Biomimetic molecularly imprinted polymers : a new quorum sensing capturing agent to prevent bacterial biofilm formation

Biofilm is a bacterial community that is responsible for most clinical infections and shows increased resistance to the conventional antimicrobials. Biofilm formation is mediated by quorum sensing (QS), by which bacteria produce and recognize autoinducers (AIs) and thereby coordinate their behaviors in a cell-density dependent manner. The purpose of this thesis project was to design and apply molecularly imprinted polymers (MIPs) to capture AIs, interrupt QS, and subsequently inhibit the formation of bacterial biofilms. Pseudomonas aeruginosa and N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C₁₂-AHL) were selected as the bacterial model and target AI molecule, respectively. Photo-initiated bulk polymerization method was conducted to synthesize MIPs using 3-oxo-C₁₂-AHL as the template, itaconic acid (IA) or 2-hydroxyethyl methacrylate (HEMA) as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, 2,2’-azobis(2-methylpropionitrile) as the initiator and N,N-dimethylformamide as the porogen. Different functional monomers and different molar ratios of template: functional monomer: crosslinker were examined to optimize the adsorption capacity and affinity of the synthesized MIPs. Equilibrium rebinding study was conducted to evaluate the adsorption performance of MIPs. MIPs captured 55.2%-61.2% of 3-oxo-C₁₂-AHL in 20% acetonitrile. However, none of them showed good adsorption affinity due to the dominant non-specific binding. In 50% acetonitrile, IA-based MIPs (i.e., 1:6:25 and 1:8:25) demonstrated good adsorption affinity with imprinting factor >1. In biofilm inhibitory studies, P. aeruginosa biofilm was incubated with or without the presence of MIPs for 24 h. Biofilm biomass and sessile cell viability were determined by crystal violet assay and 2,3,5-triphenyl-tetrazolium chloride assay, respectively. Selective HEMA-based polymers (i.e., 1:8:25, 1:6:48 and 1:8:48) significantly (P < 0.05) inhibited the formation of P. aeruginosa biofilms, while all IA-based polymers had no impact on biofilm development. The viability of sessile cells was significantly (P < 0.05) reduced by selective HEMA-based polymers (i.e., 1:6:48 and 1:8:48), but was increased by some IA-based polymers (P < 0.05). Moreover, some HEMA-based polymers (e.g., 1:6:48) showed antimicrobial effect against P. aeruginosa planktonic cells. The current study investigated the inhibitory effect of MIPs against P. aeruginosa biofilm. However, more studies need to be conducted to optimize the capturing performance of MIPs towards 3-oxo-C₁₂-AHL, thereby increase the anti-biofilm effect.Land and Food Systems, Faculty ofGraduat