Facile method of preparing silver-embedded polymer beads and their antibacterial effect

Abstract

Research designed to prevent human beings from being infected by microorganisms such as bacteria, molds, yeasts, and viruses from the living environment has attracted tremendous interest. Therefore, many researchers have tried to develop novel and effective antimicrobial materials with free of resistance and low cost [1, 2]. One of the most widely used antibacterial materials is based on silver (silver ions or silver nanoparticles) which exhibits strong biocidal effects towards a broad range of microorganisms, along with advantages such as a lack of odor, taste, and color [3– 6]. Until now, various routes for preparing antimicrobial silver compounds or silver nanoparticles (NPs) have been reported [7, 8]. Especially, silver NPs have more severe effects on bacterial cells than silver ions [9]. However, silver NPs are easily aggregated which causes the deterioration of their chemical properties and decreases their antimicrobial properties. Moreover, the fate of silver NPs for biological applications is still debatable [10, 11]. In addition, some synthetic methods of silver NPs as antimicrobial materials are time-consuming and require expensive instruments. In addition, silver NPs can easily become aggregated, which causes the deterioration of their chemical properties and decreases their antimicrobial properties. To solve these problems, silver has been introduced onto stable supporting materials, in which the antimicrobial mechanism is closely related to the release of silver ions. These methods have several advantages, such as sustained antibacterial effects based on the release of silver ions, good mechanical properties and inexpensive and easy manufacturing processes for industrial applications [12–17]. Recently, many different methods have been proposed to introduce silver NPs into polymers. Among the various polymers, polystyrene (PS)–divinylbenzene (DVB) porous resin is particularly useful, due to its large surface area, chemical stability, and low cost. Moreover, silver NPs can be easily embedded on it after sulfonation, and their size and the loading amount can be adjusted by changing of reaction condition [18]. The deposition of silver on polymer materials has been enhanced by the activation of the surface-functional groups. Among the various functional groups, sulfonated groups are good candidates to introduce silver NPs for the purpose of producing antibacterial materials. Recently, we introduced silver NPs into sulfonated PS–DVB resins (4–8 lm) with mild reduction using the polyol method for use as surface-enhanced Raman scattering (SERS) active materials for multiplex protein analysis [18, 19]. In this study, silver NPs embedded into ion-exchange resin (Ag-IER) (ca. 0.9 mm) were readily prepared by the polyol method and characterized by several instrumental analyses, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray emission (EDX), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Then, their anti-bacterial activity was tested using Escherichia coli, which is well known as indicator bacteria. Moreover, we investigated their antibacterial effect at a low silver loading level and silver ion release conditions. B.-H. Jun J. Y. Kim H.-J. Park J. Yoon Y.-S. Lee (&) School of Chemical and Biological Engineering, Seoul National University, Seoul 151-747, Korea e-mail: yslee@snu.ac.kr