PHBV wet-spun scaffold coated with ELR-REDV improves vascularization for bone tissue engineering

Abstract

A bone tissue replacement with relevant anatomical size requires the production of 3D scaffolds, which in turn limits the mass transport of nutrients and oxygen to sustain cell survival. A viable vascular network is required to overcome this problem. However, this cannot be established immediately after the implantation of a scaffold. The aim of this study was to develop a 3D wet-spun bone tissue engineering scaffold, coated with an elastin-like recombinamer (ELR) peptide with an endothelial cell-attracting REDV sequence to promote early vascularization. Scaffolds were produced using biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and an ELR was immobilized onto it after oxygen plasma treatment (PHBV-O₂-ELR-REDV). O₂ plasma treatment and ELR modification of the PHBV changed the wettability, topography, and composition of the surface. A moderately hydrophilic surface was obtained after oxygen plasma treatment and ELR-REDV coating with a contact angle of 66.63 ± 0.77°. The surface roughness decreased after plasma treatment from 343.4 to 160.0 nm and increased to 280.3 nm after ELR-REDV coating. FTIR-ATR showed amide I and amide II bonds after ELR-REDV coating showing that the coating was successful. Scaffolds were tested in vitro with rabbit bone marrow mesenchymal cells. ELR modification did not cause a significant difference in adhesion or proliferation compared to unmodified controls. On the other hand, ELR-modified scaffolds attracted a higher number of human umbilical vein endothelial cells (HUVECs) due to the REDV sequence. The Alamar Blue test and confocal laser scanning microscopy micrographs showed that HUVEC migration and attachment on PHBV-O₂-ELR-REDV scaffolds was around 2.5-fold higher than untreated PHBV scaffolds after 14 d. Plasma-treated scaffolds (PHBV-O₂) showed an increase in the number of adhered HUVECs due to increased surface wettability. It can, therefore, be suggested that PHBV-O₂-ELR-REDV scaffolds have significant potential to induce early vascularization due to increased attractiveness for endothelial cells. This could alleviate the vascularization problem of 3D implants for bone tissue engineering.