Capability of Differently Charged Plasma Polymer Coatings for Control of Tissue Interactions with Titanium Surfaces

Abstract

Titanium surfaces were equipped with positively and negatively charged chemical functional groups by plasma polymerization. Their capability to influence the adhesion of human mesenchymal stem cells (hMSCs) and inflammation processes was investigated on titanium substrates, which are representative of real implant surfaces.For these purposes, titanium samples were coated with plasma polymers from allylamine (PPAAm) and acrylic acid (PPAAc). The process development was accompanied by physicochemical surface analysis using XPS, FT-IR and contact angle measurements. Very thin plasma polymer coatings were created, which are resistant to hydrolysis and delamination. Positively charged amino groups improve considerably the initial adhesion and spreading steps of hMSCs. PPAAm and PPAAc surfaces have an effect on the differentiation of hMSCs, e.g., the expression of osteogenic markers in dependence on culturing conditions. Acrylic acid groups appear to stimulate early mRNA differentiation markers (ALP, COL, Runx2) under basal conditions, whereas positively and negatively charged groups both stimulate late differentiation markers, like BSP and OCN, after 3 days of osteogenic stimulation.Long-term intramuscular implantation in rats revealed that PPAAc surfaces caused significantly stronger reactions by macrophages and antigen-presenting cells compared to untreated control (polished titanium) samples, while PPAAm films did not show a negative influence on the inflammatory reaction after implantation.

Surface Treatments and Functional Coatings for Biocompatibility Improvement and Bacterial Adhesion Reduction in Dental Implantology

“…Different precursors and plasma excitation methods, process parameters and reactor geometries influence the plasma polymerization process and lead to a diversity of plasma-chemical reactions and thus to different film properties [58]. The low pressure plasma processes are the most widely used: microwave (2.45 GHz) [59] or capacitively coupled radio frequency (13.56 MHz) [59][60][61][62][63][64][65] activated [60], in planar parallel electrode plates geometry [63][64][65], in steel chamber [59,[63][64][65][66] or glass tubes [62,67,68] reactors, applying a continuous [61,67] or pulsed plasma discharge [59,[63][64][65]69].…”

“…Schröder and Finke [69] also explored the plasma polymers obtained by acrylic acid (PPAAc) in comparison with PPAAm, coming from allylamine, in terms of capability to influence the adhesion of human mesenchymal stem cells (hMSCs) and inflammation processes on titanium substrates, which are representative of real implant surfaces. While carboxyls (from PPAAc) lead to negative surface charges, amines (from PPAAm) are strongly basic at biological pH of 7.5, leading to positive surface charges.…”

“…In [69], PPAAc was deposited on polished Ti discs (TiP) by applying a microwave activated plasma discharge (reactor described in [59]), and using pulsed discharges with different "plasma on" times and duty cycles (DC). A liquid handling system allowed exact dosing of the precursors, by a calibrated needle valve.…”

On the Application of Gas Discharge Plasmas for the Immobilization of Bioactive Molecules for Biomedical and Bioengineering Applications

“…On the other hand, bone sialo protein (BSP) and osteocalcin (OCN) mRNA´s are expressed at very low levels in the early osteoblast differentiation stage, but transcription is enhanced during later differentiation stages (Billiard et al, 2003). In our studies (Schröder et al, 2010d) we Fig. 15.…”

Application of Low-Temperature Plasma Processes for Biomaterials

“…Hip joint implant in low pressure plasma using a mixture of argon and ethylenediamine for cell adhesive coating In contrast to these positively charged NH 2 films, a coating of Titanium implants with acrylic acid after similar plasma activation, called plasma-polymerized acrylic acid, results in a negatively charged COOH-group rich surface which was found to facilitate osteogenic differentiation by stimulation of mRNA expression of early (ALP, COL, Runx2) as well as late (BSP, OCN) bone differentiation markers (Schröder et al, 2010b). However, the longterm inflammatory response in vivo caused by this coating were increased compared to uncoated controls (Schröder et al, 2010b), highlighting the difficult balance that improving one specific aspect of implant characteristics is often accompanied by adverse changes in other parameters. Furthermore, it illustrates the problem that the results of in vitro experiments on the one hand and in vivo studies on the other are often inconsistent due to www.intechopen.com the complex nature of reactions in a living organism which can only partially and often inadequately be modelled using in vitro approaches.…”