Study On Photoelectrochemical Biosensing Based On Near-Zero-Background And Negative-Background Signal

As an emerging analytical technology,photoelectrochemical（PEC）biosensing has the advantages of miniaturization,simple operation,low c ost and rapid detection,which provides a broad application prospect in the fields of disease diagnosis,environmental monitoring and food safety.At present,most of the developed PEC sensing strategies are devoted to improving the sensitivity of the sensor and broadening the detection range.However,for PEC biosensing,reducing the influence of background signal on the detection signal is still a great challenge.In addition,during the practical application,when the coexisting substances in the tested system undergo the redox reaction or non-specific adsorption,the false-positive or false-negative signals may be generated,which would affect the results.Therefore,the development of PEC biosensors with low background signal,strong anti-interference ability and high sensitivity has become an important topic in the field of analytical chemistry.In this paper,several PEC biosensing platforms with near-zero background signal or negative background signal w ere constructed based on the new sensing strategies and new photoelectric materials,which realized the sensitive detection of Cp G methyltransferase（M.S ss I）,vascular endothelial growth factor 165（VEGF165）,prostate-specific antigen（PSA）,mucin 1（MUC1）an d arsenate[As（Ⅴ）].The main researches are as follows:（1）Taking aluminum titanium carbide as precursor,the bismuth sulfide/titanium carbide（Bi₂S₃/Ti₃C₂）Schottky junction was prepared and then used as photoactive material to construct a label-free and near-zero-background PEC biosensing platform for M.Sss I activity.Firstly,an especially designed double-strand DNA（ds DNA）,including a complementary part and an adsorption part,was formed by hybridization of a long single-stranded DNA with a short single-stranded DNA.The complementary part could be specificly recognized by M.Sss I and Hpa II,while the adsorption part could adsorb the Bi₂S₃/Ti₃C₂.With the help of glutaraldehyde,the ds DNA was immobilized on the（3-aminopropyl）triethoxysilane（APTES）-modified indium-tin oxide（ITO）electrode.In the presence of M.Sss I,it could make the cleavage sites methylated so that the blocked site could not be cleaved by Hpa II.Thus,the adsorption part on the un-cleaved ds DNA could adsorb Bi₂S₃/Ti₃C₂ nanosheets,producing a large photocurrent response.When the M.Sss I is not present,the ds DNA could be cleaved by Hpa II,resulting in a near-zero PEC signal.The photocurrent response value is linear with the concentration of M.Sss I from 0.01 to 30 U·m L^-1 and the detection limit is 0.003 U·m L^-1.This developed method opens a new way for the detection of M.Sss I activity,which has a broad application in the field of disease diagnosis and screening of anticancer drugs.（2）Taking the Cu-based metal organic framework（HKUST-1）as the precursor,the flower-shaped cuprous oxide-copper oxide（Cu₂O-CuO）composite with porous and uniform particle size was synthesized.This composite can induce the photocurrent polarity switching of CdS QDs.Based on this strategy,a highly sele ctive PEC biosensing platform was developed for the detection of VEGF165.Firstly,the hairpin DNA（HP1）was modified on the CdS QDs/ITO electrode which generate a significant anodic photocurrent.And a double-stranded DNA（ds DNA）was designed by hybridization of DNA s1 with the aptamer of VEGF165.In the presence of VEGF165,the DNA s1 would be released on account of the specific interaction between VEGF165 and its aptamer.Then the released DNA s1 could hybridize with HP1 to trigger the catalytic hairpin assembly process between HP1 and the biotin-labeled hairpin DNA2（bio-HP2）on the electrode surface.After several cycles,lots of HP1/bio-HP2 double-strand DNA could be formed on the electrode surface.Finally,the streptavidin-labeled Cu₂O-CuO was introduced to the surface of the CdS QDs/ITO electrode by the special reaction between streptavidin and biotin,causing generation of a big cathodic photocurrent.Due to the porosity,uniform particle size,large specific surface area,and high photoelectric conv ersion efficiency of Cu₂O-CuO,the PEC sensing platform achieves sensitive detection of VEGF165 with a linear range of 1-3000 f M and a detection limit of 0.3 f M.Because the polarity of the background signal is opposite to the polarity of the detection signal,the developed method has the characteristic of negative background signal and could avoid false-positive or false-negative signal,which may have a potential application prospect in the fields of biological analysis and disease diagnosis.