Bio-Functionalized PLL-g-PEG coatings

INTRODUCTION: Titanium and its alloys are widely used for long-term implants in many applications such as orthopedics and osteosynthesis. Apart from its favorable mechanical strength and low specific weight, titanium has excellent corrosion resistance due to his natural surface oxide layer with a thickness of about 3-7 nm and it is considered biocompatible because of the low immune response in the body. Since material purity is essential to maximize the interfacial strength between bone and material, commercially pure (cp) titanium has become the material of choice for dental implants¹.

There are many factors including surgical technique, implant design, surface morphology and chemistry that influence the bone ongrowth to an implant. The optimization of surgical techniques and implant design had high priority in the past; today, surface-engineering has become an important area in the development of new implants.

CURRENT STATE OF THE ART: Possible approaches for the modification of implant surfaces can be divided into two main categories: morphological and (bio)chemical surface modification².

Morphological or roughness modification of titanium surfaces have been shown to be one of the important surface characteristics affecting cell response: different cell types react differently to surface topography (e.g. fibroblast show a preference for smoother surfaces whereas osteoblasts adhere more often on rougher topographies; see figure 2 for different cell-types).

The second group is also known as biomimetic modification, where peptide sequences (e.g. RGD) found in extracellular matrix (ECM) proteins of cells are immobilized on protein-resistant biomaterial surfaces via polymer chemistry (see figure 1).

These so-called bioactive ligands are recognized and bind to specific cell surface receptors such as integrins and transmembrane proteoglycans and therefore allows the bioengineer to create a cell-selective biomaterial surface³.

Running projects:

• Multifunctional titanium dental implant surface based on biochemically modified molecular assembly systems
• Synthesis and characterization of collagen mimetic peptide for engineering integrin specific surfaces

Related Subjects:

• Influence of surface chemistry and topography on titanium surfaces on cell beahavior

Literature:

¹ T. Albrektsson et al. Annals of Biomedical Engineering, 11:1–27, 1983.
² D.A. Puleo and A. Nanci. Biomaterials, 20(23-24):2311–2321, 1999. 3 G.M. Harbers et al. Biomimetic Materials and Design, 2002.