Diagnosis of Neglected Tropical Zoonotic Disease, Leptospirosis in a Clinical Sample Using a Photothermal Immunosensor.

Photothermal biosensing based on nanomaterials has gained increasing attention because of its universality and simplicity. Diagnostics of neglected tropical diseases (NTDs) in low-resource settings are challenging in terms of speed, accuracy, and cost-effectiveness. By exploiting the photothermal property of carbon nanotubes (CNTs), simple thermometric measurements can be used to generate quantitative biochemical readouts. Herein, a photothermal immunosensor for leptospirosis detection based on a CNT-labeled monoclonal antibody is established through the sensitive monitoring of the target biomarker LipL32 with a simple thermometer. Under optimum conditions, a linear range up to 106 pg/mL with a limit of detection (LOD) of 300 fg/mL was obtained. Overall, the proposed immunoassay exhibited good precision, selectivity, and acceptable stability. Clinical patient sample analysis with the photothermal sensor proved the differential diagnosis of leptospirosis along with other febrile illnesses. On the other hand, we have also characterized the photothermal sensor platform with surface morphological and spectral techniques to confirm the robust and successful fabrication of the immunosensor. The fabricated photothermal sensor could be used as a potential diagnostic tool for the early detection of NTDs in patients from resource-limited settings, as it does not require sample pretreatment, sophisticated equipment, or skilled labor. Moreover, the developed photothermal assay follows ASSURED criteria, very crucial for diagnosis in resource-limited settings.