydrogels that improved cellular proliferation and the production and distribution of extracellular matrix for cartilage regeneration.
[Show abstract][Hide abstract] ABSTRACT: We reveal that a slight change in the functional group of the oligopeptide block incorporated into the poloxamer led to drastically different hierarchical assembly behavior and rheological properties in aqueous media. An oligo(l-Ala-co-l-Phe-co-β-benzyl l-Asp)-poloxamer-oligo(β-benzyl-l-Asp-co-l-Phe-co-l-Ala) block copolymer (OAF-(OAsp(Bzyl))-PLX-(OAsp(Bzyl))-OAF, denoted as polymer 1), which possessed benzyl group on the aspartate moiety of the peptide block, was synthesized through ring-opening polymerization. The benzyl group on aspartate was then converted to carboxylic acid to yield oligo(l-Ala-co-l-Phe-co-l-Asp)-poloxamer-oligo(l-Asp-co-l-Phe-co-l-Ala) (OAF-(OAsp)-PLX-(OAsp)-OAF, denoted as polymer 2). Characterization of the peptide secondary structure in aqueous media by circular dichroism revealed that the oligopeptide block in polymer 1 exhibited mainly an α-helix conformation, whereas that in polymer 2 adopted predominantly a β-sheet conformation at room temperature. The segmental dynamics of the PEG in polymer 1 remained essentially unperturbed upon heating from 10 to 50 °C; by contrast, the PEG segmental motion in polymer 2 became more constrained above ca. 35 °C, indicating an obvious change in the chemical environment of the block chains. Meanwhile, the storage modulus of the polymer 2 solution underwent an abrupt increase across this temperature, and the solution turned into a gel. Wet-cell TEM observation revealed that polymer 1 self-organized to form microgel particles of several hundred nanometers in size. The microgel particle was retained as the characteristic morphological entity such that the PEG chains did not experience a significant change of their chemical environment upon heating. The hydrogel formed by polymer 2 was found to contain networks of nanofibrils, suggesting that the hydrogen bonding between the carboxylic acid groups led to an extensive stacking of the β sheets along the fibril axis at elevated temperature. The in vitro cytotoxicity of the polymer 2 aqueous solution was found to be low in human retinal pigment epithelial cells. The low cytotoxicity coupled with the sol-gel transition makes the corresponding hydrogel a good candidate for biomedical applications.
[Show abstract][Hide abstract] ABSTRACT: Tissue engineering can provide alternatives to current methods for tracheal reconstruction. Here we describe an approach for ectopic engineering of vascularized trachea based on the implantation of co-cultured scaffolds surrounded by a muscle flap. Poly(L-lactic-co-glycolic acid) (PLGA) or poly(ε-caprolactone) (PCL) scaffolds were seeded with chondrocytes, bone marrow stem cells and co-cultured both cells respectively (8 groups), wrapped in a pedicled muscle flap, placed as an ectopic culture on the abdominal wall of rabbits (n = 24), and harvested after two and four weeks. Analysis of the biochemical and mechanical properties demonstrated that the PCL scaffold with co-culture cells seeding displayed the optimal chondrogenesis with adequate rigidity to maintain the cylindrical shape and luminal patency. Histological analysis confirmed that cartilage formed in the co-culture groups contained a more homogeneous and higher extracellular matrix content. The luminal surfaces appeared to support adequate epithelialization due to the formation of vascularized capsular tissue. A prefabricated neo-trachea was transferred to the defect as a tracheal replacement and yielded satisfactory results. These encouraging results indicate that our co-culture approach may enable the development of a clinically applicable neo-trachea.
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
Thermosensitive micelles composed of a copolymer of methoxy polyethylene glycol (mPEG), polylactic acid (PLA), and 1,6-bis (p-carboxyphenoxy) hexane (CPH), namely methoxy polyethylene glycol-co-polylactic acid-co-aromatic anhydride (mPEG-PLCPHA), were fabricated for application as a promising hydrophilic drug carrier. The copolymer can self-assemble into micelles in PBS by hydrophobic interaction. The diameters of these micelles increased as the environmental temperature increased. An increase in viscosity with sol-to-gel transition occurred as temperature increased from room temperature to body temperature. During the in vitro degradation process, hydrogels demonstrated a more stable degradation rate. Both in vitro and in vivo cytotoxicity results showed that the materials had excellent biocompatibility due to less acidic products formation. In vitro cefazolin release profiles showed a stable release for 30 days. The hydrogel encapsulated cefazolin exhibited a good antibacterial effect. Based on these results, mPEG-PLCPHA can serve as an injectable depot gel for drug delivery.
From the clinical editor:
In this study, thermosensitive hydrogel encapsulated cefazolin was found to exhibit good antibacterial effects with sustained levels for up to 30 days, enabling the development of an injectable depot gel for long-term drug delivery.
