Contact Active Antimicrobial Coatings Prepared by Polymer Blending

Abstract

Herein, contact active antimicrobial films are prepared by simply blending cationic amphiphilic block copolymers with commercial polystyrene (PS). The copolymers are prepared by combining atom transfer radical polymerization and "click chemistry." A variety of copolymers are synthesized, and composed of a PS segment and an antimicrobial block bearing flexible side chain with thiazole and triazole groups, 4-(1-(2-(4-methylthiazol-5-yl)ethyl)-1H-1,2,3-triazol-4-yl) butyl methacrylate (TTBM). The length of the TTBM block is varied as well as the alkylating agent. Different films are prepared from N,N-dimethylformamide solution, containing variable PS-b-PTTBM/PS ratio: from 0 to 100 wt%. Remarkably, the blend films, especially those with 30 and 50 wt% of copolymers, exhibit excellent antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi, even higher than films prepared exclusively from the cationic copolymers. Blends composed of 50 wt% of the copolymers present a more than 99.999% killing efficiency against the studied microorganisms. The better activity found in blends can be due to the higher roughness, which increases the surface area and consequently the contact with the microorganisms. These results demonstrate that the use of blends implies a reduction of the content of antimicrobial agent and also enhances the antimicrobial activity, providing new insights for the better designing of antimicrobial coatings.

Antimicrobial Porous Surfaces Prepared by Breath Figures Approach

“…Thus, these results reveal that the preparation method provides films with enough accessible active groups at the surfaces to kill the microorganisms by surface contact, even when low amounts of copolymer are incorporated in the film. Remarkably, these breath figure films provide better efficiencies than flat films prepared directly from the copolymer solution; that is, 100 wt % of PS 54 - b -PTTBM-B 44 , PS 54 - b -PTTBM-M 44 [16]. These findings demonstrate the importance of the surface roughness on the antimicrobial activity of contact-active films, which allows the use of very low amounts of antimicrobial component in the coating while maintaining excellent biocidal activity.…”

“…The block copolymers polystyrene- b -poly(4-(1-(2-(4-methylthiazol-5-yl)ethyl)-1H-1,2,3-triazol-4-yl)butyl methacrylate) ( M n = 22,000 g/mol, M w / M n = 1.53) quaternized with either butyl iodide (PS 54 - b -PTTBM-B 44 ) or methyl iodide (PS 54 - b -PTTBM-M 44 ) were synthesized as previously reported [16]. Briefly, the first block of polystyrene was prepared by atom transfer radical polymerization (ATRP) and then was used as macroinitiator for the synthesis of the PTTBM block.…”

“…The cationic copolymers PS 54 - b -PTTBM-R 44 (R = butyl or methyl) were finally obtained by quaternization of their thiazole and triazole groups. 1 H-NMR spectroscopy confirms that quaternization was achieved quantitatively [16]. Tetrahydrofuran (THF, Aldrich, St Quentin Fallavier, France, ACS reagent) was employed as organic solvent for the preparation of the porous films without further purification.…”

“…Thus, combinations of surface roughness with chemical biocidal functionalities can create more effective bactericidal properties than flat surfaces [16,17,18]. Nowadays, many techniques are available to create surfaces with finely controlled topography, including lithography approaches and colloidal templates [19,20].…”

“…In this work, we prepared porous films by a breath figures approach functionalized with high charge density by the incorporation of antimicrobial cationic polymers bearing two quaternary ammonium groups per monomeric unit. In fact, these structures are based on methacrylic monomers with 1,3-thiazolium and 1,2,3-triazolium side-chain groups, and have demonstrated a broad spectrum of antimicrobial activity in solution [31,32], and also when immobilized onto a surface [16,33]. It is well known that surface positive charge density is an important parameter for defining antimicrobial efficiency [33,34], and the incorporation of polymers with high charge density as blend component will enhance the biocidal activity of the microstructured surfaces, maintaining the physicochemical properties of the resulting coating.…”