| Pathogenic microorganisms have always posed a great threat to human beings,which have become a global public health problem.However,the lack of efficient and reliable pathogen identification platform and antibacterial methods that are not easy to produce drug resistance in actual treatment may lead to inaccurate drug treatment and delay of illness,or even life-threatening conditions.With high fluorescence intensity,large molar extinction coefficient and excellent photostability,organic conjugated molecules have been widely used in solar cells,high-sensitivity detection systems,biological imaging,anticancer and antimicrobial treatments.Photodynamic therapy(PDT),as an efficient antimicrobial treatment that is non-invasive,high temporal and spatial resolution and non-proneness to induce drug-resistance,has also inspired researchers and become a research hotspot in the field of anti-cancer and antibacterial research.Therefore,this thesis mainly studies the application of organic conjugated molecules in the detection of pathogenic microorganisms and photodynamic antibacterial field.Tetraphenyl ethyl derivative(TPE)fluorescent sensor array for microbial identification was designed and prepared,and the combination of organic conjugated molecules with the advantages of PDT led to the first discovery of hemicyanine derivatives capable of microbial detection and photodynamic antibacterial activity.The main studies are as follows.1.TPE fluorescence sensor array was constructed for the detection and identification of microbes,which consisted of three TPE materials(TPEs)with aggregation-induced emission(AIE)activity and different positive charges or alkyl chains.The multiple interactions between different pathogens and TPE materials can be applied to cause different degrees of aggregation and thus trigger changes in the fluorescence signal.With the help of linear discriminant analysis(LDA),TPE fluorescence sensor array requires only 5 μM of TPE and achieves 100% identification within 40 min.It is a powerful tool for highthroughput microbial identification,overcoming the time-consuming bacterial culture and the high dependence of specific recognition elements.2.A series of cationic hemicyanine derivatives(C3,C6 and C10),type-I photosensitizers with low oxygen dependence were designed,which displayed selective favorable damage toward different species of pathogens by producing hydroxyl radical and superoxide anion exposed to white light.Moreover,it was found for the first time that hemicyanine derivatives could be used for the detection and identification of pathogenic microbes.More importantly,they could distinguish live bacteria from dead bacteria,and realize the dual effects of combating various microbial infections and tracking pathogen status in real time under the condition of hypoxia.Therefore,these simple organic conjugated molecules based on hemicyanines are anticipated to become an effective weapon for clinical tracking detection and combatting pathogenic infections in the hypoxic region.3.The smart "antibacterial switch" based on supramolecular self-assembly principle was constructed.The regulation of antimicrobial activity is achieved mainly through a reversible self-assembly and disassembly process between hemicyanine derivatives and cucurbit[7]uril(CB[7]),which results in "turn-off" or "turn-on" bactericidal activity.This "antibacterial switch" effectively inhibits the production of reactive oxygen species in the presence of light,shielding the antibacterial molecules from their antimicrobial activity to achieve pathogen killing in demand.This strategy is simple,efficient and does not require any chemical modification of the active site of the antimicrobial agent.Not only can the goal of precise regulation of antimicrobial activity be achieved,but also it is expected to delay or even prevent the development of drug resistance in pathogenic bacteria,which is of great significance to reduce the accumulation of antibiotics in the environment. |
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