（3）Taking the cubic HKUST-1 as precursor,the CuO cube was synthesized by a calcination method.And based on this material,a environment-friendly PEC biosensing platform with negative background signal was constructed for PSA assay.Firstly,the CuO cubes were amino-functionalized by APTES.And the rhodamine（Rh B）-labeled peptide chain was immobilized on the surface of magnetic beads.In the presence of PSA,the Rh B-labeled peptide was cleaved and part of the peptide（P-Pep-Rh B）was obtained by magnetic separation.Based on the host-guest recognition betweenβ-cyclodextrin（β-CD）and Rh B,the P-Pep-Rh B was modified on theβ-CD/Ag In S₂/ITO electrode.Finally,the amino-functionalized CuO cubes were immobilized on the electrodes by using the glutaraldehyde cross-linking method,resulting in a significant cathodic photocurrent.However,without PSA,the CuO cubes could not be introduced onto theβ-CD/Ag In S₂/ITO electrode and a anodic photocurrent could be generated.The developed PEC biosensing platform displayed outstanding performance for PSA assay with a wide linear range(0.1 pg·m L^-1-100ng·m L^-1)and a lower detection limit(0.06 pg·m L^-1),which may have a potential application in the fields of biological analysis and disease diagnosis.（4）A highly selective PEC biosensing platform for the detection of MUC1 was developed by hemin induced photocurrent polarity switching of In₂S₃/ITO electrode.First,the mesoporous zirconia hollow spheres（Zr O₂ HSs）were synthesized by using the silicon dioxide as the template.After that,hemin was loaded into the Zr O₂ HSs and the aptamer of MUC1 was used to block the pores of Zr O₂ HSs based on the specific binding between zirconium ions and the phosphate groups of aptamer.When MUC1 is present,the aptamer could specifically recognize and bind with MUC1,and then leave away from the surface of Zr O₂ HSs,which resulted in the releasing of hemin.Due to the specific binding of hemin to G-quadruplex,the released hemin was captured by the G-quadruplex nanowires on the Au NPs/In₂S₃/ITO electrode,resulting in the switching of the anodic photocurrent to the cathodic photocurrent.It is noted that the polarity of the photocurrent can be observed even at a ultra-low concentration of MUC1(1 fg·m L^-1).The prepared PEC biosensing platform for MUC1 assay has the advantages of wide linear range(1 fg·m L^-1-10 ng·m L^-1),low detection limit(0.48fg·m L^-1),high selectivity and etc.,which will be expected to be used in the field of disease diagnosis.（5）A negative-background-signal PEC biosensing paltform was developed for the selective detection of As（Ⅴ）based on the ferric phthalocyanine（Fe Pc）induced photocurrent polarity switching of the Ag In S₂/ITO electrode.Firstly,the the magnetic tricobalt tetroxide-triiron tetroxide（Co₃O₄-Fe₃O₄）cubes were synthesized by calcination of cobalt iron Prussian blue analogue（Co Fe PBA）.The n the Co₃O₄-Fe₃O₄cubes were functionalized with single-stranded DNA（S1）based on the formation of surface complexes between metal ions and phosphate backbones of sin gle-stranded DNA.In presence of As（Ⅴ）,S1 would be released based on the strong er affinity between As（Ⅴ）and Co₃O₄-Fe₃O₄ cubes.After magnetic separation,the released S1was used to trigger the catalytic hairpin assembly and hybridization chain reaction on the surface of electrode,resulting in the formation of lots of G-quadruplex structures on the Ag In S₂/ITO electrode.Then,the capture of Fe Pc by G-quadruplex occurred and led to the switch of the photocurrent polarity of the Ag In S ₂/ITO electrode from anodes to cathodes.The developed PEC sensing platform for As（Ⅴ）assay has the advantages of wide linear range（10 n M-200μM）and low detection limit（1.0 n M）,which can accurately determine whether the concentration of As（Ⅴ）is more than 10n M according to the polarity of the detection signal.This may have a promising application in the environmental field.