Interaction of light and fast electrons with metallic nanoparticles

Currently, most MRI probes available for clinical use contain gadolinium, which is a high-risk paramagnetic metal that can cause severe side effects (e.g., nephrogenic systemic fibrosis). To limit such side effects and improve diagnostic efficacy, we developed a novel biocompatible MRI contrast agent using glucose, glycine, and paramagnetic iron ion. Glucose and glycine were polymerized into melanoidin by the nonenzymatic Maillard reaction, and Fe³⁺ was chelated stably with the melanoidin during polymerization. The Fe³⁺-melanoidin chelate had biocompatibility, biodegradability, and unique contrast effects on both T₁- and T₂-weighted MRI, depending on the pH and oxidative environments. The administration of the Fe³⁺-melanoidin chelate to a mouse model of liver cancer showed highly enhanced liver-to-tumor contrasts on both T₁- and T₂-weighted MRI.