Inactivation of problematic micro-organisms in collagen based media by pulsed electrical field treatment (PEF)

The potential of pulsed electric field (PEF) treatment as a novel/safe method of decontaminating collagen based biomatrices was investigated. Collagen gels (0.3% w/v) were seeded at a concentration of 106 CFU/ml with either Escherichia coli or Staphylococcus epidermidis and then treated with 100 pulses at ~45 kV/cm, using a static PEF chamber. To investigate if the collagen gel had a 'protective' effect on the bacteria, PEF inactivation was also investigated in phosphate buffered saline (PBS) and melted collagen gel (heat-treated, 10 min at 80°C, and as a result not set as a gel). When subjected to PEF, different levels of inactivation were observed with E.coli and S. epidermidis seeded in the different media. In all three media E. coli was more susceptible to PEF treatment than S. epidermidis. E. coli cell counts were reduced by ~3.3 logs in PBS, 2.6 logs in collagen gel and least inactivation (~1.5 log reduction) was observed in melted gel. S. epidermidis also showed higher inactivation levels in PBS compared to native collagen gel and melted collagen gel. Current results have established that PEF treatment can inactivate different types of bacteria seeded in collagen gels. However, complete inactivation was not achieved in any of the different types of suspending media, possibly due to the high seeding densities utilized. Previous results have established that PEF does not adversely affect the collagen structure. Future work is required to optimize microbial inactivation levels and to fully establish whether PEF treatment may offer a novel biomatrix decontamination method, which achieves sterility without damaging labile biological components.