Magnetic 3D scaffold: A Theranostic tool for tissue regeneration and non-invasive imaging In vivo.

We report an osteoconducting magnetic 3D scaffold using Fe2+ doped nano-hydroxyapatite-Alginate-Gelatin (AGHFe1) for Magnetic Resonance Imaging based non-invasive monitoring of bone tissue regeneration. In rat cranial defect model, the scaffold facilitated non-invasive monitoring of cell migration, inflammatory response and matrix deposition by unique changes in transverse relaxation time (T2). Cell infiltration resulted in a considerable increase in T2 from ~37 to ~62msec, which gradually returned to that of native bone (~23msec) by 90days. We used this method to compare in vivo performance of scaffold with bone-morphogenic protein-2 (AGHFe2) or faster degrading (AGHFe3). MRI and histological analysis over 90days showed non-uniform bone formation in AGHFe1 with ∆T2 (T2Native bone - T2 Regenerated bone ) ~13msec, whereas, AGHFe2 and AGHFe3 showed ∆T2 ~ 09 and 05msec respectively, suggesting better bone formation in AGHFe3. Thus, we show that MR-contrast enabled scaffold can help better assessment of bone-regeneration non-invasively.