Construction Of Photoelectrochemical Biosensor Using Titanium (?) Oxide Nanotube-based Nanocomposite And Its Analytical Applications

Photoelectrochemistry?PEC?is a kind of rapidly developing detection technique,which possesses merits of high sensitivity,due to the separation of excitation source,and selectivity,short response time,simple equipment,low cost,and easy miniaturization and caused more and more attention.PEC methods have been used in pharmaceutical analysis,biomolecular analysis and environmental analysis.Malignant tumors have become a major threat to human health.Sensitive detection of tumor markers is of great importance.Highly sensitive and selective PEC biosensors based on the excellent PEC properties of nanocomposites and specificities of aptamers or antibodies were proposed for detection of tumor markers,which were of great significance.The synthesized TiO₂ nanotubes?NTs?,CdS quantum dots?QDs?and CdS:Mn/TiO₂ NTs nanomaterials have favorable photoelectric activity and stability,and the proposed PEC biosensors possess high sensitivity,selectivity and stability and provide new ways for fast and sensitive detection of tumor markers.The main highlights and researchi contents are as follows.1.A label-free PEC aptasensor for the sensitive and selective determination of carcinoembryonic antigen?CEA?was constructed based on a CdS QDs sensitized TiO₂ NTs electrode.TiO₂ NTs with highly ordered structure and more active sites than bulk TiO₂ were prepared with an electrochemical anodic oxidation process.The CdS QDs were immobilized on the TiO₂ NTs using poly?diallyldimethylammonium chloride?as a bridge.Due to the energy level match between TiO₂ and CdS,the CdS QDs/TiO₂ NTs electrode exhibits excellent PEC performance.The large surface area of the electrode also allows for capturing large numbers of aptamers.The fine PEC performance and the large surface area of the electrode greatly enhanced the detection sensitivity.Under the optimal conditions,the prepared PEC aptasensor presents desirable analytical properties for the determination of CEA in the range of 0.05–10ng m L^-1 with a detection limit of 0.014 ng m L^-1.The application of the designed protocol was investigated by analyzing CEA in human serum samples with recoveries from 80.0 to 115.0%,and the relative standard deviation?RSD?was less than 8.6%.This simple and sensitive method provides an alternative tool to standard biochemical assays.2.A label-free PEC immunosensor based on CdS:Mn/TiO₂ NTs electrodes for the sensitive and specific detection of prostate specific antigen?PSA?was designed.A successive ionic layer adsorption and reaction was used to deposit CdS:Mn composite onto the surface of Ti O₂ NTs electrodes to form CdS:Mn/TiO₂ NTs electrodes.Combination of TiO₂ and CdS accelerated electron transfer from CdS to TiO₂ and augmented absorption range for light.Doping of Mn²⁺can greatly increase lifetime of electron-hole recombination and increase the PEC response.Under the optimal conditions,the prepared PEC immunosensor presents desirable analytical properties for the determination of PSA in the range of 0.005 to 50 ng m L^-1 with a detection limit of 1.6 pg m L^-1.The application of the designed protocol was investigated by analyzing PSA in human serum samples with recoveries from 90.0%to 112.0%,and the RSD was not more than 3.9%.The results were in agreement with the results offered by Xinyang Center Hospital.