Construction Of Photoelectrochemical Biosensor Based On In-situ Covalent Organic Polymer Materials And Its Applications

In recent years,photoelectrochemical(PEC),as an emerging subject,has rapidly attracted the interest of many researchers due to its advantages of cheap instrument,simple operation,high sensitivity and low background signal,and has become a hot topic in the research field.Coupling photoirradiation with electrochemical detection,PEC sensors have the advantages of both optical methods and electrochemical sensors.Here,we combined the PEC detection technology with covalent organic polymer(COP)film to develop two simple PEC biosensor with high sensitivity and high specificity,and it can specific quantitative detect of cell lung cancer(A549 cells)and M.Sss I methyltransferases(M.Sss I MTase).Sensitive detection of cancer cells plays an important role in early clinical diagnosis of cancer,and the PEC sensors with high sensitivity and good selectivity may provide new approaches for cytosensing.Herein,we constructed a novel type of cathodic PEC cytosensor based on the integration of p-type COP film and palladium nanoparticles(Pd NPs).The COP film is in-situ grew at room temperature on the transparent indium doped tin oxide(ITO)glass substrates,and they subsequently assemble with Pd NPs to immobilize aptamers via Pd-S chemistry.Pd NPs can catalyze the oxidation of dopamine by H₂O₂ to produce the oxidation product of dopamine,which can serve as the electron acceptors of COP for the generation of an enhanced photocurrent.In the absence of A549 cells,the electrons in the conduction band of COP transfer to the oxidation product of dopamine,while the electrons on the electrode transfer to the hole of the valence band,leading to a high cathodic photocurrent.In the presence of A549 cells,trapped A549 cells efficiently cover the electrode to block the contact between the Pd NPs/COP electrode and dopamine,resulting in the decrease of oxidation products and consequently the generation of a low PEC signal.This PEC cytosensor has the advantages of high sensitivity,good selectivity and stability,and it had a detection limit of 8 cell m L^-1 and a dynamic range of 6 orders of magnitude.We have proposed a novel type of dye-sensitized and gold plasmon-enhanced cathode PEC biosensor using p-type COP film as the photocathode materials for sensitive and selective detection of M.Sss I MTase activity.In this strategy,two complementary single-stranded DNAs(ss DNAs,i.e.,biotinylated DNA-1 and HS-labeled DNA-2)that contain specific recognition sequence 5?-CCGG-3?can form a double-stranded DNA(ds DNA)probe.When M.Sss I MTase is present,the methylated ds DNA probes cannot be digested by Hpa II endonuclease,leading to one end of ds DNA can be fixed on the electrode surface through specific streptavidin-biotin interaction.Meanwhile,Au NPs can be attached to the other end of the ds DNA on the electrode through Au-S bond,and rhodamine B(Rh B)can insert into ds DNA groove.When the electrode was exposed on the light,a higher photocurrent was generated due to the SPR action of Au NPs and the sensitization of dye.In the absence of M.Sss I MTase,the unmethylated ds DNA probe will be digested by Hpa II endonuclease.Without the connection and load of ds DNA,Au NPs and Rh B cannot be introduced into the electrode surface,resulting in a weak photocurrent.Under the optimum conditions,the cathode photocurrent of the PEC biosensor increases linearly with the logarithm of the M.Sss I MTase concentration(0.05?100U m L^-1.It can accurately detect the M.Sss I MTase in human serum,with potential applications in drug discovery and clinical diagnosis.