Selection of streptococcal glucan-binding protein C specific DNA aptamers to inhibit biofilm formation

Abstract

Streptococcus mutans is a commensal bacterium in the oral cavity, but its overgrowth leads to biofilm formation and dental caries. S. mutans glucan-binding protein C (GbpC) is a cornerstone of the biofilm scaffold and thus a rational target for biofilm inhibition. Here we present a selection of DNA aptamers for GbpC to aid in the development of biofilm inhibiting drugs. During SELEX, we used the extracellular domain of GbpC as the target of selection and the structurally homologous antigen I/II protein and a GbpC-deficient strain of S. mutans as counter-targets. The aptamer candidates obtained were panned using a method based on primer-blocked asymmetric PCR and AlphaScreen. The interaction between the most promising candidates of panning and GbpC was analysed by biolayer interferometry and microscale thermophoresis. Finally, we tested the biofilm inhibitory effect of the aptamers on a wild-type and a GbpC-deficient strain of S. mutans. The measurements demonstrated both the efficacy and selectivity of the aptamers. Two of the aptamers studied reduced biofilm formation by 30% in the case of wild-type strains and no reduction was detected in the GbpC-deficient strain, confirming the suitability of the selection strategy presented and providing lead molecules for the development of biofilm inhibitors.