Porous Microstructured Surfaces with pH‐Triggered Antibacterial Properties

Abstract

New antibacterial films are designed with the capability to reversibly regulate their killing and repelling functions in response to variations in environmental pH. These systems consist of porous polystyrene surfaces as the main components and a copolymer bearing pH‐sensitive thiazole and triazole groups as the minor components. These pH‐sensitive groups, located on the surfaces, can be partially protonated at acidic pH levels, increasing the positive charge density of the surfaces and their antibacterial activity. Similarly, their bacterial adhesion and killing efficiencies in response to changes in pH are evaluated by analyzing the bacterial viability of Staphylococcus aureus bacteria on the surfaces under acidic and neutral pH values. It is demonstrated that after only 1 h of incubation with the bacterial suspension in acidic conditions, the surfaces killed the bacteria, while at pH = 7.4, some of the adhered bacteria are removed. Furthermore, the surface topography exerts an important role by intensifying this response.

Chemical Hydrogels Bearing Thiazolium Groups with a Broad Spectrum of Antimicrobial Behavior

“…A variety of polymers has been prepared including homopolymers, statistical and block copolymers synthesized by conventional or controlled radical polymerization [28][29][30][31][32]. Then, some statistical and block copolymers have been also used as additives in polymer blends to obtain films, coatings or fibers [33][34][35][36]. However, their structuration as hydrogels has not been yet tested.…”

Antibacterial Designs for Implantable Medical Devices: Evolutions and Challenges

“…The antibacterial activity of pH-responsive films or coatings can be triggered by the protonation or deprotonation of their ionic groups. The thiazole and triazole groups, for example, in polymer PS54-b-PTTBM23 (on porous polystyrene surfaces) can be protonated under acidic pH levels, which increased the positive charge density on the materials surface to act against bacterial adhesion ( Figure 3 a) [ 151 ]. In addition, the killed bacteria can be further removed by increasing the pH levels (pH 7.4, for instance), which induced deprotonation of the thiazole and triazole groups in the materials [ 151 ].…”

“…The thiazole and triazole groups, for example, in polymer PS54-b-PTTBM23 (on porous polystyrene surfaces) can be protonated under acidic pH levels, which increased the positive charge density on the materials surface to act against bacterial adhesion ( Figure 3 a) [ 151 ]. In addition, the killed bacteria can be further removed by increasing the pH levels (pH 7.4, for instance), which induced deprotonation of the thiazole and triazole groups in the materials [ 151 ]. Normally, pH-responsive surfaces are designed for the controllable release of antibacterial agents by manipulating the materials’ pH-associated swelling or shrinking processes.…”

“… Typical methods toward pH-responsive surfaces: ( a ) protonation of polystyrene- b -poly(4-(1-(2-(4-methylthiazol-5-yl)ethyl)-1 H -1,2,3-triazol-4-yl)butyl methacrylate) (PS 54 - b -PTTBM 23 ) at acidic pH levels and increase of the positive charge density on the surfaces [ 151 ]; ( b ) breaking the Schiff base bonds between antibacterial gentamicin and alginate dialdehyde by acidic environments [ 157 ]; ( c ) hydrolyzation of the hemiaminal ether linkage of antimicrobial 6-Chloropurine in 4-(1-(6-chloro-7H-purin-7-yl) ethoxy) butyl methacrylate (CPBMA) by mild acidic conditions [ 158 ]; ( d ) destruction of dopamine-conjugated oxidized dextran polymer to release the contained silver nanoparticles by disintegration the Schiff base structures in the polymer [ 160 ]. ( a , c ) reused with permission from John Wiley and Sons and American Chemical Society, respectively; ( b , d ) reused with permission from Elsevier.…”

Multifunctional Antibacterial Materials for the Control of Hazardous Microbes and Chemicals: A Review

“…Albright et al explained that S. aureus and E. coli that adhere to such coatings generate highly localized acidification, even under buffered conditions, to activate pH-triggered, self-defense antibiotic release. Some antibacterial agents, such as thiazole, can be positively charged under acidic conditions to kill adhering bacteria …”