Tannic acid-modified silver nanoparticles for enhancing anti-biofilm activities and modulating biofilm formation

The formation of bacterial biofilms is a key factor in the emergence of chronic infections due to the strong resistance of biofilms to conventional antibiotics. There is an urgent need to develop an effective strategy to control the formation of biofilms. In this study, a nanocomposite of tannic acid and silver (Tannin-AgNPs) was designed and successfully prepared based on the quorum sensing (QS) inhibitory activity of tannic acid and the anti-bacterial activity of silver. The dynamic light scattering and SEM observations indicated that the obtained Tannin-AgNPs were spherical with a mean particle size of 42.37 nm. Tannic acid was successfully modified on the surface of silver nanoparticles and characterized via Fourier transform infrared (FTIR) spectroscopy. The prepared Tannin-AgNPs demonstrated a more effective anti-bacterial and anti-biofilm activity against E. coli than the unmodified AgNPs or tannic acid. In addition, the Tannin-AgNPs can modulate the formation process of E. coli biofilms, shorten the growth period of biofilms and extend the dispersion period of biofilms. Tannin-AgNPs also showed the function of decreasing the production of the QS signal molecule. The proposed strategy of constructing a nanocomposite using AgNPs and natural components with QS inhibitory activity is effective and promising for inhibiting the formation of biofilms.