Contact killing

The first contact-killing surface was described by Isquith et al., who modified glass substrates with the silane 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride, often referred to as DOW5700 [39], However, the claim was made on the basis of the DOW suspension test (see Sect. 2.2), which cannot distinguish between biocide release and contact activity. In subsequent work, neither the original authors nor followers proposed a working model for a mechanisms that was able to explain the contact activity of this surface modification. The first model for contact activity was proposed in 2001 (see Fig. 5) [40],... 

Fig. 5 Concept of contact-killing membrane-active biocides surface-coupled via a polymeric...

Fig. 6 Concept of contact-killing by the surface-induced removal of a vital hydrophobic anion from the envelope of an attached microbial cell...

A coating described by Worley and coworkers was shown to efficiently kill both on contact and by release [137], The polyurethane-based material contains quarternary ammonium groups for contact-killing and AMialamine groups for releasing chlorine... 

Fig. 9 Example of a contact-killing and microbe-repelling surface, (a) Antimicrobial cationic polyW.iV-dimethyl-iVTethoxycarbonylmethyll-iV-P -tniethacryloyloxylethyll-ammonium bromide) left structure) effectively kills bacteria, (b) The polymer is converted into the corresponding nonfouling zwitterionic derivative (right structure) upon hydrolysis, (c) Dead bacteria remaining on the surface are repelled from the nonfouling surface, (d) The zwitterionic surface itself is highly resistant to bacterial adhesion. Reproduced and adapted from [136]...

Fig. 10 Example of a contact-killing and microbe-releasing surface. The scheme shows the design of a two-level dual-functional antibacterial coating containing both quarternary ammonium salts and silver. The coating process begins with LbL deposition of a reservoir made of bilayers of PAH and PAA. (A) Cap region made of bilayers of PAH and SiC>2 nanoparticles (NP) is added to the top. (B) The SiC>2 nanoparticle cap is modified with a quarternary ammonium silane (QAS) PEM polyelectrolyte multilayer. (C) Ag+ is loaded into the coating using the available unreacted carboxylic acid groups in the LbL multilayers. Scheme was reproduced from [138]...

Li Z, Lee D, Sheng XX et al. (2006) Two-level antibacterial coating with both release-killing and contact-killing capabilities. Langmuir 22 9820-9823... 

Contact killing antimicrobial articles, devices and formulations are described which kill microorganisms... 

The QAC modifications described in the previous section are bulk phase modifications to the polymer itself. Efforts have been undertaken to concentrate the contact killing moieties, such as QACs, to the surface of the polymer by using polymer scaffold modifiers (PSMs) (Kurt et al 2007 Makal et al 2006 Waschinski et al., 2008). These modifications are driven by low solubility and/or low surface energy (Luzinov et al., 2004). Kurt et al. (2007) used a hard-block/soft-block strategy, with the bulk PU as the hard block and the antibiotic-loaded PSM as the soft block. Alkylammonium polyoxetane telechelics (Figure 17.1) react with the hard block PU formed by the reaction of 4,4 -(methylene bis(p-cyclohexyl isocyanate) and 1,4-butanediol. 

Storage for at least a month under ambient conditions of temperature and humidity also provide support for the use of zeta potentials as a predictor for polycation contact kill. 

The problem of temporal and thermal instability of the U-P[3F-C 12-( 11)] modifier was solved by utilizing a —CF2CF2H (4F) fluorous side chain and increasing the Cl2 mole fraction. Biocidal effectiveness was demonstrated after storage for at least a month under ambient conditions of temperature and humidity. This stability was correlated with zeta potential measurements of accessible near surface charge. These results suggest zeta potential measurements hold promise as a physical method for assessing effectiveness of polycation contact kill and polycation stability in contact with aqueous systems. 

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