Application Of Visible Light-excited Ir(?) Complex Photoelectric Functional Materials In Biochemical Analysis

Photoelectrochemical?PEC?bioanalysis refers to the photo to electric conversion resulting from electron excitation and subsequent charge transfer of a photoexcited material produced by a light.PEC bioanalysis has been widely used in clinical diagnosis,environmental analysis,biomedicine,food analysis and others,especially in the field of biosensing and its detection targets involves DNA/RNA analysis,immune analysis,protein and cell correlation analysis.As a new analytical method,PEC bioanalysis shows great potential,however,this method is still rudimentary.At present,there are too few effective photoelectric materials for biochemical analysis,and the sensitivity and stability are still insufficient.For that reason,based on the advantages of wide range of photophysical and electrochemical properties of Ir???complexes,three kinds of Ir???complexes with high molar absorbance in the visible long-wave direction were synthesized by designing ligands with strong light-capturing ability.Based on the specific recognition of aptamers and thrombin,as well as nanomaterials and DNA signal amplification techniques,which are used for highly sensitive and highly specific detection of thrombin and microRNA?miRNA?in complex biological systems.The main contents are as follows:1.Application of the labeled metal Iridium???complex with coumarin 6 as a cyclometallated ligand in thrombin detection.A cationic iridium???complex,[?C6?₂Ir?dcbpy?]⁺PF₆^-was prepared,employing C6 as cyclometalated ligand and 2,2?-bipyridine-4,4?-dicarboxylic acid?dcbpy?with pendent carboxyl groups as an auxiliary ligand to allow for the convenient covalent attachment.The UV-vis absorption,electrochemical,and PEC characters of the Ir???complex were studied.And the probable mechanisms for photocurrent generation were deduced.Significantly,the iridium???complex exhibits strong absorptions in the visible range with?of more 40000 M^-1·cm^-1 at 480nm.As evidenced by our research,the as-prepared Ir???complex exhibited a large cathodic photocurrent up to 245 nA/cm² using dissolved O₂ as electron acceptor irradiated by visible light.The AuNPs-based PEC nanoprobe has been constructed using[?C6?₂Ir?dcbpy?]⁺PF₆^-as signal reporter,and further been applied to construct sensitive PEC platform based on the Exo III-assisted recycling amplification for thrombin detection.Ascribed to excellent PEC performance of the Ir???complex and the efficient amplifying strategy,the photocurrent intensity was logarithmically related to the thrombin concentrations across the range from 20 fM to 10 pM with a correlation coefficient of 0.9936.The detection limit was estimated to be 9.6 fM at3?,suggesting prominent detection sensitivity compared with those of previously reported methods.The applicability of the proposed PEC assay in real samples was evaluated by the standard addition method and the feasibility of this proposed method in real biological samples with satisfactory results,which provides a more excellent sensing platform for the future fields of biomedicine,biochemical analysis and clinical diagnosis.2.Application of the intercalated metal Iridium???complex with coumarin 6 in microRNA detection.A iridium???complex based photoactive species,[?C6?₂Ir?dppz?]⁺PF₆^-,was synthesized with coumarin 6?C6?as a cyclometalated ligand and dipyrido[3,2-a:2?,3?-c]phenazine?dppz?as an ancillary ligand.The photophysical and electrochemical properties of the complex have been investigated.And the probable mechanisms for photocurrent generation were deduced.It exhibits intense visiblelight absorption with a molar extinction coefficient up to 9.8×10⁴ M^-1·cm^-1 at485 nm.By illumination with 490 nm light,cathodic photocurrent up to 260 nA/cm²was observed with dissolved O₂ as an electron acceptor.by UV-vis absorption spectrum and cyclic voltammetry data.Adopting[?C6?₂Ir?dppz?]⁺PF₆^-as photoactive intercalator,a visible-light driven PEC detection platform was successfully fabricated for microRNA detection based on an enzyme-free hybridization chain reaction as an amplification strategy.As expected,the PEC platform exhibited a wide linear response to miRNA ranging from 1 fM to 10³ fM and a low detection limit of 0.23 fM,with good stability and high specificity.At the same time,miRNA-122b was detected in human breast cancer cells?MCF-7 with high miRNA-122b expression?and human liver cancer cells?HEPG-2 with low miRNA-122b expression?.The sensor has a good photoelectric response to miRNA-122b in different cells and has important medical value.3.Application of the metal Iridium???complex with coumarin ligand in thrombin detection.A iridium???complex based photoactive species,[?C-Phen?Ir?hpba?₂]⁺PF₆^-,was synthesized with C-Phen and 4-2-pyridine benzoaldehyde?hpba?as an ancillary ligand.The visible light absorption,electrochemical and photoelectrochemical properties of the iridium complexes were systematically investigated.Studies have shown that iridium complexes with C-Phen as ligands improve charge transfer efficiency,photoelectric transfer efficiency and photocurrent intensity.The AuNPs nanoprobes were prepared by combining the advantages of the aldehyde groups of the complexes.A coumarin-sensitized labeled cyclic metal Iridium???complex and a neighboring binding-inducing chain displacement cycle and catalytic hairpin were constructed.The photoelectrochemical sensor that assembles the amplification strategy achieves an enzyme-free,sensitive detection of thrombin.Studies have shown that[?C-Phen?Ir?hpba?₂]⁺PF₆^-has good biocompatibility and the photocurrent intensity was logarithmically related to the thrombin concentrations across the range from 10^-10 M to 10^-12 M with a correlation coefficient of 0.992.The detection limit was estimated to be 0.69 pM at 3?.The PEC platform has a high specificity,stability and repeatability.And the prepared biosensors have certain potential value in future.