Electroactive graphene oxide-incorporated collagen assisting vascularization for cardiac tissue engineering.

The application of a cardiac patch over the epicardial surface has shown positive effects in protecting cardiac function postinfarction. Electroactive patches could enhance electrical signal propagation among cardiac cells. In the present study, an electrically active composite of collagen and graphene oxide (Col-GO) was fabricated as a cardiac patch. Col scaffolds were fabricated using a freeze-drying method and coated covalently with GO. Some scaffolds were also reduced by a reduction agent to restore the high conductivity of GO. GO was shown to be a single layer with suitable lateral size for biological application. The Col-GO scaffolds contained randomly oriented interconnected pores with appropriate pore sizes of 120-138 ± 8 μm. GO flakes were also well distributed in the pore walls. By increasing the GO concentration, the tensile strength of the scaffolds was enhanced from 75 kPa for Col-GO-5 to 162 kPa for Col-GO-90. Young modulus also followed the same trend. Electrical conductivity of the scaffolds was in the range of semi-conductive materials (~10-4 S/m), which is suitable for cardiac tissue engineering applications. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated no toxic effects on human umbilical vein endothelial cells (HUVECs) after 96 h. Also, a 10-days degradation product of the samples was compatible with HUVECs. Reduced scaffolds supported neonatal cardiomyocyte adhesion and upregulated the expression of the cardiac genes, including Cx43, Actin4, and Trpt-2 than their nonconductive counterparts. The obtained results confirmed the angiogenic properties of reduced Go-containing materials for cardiovascular applications where angiogenesis plays an important role, especially postinfarction.