Nonleaching Antibacterial Glass Surfaces via “Grafting Onto”: The Effect of the Number of Quaternary Ammonium Groups on Biocidal Activity

Abstract

Antimicrobial surfaces were prepared using the "grafting onto" technique. Well-defined block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) and poly(3-(trimethoxysilyl)propyl methacrylate) segments (PDMAEMA/PTMSPMA) and corresponding random copolymers were prepared via atom transfer radical polymerization (ATRP), followed by covalent attachment to a glass surface through reaction of the trimethoxysilyl groups with surface silanol groups. The density of quaternary ammonium (QA) groups available to bind small molecules in solution increased with polymer solution concentration and immobilization time. For the PDMAEMA 97- b-PTMSPMA xdiblock copolymers with a fixed length of PDMAEMA segment (degree of polymerization (DP) = 97) and varied lengths of PTMSPMA segments, maximal available surface charge was observed when the ratio of DP PDMAEMA to DP PTMSPMA was 5:1. The tertiary amino groups in immobilized PDMAEMA segments were reacted with ethyl bromide to form QA groups. Alternatively, block copolymers with prequaternized PDMAEMA segments were attached to surfaces. Biocidal activity of the surfaces with grafted polymers versus Escherichia coli ( E. coli) increased with the density of available QA units on the surface. The number of bacteria killed by the surface increased from 0.06 x 10(5) units/cm2 to 0.6 x 10(5) units/cm2, when the density of surface QA increased from 1.0 x 10(14) unit/cm2 to 6.0 x 10(14) unit/cm2. The killing efficiency of QA on all surfaces was similar with approximately 1 x 10(10) units of QA needed to kill one bacterium. The AFM analysis indicated that grafting onto the surface resulted in small patches of highly concentrated polymer. These patches appear to increase the killing efficiency as compared to surfaces prepared by grafting onto with the same average polymer density but with a uniform distribution.

A review of immobilized antimicrobial agents and methods for testing

“…17,22,30,31 Other groups, most notably Russell and Matyjaszewski, have led the surface initiated efforts using controlled ATRP reactions. 24,[26][27][28][29] The works from the Klibanov and Russell groups have systematically probed the antimicrobial impact of key properties such as the surface charge density, polymer chain length, polymer chain density, counter ion identity, and quaternary ammonium sidechain length.…”

“…26 The surface density of the immobilized quaternary ammonium (QA) groups was controlled via the polymer solution concentration, immersion time, and molecular architecture. Fluorescence and atomic force microscopy (AFM) measurements were used to quantify the density of chains on the surface, and the results were correlated with the antimicrobial efficacy, as shown in Fig.…”

“…Irreversible immobilization of the antimicrobial agents in the device offers an alternative motif that eliminates patient exposure to elutable active agents and potentially increases the duration of antimicrobial efficacy. 8,9 A wide range of antimicrobial agents have been immobilized, including small molecules (e.g., quaternary ammonium silanes), [10][11][12][13][14][15][16][17] quaternary ammonium polymers, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] polyamines, [36][37][38][39][40][41][42] chitosan, [43][44][45][46][47][48][49] enzymes, [50][51][52][53][54][55] peptides, and peptide mimetics. …”

Antibacterial Effects of Poly(2-(dimethylamino ethyl)methacrylate) against Selected Gram-Positive and Gram-Negative Bacteria

“…It is also used as a coating for soil-resistant surfaces 25 , as an ion exchange media for protein separation 26 , and to adapt the wettability of surfaces including microfluidic devices 27 . In addition to this, pDMAEMA has been attached to glass 28,29 , filter paper 28,30 , polystyrene 31 and polypropylene 32 and also as an antimicrobial surface coating to inhibit the growth of Escherichia coli (E. coli) and Bacillus subtilis. It has also been incorporated in antimicrobial copolymers to inhibit growth of E. coli 33 and S. aureus 34 .…”

Antimicrobial Properties of Glass Surface Functionalized with Silver-doped Terminal-alkynyl Monolayers

“…6 Most of these compounds have quaternary ammonium salts, biguanide groups, quaternary pyridinium salts, sulphonium salts, phosphonium salts, and other antimicrobial compounds. 5,18 By immobilizing the biocide groups, the surface will be protected against bacterial attachment for prolonged periods of time. 5 Silver (Ag) has been known as an antimicrobial agent for centuries.…”