A novel sandwich ELISA method for quantifying CHI3L1 in blood serum and cerebrospinal fluid multiple sclerosis patients using sustainable photo-irradiated zero-valence gold nanoparticles

The widespread occurrence of chronic demyelinating MS presents a significant challenge for ongoing research aimed at comprehending its progression, diagnosis, and treatment. In our research, we have devised a novel approach to quantify CHI3L1 (Chitinase-3-like protein 1), which has emerged as a valuable biomarker in MS because of its involvement in inflammation, tissue remodeling, and immune response—crucial factors in regulating damaged nerve cells and preventing their accumulation in the brain, utilizing sandwich ELISA technology. This innovative method primarily depends on gold nanoparticles synthesized through a novel process of photo-irradiation with ultraviolet light. The crystal structure and particle size of sustainable zero-valent gold nanoparticles were measured using X-ray diffraction (XRD), which proved the cubic shape, with a cubic unit cell edge length of 4.0095 Å. The transmission electron microscopy (TEM) and field emission scanning electron microscope (FE-SEM) demonstrated that the distribution of Au NPs is uniform, with an average diameter of 22 nm. The UV–Vis spectrum, displaying a pronounced absorbance peak at a wavelength of 548 nm, suggests the presence of Au NPs. The optimal conditions for the formation of the Au-biotinylated antibody-HRP complex were studied. The optimum pH was 7, the dilution ratio of AuNPs with biotinylated antibody-HRP was 1:3, and the concentration of nanogold was (1 × 10⁻³ mg/ml) to avoid increasing it. Then a standard curve was drawn for this method and compared to the traditional method, and it was found to be twice as sensitive as the traditional method, with a high accuracy of CV% (3–6 %) as well as a rapid color generation for measurement. This method, based on gold nanoparticles that are considered a carrier for biotinylated antibody-HRP, was applied for the first time to measure CHI3L1 in the sera and cerebrospinal fluid of patients with multiple sclerosis, and the results demonstrated the accuracy and sensitivity of the method. The method has the potential to be an excellent tool for evaluating CHI3L1 and may have applications in other diseases for rapid diagnosis and timely treatment.