Detection Of Folic Acid And C-Reactive Protein By Lateral Flow Immunoassay Based On Nanomaterial Labels

In recent years,with the continuous improvement of people’s living standards,people pay more and more attention to food safety issues and self-health diagnosis.Therefore,it is very important to develop rapid analytical methods that can meet the requirements of food safety detection and disease diagnosis.Lateral flow immunoassay(LFIA)is a technology based on the specific identification of antigens and antibodies and chromatographic separation,which has the advantages of low cost,simple and rapid operation,and intuitive results based on the naked eye.In addition,the label is an important factor in determining the sensitivity of LFIA detection.A good label will give LFIA higher sensitivity and better stability.nanomaterials as signal markers of LFIA have the advantages of simple preparation,stability,and good color rendering.Therefore,this paper mainly explores the LFIA established by two nanomarkers for the detection of folic acid(FA)and C-reactive protein(CRP),respectively.The specific work is as follows:(1)Detection of FA by lateral flow immunoassay test strips based on AuNPs.Preparation of AuNPs with a particle size of about 14.6 nm and coupling with anti-folate polyclonal antibody(p Ab)to make immune probe AuNPs-p Ab;FA and bovine serum albumin(BSA)were prepared by carbodiimide method to prepare antigen FA-BSA;FA-BSA and goat anti-rabbit Ig G were respectively coated on NC membrane as test line(T line)and quality control line(C line).Through a series of optimizations,the optimal labeling p H and antibody concentration,the optimal coating concentration of T line FA-BSA,the sample pad blocking solution and the optimal composition of the coating solution were determined.In the best condition,the visual limit of detection(VLOD)of the test strip for FA standard solution was 50 ng/m L,with strong specificity and no cross-reaction with other five structurally similar substances.The test strip was used for the detection of FA in milk powder samples with a visual detection limit of 50ng/m L.The method we developed is convenient,efficient and suitable for on-site detection and rapid mass screening of food samples.(2)Detection of C reactive protein by signal amplification lateral flow immunoassay strips based on Au@PdNPs nanozymes.Au@PdNPs were synthesized by a two-step method.Au@PdNPs were combined with anti-CRP monoclonal antibody(m Ab-6G5)to prepare Au@PdNPs-Ab immunoprobe by physical adsorption.Since Au@PdNPs are brown-black and have peroxidase-like activity,in the detection process,not only the color of Au@PdNPs itself can be used for colorimetric analysis,but also its peroxidase-like activity can be used to catalyze the color of the substrate,which is used to enhance the signal and improve the detection sensitivity.In addition,this paper proposes that the use of high-viscosity glue as the solvent for preparing the color developer can effectively improve the diffusion of the catalytic product on the test strip,and truly reflect the signal amplification results.A series of optimizations were carried out on the test strip.Under the optimal conditions,the VLOD of the test strip based on Au@PdNPs to CRP standard solution was 50 ng/m L,and the VLOD after catalytic signal amplification was 1 ng/m L,sensitivity is increased by 50-folds.It was successfully quantitatively analyzed with a quantitative detection limit of 0.32 ng/m L.Finally,this test strip was successfully applied to the detection of CRP in serum.In conclusion,this study provides a signal-amplifying LFIA with Au@PdNPs nanozyme as a label for sensitive detection of CRP in serum,which provides a new strategy for human health diagnosis.