Antimicrobial performance molecularly tuned by aryl ammoniums grafted to chitosan chains adsorbed on polypropylene films

Abstract

Active antibacterial biopolymers are obtained from covalently graft of quaternary aryl ammonium groups (PYR) to chitosan (CS) chains. The aryl ammonium bromide -derived chitosan series: 1-butylpyridin-1-ium (CS-PYR0), 1-butyl-2-methylpyridin-1-ium (CS-PYR1) and 1-butyl-2,4-dimethylpyridin-1-ium chitosan (CS-PYR2) is used to assess biocide activity when they are either colloidal suspensions or immobilized over a model surface such as polyacrylic acid-grafted polypropylene (PP-PAA) film. Antimicrobial activity of biocides against Staphylococcus aureus is positive and a bacteriostatic behavior is found, while the effect on Escherichia coli is poor. The CS-PYR chains adsorbed on the PP-PAA film exhibit an enhanced bacteriostatic activity when regard to biopolymer chain suspensions. On PP-PAA-CS-PYR film surfaces, antibacterial biocide activity is revealed to be closely correlated with the increase of substitution degree on the aromatic ring: CS-PYR0 < CS-PYR1 < CS-PYR2. Such a finding strongly suggests biocide activity can be tuned by controlling molecular structure features. These results contribute to the development of surfaces with biocides property requirements.