Decontamination of collagen biomatrices with combined pulsed electric field and nisin treatment.

Pulsed electric field (PEF) treatment has been proposed as a decontamination method for labile matrices used in tissue engineering applications. Through the application of PEF, a non-thermal treatment that causes bacterial inactivation through the irreversible rupture of microbial cell membranes, inactivation is achieved without loss of scaffold structure and function. However, some microorganisms are less susceptible to PEF treatment. This study shows that treatment with PEF and nisin, a food preservative bacteriocin, has a synergistic effect on the inactivation of Staphylococcus epidermidis in collagen gels. Almost complete inactivation of a 10(3) -10(4) CFU/mL S. epidermidis population was achieved when treated with a combination of PEF and 500 IU/mL nisin, with results demonstrating a 3.4 log(10) reduction, compared with 0.66 log(10) reduction with PEF alone. Nisin, at concentrations up to 3000 IU/mL, had no discernable toxicity to mammalian 3T3 cells when added to the culture medium or incorporated into the collagen gels. This combined decontamination method, involving PEF plus nisin, may provide a non-destructive process for inactivation of PEF-resistant bacteria in labile tissue engineering scaffolds.