A molecular insight into the aggregation of cisplatin in aqueous solutions

Abstract

Cisplatin (CPT), recognized as a widely used metallodrug, is a prevalent therapeutic agent for the treatment of various cancers. Given the diverse biological conditions in humans, as well as the hydrated environment within cells and the toxicity associated with CPT in cancer treatment, it is imperative to assess and optimize the solvation of CPT under various conditions. In this study, the influence of CPT on the structure of water is explored. In this regard, a systematic molecular dynamics (MD) simulation is employed to investigate the structure and dynamics of CPT in aqueous media, encompassing a range of concentrations from much diluted (0.05 M) to concentrated (5 M). The disruption of water structure by CPT molecules is determined using radial distribution function (RDF), mean-squared displacement (MSD), and combined radial/angular distribution function (CDF). Notably, the CPT aggregates exhibit an impact on the average number of water-water hydrogen bonds. Through calculations of apparent and partial molal volumes of CPT at various concentrations, we observed a sudden and dramatic change in the solution structures up to the critical aggregation concentration of CPT (0.5 molal), a finding corroborated by the calculations of diffusion coefficients. In summary, the self-aggregation of CPT molecules commences at 0.5 molal, leading to increased apparent and partial molal volumes with rising concentration. However, beyond 0.5 molal, the change in volumes becomes less significant, suggesting that while the number of CPT aggregates continues to increase, their size remains relatively constant above this concentration.