Bacteria surface contact killing

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]...

Tiller JC, Liao C-J, Lewis K et al. (2001) Designing surfaces that kill bacteria on contact. Proc Natl Acad Sci USA 98 5981-5985... 

Their research has demonstrated that covalent attachment of N-alkylated poly(4-vinylpyridine) (PVP) to glass can make surfaces permanently lethal to several types of bacteria on contact. The group found a narrow range of N-alkylated PVP compositions that enable the polymer to retain its bacteria-killing ability when coated on dry surfaces. It is believed that these are the first engineered surfaces proven to kill airborne microbes in the absence of a liquid medium. 

ToFSIMS (with XPS) is currently being used to study the deposition of commercially available alkyl-ammonium chlorides (R4br.Cl ) onto polyester fabric (i.e. PET = polyethylene-terephthalate), in order to produce coatings wUch will kill bacteria on contact with the fabric surface. In addition to being functional, the coatings have to be durable and able to survive multiple washes in many cases (i.e. clothing). 

It is important to note that antimicrobial and biofilm resistance are two different characteristics though some materials show both properties at the same time. Antimicrobial materials do not automatically prevent biofilm formation and vice versa. Antimicrobial surfaces could kill bacteria on contact but if dead bacteria cell debris blocks the active biocidal surface, biofilm formation could eventually occur. For example, quaternary anunonium polymers can effectively kill bacteria but when the surface is fouled with dead bacteria debris, biofilm formation is inevitable [188]. Materials with antibiofilm properties will repel the bacterial adhesion very effectively but may not kill the bacteria when they do colonize the surface. PEG surfaces are well known to repel bacteria adhesion. However, PEG surfaces show little antimicrobial activity. Quantitative antibiofilm efficacy tests can be divided into two categories static (minimum biofilm eradication concentration assay, MBEC) and dynamic (flow cell assay). In addition, SEM is a semiquantitative assay, which is discussed in Section 2.5. 

Contact biocidal biomaterial surfaces kill bacteria on contact as the bactericidal agents are not released and are active following direct interaction with the bacterial cells. Acting through direct contact with bacteria, however, these bioactive surfaces can... 

Tiller et al. (2001, 2002) have covalently attached poly(4-vinyl-N-alkylpyridinium bromide) to glass slides and, thus, created a surface which supposedly kills airborne bacteria on contact. The authors do not provide evidence about the mechanism of action. It is quite probable that traces of the biocide are dissolved into the water droplets in which the test organisms have been sprayed onto the surface. Killing rates up to 99% are reported, which cannot, however, be considered as sufficient, as they include only two log steps. 

Bacteria and viruses are decomposed on tile surfaces containing NS-Ti02 due to the strong oxidizing properties of titanium dioxide. If the walls, ceiling and floor of operating room are covered with photocatalytic tiles, bacteria floating in the air may be killed as they come in contact with the surface (see Table 5). 

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