Amine-functionalized silver-exchanged zeolite nay as antibacterial agent

Abstract

Bacterial resistance to antibacterial agents has becoming a serious concern worldwide. Current single-approach antibacterial agent is no longer effective towards these resistant bacteria. Hence, the aim of this research was to produce a newly modified material with multi-approach antibacterial agent with enhanced performance. The material comprised of zeolite NaY (CBV 100) as the carrier for two antibacterial compounds; silver (Ag+) and 3-aminopropyltriethoxysilane (APTES), a type of silane coupling agent was studied. The preparation of aminefunctionalized silver-exchanged zeolite (ZSA) began with the ion exchange at different Ag concentrations (25, 50, 100, and 200%) based on the zeolite cation exchange capacity (CEC) (CEC: 255 meq/100 g) producing silver-exchanged zeolites (ZS), which were then functionalized with different APTES concentrations (0.01, 0.2 and 0.4 M). All prepared materials were characterized according to their structural, morphological, elemental analysis and physicochemical properties related to their usage as a carrier and antibacterial agent. Characterization results of ZSA showed that the zeolite framework was not distorted after the modifications while the Ag-exchanged zeolite was successfully functionalized with APTES. The antibacterial activity of ZSA was investigated by using several antibacterial assays including the minimum inhibitory concentration (MIC) test, disc diffusion test (DDT) and inhibition growth study (IGS) against four types of bacteria, Escherichia coli (ATCC 11229), Pseudomonas aeruginosa (ATCC 15422); Staphylococcus aureus (ATCC 6538) and Enterococcus faecalis (ATCC 29212). All antibacterial assays showed that ZSA samples have higher antibacterial activity compared to ZS samples. Results also showed that ZSA samples were more effective towards the Gram negative bacteria compared to the Gram positive bacteria. This is possibly due to the thin peptidoglycan layer of Gram negative cell wall. The ZSA-50-0.2 (zeolite with 50% CEC Ag+ and 0.2 M APTES) had highest antibacterial activity compared to others. The Ag+ release study was carried out for ZSA-50-0.2 and ZS50 in order to study the mechanism of the antibacterial activity of ZSA and ZS. Different parameters were studied including incubation period, sodium chloride solution concentrations and type of bacteria. Results showed that Ag+ released from ZSA was very low compared to ZS at 30 minutes and 24 hours of incubation. However, there was no significant effect from the type of bacteria and sodium chloride solution concentrations towards the Ag+ released for both ZSA and ZS. These results proved that aminefunctionalized silver-exchanged zeolite (ZSA) which is a multi-approach antibacterial agent have higher antibacterial activity than ZS, a single-approach antibacterial agent and hence, ZSA could possibly be used as an alternative antibacterial agent.