Key Engineering Materials Vols. 288-289

Abstract: A variety of attempts have been made to improve small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts through cellular and tissue engineering. Some of these techniques have made their way into clinical trials. Coating of endothelial cells via surface modifications has increased graft patency in some hands but lack of firm adhesion of the seeded cells on the graft surface can lead to graft failures. We increased cell-graft and graft-tissue interactions by inducing smooth muscle cell growth into the pores of the graft wall through chemical modification of superficial surfaces, including those of the transmural pores. In contrast to non-modified surfaces seeded cells adhered on and proliferated into the modified pores and internodal surfaces. Cellular growth into these critical pores spaces seemed to arise from surface modification including defluorination and oxygenation incorporation leading to changes in chemical composition, surface tension, cell-surface interaction and modified surface fibril aggregation.

Abstract: This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postoperative tissue adhesion. For this, we synthesized poly(L-lactic acid)-PEG diblock copolymers and used them to prepare ibuprofen-loaded films as tissue adhesion barrier films. We also prepared lower critical solution temperature (LCST)-controllable Pluronic F127/F68 mixtures including mildly crosslinked alginate and ibuprofen as tissue adhesion barrier gels. The prepared films and gels with/without ibuprofen were evaluated by the observations of peritoneal tissue adhesion via animal study using a rat model.

Abstract: A kind of medical collagen was prepared by hydrogel formation method. Chemical and physical properties were investigated by FTIR, amino acid analysis, SDS-PAGE, carbohydrate content analysis, heavy metal content analysis. Degradation experiments in vivo and subsequent histological investigations were carried out to evaluate the biological performance. The results suggested that the collagen achieved is promising in tissue engineering scaffold materials for a long-term (more than 12 weeks) implantation application.

Abstract: The poly (L-lactic acid) (PLLA) porous scaffolds were prepared by porogen leaching combined freeze drying with the porogen particulates of ice in this paper. The ice particulates are made of distilled water sprayed into liquid nitrogen through a nozzle under a certain pressure. The pore morphology, porosity and residual porogen of the scaffolds was studied. There is no residual porogen when the ice particulate is used and the leaching mechanism of porogen is discussed. The scaffolds are composed of macro and micro pores and with a porosity of 80-90%. The macro pores are formed by ice particulate and the micro pores by thermal induced phase separation of solvent. The pore size can be changed easily by altering the size of ice particulate. The MTT assay was used to estimate cellular activity by L-929 cells culture in vitro. The results demonstrate that the scaffolds have no cytotoxicity. It could confidently be stated that the combined process seems to be a promising technique for the fabrication of porous polymer scaffold.

Abstract: This study describes an investigation of collagen sponge mechanically reinforced through the incorporation of poly(glycolic acid)(PGA) fiber. A collagen solution with PGA fiber homogeneously dispersed was freeze-dried, followed by dehydrothermal cross-linking to obtain collagen sponges incorporating PGA fiber. A collagen sponge without PGA fiber was prepared similarly by using the collagen solution. By scanning electron observation, the collagen sponges exhibited isotropic and interconnected pore structures with an average pore size of 180 µm, irrespective of PGA fiber incorporation. As expected, PGA fiber incorporation enabled the collagen sponge to significantly enhance the compression strength. In vitro cell culture studies revealed that the number of L929 fibroblasts initially attached was significantly greater for the collagen sponge incorporating PGA fiber than for the collagen sponge. In vitro cell proliferation studies revealed that the proliferation of cell was higher for the collagen sponge incorporating PGA fiber, by day 21, than the collagen sponge without PGA fiber. It is possible that shrinkage suppression results in the superior cell attachment and proliferation of sponge incorporating PGA fiber. After subcutaneous implantation into the backs of mice, the residual volume of collagen sponge incorporating PGA fiber was significantly large compared with that of collagen sponge. We concluded that the incorporation of PGA fiber is a simple way to reinforce collagen sponge without impairing the biocompatibility.

