Antimicrobial activity of T4 bacteriophage conjugated indium tin oxide surfaces

We report the antimicrobial activity of bare and surface functionalized indium tin oxide (ITO) conjugated with T4 bacteriophage towards E. coli. A ∼ 10³-fold reduction (99.9%) in the bacterial concentration was achieved within 2 h exposure of E. coli to the bare as well as the amine, carboxylic and methyl functionalized ITO/T4 surfaces. Despite the known differences in bacteriophage loading of these ITO/T4 systems, the almost identical extent of antimicrobial activity of all of the ITO/T4 systems resulted from the release of a comparable amount of infective T4 from the systems. As anticipated, a single dose of immobilized bacteriophage was sufficient to eliminate further surge of bacterial population. Upon the 2 h eradication of the '1st batch' of E. coli population, all of the ITO/T4 systems, each system with 10²-fold more suspended bacteriophage (due to propagation of the phage at the expense of the '1st batch' E. coli death), reduced the '2nd batch' of E. coli concentration by ∼10⁴-fold in just 30 min, suggesting the potential of immobilized bacteriophage systems as solution to the issues of antimicrobial agent depletion. All of the ITO/T4 systems maintained their antimicrobial activity in the presence of model food components. The antimicrobial activity was however, affected by pH; at pH 5 whereby the bacteria's growth was physiologically inhibited, generally no reduction in E. coli concentration was detected. The present work provides an understanding of the mode of antimicrobial activity exhibited by an immobilized bacteriophage based substrate and demonstrates efficacy in the presence of food components.