Nanofibrillar cellulose (NFC) hydrogel has emerged as a promising implantable material for therapeutic applications. In this study, the relatively longer-lived positron-emitting radionuclide zirconium-89 was chelated to the octadentate deferoxamine (DFO*)-conjugated NFC hydrogel (89ZrZr-DFO*-NFC) to enable longitudinal monitoring of its in vivo fate using positron emission tomography techniques. Following subcutaneous implantation in healthy mice, 89ZrZr-DFO*-NFC retained radioactivity at the implant site for at least 14 days, with minimal signal detected in the kidneys, urinary bladder, and overlying skin. In contrast, mice receiving a control formulation of 89ZrZr-oxalate mixed with NFC hydrogel showed progressive accumulation of radioactivity in the bones, consistent with known 89ZrZr-oxalate distribution patterns, and only limited retention at the implant site by Day 7. These findings demonstrate that 89ZrZr-DFO*-NFC hydrogel implants exhibit high in vivo stability with negligible systemic release following subcutaneous implantation, supporting their potential use as safe and traceable biomaterial platforms.
Zhuang et al. (Sat,) studied this question.