Gadolinium Nanoparticles: Emerging Platforms Beyond Imaging for Drug Delivery and Theranostics.

Gadolinium nanoparticles (GdNPs) have gained increasing attention as multifunctional metal-based nanoplatforms that extend far beyond their traditional use as magnetic resonance imaging (MRI) contrast agents. Their specific magnetic properties, tunable physicochemical features, and tunable biocompatibilities with biocompatible coatings give them great potential as drug delivery and theranostic applications. They offer greater stability, lower systemic toxicity, and more surface modification options compared to molecular gadolinium chelates. The functionalized GdNPs not only show excellent properties as drug carriers for their specific indications but also serve as agents in various imaging modalities with superior therapeutic efficacy by means of radio sensitization and magnetically assisted delivery. Note too that GdNP-based formulations have demonstrated synergistic activity when administered with chemotherapeutic agents such as doxorubicin. GdNPs have demonstrated promising preclinical outcomes, and their clinical translation remains restricted due to a number of scale-up constraints, long-term safety challenges, pharmacokinetics, and regulatory problems. This review provides information on the use of GdNPs, their key physicochemical and magnetic properties, ligand engineering for targeted delivery, and biological mechanisms of their theranostic performance.