Vascular endothelial growth factor attachment to hydroxyapatite via self-assembled monolayers promotes angiogenic activity of endothelial cells

• Published in: Thin solid films 2013-06, Vol.537, p.256-262
• Main Authors: Solomon, Kimberly D., Ong, Joo L.
• Format: Article
• Language: English
• Subjects: Angiogenesis; Biomedical materials; Condensed matter: structure, mechanical and thermal properties; Endothelial cells; Exact sciences and technology; Growth factors; Hydroxyapatite; In vitro testing; Physics; Self-assembled monolayers; Structure and morphology; thickness; Surface chemistry; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Surgical implants; Thin film structure and morphology; Vascular endothelial growth factor
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.04.113

Currently, tissue engineered constructs for critical sized bone defects are non-vascularized. There are many strategies used in order to promote vascularization, including delivery of growth factors such as vascular endothelial growth factor (VEGF). In this study, hydroxyapatite (HA) was coated with self-assembled monolayers (SAMs). The SAMs were in turn used to covalently bind VEGF to the surface of HA. The different SAM chain length ratios (phosphonoundecanoic acid (11-PUDA):16-phosphonohexadecanoic acid (16-PHDA) utilized in this study were 0:100, 25:75, 50:50, 75:25, and 100:0. Surfaces were characterized by contact angle (CA) and atomic force microscopy, and an in vitro VEGF release study was performed. It was observed that CA and root-mean-squared roughness were not significantly affected by the addition of SAMs, but that CA was significantly lowered with the addition of VEGF. VEGF release profiles of bound VEGF groups all demonstrated less initial burst release than adsorbed control, indicating that VEGF was retained on the HA surface when bound by SAMs. An in vitro study using human aortic endothelial cells (HAECs) demonstrated that bound VEGF increased metabolic activity and caused sustained production of angiopoietin-2, an angiogenic marker, over 28days. In conclusion, SAMs provide a feasible option for growth factor delivery from HA surfaces, enhancing angiogenic activity of HAECs in vitro. •Vascular endothelial growth factor (VEGF) is attached to hydroxyapatite (HA).•Self-assembled monolayers (SAMs) delay the release of VEGF from hydroxyapatite.•SAM chain length ratio affects the total mass of VEGF released.•VEGF on HA up-regulates proliferation and angiogenic activity of endothelial cells.