Surface modification of biodegradable electrospun nanofiber scaffolds and their interaction with fibroblasts.

Biodegradable polymers, such as poly(glycolic acid) (PGA), poly(L-lactic acid) (PLLA) and poly(lactic-co-glycolic acid) (PLGA), were dissolved individually in the proper solvents and then subjected to electrospinning process to make nanofibrous scaffolds. Their surfaces were then chemically modified using oxygen plasma treatment and in situ grafting of hydrophilic acrylic acid (AA). The fiber thickness, pore size and porosity were estimated to 200-800 nm, 2-30 microm and 94-96%, respectively, and these properties were insignificant in the PGA, PLLA and PLGA nanofibrous scaffolds. The ultimate tensile strength of PGA was about 2.5 MPa on average and that of PLGA and PLLA was less than 2 MPa. The elongation-at-break was 100-130% for the three nanofibrous scaffolds. When the surface properties of AA-grafted scaffolds were examined, higher ratios of oxygen to carbon, lower contact angles and the presence of carboxylic (-COOH) groups were identified. The properties were significantly different from those of the unmodified nanofibrous scaffolds. Fibroblasts once seeded on the scaffolds were spreading over large surface area on the AA-grafted surface as compared to the unmodified PGA, PLLA and PLGA nanofibrous scaffolds. Cultured for up to 6 days, the fibroblast proliferation was found to be much better on the surface-modified nanofibrous scaffolds. The present study showed that, with the use of plasma treatment and AA grafting, the hydrophilic functional groups could be successfully adapted on the surface of electrospun nanofibrous scaffolds. Those surface-modified scaffolds made significant improvement on cell attachment and proliferation in vitro.

In vivo biocompatibility of sulfonated PEO-grafted polyurethanes for polymer heart valve and vascular graft.

Sulfonated poly(ethylene oxide) (PEO)-grafted polyurethane (PU) (PU-PEO-SO(3)) prepared by bulk modification was used to coat both PU heart valves and vascular grafts, and their in vivo biocompatibility was evaluated using a canine shunt method. The two devices were implanted for up to 39 days and retrieved at specific time points for the analysis of blood compatibility, biostability, and calcium deposition. When the surface of the retrieved specimens was examined using scanning electron microscopy, platelet adhesion and thrombus formation appeared to be significantly lesser formed on the PU-PEO-SO(3)-coated implants, compared with the untreated PUs. While molecular weights of untreated PUs were found by gel permeation chromatography to be decreased after 39 days from implantation, the same remained barely changed with the PU-PEO-SO(3)-coated ones. The inductively coupled plasma study indicated that the amount of deposited calcium was significantly reduced in the surface-modified PU implants. The efficacy of PU-PEO-SO(3)-coated implants in terms of blood compatibility, biostability, and calcification resistance may render them as a promising biomedical material in the application for blood/tissue-contacting tissues and organs.

Poly (4-vinylimidazole) as nonviral gene carrier: in vitro and in vivo transfection.

We explored poly(4-vinylimidazole) (P4V) as a nonviral gene carrier. We show that P4V can form DNA condensates of small size (<110 nm) using a dye-exclusion assay with ethidium bromide and dynamic light scattering, and that the complexes form in a pH-sensitive manner, due to the amphotericity of the polymer. P4V was demonstrated to lead to transfection in vitro as effectively as polyethyleneimine (PEI), but at lower cytotoxicity, under conditions where higher amounts of either polymer are required, using luciferase and green fluorescent protein as examples. Transfection in vivo was also explored, using a gene encoding yellow fluorescent protein and human osteoprotegerin injected in the tail vein of the rat. Transfection was observed, both at the gene and protein levels in lung and spleen tissue. Transfection in vivo appeared to be at least as effective using P4V as with PEI. Based upon this good transfection and low cytotoxicity, P4V seems to show promise as a nonviral gene transfer vector.

High transfection efficiency of poly(4-vinylimidazole) as a new gene carrier.

Poly(4-vinylimidazole) (P4V) was obtained by free radical polymerization of 4-vinylimidazole (4V) prepared by decarboxylation of urocanic acid. P4V formed a complex with DNA that exhibited higher transfection effiency on Hela cells than polyethylenimine (PEI), through the proton sponge mechanism of the imidazole groups in the side chain of the P4V, and low cell toxicity.

Colorimetric reversibility of polydiacetylene supramolecules having enhanced hydrogen-bonding under thermal and pH stimuli.

To investigate the role of hydrogen-bonding on colorimetric transition of polydiacetylene supramolecules, novel diacetylene derivatives allowing various hydrogen-bonding states were synthesized by coupling carboxy-substituted (ortho-, meta-, and para-) anilide groups with a typical single-chain diacetylene lipid. One with a terminal carboxyl group at the meta position provided the resulting supramolecular Langmuir-Schaefer films with enhanced hydrogen-bonding, and hence resulted in unprecedented colorimetric reversibility under both thermal and pH stimuli.