The effect of extracellular matrix proteins on the cellular response of HUVECS and HOBS after covalent immobilization onto titanium

Biomimetic surface modifications are regarded as promising approach to stimulate cellular behavior at the interface of implant materials. Aim of the study was an evaluation of the cellular response of human umbilical cord cells (HUVECS) and human osteoblasts (HOBS) on titanium covalently coated with the extracellular matrix (ECM) proteins fibrinogen, collagen, laminin, and osteopontin. For the surface modification, titanium discs were first amino-functionalized by plasma polymerization of allylamine. The ECM protein conjugation was performed using the linker molecule a, o-bis-N-hydroxysuccinimide polyethylene glycol (Di-NHS linker). For surface characterization, infrared spectroscopy and fluorescein isothiocyanate staining (FITC) were used to evaluate the presence and distribution of primary amines in the plasma polymer film. Real-time analyses of the respective protein conjugation processes were performed via surface plasmon resonance kinetic measurements. All ECM proteins were immobilized successfully. Furthermore, the biological functionality of the conjugated factors fibronectin and collagen could be proven as they led to a distinct stimulation of cell adhesion of HUVECS and HOBS when compared to the control group. The highest cell coverage of HUVECS was observed on fibronectin-modified surfaces with approximately 35% and on collagen with 33% after 24 h (PT: 9.4%). For laminin, no additional effect was observed, and for osteopontin, only a slight enhancement of cell adhesion was found. A similar, cell-stimulating tendency of fibronectin and collagen was seen as well after 3 and 7 days. Biomimetic surface modification via plasma polymerization is a powerful method for biomolecule conjugation with a high retention of biological functionality and offer promising clinical perspectives.