Preparation of grafted starch by IPDI coupling and its antibacterial properties

Antibacterial acetate grafted starch (AGS) was synthesized by isophorone diisocyanate (IPDI) coupling acetate esterified starch (AST) and the antimicrobial agent polyhexamethyleneguanidine hydrochloride (PHMG), and the antimicrobial properties of AGS were evaluated. The process parameters of AGS were: IPDI reacted with PHMG at 120 °C for 1 h, then, reacted with starch at 60 °C for 3 h. The grafting yield of PHMG and starch reached 28.43%. The Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (1H NMR) showed that the binding of IPDI to PHMG was successfully grafted on the AS. The antibacterial effect of AGS was investigated. AGS produced inhibition zones and confirmed its significant inhibitory effect on Escherichia coli and Staphylococcus aureus, as the grafting yield increased, the inhibition effect on bacteria became stronger. When the grafting yield was 28.43%, the inhibition rate of AGS was 90.24% for Escherichia coli. and 94.45% for Staphylococcus aureus. The experiments of water washing showed that after AGS was washed 10 times with water, the inhibition rate of AGS to E. coli. only reduced 3.04% and that of S. aureus 2.95%, indicating that the combination of PHMG and starch was stable and the inhibition effect was long-lasting, AGS has huge potential to be developed into antibacterial material.