Antibody functionalized thiolated chitosan stabilized silver nanoparticles as theranostics toward visceral leishmaniasis.

Leishmaniasis (VL) is a neglected disease caused by Leishmania protozoa, transmitted through insect vectors, and can be fatal without adequate treatment. Current therapies are hindered by issues such as drug resistance and side effects, making rapid diagnosis essential. Biosensors are being explored to enhance detection, and silver nanoparticles (AgNPs) have emerged as promising tools for both diagnosis and treatment. To improve their stability and functionality, AgNPs can be coated with thiolated chitosan (TCh), which is synthesized by introducing thiol groups to chitosan using 3-mercaptopropionic acid, confirmed through 1H NMR and FTIR analysis. TCh-stabilized AgNPs (TCh-AgNPs) were created using a chemical reduction method, resulting in nanoparticles with a mean diameter of 66 ± 1 nm and a maximum absorbance peak at 418 ± 2 nm. Anti-rK39 antibodies were anchored to these nanoparticles (TCh-AgNPs@Ab), which showed enhanced interaction kinetics with the rK39 protein compared to free antibodies, indicated by a 2.3 times stronger signal. Additionally, TCh-AgNPs demonstrated greater anti-leishmanial activity in cell cultures compared to control groups. These results suggest that TCh-AgNPs could serve as a valuable platform for developing sensitive diagnostics and effective treatments for VL.