Extracellular matrix-mimic nanofibrous microspheres: fabrication and application in stem cell delivery for tissue repair and regeneration.

Stem cells, featuring remarkable self-renewal ability, unique multi-differentiation potential, distinguished paracrine effect and strong immunomodulatory function, have emerged as a powerful and competitive candidate for treating severe diseases and injuries. Direct injection of stem cells always suffers from limited cell retention in target tissues. Growing evidence suggests that nanofibrous microspheres with natural extracellular matrix-like topography, interconnected pores, high porosity, high specific surface area, and distinct injectability may serve as promising stem cell carriers that facilitate cell attachment, spreading, proliferation, retention and expression of specific genes. Over the past few decades, tremendous efforts have been devoted to developing nanofibrous microspheres with diverse composition, size, morphology and structure by using a variety of fabrication techniques. In this review, we provide an overview of recent progress in the development of nanofibrous microspheres with a focus on their preparation method, chemical composition, physicochemical property, and bioactivity, and highlight challenges and perspectives for future research directions.