Enhanced Antibacterial and Immunomodulatory Porphyrin-Based MOF Coatings for PETG Clear Aligners: A Comparative Study of Ag, Cu, and Ce Metal Centers

Prolonged use of clear aligners promotes bacterial colonization and biofilm formation, which can compromise orthodontic outcomes. There is a clear clinical demand for approaches that can suppress pathogenic activity while preserving the fundamental functional and material characteristics of the aligners. To address this need, a novel strategy of fabricating metal–organic framework (MOF) coatings on aligners was adopted. Metal–organic frameworks (MOFs) have emerged as promising antibacterial coating materials by combining antimicrobial metal ions with biocompatible organic ligands. Three distinct porphyrin-based MOFs (Ag-, Cu-, and Ce-TCPP) were synthesized and fabricated as coatings on clear aligner surfaces via a coordination-driven self-assembly approach. The coated aligners were comprehensively assessed in vitro to determine their antibacterial performance, anti-inflammatory potential, biocompatibility, and key physical characteristics. Among the three coatings, Ag-TCPP showed the most favorable overall antibacterial and anti-biofilm performance in the present experimental system and facilitated macrophage polarization toward an anti-inflammatory M2-like phenotype. Ag-TCPP exhibited a significant inhibition zone of 6.75 ± 0.25 mm and reduced biofilm biomass by 72.2%. All MOF coatings exhibited excellent biocompatibility, and their application did not compromise the aligners’ mechanical integrity or aesthetic properties (light transmittance). This study reports the successful development of a novel metal–organic framework (MOF)-based coating strategy for clear aligners. Among the formulations investigated, the Ag-TCPP coating exhibited outstanding antibacterial and immunomodulatory performance while maintaining the critical mechanical integrity and aesthetic qualities of the aligner. The findings of this work offer a practical approach to designing multifunctional orthodontic devices that may reduce biofilm-related complications and improve clinical outcomes.