Yaliang Huang,Ting Sun,Lin Liu,Ning Xia,Yuehua Zhao,Xinyao Yi
The hybridization and enzymolysis reactions for nucleic acid detection were carried out on the chip surface in the traditional surface plasmon resonance (SPR) biosensors. Herein, we proposed an innovative method for microRNA (miRNA) detection in which the hybridization-enzymolysis recycling reactions were performed in solution. Duplex-specific nuclease (DSN) and streptavidin-modified gold nanoparticles (SA-AuNPs) were employed for enhancing the assay sensitivity. In the absence of miRNA, the biotinylated DNA probe (bio-DNA-bio, biotin tags at both the 3′ and 5′ termini of DNA) was attached to the SA-modified chip through the SA-biotin binding, allowing the capture of SA-AuNPs with the same interaction. As a result, a larger SPR signal was attained. However, in the presence of miRNA, bio-DNA-bio hybridized with miRNA was digested by DSN. In this process, the miRNA strand remained intact and participated in the next hybridization-enzymolysis recycling process. Thus, one miRNA could promote the hydrolysis of many bio-DNA-bio probes and allow the generation of numerous bio-DNA fragments. Meanwhile, the produced bio-DNA competed with the undigested bio-DNA-bio to bind SA on the chip surface. The digestion of bio-DNA-bio and the competitive binding between bio-DNA-bio and bio-DNA led to the attachment of fewer SA-AuNPs and then smaller SPR signals. The change in SPR signal at the concentration as low as 1 fM miRNA has been readily determined. The strategy possessed the advantageous properties of simple operation, fast response, high sensitivity and excellent specificity, serving as a viable means for the fabrication of novel sensing platforms.
Ruihuan Zhao,Dongxiao Li,Nan Yin,Zhimin Guo,Dengchao Wang,Xin Yao
Dopamine (DA) plays vital role in diagnosis and treatment of neurodegenerative disease. It is of high clinical relevance for developing simple, sensitive and selective DA detection method. But the electrochemical detection of DA still faces the problem of insufficient sensitivity, and generally need the complex material synthesis process to realize the selective detection of DA. In this work, we established a simple electrochemical surface plasmon resonance sensor for DA detection based on its electropolymerization property. The main interfering molecules of uric acid and ascorbic acid cannot undergo electropolymerization, while DA can produce polydopamine precipitation on the surface of Au film. The formation of polydopamine precipitation could amplify the SPR signal, and ensures the high selectivity and sensitivity of DA detection. The linear range is 0.01–1000 nM and the detection limit is as low as 1.4 pM. At the same time, this sensor has high selectivity for DA detection even in the presence of 50000-fold higher concentration of ascorbic acid and uric acid. Finally, the sensor was successfully applied to determine DA content in urine samples and DA released from PC12 cells under the stimulation of K + , demonstrating great potential in clinical applications.
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