Preparation Of Nanomaterials Modified Electrodes And Their Application In Photoelectrochemical Bioanalysis

Photoelectrochemical?PEC?enzymatic biosensors,a new subclass of enzymatic biosensors,could convert the specific biocatalytic events into electrical signals via the interactions between the semiconductor species and the biocatalyzed reaction chain.PEC enzymatic biosensors integrate the inherent sensitivities of PEC bioanalysis and the selectivity of enzymes and thus share their both advantages.Ever since the very beginning of PEC bioanalysis,the study on PEC enzymatic biosensors has been a focus of significant research due to its relevant importance.At present,most of the PEC enzymatic assays were necessitate the immobilization of natural enzymes on the electrode surface,which enhence steric effect for hindering the interaction between the photoelectrochemically active materials and the enzymatically generated species,inevitably deteriorate the catalytic activity of the enzymes during in the process of enzymatic immobilization and scatter the light aimed for exciting the photoactive materials.In this paper,three kinds of split-mode PEC enzymatic biosensors were developed,which realized high throughput detection of multiple enzyme activities.In addition,the determination of?-fetoprotein?AFP?was achieved by the combination of enzymatic reaction and immune reaction.The major contents are described as follows:1.A split-mode high throughput photoelectrochemical enzymatic biosensorIn this chapter,horseradish peroxidase?HRP?catalyze the oxidation of catechol?CA?by hydrogen peroxide.And the oxidation is the electron acceptor of PbS quantum dots,which enhance the cathodic photocurrent of PbS quantum dots.We used this principle to constructed the PEC enzymatic biosensors.In this method,the catalytic reaction of HRP was carried out in96 well microtiter plates,then 1,2-benzoquinone was connected to the electrode surface via the reaction of quinone-ammonia between 1,2-benzoquinone and chitosan.This process realized the high-throughput detection.After that,this strategy was also extended to the ALP/HRP cascade and glucose oxidase?GOx?/HRP cascades,which realized the detection of glucose concentration and ALP activity.2.A split-mode multifunctional enzymatic biosensor based on electron transfer between NiO/PbS electrode and 1,2-benzoquinone with its derivativesThe tyrosinase?TYR?-stimulated oxygenation of phenols or L-tyrosine to generate 1,2-bezoquinones or L-dihydroxyphenylalanine?L-DOPA?quinone.The 1,2-bezoquinones or L-DOPA quinone generated by the TYR-based reaction are covalently attached on to the surface of the photocathode NiO/PbS/CS via quinone–amine reactions,and the attached benzoquinones compounds acted as efficient electron acceptors of NiO/PbS to promote the output of the cathodic current.To elaborate,a high-throughput split-mode protocol by coupling the microplate-based enzymatic reaction and the PEC detection was developed for probing the activity of TYR with high sensitivity.In addition,the sensitive probing of multiple enzyme was further implemented to follow bienzyme catalytic cascades involving ALP/TYR and?-galactosidase?Gal?/TYR.3.A novel PEC immunosensor based on CA to increase the photocurrent of g-C₃N₄nanosheetsWe introduce a novel,split protocol for the PEC immunoassay of without the need for fixing antibody/antigen on the surface of electrode,which is based on the separation of the PEC detection process and the enzymatic reaction process.ALP catalyzed the hydrolysis of the substrate of o-phosphonoxyphenol?OPP?to in situ generated an electron donor of CA,which greatly promoted the photocurrent intensity of graphitic carbon nitride?g-C₃N₄?.High-throughput and improved sensitivity was achieved through a split-type PEC protocol,which separated the enzyme reaction?conducted in microwell plates?and the PEC detecting?made in a PEC cell?in different sites,avoiding the steric hindrance for the reaction between the electron donor and the immobilized g-C₃N₄.This signal-on PEC sensor showed excellent analytical performance to the activity of ALP.The activity of ALP was detected from 0.07 U/L to 110 U/L.On the basis of the high sensitivity of the response of the method to ALP,immunoassay of AFP was realized with a detection linear range from 0.5 pg/mL to 100 ng/m L.A detection limit of0.2 pg/m L was achieved for AFP.