Antibacterial activity of starch/acrylamide/allyl triphenyl phosphonium bromide copolymers synthesized by gamma irradiation

• Cationic starch is prepared from AM and TP by Gamma irradiation.
• Cationic starch is characterized by FTIR, NMR, weight method and titration method.
• Grafting ratio and cationic degree depend on absorbed dose and composition.
• Cationic starch shows good antibacterial activity against Staphylococcus aureus.

Starch/acrylamide/allyl triphenyl phosphonium bromide (St/AM/TP) copolymers were synthesized by simultaneous gamma irradiation and characterized by FTIR and 1H NMR techniques, weight measurement and titration method. Moreover, their antibacterial activities against Staphylococcus aureus were explored by the viable cell counting method in sterile distilled water. At St/AM/TP 6:8.4:5.6 g, copolymers with higher graft ratio (G) and higher (AM+TP) graft efficiency (EAM+TP) were obtained at 3 and 6 kGy, while cationic degree (CD) and TP graft efficiency (ETP) continuously increased with absorbed dose from 1 to 6 kGy. All of the copolymers were capable of killing >99.75% of 107 CFU/ml S. aureus within 30 mins. Moreover, at 3 kGy, G, EAM+TP and ETP increased with AM/TP from 0:14 to 11.2:2.8 g at St/(AM+TP) 6:14 g, while the optimum CD and antibacterial activity were achieved at AM/TP 7:7 and 8.4:5.6 g. In addition, at 3 kGy, G, EAM+TP and CD increased with St/(AM+TP) from 6:3 to 6:18 g at AM/TP 8.4:5.6 g, while the optimum antibacterial activity was achieved at 6:10 to 6:18 g, and the optimum ETP was achieved at 6:14.