Ultrathin polymer fibers hybridized with bioactive ceramics: A review on fundamental pathways of electrospinning towards bone regeneration

Electrospun ultrathin polymer fibers hybridized with bioactive ceramics find use in many biomedical applications due to their unique and versatile abilities to modulate structure–performance relationships at the nano–bio interface. These organic–inorganic hybrid fibers present synergies that are otherwise rare, even when the precursors are used individually, such as bioactivity in polymers and stiffness–toughness balance in bioactive ceramics. Despite these unique advantages, a comprehensive and timely review on this important topic is still missing. Herein we describe the most recent and relevant developments on electrospun ultrathin polymer fibers hybridized with bioactive ceramics, with emphasis on bone tissue regeneration. This review addresses the preparation of bioactive ceramics, particularly (nano) hydroxyapatite (HA; nHA) and bioactive glass (BG), which stand out as the ceramics of interest for bone regeneration. The anatomy and mechanical properties of bone as well as fundamental tissue–scaffold interaction mechanisms are covered. The process–structure–property relationships of electrospun ultrathin fibers are discussed in detail from a technical standpoint, as well as fabrication strategies, process variables, characterization methods, and biological requirements (in vitro and in vivo performances). Finally, we highlight the major challenges and outline perspectives to pave the route for the next-generation hybrid materials for bone tissue engineering.