Synthesis, characterization, and DFT analysis of DMSA–arsenite complexes and their conjugation with BSA and KLH

Arsenic is a metalloid released into the environment through both natural and anthropogenic processes. It typically reacts with sulfur and oxygen to form inorganic species such as arsenate and arsenite. Additionally, it is capable of forming complexes with chelating agents, including meso‑2,3-dimercaptosuccinic acid (DMSA). The objective of this study was to synthesize and characterize DMSA–arsenite complexes, conjugate them with BSA and KLH as a basis for the future development of monoclonal antibodies, and theoretically evaluate their reactivity using Density Functional Theory (DFT). We evaluated the various protonation states (microspecies) of DMSA and DMSA-arsenite (As-DMSA) complexes using DFT. Moreover, we synthesized and characterized DMSA-BSA-As and DMSA-KLH-As complexes. Our findings indicate that progressive deprotonation of DMSA alters its reactivity, enhancing its nucleophilic properties. Furthermore, DMSA-arsenite complexes were successfully synthesized. The formation of these complexes induced a bathochromic shift in the UV–Vis spectrum and the appearance of new absorption bands in the FT-IR spectrum. A portion of the synthesized complex remained stable in aqueous solution and was capable of forming conjugates with BSA or KLH.