Antibacterial/biomarker Detection Based On Surface-enhanced Raman Light Scattering Of Specific Reactions

Antimicrobial agents are chemicals that keep the growth or reproduction of certain microorganisms below the necessary level for a given period of time.They have good biocompatibility,but poor water solubility,and are mostly hydrophobic.Biomarkers are a class of compounds closely related to the occurrence of diseases,including small molecules in organisms and biological macromolecules such as proteins,enzymes and nucleic acids.By measuring the concentration of biomarkers in the body,the progression of disease can be predicted to a certain extent.Improper use of antimicrobial agents or abnormal content of biomarkers can directly or indirectly affect or reflect human health.High performance gas/liquid chromatography and mass spectrometry were used to detect small molecular compounds of antimicrobial agents.As for biomarkers,due to their biological activity,they can usually undergo specific physical and chemical reactions,and they are mostly detected by enzyme-linked immunoassay,fluorescence probe,etc.Although these methods are accurate and reliable,the experimental process involved is very complex and time-consuming,so there is room for improvement.Surface-Enhanced Raman Scattering is a fast,non-invasive and highly specific spectroscopic technique,which has a very great application prospect in food safety,environmental monitoring and biomolecular detection.As the molecular fingerprint spectrum,SERS contains rich fingerprint information and can identify specific substances in complex samples without labeling.What’s more,SERS has super high sensitivity and can realize single molecule detection.Commonly used SERS substrates are mostly hydrophilic gold(Au)and silver(Ag)nanosols,which are friendly to watersoluble molecules to be tested.However,the antimicrobial molecules with poor water solubility are far away from the SERS substrate surface,leading to unsatisfactory test results.As for the SERS detection of biomarkers,the existing problem is that the cross-sectional area of the biomarker molecule itself is small,so both Raman and SERS signals are relatively low.In this paper,by introducing intermolecular force or specific biochemical reaction,the molecules to be measured were actively pulled to the surface of SERS substrate or transformed through specific chemical reaction,so as to realize direct or indirect SERS determination of them.The main research contents and achievements are as follows:1.Triclocarban(TCC)is a small antimicrobial molecule with poor water solubility,and it is difficult to get close to the surface of hydrophilic Au nanoparticles,so the SERS detection effect is not so well.According to the literature review,triclocarban has a high solubility in acidic medium,so it can be changed by adjusting the p H of the solution.In this work,hydrophilic and stable Au nanoparticles were synthesized.Acids were used to regulate the p H of the Au nanoparticles,so as to increase the solubility of triclocaraban and make more triclocaraban molecules close to the substrate surface.At the same time,Au nanoparticles were properly aggregated to improve the SERS enhanced effect.Through this measure,the SERS response of triclocarban was enhanced from both sides to realize the rapid and sensitive detection of triclocarban.2.Studies have shown that high intracellular nitroreductase(NTR)content is associated with reduced intracellular oxygen content.Because NTR belongs to biological macromolecule and its own Raman scattering cross-sectional area is small,NTR cannot be directly detected by SERS.However,NTR has a specific biological enzyme activity,that is,in the presence of coenzyme reduced nicotinamide adenine dinucleoside acid(NADH),NTR can catalyze the reduction of the nitro group on the aromatic compounds to the corresponding amino group.In this work,NTR specific recognition and catalytic reduction of probe molecule p-nitrophenylthiophenol(4-NTP)were used to generate the product p-aminophenol(4-ATP),and then 4-ATP was modified on the surface of Au@Ag substrate with good SERS enhanced performance through Ag-S bond,and the NTR activity was determined through the conversion rate of quantitative reaction.Based on the SERS sensing strategy,the specificity and sensitivity detection of NTR were realized,and the inhibitors of NTR were effectively screened.This SERS sensor is expected to be applied to the detection of intracellular nitroreductase and provide a new technical means for clinical diagnosis.3.Resveratrol(RES)is a kind of natural polyphenols with good antioxidant activity,which plays an important role in the prevention of cancer,cardiovascular protection and anti-aging,etc.,and is widely added in some skin care products.Therefore,in order to effectively evaluate the efficacy of skin care products,it is necessary to carry out quantitative determination of RES.However,RES is hard to dissolve in water,and the effect is not ideal when the common Au nano-sol substrate is used for SERS detection.In this work,we first synthesized SERS enhancement performance of popcorn shaped Au nanoparticles,then on the basal surface through the Au-S key link molecules 3-mercaptopropionic acid(MPA).The introduction of MPA can produce molecular inter-atomic forces-hydrogen bonding,and RES will be close to the basal surface.Thereby it can enhance the SERS response of RES and realize the specifical rapid sensitive detection.