Controlled heparin conjugation on electrospun poly ($varepsilon$-caprolactone)/gelatin fibers for morphology-dependent protein delivery and enhanced cellular affinity

Electrospun fibrous scaffolds have now been shown to possess great potential for tissue engineering applications, owing to their unique mimicry of natural extracellular matrix structure. In this study, poly(e-caprolactone) and gelatin were electrospun to fabricate tissue-engineered scaffolds with three different fibermorphologies (1.0 µm, 3.0 µm and co-electrospun containing both 1.0 and 3.0 µm diameter fibers). Subsequently, these scaffolds were conjugated with heparin to immobilize a bioactive molecule by electrostatic interactions. This study determined the quantity of heparinconjugation on the scaffolds and that the crosslinking time and the fibermorphologies govern the extent of heparinconjugation on the fibers. In order to evaluate the release capacity of the heparin-conjugated scaffolds, lysozyme was used as a model protein for conjugation. The heparin-conjugated scaffolds provided high loading efficiency and cumulative release of lysozyme with a relatively linear relationship. In addition, the release kinetics was significantly dependent on heparinconjugation and fibermorphology. This fundamental investigation into how fibermorphology and crosslinking protocols can affect the heparin binding ability of electrospunfibers is crucial for predicting the delivery of many different types of bioactive molecules from an electrospun scaffold for tissue engineering applications.