A Photoelectrochemical Cell Analysis Platform Constructed By Sulfide Semiconductor Nanocomposites

In recent years,a novel analytical technique was developed based on the marriage of photoelectrochemical(PEC)process and biological recognition.That was PEC bioanalysis.The complete separation of excitation source and detection signal in PEC bioanalysis could greatly reduce the background signal,which would improve the sensitivity.The PEC biosensor with lots of advantages,including quick response,high sensitivity,simple design,might show widespread application in biological analytical chemistry.Cell is a component unit of organism,and the research of cells have significance for clinical diagnostics.Semiconductor nanomaterials were widely used in PEC biosensor due to their excellent optical properties,electrical properties and good biocompatibility.In this paper,on the basis of sulfide semiconductor nanocomposites,three PEC biosensing platforms for cell analysis with signal amplification induced by the formation of heterojunction or localized surface plasmon resonance(LSPR)of Au nanoparticles were developed.1.A novel PEC bioanalysis platform was developed based on dual signal amplification by C3N4/PbS heterojunction as PEC substrate and enzyme catalysis of catalase.The photoelectric conversion efficiency of C3N4 nanosheets was greatly improved,and it achieved about 10 times improvement of photocurrent compared to that of pure C3N4 nanosheets modified electrode due to the formation of heterostructure.After introducing with catalytic effect of G-quadruplex/hemin@Pt NPs towards H2O2,oxygen was in situ generated and acted as electron acceptor,which blocked the recombination of electron-hole pairs and further enhanced the photocurrent response.On the basis of C3N4/PbS heterojunction as PEC substrate and the catalase-like catalytic activity of G-quadruplex/hemin@Pt NPs,the developed PEC bioanalysis platform was used for H2O2 detection.Under the applied potential of-0.15 V and the light irradiation of 405 nm,the fabricated PEC analysis platform detected H2O2 in vitro with a linear range of 10 to 7000?M.The detection limit was estimated to be 1.05 ?M at a signal-to-noise ratio of 3.Besides,the analysis platform with good selectivity was successfully applied to the detection of H2O2 release from cells,which had a promising prospect for living cells monitoring and diagnosis of oxidative stress-related diseases.2.Under red light excitation,a highly sensitive and simple PEC biosensing strategy based on LSPR of Au NPs as signal amplification was designed for scatheless cell assay.The two-dimensional layered WS2 nanosheets were employed as photoelectrochemically active species,which could harvest red light to produce electron-hole pairs.Subsequently,the photoinduced electrons were injected into indium tin oxide(ITO)electrode and the holes were scavenged by electron donor(ascorbic acid)in solution,generating anodic photocurrent.After the assembly of Au NPs on WS2 nanosheets,the photocurrent enlarged?31 times due to the LSPR of Au NPs improved the photoelectric conversion efficiency of WS2 nanosheets and amplified the PEC signal.MUC1 was introduced as a marker to monitor the breast tumors.Using MCF-7 cells as model analyte,MUC1 aptamer specifically anchored MCF-7 cells because of their high overexpression of MUC1.When the MCF-7 cells were specifically captured by the aptamer,an obvious decline of photocurrent response was observed.Based on the variation of photocurrent intensity before and after capturing the cells,a biosensing platform for scatheless detection of MCF-7 cells under the irradiation of long wavelength light was proposed.The developed PEC biosensor detected MCF-7 cells in a wide linear range from 1×102 to 5×106 cells/mL with a low detection limit of 21 cells/mL at a signal-to-noise ratio of 3 under red light irradiation of 630 nm and the applied potential of 0.1 V.Besides,due to the use of low toxic PEC active material,red light irradiation,the LSPR of Au nanoparticles and high specificity of aptamer in the proposed PEC biosensor,it exhibited good performances such as scatheless detection,high sensitivity,good selectivity and so on.3.Water-dispersible Ag2S QDs with bright fluorescent emission in the near-infrared(NIR)window were synthesized directly by one-pot synthesis.Under NIR light excitation,a highly sensitive and super-simple PEC biosensor based on LSPR of Au NPs as signal amplification was designed for scatheless cell assay.After the assembly of Au NPs with Ag2S QDs,the photocurrent enlarged?3.5 times due to the LSPR of Au NPs improved the photoelectric conversion efficiency and amplified the PEC signal.Beside,NIR Ag2S QDs are suitable for the construction of PEC biosensing platform owing to their good water solubility,high biocompatibility,hypotoxicity and NIR-emission.Based on highly specific binding between 4-mercaptophenylboronic acid and sialic acid in the terminal of cell surface carbohydrates,the PEC biosensor was successfully applied to the quantitative determination of cells and dynamic evaluation of cell surface glycosylation.Under NIR light irradiation of 810 nm and the applied potential of 0.15 V,the PEC cytosensor for MCF-7 cells determination exhibited a linear range from 1x102-1x107 cells/mL with a detection limit of 100 cells/mL.The simple construction process greatly reduced the time.The biosensor exhibited some excellent performances such as facile fabrication,rapid response,widely linear range and scatheless detection.Furthermore,the biocompatibility and NIR light excitation of Ag2S QDs realized scatheless assay,which would have an expansive perspective of applications to the detection of any other biomolecule by the construction of versatile PEC platforms.