Synthesis and characterization of acrylic copolymers with RGD peptide to promote endothelial cell adhesion

The goal of this research was to design a biomaterial, using acrylic copolymers, which could support endothelial cells and function in small diameter vascular grafts, with fewer thrombosis problems than typical materials. Hexyl methacrylate (HMA) and octyl methacrylate (OMA) were used as comonomers to produce a material with a low glass transition temperature (T_g), so the material would be flexible. Methacrylic acid (MAA) provided ionic character to the copolymer, and methyl methacrylate (MMA) was selected because of its usage in other biomedical applications. Neutralization with sodium was employed to modify the mechanical properties. RGD peptides were attached to the copolymers to promote endothelial cell adhesion. Two methods were used to incorporate the peptide sequences. The first method explored the ability of peptide sequences to attach to a copolymer via chain transfer. The second method coupled the amine terminus of the peptides to the carboxyl groups in the copolymer. Human umbilical vein endothelial cell (HUVEC) adhesion to the copolymers was studied using confocal and optical microscopy.; The copolymer compositions that produced T_gs of approximately 0°C were 75 mol% OMA and 92 mol% HMA. The Young's moduli of the copolymers with 75 mol% OMA and 92 mol% HMA were approximately 0.50 and 0.37 MPa, respectively. These were below the desired value of 0.9 MPa. After partially neutralizing the HMA and OMA based copolymers with sodium cations, the Young's moduli increased to approximately 0.93 MPa and 0.99 MPa, respectively. The chain transfer method of peptide incorporation lowered the molecular weights and mechanical properties, while the coupling reaction method had little effect. The peptide concentrations for the chain transfer method of peptide incorporation ranged from 0.17 × 10−5 to 0.70 × 10−5 moles of peptide per gram of copolymer, compared with 0.83 × 10−5 and 8.1 × 10−5 moles/g for the coupling reaction method. Endothelial cell adhesion was not greatly affected by the method of peptide incorporation. As the peptide concentration increased, the number of cells adherent increased, up to a peptide concentration of approximately 0.50 × 10−5 moles/g. This indicates that endothelial cells achieve maximal adhesion at this peptide concentration.