Biomass-Derived Organonanomaterials\nas Contrast Agents\nfor Efficient Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a popular imaging\ntool that\nis valuable for the early detection and monitoring of malignancies\nbecause it does not involve radiation and is noninvasive. Metal-based\ncontrast agents (CAs) are commonly used in clinical settings despite\nconcerns about the toxicity of free metals. Therefore, finding alternative\nnontoxic imaging probes is vital. In this work, we have synthesized\nand effectively utilized sustainable biomass lignin-based all-organic\nnanoconjugates linked with nitroxide radicals as MRI CAs. Lignin grafted\nwith poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (LPGT)\nexhibits a longitudinal relaxivity of 0.54 mM<sup>–1</sup> s<sup>–1</sup>. LPGT shows exceptional characteristics, including\nresistance to reduction and nontoxicity toward living organisms. LPGT\ndisplays enhanced MRI contrast in the BALB/c mouse model for a duration\nexceeding 4.35 h. Our primary goal is to design MRI agents that are\nexceptionally effective sustainable biomass-derived materials and\ndo not require the use of metals. Nicely, LPGT offers adequate contrast\nenhancement at 5-fold lower (0.020 mmol/kg) than the standard dose\n(0.1 mmol/kg), easing worries about toxic metal buildup. Consequently,\nLPGT shows promise as a feasible CA for metal-free MRI.