Multifunctional PAMAM nanoparticles with sequential antimicrobial-remineralization therapy for dentin caries management

Dentin caries is a multifactorial pathological process characterized by bacterial colonization and biofilm formation that result in concurrent acid-mediated demineralization and matrix metalloproteinase (MMP)-mediated degradation of the collagenous matrix. While remineralization therapies offer minimal invasiveness, their long-term efficacy is compromised by ongoing collagen degradation and persistent bacterial acid production that counteract remineralization efforts. To address these limitations, we designed PAMAM-G4@EG (PGE) nanoparticles (NPs) using polyamide amine (PAMAM) dendrimers as mineral deposition templates, with antimicrobial peptide G(IIKK)₄I-NH₂ (G4) grafted onto the external surface groups and epigallocatechin gallate (EG) encapsulated within the internal cavities to provide biofilm disintegration and collagen protection for comprehensive dentin caries intervention. First, the PGE NPs reach lesion surfaces and accelerate EG release under acidic conditions. EG loosens <i>Streptococcus mutans</i> (<i>S. mutans</i>) biofilms, followed by G4-mediated disruption of planktonic <i>S. mutans</i> cell membranes. <i>In vitro</i> antimicrobial assays demonstrated a bactericidal efficacy of 99.75% after PGE intervention. Upon deeper lesion penetration, PGE releases EG to inhibit MMP activity and preserve the collagen scaffold, achieving a 74% reduction in hydroxyproline (HYP) levels. Simultaneously, PAMAM promotes controlled hydroxyapatite (HA) deposition, facilitating dentin remineralization. Treatment with PGE in artificial saliva containing collagenase restored dentin hardness to 89.88% of intact values. <i>In vivo</i> validation using a rat caries model confirmed therapeutic efficacy through significant reductions in Keyes scores, decreased salivary <i>S. mutans</i> counts, and increased molar mineral density. These findings demonstrate the therapeutic efficacy of PGE in dentin caries prevention and treatment, supporting its potential for clinical application.