Hybrid nanoparticles of quaternary ammonium cellulose derivatives and citric acid for enhancing the antibacterial activity of polyvinyl alcohol composites

Quaternary ammonium compounds are active functional groups that can inhibit bacterial growth and reduce drug resistance. In this study, we prepared hybrid nanoparticles (NPs) comprising quaternary ammonium cellulose derivatives (CBHE-QA n ) and citric acid (CA). Firstly, cellulose 6-bromohexanoyl ester (CBHE) was synthesized by esterification of cellulose with 6-bromohexanoyl chloride. Then, diverse CBHE-QA n (CBHE-QA 8 , CBHE-QA 10 , CBHE-QA 12 , CBHE-QA 14, and CBHE-QA 16 ) were synthesized by the reaction of CBHE with five tertiary amine compounds, namely, N,N-dimethyloctylamine, N,N-dimethyldecylamine, N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, and N,N-dimethylhexadecylamine. The hybrid NPs were formed through electrostatic interactions between CBHE-QA n and CA and named CBHE-QA n /CA x (where x represents the mass ratio of CA). These spherical NPs with average diameters of 70–145 nm exhibited excellent antibacterial activity against gram-positive bacterium S. aureus and gram-negative bacterium E. coli . Furthermore, adding CBHE-QA 16 /CA 35 NPs to a polyvinyl alcohol (PVA) matrix via a solvent casting method significantly enhanced the antibacterial activity and improved the tensile strength. With 5 wt.% of CBHE-QA 16 /CA 35 NPs, the tensile strength of the PVA composite film increased to 53.4 MPa (47.2% higher than that of the pure PVA film). Moreover, the PVA/CBHE-QA 16 /CA 35 composite films showed excellent antibacterial efficiency.