Quantitative Detection System For Lateral Flow Immunochromatographic Strips Based On Plasmonic Thermal Sensing

With the emphasis on human health,medical testing has gradually expanded from hospitals to homes.Point-of-care testing(POCT)products with miniaturized equipment,simple operation,and timely results were born and developed rapidly.The operation of the POCT equipment is simple,the detection cost is low so that it can meet the detection needs in many limited medical environments.With the continuous development of scientific research,POCT equipment has gradually developed from qualitative detection to quantitative detection.Higher requirements are imposed on performance indicators such as stability,sensitivity and detection limit of the equipment.In response to the new requirements of POCT equipment,a set of detection equipment based on the principle of plasmonic thermal sensing was developed for the quantitative detection of immunochromatographic test strips.Different from the traditional colorimetric detection method of lateral flow immunoassay,heat is produced by the localized surface plasmon resonance of gold nanoparticles.The thermal signal is related to the content of nanoparticles,so the concentration of target analyte can be detected by measuring the heat generated by the lateral flow immunoassay strip.For the calculation of heat sensing signal,two common algorithms are compared.Compared with the temperature change algorithm,the algorithm of area under the curve has higher repeatability and stability,and the detection error is smaller,so it is more suitable for the thermal sensing detection studied in this paper.Experiments were performed on the affecting factors:detection time and light source distance to obtain better thermal sensing conditions.The results show that the gold nanoparticles can generate high heat in about 2 minutes,and the environmental noise has little effect on the detection signal.The heat generation will decrease as the distance of the light source increases.Thus,the distance of the light source should be shortened as much as possible.In the thesis,a prototype based on the embedded system and microelectronics technology has been developed.The size of the prototype is 133×108×73mm~3,which is a small,portable,POCT device.The POCT prototype is composed of hardware and software system.The hardware system mainly includes central control module,light source and sensor module and man-machine interaction module.The main functions of the software include target analyte detection,test result query,equipment function setting and maintenance,etc.In the performance verification of the device,test strips containing gold nanoparticles only and test strips containing human chorionic gonadotropin(HCG)markers were used for experiments.According to the results,radiation mode has higher sensitivity and lower detection limit,but conduction mode has better repeatability and stability.The results show that the thermal sensing has a lower detection limit than the colorimetric detection.In conclusion,this POCT device has higher sensitivity(HCG detection limit:2.8 mUI/mL),wider linear range(35-700 mUI/mL),High stability(RSD=3.03%),smaller device volume(about 1 L),and shorter detection time(2 minutes).The results show that this POCT device has great potential in practical applications.