Study On The Fabrication Of High-performance Fe₃O₄@Au SERS Substrates And The Application In Immunochromatography

Accurate and rapid detection of common inflammation biomarkers such as C-reactive protein（CRP）,interleukin-6（IL-6）,procalcitonin（PCT）and serum amyloid A（SAA）is crucial for the early diagnosis,real-time monitoring and prognosis treatment of infectious diseases in clinical practice.Hence,a novel lateral flow immunoassay（LFA）detection method based on surface enhanced Raman scattering（SERS）was proposed for ultrasensitive and quantitative analysis of multiple inflammation biomarkers by using Fe₃O₄@Au magnetic nanoparticles（MNPs）as multifunctional SERS tags.The main research contents are as follows:1、Fe₃O₄@Au MNPs with uniform particle size,good dispersion,strong magnetic response and SERS performance were prepared by PEI-mediated seed growth strategy.The structures of Au-coated magnetic nanoparticles were characterized by TEM,SEM,XRD,UV-vis and Zeta potential.The SERS activities of as-prepared magnetic SERS nanoparticles were tested by modifying DTNB as Raman report molecule.2、After being modified with DTNB and specific antibodies for inflammatory markers,the Fe₃O₄@Au SERS tags were used to established a novel immunochromatographic detection system.First,15μg of detection antibody was optimized for preparing SERS tags.Then,we optimized the impact factors which was associated with performance of LFA.The experimental results verified that CN95 membrane and running solution containing 10%FBS and 1%BSA was the best detection condition.3、In this study,Fe₃O₄@Au MNPs were used as separation tools for the magnetic enrichment of target inflammation biomarkers in complex samples and as magnetic SERS tags for the quantitative detection of target objects on LFA strips.Hence,we utilized Fe₃O₄@Au SERS tags-based LFA strips to quantitative analysis of CRP,IL-6 and PCT,respectively.The visualization result of CRP was 0.5 ng/mL,and the SERS detection result was 0.05 ng/mL.The visualization result of IL-6 was 0.1 ng/mL,and the SERS detection result was 0.005 ng/mL.The visualization result of PCT was 1 ng/mL, and the SERS detection result was 0.05 ng/mL.The highly sensitive test results show that the strategy is feasible for practical application.4、Based on the multi-channel detection ability of LFA strips,dual target inflammatory markers were simultaneously analysis by using Fe₃O₄@Au SERS tags-based LFA strips in unprocessed blood sample.The limits of SERS detection for SAA and CRP were 0.1ng/mL and 0.01 ng/mL,respectively.By comparison,the proposed assay for SAA and CRP was 100-fold and 1000-fold more sensitive than standard colloidal gold strip,respectively.Moreover,the sensitivity was 10 and 100 times higher than that of commercial ELISA kits,respectively.The magnetic SERS-LFA strips also exhibited excellent stability,specificity,and selectivity for complex samples and has the potential to be an effective tool for diagnosis of infectious diseases.