Construction And Application Of Point-of-care Testing Based On Signal Conversion Strategy

Point-of-care testing?POCT?is rapid diagnostic testing performed at or near the site where the patient is located or the event occurred.Compared to traditional laboratory testing,POCT is affordable,specific,rapid,robust,user-friendly and equipment-free.In recent years,relevant reports of POCT based on various signal readouts have been emerging endlessly.However,there are still few researches on POCT based on signal conversion strategy,especially the POCT platform with simple and sensitive signal readout.In this paper,several POCT sensing platforms based on signal conversion strategies are designed and successfully applied to the analysis of life-related substances and environmental pollution monitoring.This thesis consists of five parts which its main contents are as follows:1.The concept,significance and future development trend of POCT were introduced,and the application of POCT in analytical sensing field based on various signal readout methods was reviewed in detail.2.A simple strategy for converting the color signal of the 3'3,5'5-tetramethylbenzidine?TMB?-Ag⁺colorimetric system into a thermal signal was developed,thereby developing a temperature signal-based POCT assay for alkaline phosphatase?ALP?activity.The colorimetric system based on simply mixing commercially available chemicals of TMB and Ag⁺,provides straightforward blue color readout owing to the generation of oxidized TMB?TMBox?.In the presence of the target alkaline phosphatase?ALP?,ascorbic acid phosphate?AAP?in the system could be hydrolyzed into ascorbic acid?AA?,subsequently reducing the blue colored TMBox into colorless TMB.The proposed TMB-Ag⁺colorimetric reaction system could provide a colorimetric detection result for ALP.In addition,due to the stronger near-infrared?NIR?laser-driven photothermal effect of the TMBox,the colorimetric system also exhibited a sensitive ALP concentration-dependent photothermal performance.Therefore,through this simple conversion strategy for color-to-thermal signal readout,the quantitative detection of ALP activity based on the temperature signal readout can be achieved just using a common thermometer,and the limit of detection?LOD?of our photothermal method for ALP detection was obtained to be0.08 U/L?S/N=3?.3.The aforementioned TMB-Ag⁺colorimetric reaction system was used to develop photothermal and paper-based analysis sensors based on signal conversion strategies for detecting AA.First,we used the strong photothermal effect of TMBox to achieve the conversion from color to thermal signal.And then,we used a thermometer as a signal reader to achieve quantitative detection of AA.In addition,we have developed a more stable paper-based sensor based on height signal readout.The TMBox was fixed on the test strip as a signal label.The AA in the test solution automatically moved up the paper strip due to capillary action and reacted with the TMBox on the test strip to cause it to fade.The visual height of the fading band was proportional to the concentration of AA.A ruler can be used as the signal reader quantitatively detected AA.The LOD for AA by photothermal and paper-based analysis sensor is 0.87?M and 13.3?M,respectively.4.We explored a simple but sensitive thermometric strategy for arsenic determination based on signal conversion and integration strategy.Cobalt oxyhydroxide?CoOOH?nanoflakes can effectively decompose hydrogen peroxide into oxygen in a sealed reaction vessel,accompanied with marked pressure and significant temperature increase due to the exothermic reaction effect.The increased pressure then compelled a certain amount of H₂O overflowing from the drainage device into another vessel,leading to a significant temperature decrease due to the pre-loaded ammonium nitrate?NH₄NO₃?and its good dissolution endothermic effect.In the presence of arsenic,the catalytic activity of CoOOH nanoflakes for H₂O₂ decomposition was inhibited dramatically,resulting in an obvious decrease of the pressure,weighting water and temperature response.The arsenic sensor analysis platform with enhanced temperature signal readout can be effectively constructed by superimposing the two temperature responses with increasing and decreasing feature.It is noted that the LOD value obtained by this enhanced thermometric method is 51 nM.5.The advantages of the POCT sensing platform based on signal conversion strategy developed in this paper were summarized,and the future research directions were prospected.