Nucleic acid detection is widely used in life science and clinical medical diagnosis. Innovative methods and platform research to improve its key performances are of great significance to ensure population health, promote precision medical technology, and even ensure social stability and development. Most of the existing nucleic acid detection technologies utilized PCR as the amplification method, relying on professional and complex scientific instruments and thus is time-consuming and laborious. Fortunately, RPA offers a feasible alternative. It has the advantages of fast amplification speed, high sensitivity, simple primer design, no temperature cycle control and complex manual operations. However, the detection of amplified products is difficult and costly, and there is a lack of low-cost real-time detection methods with parallel multiple detection abilities. In this work, a label-free and real-time RPA amplicon detection method based on hyperspectral interferometry is presented. A solid-phase biochip helps to capture the RPA product in a real-time meaner and the interference spectrum signal is used to read the solid thickness increment brought by the amplicon. A Fourier domain thickness computation method contributes to calculating the thickness increase and excluding scattering noise. The detection sensitivity reaches 6 copies/reaction and the consuming time is less than 20 min. Moreover, the detection method can also be used for single point mutation readout with the specificity of merelya1%mutation-wild type ratio. Combined with a microfluidic platform, parallel, simultaneous and multiple tests can be realized with 3 microliters.
As a biomarker for the diagnosis and treatment monitoring of various diseases, exosomes widely exist in body fluids such as blood, urine and saliva. However, its small particle size and low content are difficult to enrich. Therefore, a fast, high-purity enrichment method, and a fast, high-sensitivity, high-resolution, and low detection limit detection method are particularly important. We developed an automated fully integrated system for the enrichment and detection of exosomes. Using magnetic beads modified with anionic polymers to capture exosomes, adjust the pH of the exosome solution to acidic, and use the electrostatic adsorption between the positive charge on the surface of exosomes and the negative charge on the surface of the anionic polymer-modified substrate to achieve exosome capture. The captured extracellular vesicles are eluted from the surface of the magnetic beads by using a neutral or slightly alkaline eluent and using electrostatic repulsion to achieve the purpose of separation and enrichment of extracellular vesicles. The method is fast and efficient, can be automated with a small instrument, and can exclude favorable nucleic acid interferences. The eluted exosome protein is fixed on the substrate by chemical modification using quantitative interference exosome surface protein detection technology, and the connection between the exosome surface protein and the antibody is realized by immunoadsorption. Hyperspectral interferometry was used to quantitatively analyze the optical path increment on the substrate surface, to determine whether the exosome sample was bound to the antibody, and to detect the protein content of the exosome surface in parallel. This method can achieve sub-nanometer detection accuracy, and can detect exosomes whose size is smaller than the diffraction limit. Finally, the enrichment and detection of exosomes were automated.
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