Enhancing magnetic resonance imaging of bio-based nano-contrast via anchoring manganese on rod-shaped cellulose nanocrystals

Manganese-based nano materials used to enhance nano-contrasts in magnetic resonance imaging have low toxicity but suffer from a weak contrast imaging effect due to their low longitudinal relaxivity (r1). Moreover, the nanoparticle contrasts of manganese salt probably release manganese ions into the patient body during and after imaging process, causing potential toxicity problems. Thus, we took advantage of rod-shaped cellulose nanocrystals (CNCs) functionalized by diethylenetriamine pentaacetic dianhydride (coded as DCNCs) to anchor Mn2+ and improve its r1 for biocompatibility, highly chemical activity, and high specific area. Theoretical analysis indicated that the r1 could increase with the anchoring rate of Mn2+ on rod-shaped particles, and the large number of hydroxyl groups on CNCs made them able to carry as much as 5.9 mmol·g−1 of Mn2+. Then, we found the r1 increased linearly as the anchoring degree increased, up to 57.71 mM−1·s−1. The obtained DCNCs anchoring Mn2+ (Mn2+@DCNCs) nano-contrast showed low toxicity on RAW 264.7 and HUVEC, where the viability of the two cells was higher than 80%. Therefore, such a high r1 Mn2+-based material presents great advantage of commercial manganese and gadolinium contrasts, making the Mn2+@DCNCs of potential on diagnosing tumors and drug release.