Influence of aptamer-enclosed silver nanocluster on the prevention of biofilm by bacillus thuringiensis

The aim of the present study was to determine the effectiveness of silver nanocluster (Ag-NC) against biofilm of Bacillus thuringiensis (BT). A 60-bases long DNA aptamer specific for BT, tied to the 5′ end of a 16-bases long cytosine-rich DNA oligonucleotide, was chosen as template for growing the Ag-NC. Absorption and fluorescence spectroscopic studies confirmed the formation of the fluorescent Ag-NC on the DNA template. A comparative study was then performed on a series of concentrations of the applied agents, like Ag⁺ ions and DNA-enclosed Ag-NC in absence and presence of methyl-beta-cyclodextrin, on the prevention of biofilm by BT. Quantification of the biofilm formation in 96-well microtiter plates was performed by means of crystal violet staining, which along with phase contrast and transmission electron microscopy indicated that as little as 5 μM of cyclodextrin-conjugated DNA-Ag-NC was sufficient to inhibit the biofilm formation. Implications of these results are discussed. In conclusion, cyclodextrin-bound aptamer enclosed Ag-NC enabled biofilm control, which opens the door to a new theme and paradigm of biofilm prevention.