Antimicrobial surfaces based on self-assembled nanoreactors : from block copolymer synthesis to bacterial adhesion study

The aim of this work is to develop a new strategy for the prevention of biofilm growth. For this purpose, we prepared bioactive surfaces resulting from the surface-immobilization of nanoreactors self-assembled from amphiphilic poly(isobutylene)-block-oligonucleotide copolymers. The block copolymer was synthesized and characterized via appropriate complementary techniques. Self-assembly into vesicles allowed the functional encapsulation of enzymes, as assayed through enzyme activity monitoring, leading to a prodrug-drug system. The self-assembled structures were specifically immobilized on surfaces via base pairing between the oligonucleotide block of the copolymer and the surface tethered complementary nucleotide sequence.
Using E.coli strains, we first observed an influence of the two density of oligonucleotides immobilized on the surface on the number of adherent bacteria. This influence may be due to an effect of surface charge density. We then confirmed the well-known role of curli in biofilm cohesion, and we showed gene over-expression associated with curli production on oligonucleotide-modified surfaces. We demonstrated that gene over-expression does not depend on the topographical features of the surface or on the composition of the nucleotide sequences used in this study. Finally, we demonstrated that the presence of the vesicular structure is able to produce strong anti-adhesive properties of the surface. We assume, from observations of bacterial response in dynamic conditions, that this effect is due to increased bacterial motility on the surface, leading to a high detachment rate. Which is further confirms by a comparable bacterial response observed on agar hydrogel of different hardnesses. This result provides a preliminary outcome, paving the way to new approaches to antimicrobial strategies.