Novel Biodegradable Polymers as Gene Carriers

Optimization of entrapping conditions to improve the release of BMP-2 from PELA carriers by response surface methodology

A microcapsule prepared from triblock copolymer poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA, PELA) was investigated as a controlled release carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2). The rhBMP-2/PELA microspheres were prepared using the water-in-oil-in-water (W/O/W) solvent evaporation method. This work was conducted to optimize the entrapping conditions of the rhBMP-2 loaded PELA copolymer. The effects on encapsulation efficiency (EE) of different molecular weights (MW) of PEG in the copolymer, the amount of PELA, the amount of rhBMP-2, the span-20 concentration, the polyvinyl alcohol (PVA) concentration and stirring time were tested. On the basis of single-factor experiments, the optimum parameters were achieved using response surface methodology (RSM). The results showed that the highest EE of BMP-2 was achieved with a span-20 concentration of 0.5%, PEG MW 4000 Da, a stirring time of 30 min at 800 rpm min(-1), 282.3 mg of PELA, 1 μg of rhBMP-2 and PVA concentration 0.79%. Under these optimal conditions, it was predicted that the highest EE to be achieved would be 76.5%; the actual EE achieved was 75%.

Chemo-physical and biological evaluation of poly(L-lysine)-grafted chitosan copolymers used for highly efficient gene delivery

For the success of non-viral gene delivery, it is of great importance to develop gene vectors with high efficiency but low toxicity. We demonstrate that PLL-grafted chitosan copolymers combine the advantages of PLL with its good pDNA-binding ability and of chitosan with its good biocompatibility. The chemo-physical properties of the prepared Chi-g-PLL copolymers are thoroughly characterized. The in vitro transfection study shows that the copolymers have a much higher gene transfer ability than the starting materials chitosan and PLL. A positive correlation between PLL chain lengths and transfection efficiency of the copolymers is found. Our results suggest that these novel Chi-g-PLL copolymers are good candidates for gene delivery in vivo.

LbL multilayer capsules: recent progress and future outlook for their use in life sciences

In this review we provide an overview of the recent progress in designing composite polymer capsules based on the Layer-by-Layer (LbL) technology demonstrated so far in material science, focusing on their potential applications in medicine, drug delivery and catalysis. The benefits and limits of current systems are discussed and the perspectives on emerging strategies for designing novel classes of therapeutic vehicles are highlighted.

PEG-PBLG nanoparticle-mediated HSV-TK/GCV gene therapy for oral squamous cell carcinoma

AIMS

Previous studies revealed that drug-loaded poly(ethylene-glycol)-poly(gamma-benzyl-L-glutamate) (PEG-PBLG) nanoparticles exhibit favorable pharmacokinetic characteristics in the treatment of oral squamous cell carcinoma (OSCC). In this study, the characteristics and anticancer effect of herpes simplex virus thymidine kinase (HSV-TK)-loaded PEG-PBLG nanoparticles for OSCC were investigated.

MATERIALS & METHODS

HSV-TK-loaded PEG-PBLG nanoparticles were prepared and their morphology, DNA protection and gene-transfer efficiency were evaluated. Their anticancer effect in vitro and in vivo was determined.

RESULTS & DISCUSSION

HSV-TK-loaded PEG-PBLG nanoparticles have a core-shell structure and DNA protection and higher gene-transfer efficiency. PEG-PBLG nanoparticle-mediated HSV-TK/ganciclovir (GCV) had a strong anticancer effect on Tca8113 cells in vitro and buccal carcinoma induced in golden hamsters.

CONCLUSION

PEG-PBLG nanoparticles may be a superior gene carrier in future clinical applications because of their DNA protection and higher gene-transfer efficiency. The HSV-TK/GCV suicide-gene system had significant antitumor effects on OSCC.

Synthesis and characterization of cyclic acetal based degradable hydrogels

While many synthetic, hydrolytically degradable hydrogels have been developed for biomedical applications, there are only a few examples whose polymer backbone does not form acidic products upon degradation. In order to address this concern, we proposed to develop a hydrogel based on a cyclic acetal unit that produces diols and propanals upon hydrolytic degradation. In particular, we proposed the fabrication of hydrogels formed by the free radical polymerization of two diacrylate monomers, 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD), a cyclic acetal having two acryl groups, and poly(ethylene glycol)diacrylate (PEGDA). However, the hydrophobicity of the EHD monomer inhibits hydrogel fabrication. Therefore this work develops a strategy to form hydrogels with a co-monomer system, one of which is hydrophobic, and subsequently describes the properties of the resulting hydrogel. Using benzoyl peroxide as an initiator and N,N-dimethyl-p-toluidine as an accelerator, the EHD and PEGDA monomers were reacted in an acetone/water co-solvent system. The chemical structure of the resulting EH-PEG [5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol-co-PEG] hydrogel was then characterized by FT-IR. Physicochemical properties of the EH-PEG hydrogel, including swelling degree, sol fraction, and contact angle, were determined so as to characterize the properties of these materials and ultimately investigate their use in drug delivery and tissue engineering applications. Results showed that EH-PEG hydrogel may be formed using the co-solvent system. Further results indicated that swelling degree is dependent upon initiator concentration, monomer concentration, and molar ratios of monomers, while sol fraction significantly depended on initiator concentration and monomer concentration, only. These results demonstrate the ability to fabricate hydrogels using EHD and PEGDA system as well as to control the properties of the resulting hydrophilic networks.

Synthesis and characterization of biocompatible Fe3O4 nanoparticles

In this study, magnetite (Fe3O4) nanoparticles with a size range of 8-20 nm were prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. In the process, two kinds of surfactant (sodium oleate and polyethylene glycol) were studied; then, sodium oleate was chosen as the apt surfactant to attain ultrafine, nearly spherical and well-dispersed (water-base) Fe3O4 nanoparticles, which had well magnetic properties. The size and size distribution of nanoparticles were determined by particle size analyzer. And the magnetite nanoparticles was characterized by X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), electron diffraction (ED) photography, Fourier transform infrared spectrometer (FT-IR), and vibrating-sample magnetometer (VSM). Also the effect of many parameters on the Fe3O4 nanoparticles was studied, such as reaction temperature, pH of the solution, stirring rate and concentration of sodium oleate. And the 5-dimethylthiazol-2-yl-2,5- diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of magnetite nanoparticles. The results showed that the Fe3O4 nanoparticles coated by sodium oleate had a better biocompatibility, better magnetic properties, easier washing, lower cost, and better dispersion than the magnetite nanoparticles coated by PEG.

Microparticles for oral delivery of vaccines

Nonreplicating antigens are poorly immunogenic when given orally, either due to their degradation in the gastrointestinal tract or because they are not efficiently taken up in the gut. Studies in laboratory animals have clearly demonstrated that microparticles can significantly improve the immunogenicity of orally administered antigens. However, the oral delivery of vaccines using microparticles has not been explored extensively in humans and large animals. In this article the progress in oral microparticle antigen delivery will be reviewed and, where possible, studies in humans and large animals will be highlighted. In addition, possible approaches that have the potential to significantly improve microparticle delivery of oral vaccines will be suggested.