Electrochemically assisted bacteria encapsulation in thin hybrid sol–gel films

Abstract

A novel method, based on the electrochemical manipulation of the sol–gel process, was developed to immobilize bacteria in thin hybrid sol–gel films. This enabled the safe immobilization of Escherichia coli on electrode surfaces. E. coli strains C600, MG1655 pUCD607 and MG1655 pZNTA-GFP were incorporated and physically encapsulated in a hybrid sol–gel matrix and the metabolic activity and membrane integrity of the bacteria were assessed as a function of the aging time in the absence of nutrients at +4 °C or −80 °C. LIVE/DEAD BacLight bacterial viability analysis detected by epi-fluorescence microscopy indicated the preservation of 95% of E. coli C600 membrane integrity in the sol–gel film. The presence of chitosan, trehalose and polyethylene glycol additives was shown to strongly improve the viability of E. coli cells in the electrodeposited matrix for 1 month after encapsulation. Finally, the bioluminescent activity of E. coli MG1655 pUCD607 was preserved by approximately 50% of the cells present in such composite films.