Cell Response Toward Inflammation of DPSCs Co-Cultured With Streptococcus mutans in the Presence of Alginate/Hydroxyapatite-Based Scaffolds Enriched With Silver Nanoparticles

Managing bone defects is challenging, with autologous grafts being the most effective treatment. Biomaterials like alginate/hydroxyapatite (Alg/Hap) composites are increasingly used due to their biocompatibility and osteoconductive properties. Graft implantation in the oral cavity may trigger inflammatory responses, such as periodontitis, pulpitis, or caries, due to biomaterial recognition as non-self and the presence of pathogens like Streptococcus mutans. Conjugating Alg/Hap composites with antimicrobial silver nanoparticles (nAg) offers a strategy to counteract oral inflammation caused by microbial biofilms. This study explores the anti-inflammatory and antibiofilm activities of these biomaterials during early implantation (24–72 h), as well as DPSC viability and collagen expression. A co-culture model of dental pulp stem cells (DPSCs) and Streptococcus mutans UA 159 strains was established. Streptococcus mutans viability and biofilm formation on scaffolds were evaluated through the live/dead assay and confocal microscopy. Lactate dehydrogenase (LDH), interleukin-6 (IL-6), and collagen type 1 from DPSCs were measured via ELISA assays. Nrf2 and COX-2 protein expression was evaluated by western blotting. Alg/Hap/nAg composites reduce S. mutans-derived biofilm formation, preserving biocompatibility toward DPSCs. Decreased IL-6 levels, restored collagen type 1 secretion (5.98 pg/mL in DPSCs-MOI 0.1-Alg/Hap/Ag vs. 3.04 pg/mL in DPSCs-Alg/Hap/Ag at 72 h), and modulation of antioxidant and inflammatory proteins were observed, including a two-fold increase of Nrf2 expression in cells seeded onto scaffolds in the presence of nAg. These findings highlight the potential of smart biomaterials to promote DPSC osteogenic and odontogenic differentiation, advancing oral tissue regeneration strategies.