Abstract: Phenylalanine linked to cellulose beads was designed as an adsorbent in whole blood hemoperfusion for the therapy of rheumatoid arthritis. In whole blood perfusion tests, the adsorbent adsorbed rheumatoid factors directly from whole blood. In vitro test showed that the adsorbent had good biocompability properties. No acute systemic toxicity and dermal irritancy with extremely low skin sensitizing activity were observed. In vivo animal test with satisfactory results was perfumed with rabbits. Experimental results show that the adsorbent holds promise as a highly effective and safe hemoadsorbent in clinical therapy for rheumatoid arthritis patients by hemoperfusion.

Abstract: Polyacrylamide (PAM) was usually atoxic, stable. Its hydrogel (PAMG) has been used in plastic and aesthetic surgery more than 10 years in P.R.China, Ukraine and Russia. But there were some complications with PAMG injected in patients. Considering the complicacy in vivo, it was necessary to study the PAMG’s stability. In this paper, H2O2 was added in PAMG in vitro and acrylamide (AM) content after oxidating was determined using HPLC method. Detection limit for AM can be achieved in the parts-per-billion rang. The AM content in supernatant at 0.5, 1,2 and 3 hr after oxidating of PAMG was 1.27e-8g/ml, 1.35e-8g/ml, 1.03e-7g/ml and 2.74e-7g/ml, respectively. The AM content in supernatant of PAMG was 7.70e-9g/ml. These results indicated that PAMG can be degraded to AM by hydroxyl radical. Under the same condition, the AM content was stable. So, AM can exist for a while when it was produce by degrading of PAMG. That can increase the toxicity of PAMG.

Abstract: Chitin/Chitosan membrane has been used as wound dressing materials to facilitate clinical wound healing for many years. However, there are fewer articles studying the cell-biomaterial interaction in vitro or in vivo. In this study, the biological characteristics of human keratinocytes cultured on chitosan membrane that was mixed with gelatin in different ratio were investigated in vitro. Chitosan-gelatin membrane (CGM) in different ratio were prepared with N, N-(3 dimethylaminopropyl)-N'-ethyl carbodiimide (EDC). CGMs were divided into four groups: pure chitosan membrane, 7:3 (chitosan: gelatin), 5:5 and 3:7 groups. Human keratinocytes were isolated from foreskin by Dispase/Trypsin-EDTA digestion. Keratinocytes of passage3 were then seeded on the surface of CGM. Cloning forming efficiency (CFE) and migration distance of cultured keratinocytes on CGM were measured. The CFE of keratinocytes cultured on the surface of pure chitosan membrane was 9.8±2.08%; cultured on 7:3 CGM was 14.33±1.53%, 5:5 CGM was 19.17±1.26%, 3:7 CGM was 18.33±2.08%. The migration distance of cultured keratinocytes on pure chitosan membrane was 61.47±2.70µm, 7:3 CGM was 66.22±9.39µm, 5:5 CGM was 120.31±15.82µm, 3:7 CGM was 225.38±10.48µm. This sutdy demonstrated that increasing contents of gelatin in CGM could promote keratinocyte proliferation and migration. The results also suggested the membrane prepared from chitosan and gelatin can be utilized as a good keratinocyte delivery system.

Abstract: The polyacrylamide hydrogel (PAMG) has been used in cosmetology in China, Ukraine and Russia since 1990s. Because the monomer acrylamide(AM) used to produce PAMG has been implicated as a potential mutagen and reproductive toxicant[1,2], it is important to accurately determine the amount of residual AM monomer in the PAMG. In this study, a quick, practical and simple method to determine AM is presented with respect to the hydrogel. AM is analysed quantitatively by ODS-3 column with ultraviolet (UV) absorbance detector. AM is separated from interferential component with an aqueous solution of 0.9%NaCl (NS) adjusted at pH~3.7 using hydrochloric acid and then detected at a UV wavelength of 210 nm. The results show that ODS-3 is effective approach for quantifying AM concentrations in PAMG. This method has a lower detection limit of 0.003µg/ml and a linear response range of 0.003 and 0.9 µg/ml (depending on the range required for analysis). Precision studies give coefficients of variation of <3.2%(n=5) for 0.003µg/ml. The recoveries for this method are greater than 90%. When AM content in PAMG is lower than the detection limit of this method, SPE (solid phase extraction) could be used to concentrate AM. In the case, C18 cartridge is used. And the recoveries are about 70% for SPE when AM concentration is lower than ppb.