Research On The Detection Of MicroRNA-21 And Carcinoembryonic Antigen Using Photoelectrochemical Sensors

Photoelectrochemical（PEC）analysis method is a newly developed detection method in recent years.Photoelectrochemical sensors generate electrical signals under the excitation of light.The separation of their excitation source and output signal makes them have higher sensitivity and lower background signals.In addition,PEC biosensors are simpler,reliable,and easier to miniaturize.These advantages enable its rapid application in the detection of environmental pollutants,proteins,nucleic acids,various biological molecules,and tumor cells.In this work,we focused on several photoactive materials and several signal amplification techniques,and applied them to PEC biosensors,realizing the trace detection of cancer markers miRNA-21 and carcinoembryonic antigen（CEA）.（1）A new type of labeling free photoelectric chemical biosensor was constructed.Firstly,the photosensitive materials DBCO modified carbon nitride（g-C₃N₄）and azide modified Cd Qds were synthesized,which obtained extremely strong photocurrent response through the formation of heterojunctions through click chemistry.The synthesized DNA hydrogel can block the contact of optoelectronic materials from forming a heterojunction structure,which in turn led to a reduction in photocurrent.In the presence of miRNA-21,RCA reaction was initiated,which in turn produces many repetitive sequences used to activate the CRISPR/Cas12a system.The activated Cas12a enzyme is used to cleave the DNA hydrogel by its trans cleavage activity.Thus,the photocurrent was enchanced due to the Click reaction between the photoactive material.In this way,highly sensitive deection of miRNA-21was achieved through the increase of photocurrent.Through the amplification of RCA and CRISPR/Cas12a systems,the sensitivity of PEC biosensors has been significantly improved.（2）A self powered photoelectrochemical aptasensor was constructed.Bi VO₄/Zn In₂S₄with a Z-type heterojunction was used as a photoelectric anode to provide a stable carrier for the cathode and enhance the cathode signal.Au NP/Cu Bi₂O₄served as a photocathode for the construction of a sensor platform.In the presence of CEA,the CEA was captured by the aptamer Apt-1 fixed to the electrode.Then the aptamer Apt-2 with a Hemin/G4 structure was captured to the electrode forming a sandwich structure.Hemin/G4 can catalyzes the oxidation of4-chloro-1-naphthol（4-CN）into insoluble precipitates,which greatly reduces the photocurrent signal and enables the trace detection of CEA.