Research On Optical Biosensor Based On PCERS And Nucleic Acid Amplification Technique

In recent years, with the continuous improvement of the development of social economy and people's living standards, photochemical biosensor plays an important role in people's health and daily life, especially in the field of food safety, environmental safety, public health safety and other applications. The main contents of this thesis are as follows:Cholera, a kind of acute infectious disease featured by watery diarrhea, remains a global threat especially in areas where access to safe drinking water and adequate sanitation cannot be guaranteed. Early detection is critical for the prevention of death and outbreaks caused by cholera. As a distinctive biomarker, CT has to be identified rapidly and reliably in a cost-effective manner. In chapter 2, we report the development of a novel PCERS nanobeacon method for ultrasensitive, single-step, homogeneous detection of CT. This method relies on our realization of monosialoganglioside (GM1) modified plasmonic nanoparticles which are able to assemble into cross-linked aggregates in response to CT with a concomitant substantial enhancement of SERS signals, we design and synthesize the plasmonic nanoparticles with a Raman dye-labeled gold nanoparticle (AuNP) core and a bilayer phospholipid coating. The results have demonstrated that the PCERS nanobeacon showed very high sensitivity with a low detection limit of 0.3 pg/mL, a wide dynamic range of five orders of magnitude, large signal-to-background ratio of ?24 and excellent resistance to interferents in complex matrices in CT detection. Therefore, the PCERS nanobeacon may create a useful platform for ultrasensitive and point-of-care detection of CT and for preventive and diagnostic monitoring of cholera.MicroRNAs (miRNAs) are a class of small endogenous nonprotein-coding (approximately 19-25 nucleotides) RNA molecules, which play important regulatory roles in a wide range of biological processes. Despite the importance, MiRNA detection is challenging attributing to their short lengths, sequence homology among family members, lability to degradation, and low abundance in total RNA samples. Thus, it is of great importance and urgent need to develop rapid, specific, and sensitive methods for miRNA detection. In chapter 3, Herein, we developed a novel isothermal nucleic acid amplification technology based on target-catalyzed hairpin assembly (CHA) and cyclic enzymatic repairing amplification for sensitive miRNA detection, named CHA-ERA. CHA amplification is triggered specifically by target nucleic acid, which motivates the ensuing enzymatic repairing amplification (ERA) reaction. When used for miRNA detection, the CHA-ERA assay was shown to give a favorable detection limit as low as 50 fM across a wide dynamic range up to 1 nM. The proposed method also exhibits excellent selectivity with the capability of discriminating single-base mismatch. The proposed CHA-ERA strategy indeed provides a new paradigm for efficient nucleic acid amplification and might hold the potential for miRNA expression profiling and related theranostic applications.