片上集成光学模块具有集成小型化、低成本等优点,可在芯片尺度上实现“样品进、结果出”的即时定点检测。本文研制了一个工作波长为647 nm的荧光激发模块,集成聚合酶链式反应(PCR)生物微流控芯片和光电探测器,实现了片上荧光激发和病原体核酸检测。该荧光激发模块主要由光栅和多模干涉器两个微纳器件构成,经有限时域差分法优化,光栅激发效率可达26.3%,多模干涉器损耗低至2.8%。结合生物微流控芯片,采用等浓度梯度的Cyanine 5 (Cy5)荧光素溶液对荧光激发模块性能进行验证,光电探测器输出电压值与Cy5荧光素溶液浓度之间成线性关系,拟合曲线方差为0.9944,最低检测下限为0.0625 µmol/L。利用200 copies/μL的新型冠状病毒质粒做生物应用测试,结果表明本文所提出的荧光激发模块能满足实际PCR应用中对荧光信号激发的要求。本系统在生物荧光定量PCR、数字PCR、蛋白等实时生物荧光检测方面具有应用前景。On-chip integrated optical modules have the advantages of integrated miniaturization, low cost, etc., and can realize “sample in, result out” real-time fixed-point detection on a chip scale. In this paper, a fluorescence excitation module with an operating wavelength of 647 nm was developed to achieve on-chip fluorescence excitation and pathogen nucleic acid detection by integrating a polymerase chain reaction (PCR) bio-microfluidic chip and a photodetector. The fluorescence excitation module is mainly composed of two micro-nano devices, grating and multimode interferometer (MMI). Optimized by the Finite-difference time-domain method, the grating excitation efficiency can reach 26.3%, and the multimode interferometer loss is as low as 2.8%. The performance of the fluorescence excitation module was verified by using an equal concentration gradient of Cyanine 5 (Cy5) fluorescein solution in combination with a bio-microfluidic chip. The output voltage value of the photodetector and the concentration of Cy5 fluorescein solution were linearly correlated with the variance of the fitted curve being 0.9944, and the lowest limit of detection being 0.0625 µmol/L. Biological application tests were performed with 200 copies/μL of the SARS-CoV-2 plasmid, and the results show that the fluorescence excitation module proposed in this paper can meet the requirements for fluorescence signal excitation in practical PCR applications. This module has promising applications in real-time biofluorescence detection of biofluorescence quantitative PCR, digital PCR, and proteins.
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