Electrospun Scaffolds Functionalized with a Hydrogen Sulfide Donor Stimulate Angiogenesis

Tissue-engineered constructs are currently limited by the lack of vascularization necessary for the survival and integration of implanted tissues. Hydrogen sulfide (HS), an endogenous signaling gas (gasotransmitter), has been recently reported as a promising alternative to growth factors to mediate and promote angiogenesis in low concentrations. Yet, sustained delivery of HS remains a challenge. Herein, we have developed angiogenic scaffolds by covalent attachment of an HS donor to a polycaprolactone (PCL) electrospun scaffold. These scaffolds were engineered to include azide functional groups (on 1, 5, or 10% of the PCL end groups) and were modified using a straightforward click reaction with an alkyne-functionalized -thiocarboxyanhydride (alkynyl-NTA). This created HS-releasing scaffolds that rely on NTA ring-opening in water followed by conversion of released carbonyl sulfide into HS. These functionalized scaffolds showed dose-dependent release of HS based on the amount of NTA functionality within the scaffold. The NTA-functionalized fibrous scaffolds supported human umbilical vein endothelial cell (HUVEC) proliferation, formed more confluent endothelial monolayers, and facilitated the formation of tight cell-cell junctions to a greater extent than unfunctionalized scaffolds. Covalent conjugation of HS donors to scaffolds not only promotes HUVEC proliferation , but also increases neovascularization , as observed in the chick chorioallantoic membrane assay. NTA-functionalized scaffolds provide localized control over vascularization through the sustained delivery of a powerful endogenous angiogenic agent, which should be further explored to promote angiogenesis in tissue engineering.