No preview · Article · Oct 2013 · Nanomedicine: nanotechnology, biology, and medicine
[Show abstract][Hide abstract] ABSTRACT: Human embryonic stem cells (hESCs), due to their self-renewal capacity and pluripotency, have become a potential source of transplantable β-cells for the treatment of diabetes. However, it is imperative that the derived cells fulfill the criteria for clinical treatment. In this study, we replaced common Matrigel with a synthetic peptide-acrylate surface (Synthemax) to expand undifferentiated hESCs and direct their differentiation in a defined and serum-free medium. We confirmed that the cells still expressed pluripotent markers, had the ability to differentiate into three germ layers, and maintained a normal karyotype after 10 passages of subculture. Next, we reported an efficient protocol for deriving nearly 86% definitive endoderm cells from hESCs under serum-free conditions. Moreover, we were able to obtain insulin-producing cells within 21 days following a simple three-step protocol. The results of immunocytochemical and quantitative gene expression analysis showed that the efficiency of induction was not significantly different between the Synthemax surface and the Matrigel-coated surface. Thus, we provided a totally defined condition from hESC culture to insulin-producing cell differentiation, and the derived cells could be a therapeutic resource for diabetic patients in the future.
No preview · Article · Oct 2013 · Stem cells and development
[Show abstract][Hide abstract] ABSTRACT: Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA) polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.
[Show abstract][Hide abstract] ABSTRACT: The long term in vivo biocompatibility is an essential feature for the design and development of sustained drug release carriers. In the recent intraocular drug delivery studies, hydrogels were suggested as sustained release carriers. The biocompatibility test for these hydrogels, however, was commonly performed only through in vitro cell culture examination, which is insufficient before the clinical applications. We compared three thermosensitive hydrogels that have been suggested as the carriers for drugs by their gel-solution phase-change properties. A new block terpolymer (PEOz-PCL-PEOz, ECE) and two commercial products (Matrigel® and Pluronic F127) were studied. The results demonstrated that the ocular media remained translucent for ECE and Pluronic F127 in the first 2 weeks, but cataract formation for Matrigel occurred in 2 weeks and for Pluronic F127 in 1 month, while turbid media was observed for both Matrigel and Pluronic F127 in 2 months. The electrophysiology examinations showed significant neuroretinal toxicity of Matrigel and Pluronic F127 but good biocompatibility of ECE. The neuroretinal toxicity of Matrigel and Pluronic F127 and superior biocompatibility of ECE hydrogel suggests ECE as more appropriate biomaterial for use in research and potentially in intraocular application.
[Show abstract][Hide abstract] ABSTRACT: Bioceramic or inorganic nanoparticles made of SiO2, TiO2, SrO, and hydroxyapatite (HAP) have been reported to improve cell adhesion onto polymers. However, direct mixing of these nanoparticles with polymers often leads to their aggregation within the polymer matrix and subsequent deterioration of the material’s mechanical strength. A novel method for modifying the surfaces of the nanoparticles by grafting ε-caprolactone using a ring-opening condensation reaction was developed to improve the interconnection of the nanoparticles within the polymer matrix. The mechanical studies showed that adding grafted nanoparticles into the polycaprolactone (PCL) matrix improved the initial mechanical strength. MTT assay and a live/dead stain showed higher cell viability in the tablets with grafted SiO2, TiO2, and HAP nanoparticles, except the SrO-containing tablets. The cell adhesion and alkaline phosphatase activity assay confirmed that the composite tablets with PCL-grafted HAP nanoparticles had better osteoconductivity. HE stains showed that composite tablets with PCL-grafted SiO2, TiO2, and HAP nanoparticles produce less immune response than the pure PCL. We thus conclude that a PCL matrix incorporating PCL-grafted HAP nanoparticles has enhanced mechanical strength, improved osteoconductivity, and a slower degradation rate than pure nanoparticles.
Full-text · Article · Jun 2013 · Composites Science and Technology
[Show abstract][Hide abstract] ABSTRACT: The acinus-mimicking microfluidic chip, which simulates the in vivo condition of the liver, was developed and reported in this paper. The gradient microenvironment of the liver acinus is replicated within this proposed microfluidic chip. The advantage of this acinus-mimicking chip is capable of adjusting the concentration gradient in a relatively short period of time at around 10 s. At the same instance the non-linear concentration gradient can be presented in the various zones within this microfluidic chip. The other advantage of this proposed design is in the convenience of allowing the direct injection of the cells into the chip. The environment within the chip is multi-welled and gel-free with high cell density. The multi-row pillar microstructure located at the entrance of the top and bottom flow channels is designed to be able to balance the pressure of the perfusion medium. Through this mechanism the shear stress experienced by the cultured cells can be minimized to reduce the potential damage flow from the perfusion process. ((3))The fluorescence staining and the observations of the cell morphology verify the life and death of the cells. The shear stress experienced by the cells in the various zones within the chip can be effectively mapped. The serum glutamic oxaloacetic transaminase (SGOT) collected from the supernatants was used to determine the effects of the degassing process and the shear stress of the medium flow on the cultured cells.
