Spraying layer-by-layer assembly of tannin-Fe3+ and polyethyleneimine for antibacterial coating

Tannic acid (TA), as a natural molecule, possesses many excellent properties. It has attracted wide interest in various fields of functional coatings, food, and medicine. A simple method to prepare thick and stable TA-contained coating is required, which may promote practical applications of TA. Here, we proposed a simple and effective method of generating a stable TA-rich coating by spraying layer-by-layer technology. The coating was stabilized basing on the complexation of TA and ferric (Fe 3+ ) ions and poly(ethyleneimine) (PEI). Because both TA and PEI have good antibacterial properties, the (TA-Fe 3+ /PEI) coating displayed the contact-killing against E. coli . Further, because of the reductive nature of the TA, the coating was able to incorporate nano‑silver particles by reducing silver ions . Consequently, the enhanced antibacterial property was achieved. The (TA-Fe 3+ /PEI) coating was then spraying coated on the nonwoven mask, showing the potential application in medical protection.