An Innovative Hydrogel Incorporating Antibacterial Nanoparticles for Dental Pulp Regeneration

Objectives: Regenerating a functional dental pulp (DP) in the pulpectomized root canal was recently proposed as a novel therapeutic strategy in human endodontics. However, residual bacteria have been shown to hinder DP regeneration. In this context, designing antimicrobial scaffolds able to eliminate bacteria, while being not deleterious for DP-mesenchymal stem cell (DP-MSC) survival and pulp-like tissue regeneration, is needed. Our aim was to develop an innovative hydrogel incorporating clindamycin (CLIN)-releasing poly (D,L) lactic acid (PLA)-nanoparticles (CLIN/PLA-NPs) to confer this scaffold antibacterial property.
Methods: PLA-NPs and CLIN/PLA-NPs were synthesized by the solvent diffusion method. NP diameter and polydispersity index (PDI) were determined by dynamic light scattering, NP zeta potential by electrophoretic mobility and NP morphology by scanning electron microscopy. Efficiency of CLIN entrapment into PLA-NPs was determined by high performance liquid chromatography. NP release from the hydrogel was assessed using fluorescent PLA-NPs. Antibacterial activity of fibrin hydrogels containing CLIN/PLA-NPs, PLA-NPs or CLIN alone, was determined on Enterococcus fæcalis using the agar diffusion method. Human DP-MSCs and CLIN/PLA-NPs or CLIN alone were co-incorporated into 10 mg/mL fibrin hydrogels to get a final CLIN concentration of 50 µg/mL hydrogel. DP-MSC viability was determined with a Live/Dead^® kit in fibrin-alone, CLIN/PLA-NP/fibrin, PLA-NP/fibrin and CLIN/fibrin hydrogels.
Results: PLA-NPs and CLIN/PLA-NPs showed similar diameter, PDI and zeta potential, and a spherical morphology. CLIN entrapment efficiency was about 42%. The release of fluorescent NPs from the fibrin hydrogel was of 3% after 24 h. Fibrin hydrogels incorporating CLIN/PLA-NPs or CLIN alone had similar antibacterial activity. DP-MSC viability into the hydrogels was similar (about 75%) in the 4 conditions tested.
Conclusions: Incorporating CLIN/PLA-NPs within a fibrin hydrogel could be beneficial to promote DP regeneration thanks to the antibacterial effect of the CLIN/PLA-NPs and the absence of significant detrimental effect of CLIN, PLA-NPS and CLIN/ PLA-NPs on DP-MSC viability.