Harnessing the Periodic Table for Human Well-being: A Systematic Mechanistic Exploration of Metallo-Pharmaceuticals towards Diagnostic and Therapeutic Applications

Background: Metal ions are vital for life, playing critical roles in oxygen transport, catalysis, and electron transfer. Unlocking the inherent chemical reactivity, metallo-pharmaceuticals have evolved as pillars of modern medicine, particularly in cancer therapy and diagnostic imaging. From the serendipitous discovery of cisplatin to the rational design of gadolinium-based contrast agents, the characteristic properties of metal centers—redox activity, ligand exchange kinetics, and multimodal coordination geometries—are leveraged for therapy and diagnostics. Aim: The purpose of this overview is to provide a broad assessment of the chemistry, mechanism of action, and clinical use of major metallopharmaceuticals. It focuses on understanding how the inherent properties of metal ions are expressed in biological activity, and how this results in challenges of stability and toxicity. Methods: A systematic literature review was conducted, focusing on primary research articles and reviews. The review was structured according to metal ion and application, discussing the coordination chemistry, biochemical reaction, and structure-activity relationships of platinum-based chemotherapeutics, gadolinium-containing imaging agents, and iron-based biologics. Results: The review summarizes how cisplatin aquation reaction enables DNA cross-linking, how paramagnetism of gadolinium enhances MRI contrast, and how iron's role in heme is pivotal for cellular respiration. It also identifies ways to modulate metal-specific toxicity, e.g., designing platinum analogs with reduced side effects and macrocyclic chelators for gadolinium. Conclusion: The metallo-pharmaceuticals' activity lies at its core, linked to its underlying inorganic chemistry. Progress in the future depends on the rational design of metal complexes that provide maximum therapeutic or diagnostic benefit and minimum off-target metal toxicity by novel ligand design and targeting methods.