Papers by Author: Ting Fei Xi

Abstract: Nano-bacterial cellulose (nBC), secreted by Acetobacter xylinum, is expected to have potential applications in tissue engineering. In this paper, the in-vitro degradation performance and the corresponding mechanism of nBC immersed in phosphate buffer solution (PBS) for different time periods was investigated. The pH value variation of solution, material degradation, and the swelling and structural changes of nBC was analysed successively. The results indicate that water molecules attack the exposed nBC fibrils, weakening the bonding strength of inter- and intra-molecular chains and disconnecting partial C-O-C bonds. The disconnection of C-O-C bonds is considered the primary reason for the degradation of nBC large molecular chains after nBC is immersed in PBS. The present work is instructive for controlling the in-vivo degradation performance of nBC acting as bone tissue engineered scaffold materials.

Abstract: Aim In this study, the adaptability of an ELISA kit for quantification the residual BSA in TEMPs, the influence of rinsing protocol on reducing the residual BSA in TEMPs and the effectiveness of ultra-filtration on reducing the matrix effects of TEMPs immersion on BSA quantitative by ELISA were discussed. Methods Three kinds of TEMPs used in this study were: tissue engineered skin (TES), recombination human acellular dermal matrix (rhADM) and combination chitosan tissue engineered skin (cC-TES). The devices were rinsed according to the Directions for Use firstly. To investigating the influence of rinsing protocol on reducing the residual BSA in TEMPs, TES were rinsed by two different protocols separately. Then TEMPs immersions were prepared according to ISO10993.12, physiological saline (NS) was used as immersion medium. BSA concentration in immersions and filtrate were determined by using the “Quantitative measure of residual BSA ELISA kit” (detection range was 12.5-200ng/mL, manufactured by WUXI BOSHENG MEDICAL BIO-TEC DEVELOPMENT CO., LTD. As suspected to have some matrix effect on BSA quantification by ELISA kit, rhADM immersion was ultra-filtrated before detection. Results The results showed good correlation between dilution factors and the A450nm of TES and cC-TES immersions, correlation coefficient (r) was 0.9943±0.0007 and -0.9835±0.0037, respectively. No significant effect on BSA detection was found when NS was used as immersion medium. Comparing the results of protocol 1 and 2, the A450nm of TES immersion was significantly decreased after rising by protocol 2. After ultra-filtration, the correlations between absorption and dilution factors of rhADM immersion were improved significantly; the correlation coefficient (r) was raised from -0.7264±0.0089 to -0.9606±0.0039. Conclusions The quantitative ELISA kit was considered to be adaptability for detect the BSA in TEMPs. Different rinsing protocol may obviously affect on reducing the residual BSA in TEMPs. The matrix effects of rhADM immersion can be reduced obviously by using ultrafiltration.

Abstract: The nanocomposite of nano-hydroxyapatite/bacterial cellulose (nHA/BC) obtained by depositing in simulated body fluid (SBF), incorporating their excellent mechanical and biological properties, is expected to have potential applications in bone tissue engineering. However, the biological response evaluation of biomaterials is required to provide useful information to improve their design and application. In this article, the in vitro cytotoxicity of composites nHA/BC as well as its degradation residues was studied. Scanning electron microscopy (SEM) was used to observe the morphology of original materials and their degradation residues. The degree of degradation was evalued by measuring the concentration of reducing sugar (glucose) by ultraviolet spectrophotometer. Bone-forming osteoblasts (OB) and infinite culture cell line L929 fibroblasts were used to measure the cytotocixity of materials with MTT assay. Both kinds of cells in infusion proliferate greatly in a normal form and their relative growth rate (RGR) exceeds by 75%, which shows the cytotoxicity of materials is graded as 0~1, according to the national standard. Nevertheless, bone-forming OB cells, as a kind of target cells, are more susceptive on the cytotoxicity than infinite culture fibroblast cells L929. The results suggest the nanocomposite of nHA/BC without cytotoxicity is greatly promising as a kind of scaffold materials for bone tissue engineering and tissue functional cells are more suited to evaluate the cytotoxicity of biomedical materials.

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: 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.