Fibrin-based scaffolds for dental pulp regeneration: from biology to nanotherapeutics.

Tissue engineering-based endodontic therapies, designed to regenerate the dental pulp (DP) in the devitalised endodontic space, have been proposed to improve tooth longevity compared to conventional root-filling therapies. Their aim is to restore tooth vitality and major DP functions necessary to maintain tooth health such as immunosurveillance, sensitivity and healing/repair/regenerative capacities. Several formulations based on the use of fibrin, the main component of the blood clot matrix, recently gave valuable results in the regeneration of the human DP. This review describes recent fibrin-based scaffolds designed for that purpose. After having presented the various strategies for DP regeneration, the main fibrin-based scaffolds reported so far for clinical use in endodontics were reviewed. Particular emphasis was given to hydrogel devices that may be improved by incorporation of bioactive molecules that stimulate vascularisation and tissue neoformation or provide antibacterial properties. Data indicate that fibrin-based scaffolds constitute a highly favourable environment for mesenchymal stem cells, which is maintained upon functionalisation. Additional knowledge is needed to understand how fibrin and functionalising agents affect adhesion, survival, proliferation, migration and differentiation of cells incorporated in the scaffold or which will colonise it from neighbouring host tissues. This knowledge is needed to adapt the hydrogel formulation for various clinical conditions.

Development of an antibacterial nanocomposite hydrogel for human dental pulp engineering.

Hydrogel-based regenerative endodontic procedures (REPs) are considered to be very promising therapeutic strategies to reconstruct the dental pulp (DP) tissue in devitalized human teeth. However, the success of the regeneration process is limited by residual bacteria that may persist in the endodontic space after the disinfection step and contaminate the biomaterial. The aim of this work was to develop an innovative fibrin hydrogel incorporating clindamycin (CLIN)-loaded Poly (d,l) Lactic Acid (PLA) nanoparticles (NPs) to provide the hydrogel with antibacterial properties. CLIN-PLA-NPs were synthesized by a surfactant-free nanoprecipitation method and their microphysical properties were assessed by dynamic light scattering, electrophoretic mobility and scanning electron microscopy. Their antimicrobial efficacy was evaluated on Enteroccocus fæcalis by the determination of the minimal inhibitory concentration (MIC) and the minimal biofilm inhibition and eradication concentrations (MBIC and MBEC). Antibacterial properties of the nanocomposite hydrogel were verified by agar diffusion assays. NP distribution into the hydrogel and release from it were evaluated using fluorescent PLA-NPs. NP cytotoxicity was assessed on DP mesenchymal stem cells (DP-MSCs) incorporated into the hydrogel. Type I collagen synthesis was investigated after 7 days of culture by immunohistochemistry. We found that CLIN-PLA-NPs displayed a drug loading of 10 ± 2 µg per mg of PLA polymer and an entrapment efficiency of 43 ± 7%. Antibiotic loading did not affect NP size, polydispersity index and zeta potential. The MIC for Enterococcus fæcalis was 32 µg mL-1. MBIC50 and MBEC50 were 4 and 16 µg mL-1, respectively. CLIN-PLA-NPs appeared homogenously distributed throughout the hydrogel. CLIN-PLA-NP-loaded hydrogels clearly inhibited E. faecalis growth. DP-MSC viability and type I collagen synthesis within the fibrin hydrogel were not affected by CLIN-PLA-NPs. In conclusion, CLIN-PLA-NP incorporation into the fibrin hydrogel gave the latter antibacterial and antibiofilm properties without affecting cell viability and function. This formulation could help establish an aseptic environment supporting DP reconstruction and, accordingly, might be a valuable tool for REPs.