Serological diagnosis of Toxoplasmosis disease using a fluorescent immunosensor with chitosan-ZnO-nanoparticles

This article describes a microfluidic LIF immunosensor for the quantitative determination of anti-Toxoplasma gondii IgG (anti-T. gondii) specific antibodies. The serological detection of these antibodies plays a crucial role in the clinical diagnosis of toxoplasmosis. Zinc oxide nanoparticles (ZnO-NPs) obtained by wet chemical procedure were covered with chitosan and then used to conjugate T-gondii antigens into the central microfluidic channel. Serum samples containing anti-T-gondii IgG antibodies were injected into the immunosensor where they interact immunologically with T. gondii antigens. Bound antibodies were quantified by the addition of anti-IgG antibodies labeled whit alkaline phosphatase (ALP). ALP enzymatically converts the non-fluorescent 4-methylumbelliferyl phosphate (4-MUP) to soluble fluorescent methylumbelliferone that was measured using excitation at 355 nm and emission at 440 nm. The relative fluorescent response of methylumbelliferone is proportional to the concentration of anti-T. gondii IgG antibodies. The coefficients of variation are less than 4.73% for within-day assays and less than 6.34% for between-day assays. Results acquired by LIF immunosensor agree with those obtained by enzyme-linked immunosorbent assay method, suggesting that the designed sensor represents a promising tool for the quantitative determination of anti-T. gondii IgG antibodies of clinical samples.