Preparation Of Novel Optoelectronic Nanocomposites And Their Application In Disease Marker Detection

The early detection of biomarkers is of great significance for the clinical diagnosis and follow-up treatment of diseases.Photoelectrochemical(PEC)bioanalysis technology is a novel and promising method of biomolecule detection emerging in recent years.PEC biosensor uses light as the excitation source and electric signal as the output detection signal,which can effectively reduce the background signal and has the advantages of high sensitivity,fast response and strong specificity.In the design of PEC sensor,the determination of photosensitive materials is particularly critical.The photoelectric materials with excellent photoelectric performance and high photoelectric conversion efficiency are the key factors to improve the performance of biosensor.In this thesis,a series of photoelectric chemo-biosensors were constructed for biomarker detection based on the preparation and synthesis of novel nanocomposite materials.The main research contents are as follows:(1)A facile and sensitive self-powered cathodic photoelectrochemical(PEC)aptasensor is reported for the detection of prostate-specific antigen(PSA)based on CuO-Cu₂O nanowire array grown on Cu mesh(CuO-Cu₂O NWA/CM)as electrode.The CuO-Cu₂O nanowire arrays grown directly on the substrate have high specific surface area and abundant active sites,which ensure their high photocatalytic efficiency.In addition,CuO-Cu₂O nanowire array is a heterostructure with narrow mixing band gap and wide absorption band,which can effectively inhibit electron/hole recombination,so it has a high photoelectric conversion efficiency.The experimental results show that the sensor has high response speed,wide linear range,high stability,high sensitivity,high detection limit of 3 pg/m L,and high stability and specificity.The proposed CuO-Cu₂O NWA/CM can be considered a promising visible light-responsive photoactive material for fabrication of PEC aptasensor with high performance.(2)MicroRNA-21(miRNA-21)is a vital biomarker for the early diagnosis of cancers.However,miRNA-21 occurs in low abundance,thus making its sensitive detection especially important,but difficult to achieve.Therefore,in this work,a novel photoelectrochemical(PEC)biosensor based on an enzyme-free nucleic acid dual-amplification strategy combined with an enzyme mimic to catalyze the deposition of benzo-4-chlorohexadienone(4-CD),as an efficient quencher,is reported for the ultrasensitive detection of miRNA-21.Bi OCl-Bi OI,a photosensitive material,is used as a tag to provide a strong initial PEC signal.A limited amount of target miRNA-21 can trigger the formation of long DNA duplexes on an electrode,owing to the synergistic effect from the enzyme-free nucleic acid dual-amplification strategy of entropy-driven strand displacement reaction(ESDR)amplification and hybridization chain reaction(HCR)amplification.Abundant manganese porphyrin(Mn PP)can be embedded in the long DNA duplexes to act as a horseradish peroxidase(HRP)-mimicking enzyme to catalyze the transformation of some reductive reagents on the electrode surface,resulting in a significant reduction in photocurrent intensity by effectively hampering electron transfer.Based on the cascading integration between enzyme-free nucleic acid dual-amplification strategy and catalytic precipitation reaction by enzyme mimic,the current PEC biosensor exhibits outstanding performance for miRNA-21 detection with an ultralow detection limit of33 a M in a very wide range from 100 a M to 1 n M.This work provides a new avenue to-ward the ultrasensitive detection of various miRNAs with low abundance and holds promise for the ultrasensitive detection of clinical and biochemical samples.(3)A unique bi-enzyme photoelectrochemical(PEC)biosensor is developed for selective and sensitive detection of glucose based on bi-enzyme cascade catalytic in-situ precipitation for signal amplification.In this design,the composites of In₂S₃and In₂O₃ with better photoelectrochemical properties are used as the photoactive material.It is noteworthy that In₂S₃ and In₂O₃ are able to produce a heterojunction with overlapped band gap structure,which can effectively separate photogenerated electrons and holes,and increase their photoelectric conversion efficiency.In the presence of target molecules glucose and 4-CN,glucose oxidase(GOx)and horseradish peroxidase(HRP)can catalyze the formation of insoluble precipitates4-CD on the electrode surface,which effectively hinders the electron transfer on the electrode surface,thus significantly reducing the photocurrent response of glucose detection.The results show that the detection range of the sensor is 0.1?M to 10 m M,and the detection limit is 0.04?M.This strategy provides a new method for the determination of glucose.