Thiol derivatives and CdTe quantum dots as larvicides and biomarkers against the yellow fever mosquito Aedes aegypti.

The increasing resistance of the yellow fever mosquito, Aedes aegypti, to conventional larvicides underscores the critical need for novel vector control strategies. This work investigates the intrinsic larvicidal activity of free-thiol derivatives (3-mercaptopropionic acid (MPA) and cysteamine (CA)) and evaluates how their specific functional groups (carboxylic acid and amine) govern molecular interactions within the larval digestive system. The free MPA and CA compounds exhibited remarkable larvicidal efficacy against fourth-instar (L4) larvae, presenting LC50 values of 18.34 ± 0.68 mg L-1 and 8.26 ± 0.58 mg L-1, respectively. Ingestion assays revealed that spatial nanoprobe distribution is strictly regulated by the larval intestinal pH gradient and ligand pKa. While negatively charged CdTe-MPA maintained broad colloidal stability across the midgut, CdTe-CA underwent charge neutralization in the alkaline central midgut, triggering localized colloidal deposition at neutral-to-acidic boundaries. Both probes showed strong affinity for chitinous structures, compromising gut homeostasis. This study provides mechanistic proof of concept that surface-charge tailoring can exploit vector physiology for targeted pest control.