Quantitative Detection Of Colloidal Gold Test Strip Based On Smartphone Portable Equipment

In recent years,the colloidal gold immunochromatographic strip as a new method for instant diagnosis has been widely used in many fields due to its advantages of good comparability,rapidity,simplicity and low cost.However,most of the existing test papers were qualitative or semi-quantitative,which could not meet the quantitative requirements,limited the application and promotion of test papers to some extent.For these reasons,smartphones used as a quantitative tool for portable device detection had become a hotspot in the field of biosensor detection.The smartphone had a large-capacity internal memory,a high-quality camera and an open source operating system,and its microprocessor could easily achieve image acquisition,information processing,and result quantification.In the case that the test strip can only provide qualitative test result but the quantitative test is urgently needed,the smartphone as the quantitative analysis tool of test strip can not only greatly reduce the development cost,but also be more conducive to the promotion and application of test strip.In this paper,a portable test strip quantitative detection device based on smartphone was designed and developed.The main research contents are as follows:1)A human chorionic gonadotropin(HCG)test strip was constructed,which used the colloidal gold(Au NP)labeled HCGβsubunit monoclonal antibody(Anti-β-HCG)as the gold-labeled probe(Anti-β-HCG-Au NP)to fix on the gold-label pad of test strip.At the same time,the monoclonal antibody of theαsubunit(Anti-α-HCG)and the secondary antibody(goat anti-mouse polyclonal antibody Ig G)were coated on test(T)line and control(C)line,respectively.When HCG was present in the test sample,the gold-labeled probe could form a sandwich structure through HCG with the antibody on T line,thus fixing the Au NP there for color development.The detection limit of the test strip is 3 ng/m L,and the linear range is 6～300 ng/m L.2)Three different quantization algorithms for test strip detection were designed,and the image algorithms were compared and optimized.The threshold processing algorithm based on position information was relatively simple,but it was necessary to determine the relative position of T line and C line in advance,so the consistency requirement of the test strip preparation was strict.The RGB channel extraction algorithm was the most direct method for extracting color channels,however,the relationship between the RGB three channels required continuous debugging to obtain the ROI.The method of processing the grayscale projection value based on the test strip was simple and intuitive,and had good stability and portability.3)Designed and developed a mobile phone application(App)that could achieve quantitative detection,and successfully installed in Android mobile phones,which could detect and quantify HCG levels at any time.The biosensor was successfully used to measure HCG in spiked urine(R~2=0.988),which could obtain accurate values of analyte concentration in urine,which indicated that the application may be used for real-time colorimetric diagnosis.The biosensor will provide new ideas for quantitative detection of colloidal gold immunochromatographic test paper.