No preview · Article · Apr 2013 · Biomedical Microdevices
[Show abstract][Hide abstract] ABSTRACT: Human embryonic stem cells (hESCs), due to their self-renewal capacity and pluripotency, are an important source of cells for regenerative medicine. The immediate obstacles that need to be addressed are the poor cell survival rate of hESCs and their cell quality after cryopreservation. In this study, we used the Cell Alive System (CAS) which combines a programmed freezer with an oscillating magnetic field to reduce cryo-injury during the freezing process. The hESC clumps suspended in freezing medium were divided into three groups: (i) cells frozen by a conventional freezing container, Mr. Frosty and kept in a -80°C freezer (MF); (ii) cells frozen to -32°C by CAS, and then transferred to a -80°C freezer (CAS); (iii) cells frozen to -32°C by CAS, and then transferred to a pre-cooled Mr. Frosty and kept in a -80°C freezer (CAS-MF) for overnight. All cryovials were placed in liquid nitrogen for one week, and hESCs were then thawed and cultured on feeder for 7 days. The results of alkaline phosphatase (AP) staining showed that the attachment efficiency of the cells cryopreserved by CAS and CAS-MF was significantly higher (29.0% and 44.0%) than in the MF method (7.0%). Furthermore, we confirmed the cells cryopreserved using CAS-MF could be subcultured while expressing pluripotent markers, differentiate into three germ layers, and maintain a normal karyotype. These results demonstrate that the use of CAS-MF offers an efficient method of hESC banking.
[Show abstract][Hide abstract] ABSTRACT: Background/Purpose
Durable mechanical strength and biocompatibility are the two major requirements for osteogenic scaffolds. Polyanhydrides are a class of biodegradable polymers characterized by anhydride bonds that connect repeating units of the polymer backbone chain. Hydroxyapatite (HAP) is the main component of human bone and is a good osteoinductive factor that promotes bone mineralization. This work validates the combination of polyanhydrides and HAP for biomedical application.
Polyanhydride copolymers were fabricated from sebacic acid (SA) and 1,6-bis(p-carboxyphenoxy)hexane (CPH). HAP was surface-modified by polycaprolactone (PCL), and testing tablets were made using different ratios of copolymers and surface-grafted HAP (g-HAP). Degradation tests were performed to evaluate mechanical strength, pH, and weight loss. Biocompatibility was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and live/dead stain test. Cell affinity was measured using scanning electronic microscopy (SEM).
The favorable surface erosion property of polyanhydrides prevented marked changes in the mechanical properties over time. In addition, the degradation byproducts of the copolymer did not cause a serious decline in pH and were less harmful to the cells. g-HAP increased cell affinity for the polymer surface.
The research team synthesized polyanhydride/g-HAP composites with high mechanical strength, slow degradation, and excellent biocompatibility. The result showed that a CPH/SA ratio of 7:3 in combination with 10 wt% g-HAP was optimal as bone substitute.
Full-text · Article · Feb 2013 · Formosan Journal of Musculoskeletal Disorders
[Show abstract][Hide abstract] ABSTRACT: This paper reports a gel-free multi-well microfluidic chip for cell cultures. Polydimethylsiloxane (PDMS) material was used because of its hydrophobic and gas-permeable features. Surface tension and fluidic channel resistance simplified the procedure of cell injection into the system. The shear stress and the mass-transfer perfusion medium reached a balance through the multi-row square-pillar microstructure and the driven pressure. The cell seeding was completed in 10-mm scaled culture wells in less than 6 s using the microstructure composed of PDMS. The adjustable initial cell density and length of the culture area facilitate its use in desired biological experiments. To verify whether the operation caused cell damage or not, the biological index of supernatants with glutamic oxaloacetic transaminase (GOT) and blood urea nitrogen (BUN) were monitored for 4 days. The 1–4-mm-long multi-rows square-pillar microstructure can sustain HA22T cells for 5 days and still maintain cell viability for up to 90% of seeded cells.
No preview · Article · Feb 2013 · Sensors and Actuators B Chemical
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to design a thermosensitive composite gel to be used as a bone graft substitute. This gel can provide a more suitable microenvironment by using the amphiphilic triblock copolymer (mPEG550PLGA1405) consisting of methoxy poly(ethylene glycol) (mPEG), poly(lactic-co-glycolic acid) (PLGA). An aqueous dispersion of mPEG550PLGA1405 mixed with different ratios of HAP/β-TCP (composite gel) underwent a sol–gel–sol transition as the temperature was increased from 4 to 70 °C. The particle size and critical micellization concentration (CMC) were increased by adding ceramics. During the in vitro degradation process, composite gels demonstrated a slight decrease in pH value, a slower degradation rate, less toxicity, and a higher cell survival rate. The biocompatibility of the composite gels was validated by hemolysis test. In vivo animal studies demonstrated both radiographic and gross bone union when the ratio of HAP/β-TCP was 7:3. Based on the results, we have developed novel thermosensitive composite gels as bone substitutes.
No preview · Article · Feb 2013 · Chemical Engineering Science