Inorganic PVD and CVD Coatings in Medicine — A Review of Protein and Cell Adhesion on Coated Surfaces

Abstract

The functionalization of biomaterials for implants becomes increasingly important for designing bioinert and bioactive surfaces to reduce the impact of implantation to human body (inflammation, encapsulation) and extend the lifetime of implants. Even pharmacological effects can be triggered by nanomaterials like thin films and nanoparticles in medical treatment. However, the systematic knowledge of the interactions between cells and artificial, inorganic materials is poor yet. Finding the decisive influences for high hemocompatibility or osseointegration is very difficult. Surface chemistry including wetting behaviour, surface charge, homogeneity and functional groups as well as surface topography are some of the fundamental surface parameters defining the cell-surface interaction. Focusing on physical and chemical vapour deposited thin films and coatings, this review will provide for a better understanding of biocompatible coating materials like titanium-and carbon-based compounds and calcium phosphates. of the main goals of biomaterials research [3,4]. However, the precise mechanisms involved in this cell-surface and protein-surface interactions are still unknown.Generally, surfaces of synthetic biomaterials (e.g., polymers, metals and ceramics) are not bioactive themselves. Rather, surface bioactivity is provided by the proteins that adsorb to the biomaterial surface following exposure of the surface to biological fluids. The first molecules are water molecules reaching the surface in a biological milieu containing cells. When cells arrive at the surface, they 'see' a protein-covered surface whose bioactive protein layer has properties that were initially determined by the pre-formed water shells. To control cellular response, it is important to first understand how surface chemistry, surface topography and mechanical forces influence the formation of the adsorbed protein layer and the bioactive sites presented by this layer. Besides water, proteins and cells, biological model systems for biointerfaces (or surfaces) must contain amino acids, nucleic acids and lipids, peptides and DNA (segments), and tissue to describe the sequences occurring in the human body [5]. The recognition of these molecular-scale features is programmed into the molecules through the combination of their 3-D topographic architecture, the superimposed chemical architecture, and the dynamic properties [5]. Although the fundamental interactions occur on the molecular scale, there is an interesting and unique synergistic connection between the nanometer and the micrometer length scales [6-8], when cells are present.Recent advances in topographical surface modification techniques such as electron beam lithography [9], photolithography [10], colloidal lithography [11,12], laser ablation [13] and polymer demixing [14] have allowed the fabrication of surfaces with nano-sized features. In addition, the modification of the surface chemistry by coating with biomaterials or biomolecules of 'higher biocompatibility' helps to separate between bulk pr...

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Molecular layer deposition builds biocompatible substrates for epithelial cells

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