Conformation-Engineered Silk Fibroin Microspheres: Controllable Fabrication toward Precision Biomedical Platforms

Abstract Polymer microspheres have garnered significant interest in biomedical applications owing to their tunable size, high specific surface area, and high drug-loading capacity. Silk fibroin (SF), a natural protein with excellent biocompatibility, controllable biodegradability, and favorable mechanical properties, has emerged as a promising building block for biomedical microspheres. Despite rapid progress, a systematic review of the structural design, functional regulation, and application landscape of SF microspheres remains lacking. This review provides a comprehensive overview of fabrication techniques, hierarchical structural modulation strategies, and biomedical applications of SF microspheres. We first critically assess mainstream fabrication methods, including emulsification, phase separation, electrospray, and microfluidics, highlighting their advantages and limitations. We then discuss strategies for modulating the physical properties of microspheres through controlled manipulation of SF secondary conformations, particularly β-sheet formation, and summarize approaches to tune their size, morphology, porous architecture, and surface and interfacial properties. Next, we review recent advances in drug delivery, soft tissue repair, hard tissue regeneration, and tumor therapy, highlighting the multifunctional performance of SF microspheres in complex biological environments. Finally, we identify key challenges, including scalable manufacturing, batch-to-batch reproducibility, and long-term in vivo safety, and provide perspectives on future directions for advancing SF microspheres toward biomedical translation.