Construction And Application Of Photoelectrochemical Sensors Sensitized With Cyclometalated Iridium Complex

As a high-risk disease with mortality,highly sensitive detection of biomarkers miRNAs is extremely important,which is helpful for early diagnosis and disease monitoring.As a new analytical technique,photochemical analysis has the advantages of low background signal and high sensitivity.Therefore,the application of photochemical biosensor in the detection of cancer markers has a broad application prospect.However,the detection sensitivity of photochemical biosensors still needs to be improved.Sensitization strategy is an ideal choice to improve the photoelectric conversion efficiency of photoactive materials in PEC biosensors.Therefore,in this paper,ring metal iridium complexes and quantum dots were synthesized,and a super-sensitive photoelectrochemical biosensor for miRNAs detection was constructed by means of signal amplification technology through synergistic sensitization between them.The main contents are as follows:(1)A series of iridium complexes with 2-phenylpyridine as the main ligand and 1,10-phenanthroline as the auxiliary ligand were synthesized,and their structures were characterized by ¹HNMR and MS.The optimal sensitization conditions between iridium complexes and quantum dots were studied.Finally,under the condition of 0.2V bias potential,[Ir(ppy)₂(pha)]⁺PF₆^-can amplify the signal of CdSe quantum dots 1.5times.[Ir(ppy)₂(pha)]⁺PF₆^-.Under the condition of 0.2 V bias potential,the signal of CdS quantum dots can be amplified by 5 times.(2)A super-sensitive photoelectrochemical biosensor was constructed based on the amplification of self-assembled biological signals of catalytic hairpins and the synergistic sensitization between iridium complexes and CdSe quantum dots.miRNA-20b formed a double helix structure of H1-H2-S1 through enzyme-free catalytic hairpin cycle,which was used for cutting iridium complexes.Super-sensitive detection of miRNA-20b was successfully carried out through co-sensitization between the two.The linear range of the constructed sensor is between 1 amol L^-1 and 500 fmol L^-1,and the detection limit is 0.36 amol L^-1.This efficient PEC biological detection system can be extended to detect a variety of other biomarkers,providing a new approach for early clinical diagnosis.(3)An"off-on"type photoelectrochemical biosensor was constructed based on entropy-driven biological signal amplification technology and the synergistic sensitization between iridium complexes and CdS quantum dots.The low concentration of miRNA-126 triggered the entropy-driven DNA cycle amplification of the thermal stability,and eventually generated a large number of CdS QDS-1*2*3*4*-123-Fe₃O₄@SiO₂ double-chain structure,which was used for cutting iridium complexes.Through the co-sensitization between the two,the ultra-sensitive detection of miRNA-12 was realized.The sensor has the advantage that the background signal is nearly zero.The entropy-driven amplification system and superparamagnetic Fe₃O₄@SiO₂ particles make the photochemical sensor characterized by good thermal stability,high reaction efficiency and good selectivity.Finally,the successfully constructed photochemical biosensor realized the ultra-sensitivity detection of mir NA-126,with a linear range of10 amol L^-1 to 1 pmol L^-1 and a detection limit of 3.7 amol L^-1,and was successfully applied to the detection of mir NA-126 in human serum.