Bioassay For Detection Of Enzyme Activity Constructed By Prussian Blue Nanoparticle And Sulfur Quantum Dots

Biosensors for biomarker detection are simple,convenient and widely used.Nanoparticles have good biocompatibility,large specific surface area,and have interesting physical as well as chemical propertis.Combining the above advantages,we did the following two research works:1.Sensitive colorimetric assay for the determination of alkaline phosphatase activity utilizing nanozyme based on copper nanoparticles modified Prussian Blue Nanocubes（named Cu@PB NCs）.In this work,we synthesized Cu@PB NCs nanomaterials by depositing copper nanoparticles（Cu NPs）onto the surface of PB NCs（PB Nanocubes）.Utilizing peroxidase（POD）activity of Cu@PB NCs,a colorimetric biosensor with high efficiency and sensitivity for ALP activity was developed.The modification of PB NCs by Cu NPs improved the catalytic activity of PB NCs.The POD catalytic activity of Cu@PB NCs was used to catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB）to form blue compound ox TMB in the presence of H₂O₂.In addition,pyrophosphate radical（PPi）has a strong inhibitory effect on the peroxidase activity of Cu@PB NCs.However,ALP can hydrolyze PPi into phosphate ions and restore the peroxidase activity of Cu@PB NCs.Therefore,ALP activity was detected based on the change of Cu@PB NCs peroxidase activity.The linear range of the assay towards ALP was 0.1-50 m U·ml^-1,and the detection limit（LOD）was 0.08 m U·m L^-1（S/N=3）.It is expected to be used to detect the activity of ALP in actual samples.2.Sulfur quantum dot based fluorescence assay for lactate dehydrogenase（LDH）activity detection.The fluorescence of sulfur quantum dots（SQDs）synthesized by the microwave method can be specifically enhanced by nicotinamide adenine dinucleotide（NAD⁺）.Based on this characteristic,we reported a sensitive fluorescence assay for LDH detection.In the presence of reductive coenzyme I（NADH）,LDH catalyzes the reduction of pyruvate to lactic acid,and transform NADH to NAD⁺,which specifically enhances the fluorescence intensity of SQDs.Based on the fluorescence intensity increase,the assay achieved detection of LDH in the range from 500–40000 U·L^-1,with limit of detection of 262U·L^-1.The assay was successfully applied for the detection of LDH activity in serum,indicating potential clinical applications.