Quantitative characterization of functionally modified micron–submicron fibers for tissue regeneration: a review

Tissue regeneration relies on building carefully crafted scaffold material in the micron–submicron scale and imparting specific functionality in order to best mimic the in vivo environment in terms of chemical composition, morphology, and surface functional groups. Fibrous meshes with structural features at the micron to submicron level for ideal three-dimensional tissue regeneration scaffolds can be an inexpensive scale-up option. Bio-inert polymers lack the functional motifs for specific bioactivity; however, functionalization of the scaffolds can provide biological functions to actively induce tissue regeneration and promote cell adhesion by targeting specific cell–matrix interactions. It is therefore important to characterize the scaffolds and understand the relationship between the efficacy of the functionalization, the surface properties of the scaffolds, and their biological performance. This paper is a comprehensive review of the current understanding in functionalization and characterization of fibrous scaffolds and their biological efficacy. We begin with a compilation of various functionalization schemes including physical adsorption, co-electrospinning, wet chemical techniques, and surface graft polymerization methods and their application to fibers. After a critical literature review, the state of the art for characterization of these functionalized nano-fibers is then discussed. We emphasize the importance of covalent binding of biomolecules and the subsequent need for characterization of functional group distribution, or local density of functionalization, on the scaffold surface. Current challenges and future directions are outlined so that quantitative characterization of scaffold surfaces can aid in the development of next generation scaffolds.