ABSTRACT
Adhesion and spreading of cells on biomaterials are integrin-mediated processes. But recent findings indicate a key role of the cell membrane associated matrix substance hyaluronan (HA) in interface interactions. Because HA is a negatively charged molecule we assume that a biomaterial surface with an opposed charge could boost the first contact of the cell to the surface. Polished cp titanium (R(a)=0.19 microm) was coated with an amino-group containing plasma polymer (Ti PPA). For this purpose, a microwave excited, pulsed, low-pressure plasma was used. Additionally, collagen was immobilized on Ti PPA with polyethylene glycol diacid (PEG-DA), catalyzed by carbodiimide (CDI). The physico-chemical surface analytical techniques like XPS, FT-IR, water contact angle and zeta-potential verified the retention of the allylamine precursor structure. Human osteoblasts were cultured in serum-free Dulbecco's modified Eagle medium (DMEM). Adhesion and cell cycle phases were calculated by flow cytometry. Spreading and actin cytoskeleton were visualized by confocal microscopy. Gene expression of osteogenic markers was detected by real-time RT-PCR. Ti PPA is significantly advantageous concerning initial adhesion and spreading during the first hours of the cell contact to the surface. The proliferation of osteoblasts is positively influenced. Gene expression of the differentiation marker bone sialoprotein was upregulated after 24h. Our results demonstrate that functionalization of titanium with positively charged amino-groups is sufficiently enough to significantly improve initial steps of the cellular contact to the material surface.
Subject(s)
Allylamine/chemistry , Osteoblasts/physiology , Polymers/chemistry , Titanium/chemistry , Actins/chemistry , Alkaline Phosphatase/genetics , Carbodiimides/chemistry , Catalysis , Cell Adhesion/physiology , Cell Cycle , Collagen Type I/chemistry , Collagen Type I/genetics , Collagen Type I/radiation effects , Cytoskeleton/chemistry , Flow Cytometry , Gene Expression Profiling , Humans , Microwaves , Polyethylene Glycols/chemistry , Polyethylene Glycols/radiation effects , Polymers/radiation effects , Procollagen/chemistry , Procollagen/genetics , Procollagen/radiation effects , Reverse Transcriptase Polymerase Chain Reaction , Surface Properties , Titanium/radiation effects , Tumor Cells, CulturedABSTRACT
The crucial factor of metal implant ingrowth in the bone is the rapid cellular acceptance. Therefore, the knowledge about additionally used adhesion mechanisms of osteoblasts, like their negatively charged hyaluronan coat, generates new surface functionalization strategies. Here, titanium was coated with a very thin, adherent, cross-linked, pinhole- and additive-free allylamine plasma polymer layer (PPAAm) resistant to hydrolysis and delamination and equipped with a high density of positively charged amino groups. This plasma polymer-functionalization of titanium is advantageous concerning osteoblastic focal adhesion formation as vinculin and paxillin, actin cytoskeleton development and, in consequence in differentiated cell functions, compared to a pure titanium surface-but similar such as the collagen I bonded surface via a polyethylenglycol-diacid (PEG DA)-spacer.
