Design And Application Of Sensors For Rapid Detection Of Tumor Markers

Tumor markers play an important role in the early diagnostics and screening of tumors,as well as the monitoring of the curative effect in the process of tumor treatment.It is important to construct nano-biosensors to detect tumor markers with high speed,sensitivity and specificity for tumor diagnostics and treatment.In order to void the disvantages of high-cost,complicated operation and time-consuming of traditional immunoassays against tumor markers,we construct two types of fluorescent nanobiosensors based on mesoporous silica microspheres and Fe₃O₄ nanomagnetic beads with single strand DNA molecules and G-quadruplexes as biomarker receptors.The biosensors can detect CEA,PSA and AFP simultaneously based on multicolor fluorescent signals with high accuracy and speed.The specific work is divided into the following two parts:Firstly,based on mesoporous silica microspheres,two different types of gate switch nano-biosensors are constructed with single DNA molecules and g-quadruplex molecules respectively.Fluorescent dyes are filled in the pores of mesoporous silica microspheres,and DNA molecules designed according to the nucleic acid aptamers corresponding to each tumor marker are used as the gate control to coat the silica microspheres.The substance under test can open the gate of DNA molecule,and the escape of dye will restore the fluorescence signal in the system,so as to determine the presence and concentration of the substance under test.The scheme realizes sensitive detection of three markers.The detection range of CEA,PSA and AFP in the biosensor with single DNA molecule as the gate switch is 10 ng/ml-200 ng/mL,and the minimum detection limit is up to 1 ng/mL.However,biosensor with g-four-stranded DNA molecule as the gating switch has excellent detection effect on CEA,with detection range of 5 ng/ml-200 ng/mL and detection lower limit of 1 ng/mL.In addition to using the fluorescence signal strength of the fluorescence spectrophotometer to determine the target,we can also use ultraviolet lamp for visually detection.Secondly,based on the surface functionalized Fe₃O₄ nanometer magnetic beads and fluorescent-labeled single-stranded DNA molecules,a biosensor for the detection of CEA,PSA and AFP was constructed.Nanometer magnetic beads with superparamagnetism and specific DNA molecules constitute a probe,which relies on the DNA carrying fluorescent substances at the end to achieve signal transmission.When the target substance was present in the system,the DNA carrying the fluorescent substance was replaced,and the approximate concentration of tumor markers was determined by detecting the fluorescence signal strength in the system.This scheme realized the independent and specific sensitive detection of three kinds of markers and the simultaneous detection of three kinds of markers.The biosensor designed in this scheme can realize linear detection of CEA within the range of 0.1 ng/ml-300 ng/mL.The linear fitting formula is y=1.05x+113.03,R2=0.98,and its minimum detection limit is less than 0.1 ng/mL.The PSA can be detected linearly within the range of 0.1 ng/ml-300 ng/mL.The linear fitting formula is y=2.11x+160.67,R2=0.96,and the minimum detection limit is less than 0.1 ng/mL.AFP can be detected in the range of 0.1 ng/ml-300 ng/mL,and the minimum detection limit is lower than 0.1 ng/mL.After the three probes were mixed equally,the sensitivity and specificity detection of the three markers was successfully achieved,and the detection effect was good.In this paper,the presence and approximate concentration of tumor markers to be tested can be detected by both of the above probes,and the detection performance in human serum samples is also good.Compared with traditional immune detection methods,the methods proposed in this paper have the advantages of high sensitivity,short response time,simple and convenient probe making process,and low cost.Especially,the potential of simultaneously detecting a variety of tumor markers holds a broad application prospect in tumor screening and other fields.