Development of a Thermoresponsive Core-Shell Hydrogel for Sequential Delivery of Antibiotics and Growth Factors in Regenerative Endodontics.

Abstract

Background: Regenerative endodontics requires an innovative delivery system to release antibiotics/growth factors in a sequential trend. This study focuses on developing/characterizing a thermoresponsive core-shell hydrogel designed for targeted drug delivery in endodontics.

Methods: The core-shell chitosan-alginate microparticles were prepared by electrospraying to deliver bone morphogenic protein-2 for 14 days and transforming growth factor-beta 1 (TGF-β1) for 7-14 days. Methylcellulose (MC) and gelatin were utilized to create the core-shell hydrogel to load a modified triple antibiotic combination (penicillin G/metronidazole/ciprofloxacin (PMC)) and growth factor-loaded microparticles in the shell and the core compartments, respectively. Morphological assessment, core-shell structural analysis, FTIR analysis, rheological analysis, swelling, and degradation rate studies were conducted for characterization. The viability of dental pulp stem cells (DPSCs) upon antibiotic exposure, antibacterial activity, and release studies of PMC and growth factors were investigated. Cellular studies (cell viability, alkaline phosphatase (ALP) activity, osteo/odontoblast gene expression (using Reverse transcription-polymerase chain reaction (RT-PCR)) and in vivo studies (inflammatory response and differentiation potential of the developed hydrogel by subcutaneous implantation in rats via histological examination) were assessed.

Results: The hydrogel showed a porous microstructure with interconnected pores. Core-shell structure analysis confirmed the successful extrusion of the MC hydrogel to the surface. FTIR analysis revealed interactions between MC and gelatin. Rheological analysis indicated time-dependent gel formation, supporting thermosensitivity at 37 °C. Swelling occurred rapidly, and degradation reached 62.42% on day 45. Further, antibiotics exhibited no cytotoxicity on DPSCs. Sequential release of antibiotics and growth factors was observed for up to 5 and 14 d, respectively. The hydrogel showed antibacterial activity. DPSCs exhibited increased proliferation, ALP activity, and odontoblast gene expression. In vivo studies showed that the biocompatible drug-loaded hydrogel exhibited more mineralization than the control.

Conclusions: The developed core-shell hydrogel containing PMC and growth factor-loaded core-shell microparticles provided a versatile and biocompatible platform for sequential drug delivery in regenerative endodontics. The system demonstrates promising characteristics for dentin regeneration, making it a potential candidate for clinical applications.