A Multifunctional Injectable Platform for Regenerative Endodontics

Objective: In this study, we aim to develop and characterize an injectable, photocrosslinkable gelatin methacryloyl (GelMA) hydrogel incorporating manganese dioxide (MnO₂) nanoparticles as a multifunctional scaffold for dental pulp stem cell (DPSC) delivery in regenerative endodontics.

Methods: MnO₂ nanoparticles were synthesized via redox precipitation and characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS) to confirm morphology and particle size. Gelatin methacryloyl (GelMA) was synthesized by reacting porcine gelatin with methacrylic anhydride, followed by dialysis and lyophilization. Structural confirmation was done using proton nuclear magnetic resonance (¹H NMR). MnO₂ nanoparticles were incorporated into 10% (w/v) GelMA at concentrations of 25, 50, and 100 µg/mL. FTIR analysis was performed to assess nanoparticle–GelMA interactions. Hydrogel injectability was evaluated using a 25G needle. Swelling behavior was measured after 24 h of immersion in PBS. Enzymatic degradation was assessed over 14 days in 1 U/mL collagenase. Biocompatibility was assessed via the MTS assay using human dental pulp stem cells (DPSCs).

Results: TEM and DLS analyses confirmed spherical MnO₂ nanoparticles with an average size of ~60 nm. GelMA methacrylation was validated by ¹H NMR, with distinct vinyl proton peaks observed at ~5.5 and ~5.7 ppm, confirming successful functionalization with methacryloyl groups. FTIR spectra of MnO₂ revealed characteristic Mn–O stretching vibrations around 500–530 cm⁻¹ and broad –OH stretching peaks near 3400 cm⁻¹, confirming the presence of surface hydroxyl groups and metal–oxide bonding. All MnO₂-GelMA formulations maintained smooth injectability through a 25G needle. Swelling studies showed no statistically significant differences among groups. However, incorporation of MnO₂ reduced enzymatic degradation, with higher concentrations exhibiting slower mass loss over 14 days in 1 U/mL collagenase. MTS assays demonstrated high DPSC viability at 24 and 72 hours, with the 100 µg/mL MnO₂–GelMA group exhibiting the highest metabolic activity.

Conclusion: The MnO₂–GelMA hydrogel system exhibits promising characteristics as an injectable, cytocompatible, and degradation-resistant scaffold for regenerative endodontics.