Progress of Palladium Nanomaterials for Tumor Diagnosis and Therapy

Tumors are the most serious threats to global health. While conventional treatment methods, such as chemotherapy and radiotherapy, often result in harsh side effects due to poor targeting, palladium-based nanomaterials (Pd-NMs) offer new possibilities for improved treatment outcomes. With exceptional photothermal conversion, a long circulation half-life, high tumor accumulation, favorable optical/magnetic properties, and great biocompatibility, Pd-NMs may reshape the diagnosis and treatment of tumors. Building upon these potential benefits, Pd-NMs play critical roles in diagnosis by serving as imaging agents, tumor cell detectors, and biological probes. In treatment, most Pd-NMs are administered intravenously, allowing for passive tumor targeting through the effect of enhanced permeability and retention (EPR), which inhibits cancer cell proliferation and migration. Their small size reduces the impact on normal tissue and adverse reactions, and they are widely used in photothermal therapy, photodynamic therapy, chemotherapy, radiotherapy, chemodynamic therapy, and combined therapy. However, the Pd-NMs could interfere with immune cell functions and induce oxidative stress. Prolonged exposure to Pd-NMs can lead to organ damage, including the kidneys, lungs, and liver. They are mainly excreted via the kidneys, with clearance affected by size, surface modification, and exposure routes. Looking ahead, clinical applications need to overcome challenges (e.g., improved tumor targeting, long-term biosafety, cost reduction, and large-scale production). Consequently, future research should focus on improving efficacy, developing new strategies, and exploring long-term biosafety to promote clinical translation. This review aims to support related studies.