Synergistically enhanced aspirin loading and pH-triggered controlled release via a ZIF-L/ZIF-8 hierarchical coating on titanium

To address the challenge of preventing peri-implantitis, the present study developed a pH-responsive drug delivery coating on titanium (Ti) implants for controlled aspirin release. A hierarchical metal-organic framework coating was constructed on alkali- and heat-treated titanium by sequentially synthesizing Zeolitic imidazolate framework-L (ZIF-L) and ZIF-8 (denoted AHTL8). Material characterization confirmed the successful fabrication of a hierarchical micro–nano structure, which significantly enhanced surface hydrophilicity. The AHTL8 system exhibited a remarkably high aspirin-loading capacity (0.227 mg) and intelligent release kinetics, with sustained delivery (77.36% over 72 h) at physiological pH (7.4) and rapid, extensive release (97.39% over 72 h) under acidic conditions pH (6.5). Furthermore, the coating demonstrated excellent cytocompatibility, and the aspirin-loaded AHTL8 significantly promoted the proliferation of mouse osteoblastic MC3T3-E1 cells. These findings indicate that the ZIF-L/ZIF-8 composite coating serves as a highly efficient pH-triggered platform with high drug-loading and responsive release capacity, and its excellent cytocompatibility and MC3T3-E1 proliferation-promoting effect provide a preliminary basis for its potential application in promoting osseointegration.