Biocides contact-active

Keywords Antibacterial Antimicrobial Bacteria Biocide Contact-active Light-activated Photocatalytic Release Self-polishing Surface... 

Abstract In this review, the general principles of antimicrobial surfaces will be discussed in detail. Because many common products that keep microbes off surfaces have been banned in the past decade, the search for alternatives is in full run. In recent research, numerous new ways to produce so-called self-sterilizing surfaces have been introduced. These technologies are discussed with respect to their mechanism, particularly focusing on the distinction between biocide-releasing and non-releasing contact-active systems. New developments in the catalytic formation of biocides and their advantages and limitations are also covered. The combination of several mechanisms in one surface modification has considerable benefits, and will be discussed. 

Another way to measure the efficiency of a biocidal surface is by detection of the ATP bioluminescence of the adhering microbial cells [18], With this elaborate method, the killing rate of a surface can be measured and it is possible to distinguish between growth inhibition and killing. However, the method does not distinguish between release and contact activity. In general, there is no test that can clearly tell the difference between a contact-active and a release system. 

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],... 

Waschinski CJ, Zimmermann J, Salz U et al. (2008) Design of contact-active antimicrobial acrylate-based materials using biocidal macromers. Adv Mater 20 104-108... 

Nurdin N, Helary G, Sauvet G. Biocidal polymers active by contact. 11. Biological evaluation of polyurethane coatings with pendant quaternary ammonium salts. JAppl Polym Sci 1993 50 663-70. http //dx.doi.Org/10.1002/app.1993.070500411. 

Waschinski, C.J., Zimmermann, J., Salz, U., Hutzier, R., Sadowski, G., Tiller, J.C., 2008. Design of contact-active antimicrobial acrylate-based materials using biocidal macro-mers. Advanced Materials 20, 104-108. http //dx.doi.org/10.1002/adma.200701095. 

Several factors are known to influence biocidal activity these include the period of contact, biocide concentration, pH, temperature, the presence of oigartic matter and the nature and condition of the microorgartisms being treated. Bacterial resistance to antibiotics is a well-established phenomenon and has been widely studied for luar years. By contrast, the mechanisms of insusceptibility to non-antibiotic chemical agents are less well understood. 

It does have a number of draw backs. It has poor thermal stability (a property common to most formaldehyde release biocides) and, in some instances, may cause blackening of metalworking fluid concentrates if heated above 50°C for a period of time. Recently, this active ingredient was placed on Annex 1 of the Dangerous Substances Directive having been identified as a potential skin sensitiser. This means that formulations containing efficacious levels of this class of triazine in them would have to be labelled with R43 - may cause sensitisation by skin contact. This is unacceptable to many UK customers. As this material is only bactericidal, it needs to be co-formulated with a fungicide to provide complete protection for a product. 

Because chlorine is inactivated by blood, serum, feces, and protein-containing materials, surfaces should be cleaned before chlorine disinfectant is applied. Undissociated hypochlorous acid (HOC1) is the active biocidal agent. When pH is increased, the less active hypochlorite ion, OC1 , is formed. When hypochlorite solutions contact formaldehyde, the carcinogen /v.v-chloromethyl is formed. Rapid evolution of irritating chlorine gas occurs when hypochlorite solutions are mixed with acid and urine. Solutions are corrosive to aluminum, silver, and stainless steel. 

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

Repelling microbes or killing them on contact are obviously the optimal ways for an antimicrobial surface to function. However, most moist and biologically contaminated areas contain large amounts of material that nonspeciflcally attach to a surface and deactivate it fully. Furthermore, high concentrations of microbes will eventually cover any surface with dead cells, which also deactivate the surface. In the latter case, only surfaces that release biocides will retain their activity. 

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