A Nanomedicine Strategy: Spatiotemporally Programmed Delivery of Engineered Exosomes via Smart Scaffolds for...

The convergence of nanomedicine and regenerative biology offers new paradigms for tissue repair. The reconstruction of critical-sized bone defects, particularly within the anatomically intricate and physiologically distinct landscape of the craniomaxillofacial (CMF) region, represents a formidable frontier in regenerative medicine. Bone regeneration is not a singular biological event but a temporally orchestrated symphony, necessitating the precise, sequential coordination of immunomodulation, angiogenesis, and osteogenesis. While mesenchymal stem cell-derived extracellular vesicles (MSC-Exos) have emerged as a paradigm-shifting cell-free therapeutic - circumventing the engraftment instability, tumorigenicity, and immunogenicity limitations of live cell therapies-their clinical translation remains hindered by a fundamental kinetic mismatch: the delivery of a static, unmodulated bolus to a highly dynamic wound microenvironment. Current therapeutic strategies predominantly rely on simple injection or bulk incorporation of MSC-Exos into scaffolds. These static delivery paradigms fail to recapitulate the physiological rhythm of healing, often creating a kinetic mismatch between a single therapeutic cargo and the host's changing needs. This review bridges a critical synthesis gap by proposing a novel "spatiotemporal programming" framework for bone regeneration. We systematically integrate cargo engineering strategies (eg, hypoxic/inflammatory priming, genetic modification) with smart biomaterial design (eg, stimuli-responsive hydrogels, core-shell scaffolds) to achieve sequential, phase-specific delivery. By aligning exosomal bioactivity with the intrinsic immuno-angiogenic-osteogenic cascade and emphasizing cargo tailoring for craniomaxillofacial specificity, this work provides a translational roadmap for next-generation, precision-guided skeletal reconstruction.