PH‐Responsive Psoralen Delivery System for Infected Bone Defects: Spatiotemporal Photothermal Disinfection Coupled with Osteogenesis and Osteoclast Regulation

Why It Matters

It offers a single, targeted solution to the twin challenges of infection control and bone regeneration, potentially reducing reliance on systemic antibiotics and multiple surgeries.

Key Takeaways

• pH-sensitive ZIF-8 releases psoralen in acidic infection sites
• Polydopamine coating adds photothermal antibacterial capability
• Optimized psoralen loading balances osteogenesis and antimicrobial action
• In rat calvarial defects, pathogens eliminated, bone growth increased
• Platform enables sequential therapy via microenvironment-triggered degradation

Pulse Analysis

Infected bone defects remain one of the most stubborn clinical problems, demanding both aggressive antimicrobial treatment and robust tissue regeneration. Traditional approaches often separate these goals, using systemic antibiotics to clear infection followed by grafts or scaffolds for bone repair. This fragmented strategy can lead to prolonged hospital stays, antibiotic resistance, and suboptimal healing. Emerging nanomedicine platforms aim to merge these functions, delivering drugs directly to the pathological site while providing cues that stimulate the body’s own repair mechanisms.

The PSO/ZIF‑8@PDA (PZP) nanoparticle exemplifies this convergence. Its core of zeolitic imidazolate framework‑8 (ZIF‑8) is inherently pH‑sensitive, disintegrating quickly in the acidic milieu typical of infected bone while remaining stable in neutral tissue. Encapsulated psoralen, a photo‑active compound, is released in a controlled, concentration‑dependent manner, first exerting antibacterial effects. A polydopamine shell adds a photothermal dimension: upon near‑infrared irradiation, localized heating further kills microbes and accelerates drug diffusion. The sequential release profile ensures that pathogen eradication precedes osteogenic signaling, aligning therapeutic timing with the body’s natural healing phases.

Preclinical testing in polymicrobial rat calvarial models demonstrated the platform’s dual efficacy: complete clearance of Staphylococcus aureus and Escherichia coli, followed by significant new bone formation and reduced osteoclast activity. These findings suggest a pathway toward clinical translation, where a single injectable nanocarrier could replace multiple interventions. Beyond orthopedic infections, the design principles—microenvironment‑responsive degradation, photothermal augmentation, and spatiotemporal drug release—could be adapted for other infected or inflamed tissues, expanding the impact of regenerative nanomedicine across specialties.