Polycationic Agents For Efficient Anti-infective Therapy And Rapid Discrimination Of Bacterial Pathogens

Bacteria infections have been already one of the world's major public health challenges especially in developing countries where the medical resources and public hygiene are limited.As a result,the efficient treatment and rapid detection of bacterial pathogens are of great importance.However,traditional antibiotics are becoming less efficient because of the development of drug-resistant bacterial strains.Reported antibacterial agents include antimicrobial peptides,bacteriophages,silver,carbon-based materials,and cationic polymers.Positively charged cationic antimicrobial agents show an efficient membrane-damaging effect toward negatively charged bacteria,regardless of normal or drug-resistant bacteria.With the development of antimicrobial agents,cationic compounds such as quaternary ammonium(QA)are extensively used for the biocidal properties against a broad spectrum of bacteria.Positively charged cationic antimicrobial agents show an efficient membrane-damaging effect toward negatively charged bacteria,regardless of normal or drug-resistant bacteria.However,the antimicrobial efficacy would be highly reduced when cationic polymers are immobilized as antimicrobial coatings,where the diffusion of cationic polymers into cell membranes is highly hindered.As a result,development of novel antimicrobial agents is in constant demand.The conventional methods for pathogen detection include 16S rDNA,polymerase chain reaction(PCR),immunoassay-based methods.However,the above methods are time-consuming and require tedious operations.And thus,rapid detection and preliminary discrimination of bacterial pathogens are of great importance.The first part of this work was aimed at the issue of bacterial infections.A series of polycationic synergistic antibacterial polymers with broad spectrum and efficient antibacterial properties were synthesized via a ring-opening reaction of the primary amine and epoxy.The antibacterial polycations with versatile types of functional components including quaternary ammonium and photosensitizer.In the presence of light irradiation,such antibacterial polymers exhibit high antibacterial efficiency against both Escherichia coli and Staphylococcus aureus,owing to the combined photodynamic and quaternary ammonium antibacterial effects.Due to its rich primary amine groups,the synergistic antibacterial polycations also can be readily coated on different substrates via an adhesive layer of polydopamine.The second part of this work was aimed at the issue of rapid discrimination of bacterial pathogens.In the presence of LPS of Gran-negative bacteria,[Pt(N^N^N)Cl]+binds to negatively charged LPS to form LPS-Pt(?)aggregates.The formation of LPS-Pt(?)aggregates consequently leads to luminescence emission,and thus,realizing a rapid and washing-free discrimination of Gram-negative and Gram-positive bacteria.