Multifunctional Ph-Responsive Nanozymes For Vital Pulp Therapy

Aim or purpose This study develops pH-responsive nanozymes to overcome impaired pulp repair in caries-induced pulpitis by sequentially eliminating bacterial infection through enzymatic cascades, modulating inflammatory responses, and promoting hDPSC differentiation, thereby offering an integrated therapeutic strategy for vital pulp preservation. Materials and methods Zn-Fe nanozymes (ZFNs) were synthesized via the solvothermal method. The enzymatic activities of ZFNs at different pH levels were assessed. Antibacterial efficacy against Streptococcus mutans biofilms was quantified through colony-forming unit (CFU) assays. Primary hDPSCs were cultured under four conditions: control, LPS-induced inflammation (10 μg/mL), and LPS with ZFNs treatment (20 or 40 μg/mL). Comprehensive evaluations included: cell viability (CCK-8), intracellular ROS (DCFH-DA), osteogenic differentiation capacity (ALP activity and Alizarin Red S staining), and gene expression analysis (qPCR for inflammatory markers IL-6/IL-1β/TNF-α and mineralization markers RUNX2/OCN/DSPP/DMP-1). Results ZFNs demonstrated pH-responsive therapeutic effects, with 20 μg/mL combined with 200 μM H₂O₂ achieving 95% S. mutans eradication. Both ZFNs concentrations (20 and 40 μg/mL) significantly enhanced hDPSC proliferation while reducing inflammatory cytokine expression. The ZFNs promoted osteo/odontogenic differentiation, evidenced by increased ALP activity, enhanced mineralization, and upregulated differentiation marker expression in inflammatory conditions(P<0.05). Conclusions The ZFNs represent pH-responsive nanozymes capable of exhibiting POD-like activity in acidic conditions and CAT-like activity in neutral environments. These nanozymes demonstrate excellent antibacterial properties while effectively mitigating LPS-induced inflammatory damage in hDPSCs and promoting osteogenic/odontogenic differentiation of hDPSCs under inflammatory conditions.