Deciphering Gold Nanoparticle-Induced Cytotoxicity for Safer Nanomedicine Applications: Exploring the Impact of Conjugation Chemistry, Functional Groups, and Metal Core Properties

Gold nanoparticles (AuNPs) have been widely investigated for biomedical applications owing to their biocompatibility and tunable physicochemical properties. However, the limited understanding of their potential cytotoxic effects remains a major challenge to clinical translation. This study aimed to systematically examine how conjugation chemistry, surface functional groups, and core structure influence AuNP-induced cytotoxicity to develop safer nanoparticles for biomedical applications. Specifically, we evaluated the safety profile of these nanoparticles as potential drug carriers exhibiting high stability and minimal cytotoxicity. A well-defined library of AuNPs with diverse surface modifications and core designs was employed. Cytotoxic effects were assessed by comparing covalent and coordination-ligand conjugation, analyzing the influence of different surface functional groups, and evaluating variations in core architecture, including the platinum-sponge-coated gold core. Cellular responses, including reactive oxygen species (ROS) generation, DNA damage, cytoskeletal dynamics, and proliferation, were comprehensively analyzed. Our results show that covalent ligand conjugation, compared with coordination bonding, increased cytotoxicity as a result of enhanced nanoparticle stability. The chemical reactivity of surface functional groups also markedly influenced toxicity: amine groups showed a time-dependent reduction in toxicity when conjugated via polydopamine, whereas trimethylammonium groups retained toxicity. Substituting conventional gold nanospheres (AuNS) with platinum-sponge-coated gold core (AuPt) intensified cytotoxicity, likely by promoting cellular uptake, resulting in elevated ROS levels, DNA damage, impaired cytoskeletal dynamics, and decreased cell proliferation. These findings demonstrate that specific physicochemical properties of AuNPs, including conjugation chemistry, surface functionality, and core structure, critically modulate cytotoxic responses. These mechanistic insights provide predictive guidance for designing safer and more effective nanomaterials for biomedical applications.