Long-term delivery of growth factors and immunomodulatory agents is highly required to support the integrity of tissue in engineering constructs, e.g., formation of vasculature, and to minimize immune response in a recipient. However, for proteins with a net positive charge at the physiological pH, controlled delivery from negatively charged alginate (Alg) platforms is challenging due to electrostatic interactions that can hamper the protein release. In order to regulate such interactions between proteins and the Alg matrix, we propose to complex proteins of interest in this study - CXCL12, FGF-2, VEGF - with polyanionic heparin prior to their encapsulation into Alg microbeads of high content of α-L-guluronic acid units (high-G). This strategy effectively reduced protein interactions with Alg (as shown by model ITC and SPR experiments) and, depending on the protein type, afforded control over the protein release for at least one month. The released proteins retained their in vitro bioactivity: CXCL12 stimulated the migration of Jurkat cells, and FGF-2 and VEGF induced proliferation and maturation of HUVECs. The presence of heparin also intensified protein biological efficiency. The proposed approach for encapsulation of proteins with a positive net charge into high-G Alg hydrogels is promising for controlled long-term protein delivery under in vivo conditions.

Centre for Advanced Materials Application of the Slovak Academy of Sciences Dubravska cesta 9 845 11 Bratislava Slovakia

Department of Biomaterials and Tissue Engineering Institute of Physiology of the Czech Academy of Sciences Videnska 1083 142 20 Prague Czech Republic

Department of Chemical Engineering University of Chemistry and Technology Technicka 5 166 28 Prague Czech Republic

Institute of Macromolecular Chemistry Czech Academy of Sciences Heyrovsky sq 2 162 06 Prague Czech Republic

Polymer Institute of the Slovak Academy of Sciences Dubravska cesta 9 845 41 Bratislava Slovakia

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