Construction Of Electrochemical Sensor Based On Signal Amplification Strategy And Magnetic Separation Technique

The development of economy promotes the continuous improvement of living standards and also raises people's attention to health.Nevertheless,some high-risk diseases still pose a serious threat to human health.As far as human health is concerned,it is of great significance to realize the early diagnosis and prognosis evaluation by sensitive detection of related markers.Among the many detection methods,electrochemical analysis is widely used in the detection of all kinds of substances because of its high sensitivity,low cost,simple instrument,easy miniaturization and so on.However,the low concentration of target substances and the interference of complex matrix in clinical diagnosis are still obstacles to sensitive detection of biomarkers.In order to realize the sensitive detection of disease markers in complex matrix,we applied the signal amplification strategy into electrochemical analysis,combing with magnetic separation technique,to construct sensitive electrochemical sensors with strong anti-interference ability,which mainly includes the following contents:(1)Based on the combination of double signal amplification strategy of hybridization chain reaction(HCR)and enzyme-induced metallization(EIM)with anodic stripping voltammetry(ASV),an ultrasensitive electrochemical sensor was constructed for the detection of microRNA-21 with a wide linear dynamic range.The target nucleic acid was captured by magnetic nanobeads(MBs)modified by capture probe(CP)and amplified by hybridization chain reaction.Furthermore,a large number of alkaline phosphatase(ALP)could be coupled to nucleic acid fragments through the specific action between biotin and avidin.The combination of hybridization chain reaction and enzyme-induced metallization could effectively enhance the electrochemical signal by about 120-fold from the perspectives of target amplification and detection signal amplification,which decreased the detection limit to 0.12 fM.Compared to the reports previously reported,a wider linear dynamic range of 2.5 fM to 25 nM spanning 7 orders of magnitude was obtained.In addition,the combination of magnetic separation technique successfully realized the detection of microRNA-21 in serum.The method provides high sensitivity,specificity and a wider linear dynamic range,which shows a great potential in the early diagnosis of diseases.(2)In the previous chapter,we found that the hybridization chain reaction is easy to design and easy to operate,which could be regarded as an efficient target amplification strategy.Considering another common disease marker-protein,we used the competitive binding of thrombin and aptamer with its nucleic acid complementary strand to convert the detection of the protein into the detection of its nucleic acid complementary strand,which was easy to introduce hybridization chain reaction to realize the amplification of thrombin indirectly.Horseradish peroxidase(HRP)was used as signal markers to amplify the detection signal and output the dual mode signal based on the enzyme catalytic amplification.Magnetic separation technique combined with nanoscale gold islands modified magnetic electrode array had been used to capture the magnetic complex and successfully avoided the toxicity of the electrode.This method reduced the detection limit of thrombin to 0.35 nM,and has strong anti-interference ability in serum and strong specificity,which provides a way for the early diagnosis of related diseases.