Detection Of Cancer Biomarker MUC1 Based On Quantum Dots-aptamer Sensor With Fluorescent Analysis

Currently,cancer is a major threat to human health.The cure of cancer is also the difficulty that researchers need to overcome.Interventional therapy in patients at an early stage of cancer is the best treatment period.Biomarkers are a kind of indicator molecule that can measure the current and future state of the disease.Accurate detection can help doctors to make the most effective clinical diagnosis for patients.Therefore,it is particularly important to realize sensitive detection of biomarkers.MUC1 is a protein located in the apical membrane of epithelial cells that is overexpressed on the surface of cancer cells that have lost polarity.Therefore,its content in the human body can be used as an indicator for early diagnosis of cancer.However,it’s difficult to detect MUC1 in the early stage of cell carcinogenesis as the concentration of MUC1 was at low level.So it is necessary to explore a simple,efficient and sensitive method for MUC1 detection.Quantum dots are one of the most usually fluorescent probes.They have been widely used in different research fields due to their unique advantages such as wide excitation,narrow emission spectra,tunable size and high quantum yields.Aptamer is an oligonucleotide or peptide that has a specific affinity for a target molecule and is often designed as a probe for specific sensitive detection of target.Based on the specific binding of the aptamer to the MUC1,the aptamer can be designed as probes for sensitive detection of MUC1.As magnetic microparticles have many characteristics,such as high specific surface area,easy modification and easy separation,they can be widely used in the detection of nucleic acids,proteins,small molecules and cancer cells.Hybridization strand reaction（HCR）is a commonly technique used as signal amplification.With the initiation chain,the hairpin H ₁ and H₂ can self-assemble to a long dsDNA without any nuclease.Based on the specific recognition of aptamer-proteins,the hybridization chain reaction（HCR）signal amplification,and the characteristics of easy separation of magnetic micropartic-les,two quantum dot fluorescent probes of MUC1 detection were designed.The main research contents were as follows:（1）CdZnTeS quantum dots were prepared by reference to the previous synthesis methods of our group.Ruthenium（II）complex is one of typical DNA molecular“light switches”,which abnormally has no fluorescent signal in aqueous solution,and when it embedded in the dsDNA double strand,an obvious fluorescent peak can be measured.What’s more,it can efficiently quench QDs via the photo induced electron transfer process.However,when the ruthenium（II）complex is embedded in the dsDNA,it cannot quench the quantum dots anymore.The aptamer that specifically recognizes MUC1 wsa designed as a hairpin structure.The fluorescent signal was amplified by hybridization chain reaction（HCR）and the background can be reduced by magnetic separation.MUC1 can be quantitatively detected based on the degree of the quenching between ruthenium（II）complex and CdZnTeS quantum dots.The linear range of MUC1 detection was 0.2-100 ng/mL（LOD=0.13 ng/mL,S/N=3）.The method was applied to the determination of MUC1 in spiked human serum samples.（2）In this chapter,the method of MUC1 detection was further improved without introducing the ruthenium（II）complex.DNA functionalized quantum dots were directly synthesized by a one-pot method.Aptamer that specifically recognizes MUC1coupled to the surface of the magnetic microparticles and initiated hybridization chain reaction（HCR）by hybridization with complementary single strands to form long double strands DNA,and DNA functionalized quantum dots were hybridized with dsDNA.After magnetic separation,the quantitative detection of MUC1 can be realized by directly detecting the fluorescence intensity of the supernatant.The linear range of MUC1 detection was 0.2-100 ng/mL（LOD=0.13 ng/mL,S/N=3）.