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Research progress of LFIA detection system

Lateral flow immunochromatography assay(LFIA) is a classical point of care testing (POCT) based on the immune responses of antigens and antibodies. Initially, the researchers used nanometer gold to prepare chromatographic strips for urinary human chorionic gonadotropin detection, known as colloidal gold. However, the detection results depend on manual interpretation, and the detection sensitivity is low and the false negative rate is high. Subsequently, some instruments for simple image acquisition and processing of NC membrane emerged one after another, and automatic and semi-quantitative interpretation of LFIA results was realized.

In recent years, with the continuous development of LFIA, the detection performance has been greatly improved, and it has gradually shifted to quantitative detection. It can detect various samples (such as whole blood, plasma, sweat, saliva, urine, etc.), and can also detect nucleic acid.

LFIA strip consists of five parts, namely, sample pad, binding pad, NC membrane, absorbing paper and polyvinyl chloride (PVC) pad. Monoclonal antibodies and secondary antibodies are pre-fixed to the NC membrane to form test lines or control lines. After adding the sample containing the tested object, the tested object binds to the labeled antibody on the binding pad and is further captured by the monoclonal antibody fixed on the T-line with the chromatography. Excessive labeled antibodies are captured by the secondary antibodies on the C line, and the signal strength of the markers on the T/C line is read by the specific detection instrument, and then replaced into the pre-drawn standard curve, so as to achieve the quantitative analysis of LFIA on the measured objects while retaining the advantages of LFIA. For a complete LFIA quantitative detection system, markers, chromatography films and detection instruments are the basis for ensuring rapid, sensitive and accurate quantitative results. In the last decade, sensitive markers of different signal types have been developed, as well as a variety of new chromatography materials, and a series of affordable and compact detection devices have been designed for recording and quantifying immunochromatography results. In particular, in order to ensure the traceability of quantitative results, quantitative value traceability of markers, consumables, reagents, instruments and testing procedures used in the test can be carried out, so as to make the detection results of LFIA products traceable to national or international standards. Enzyme linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) were used as reference methods to verify the diagnostic efficacy of LFIA.

LFIA realizes quantitative detection so that the detection results are not subject to subjective factors, which greatly improves the depth and breadth of its application in the field of real-time detection.

With the improvement and upgrading of LFIA detection system, its detection sensitivity has been constantly improved, and it has been widely used in disease diagnosis, drug monitoring, food safety and other aspects. The use of sensitive markers significantly amplifies LFIA detection signals; Detectors based on portable devices such as smartphones have been developed to make LFIA home friendly; The new NC membrane can effectively reduce the background fluorescence and make the results more accurate. In practical application, LFIA begins to turn to quantitative detection, including nucleic acid detection, making LFIA an effective, accurate and reliable method for object analysis to be tested. It is believed that soon, with the development of detection instruments, the update of NC membrane materials and the application of more sensitive markers, LFIA detection items will be more and more popular. Its operation mode will be more intelligent, portable and household; The output of quantitative results will also be more rapid, sensitive and accurate.

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