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 ~62 ms, which gradually returned to that of native bone (~23 ms) by 90 days. 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 90 days showed non-uniform bone formation in AGHFe1 with ∆T2 (T2_{Native bone} - T2 _{Regenerated bone}) ~13 ms, whereas, AGHFe2 and AGHFe3 showed ∆T2 ~ 09 and 05 ms respectively, suggesting better bone formation in AGHFe3. Thus, we show that MR-contrast enabled scaffold can help better assessment of bone-regeneration non-invasively.