Rapid Detection Of Multidrug Resistant Bacteria Based On Magnetic Nanomaterials And Quantum Dots

Nowadays,bacteria resistance is one of the most complex public health threats over the world.Infections caused by drug-resistant bacteria are occurring more frequently and associated with longer hospital stays,increased treatment costs,and increased mortality.The detection of drug-resistant bacteria plays vital roles in diagnosis of infectious diseases,drug usage,monitoring the progress of treatments and infection control.However,the traditional methods such as drug sensitivity tests usually need a long period of extended culture,so the timeliness of the test cannot be guaranteed.The commonly detection methods of drug-resistant genes are based on PCR technologies,which require specific instruments and professional operators,and cannot detect unknown drug-resistant genes.Therefore,the development of simple,rapid,sensitive and specific detection methods is still an urgent need for the diagnosis and treatment of drug-resistant bacteria.Magnetic nanomaterials own the merits of superparamagnetism,magnetic conductivity,biological compatibility and surface activity that can achieve enrichment and separation efficiently and biofriendly.Separation technologies based on magnetic nanomaterials could provide strong foundation for the detection of low concentration bacteria without culture.As a new type of luminescent materials,quantum dots own the characteristics of good optical stability,multi-color labeling and good biocompatibility.Moreover,cadmium-based quantum dots show great application potential in the field of electrochemiluminescence（ECL）.In this study,a series of simple and rapid biosensing methods have been developed for the detection of multidrug resistant bacteria based on vancomycin-modified Fe₃O₄@Au nanoparticles and zinc-doping cadmium sulfide quantum dots.Taking advantages of nanomaterials and electrochemical/ECL platform,the developed methods show highly sensitivity and specificity for multidrug resistant bacteria detection in clinical diagnosis,which has a good prospect of clinical application.The research mainly has two parts as follows:1. Rapid detection of multidrug resistant bacteria by p H response based on vancomycin-modified Fe₃O₄@Au nanoparticles enrichment and carbapenemase hydrolysis reactionCarbapenem-resistant Enterobacteriaceae（CRE）is one of the most important multidrug resistant bacteria that attract people’s attention.Rapid and simple detection of CRE is important to manage infection and prevent the spread of these bacteria.In this work,we utilize p H response to detect CRE in urine rapidly.By using vancomycin-modified Fe₃O₄@Au nanoparticles（Fe₃O₄@Au@Van NPs）,CRE in urine were enriched and separated efficiently via vancomycin-cell wall interaction.More importantly,carbapenemases released via CRE lysis was detected by a p H metre which responded to hydrogen ions generated from imipenem hydrolysis.Thus,the concentration of CRE in urine was detected via carbapenemase hydrolysis reaction.The proposed method demonstrated good linear relationship in the range of 10⁴-10⁸ cfu?m L^-1 for CRE with the limit of detection was estimated to be 1.0×10³ cfu?m L^-1.More importantly,this method successfully detected clinically isolated CRE strains in urine samples within 3.5 h.This biosensing strategy is simple,rapid,stable and enzyme-free.Thus,it offers a powerful tool for clinical diagnosis,therapeutic monitoring and prognosis evaluation of infectious diseases caused by drug resistant bacteria.It might have potential for practical application in the rapid detection of various resistant bacteria.2. Electrochemiluminescent immunosensor based on zinc-doping cadmium sulfide and Pd Mo bimetallene quenching for the rapid detection of multidrug resistant bacteriaBased on zinc-doping cadmium sulfide（Zn Cd S）as luminescent reagent and S₂O₈^2-as coreactant of ECL system,and functional Pd Mo bimetallene as quenching agent,an"on-off"high-sensitive ECL immunosensor for methicillin-resistant staphylococcus aureus（MRSA）detection was constructed.In this study,Zn Cd S shows the stable and strong ECL emission in the presence of coreactant K₂S₂O₈,which makes the ECL signal"on".Through antigen-antibody reaction,MRSA binds Pd Mo-anti-SA and anti-PBP2a modified on the surface of Zn Cd S to form double-antibody sandwich-like complexes.The Pd Mo-anti-SA plays a quenching role by receiving electrons from S₂O₈^2-that block the formation of excited state Zn Cd S*,which makes the ECL signal"off".Thus,the concentration of MRSA was detected via detecting ECL signal.There was a linear relationship between the ECL intensity and the logarithm of MRSA concentration in the range of 1.5×10²-1.5×10⁸ cfu?m L^-1,and the detection limit was 22 cfu?m L^-1.The proposed ECL immunosensor also showed good stability,specificity,reproducibility and acceptability in urine samples.Therefore,this method may become a potential application tool for the detection of drug-resistant bacteria in early clinical diagnosis.In conclusion,detection methods of multi-resistant bacteria with the features of easy operation,low cost and short time were established in the research.The proposed methods also have good analytical performance and cover the shortage of the traditional analysis methods.Therefore,the methods may provide a potential technology platform for clinical diagnosis,drug usage,treatment monitoring and prognosis evaluation of multidrug resistant bacteria infection.Moreover,the research could afford new ideas to explore detection technologies of drug-resistant bacteria.