Preparation of bioelectret collagen and its influence on cell culture in vitro

Collagen extracted from pigskin was corona-charged negatively by a specifically designed device. Different charging voltages, temperatures and times were applied to prepare collagen bioelectret. The decline of the surface potential of the bioelectret under different treatment was then determined. The data showed that the surface potential was markedly varied with the charging conditions. The optimal values of three parameters for charging collagen coatings were defined as follows: voltage, 8 KV; temperature, 40 degrees Celsius; time, 25 min. Treatment of the bioelectret with distillated water, or saline solution (0.9%) or culture medium induced a sharp decrease of the surface potential. In addition, we investigated the effects of the charged collagen on cell growth and intracellular calcium level of three types of cultured mammalian cell lines, including Chinese hamster ovary CHO cells, human cervix uteri tumor HeLa cells and human promyelocytic HL-60 cells. Cell growth and the intracellular calcium level were determined by MTT reagent-based assay and a fluorescent probe Fura-2, respectively. The results showed that negatively charged collagen stimulated the growth of CHO or HL-60 cell line but inhibited the growth of HeLa cell line. Furthermore, after attaching to the charged collagen, the intracellular calcium level of CHO cells increased, while that of HeLa cells decreased. Thus we proposed for the first time that collagen bioelectret could differentially modulate the growth of different cells, by an unknown mechanism that probably involves a role of intracellular calcium.