Implant Surfaces and Interface Processes

Abstract

The past decades and current R&D of biomaterials and medical implants show some general trends. One major trend is an increased degree of functionalization of the material surface, better to meet the demands of the biological host system. While the biomaterials of the past and those in current use are essentially bulk materials (metals, ceramics, polymers) or special compounds (bioglasses), possibly with some additional coating (e.g., hydroxyapatite), the current R&D on surface modifications points toward much more complex and multifunctional surfaces for the future. Such surface modifications can be divided into three classes, one aiming toward an optimized three-dimensional physical microarchitecture of the surface (pore size distributions, "roughness", etc.), the second one focusing on the (bio) chemical properties of surface coatings and impregnations (ion release, multi-layer coatings, coatings with biomolecules, controlled drug release, etc.), and the third one dealing with the viscoelastic properties (or more generally the micromechanical properties) of material surfaces. These properties are expected to affect the interfacial processes cooperatively, i.e., there are likely synergistic effects between and among them: The surface is "recognized" by the biological system through the combined chemical and topographic pattern of the surface, and the viscoelastic properties. In this presentation, the development indicated above is discussed briefly, and current R&D in this area is illustrated with a number of examples from our own research. The latter include micro- and nanofabrication of surface patterns and topographies by the use of laser machining, photolithographic techniques, and electron beam and colloidal lithographies to produce controlled structures on implant surfaces in the size range 10 nm to 100 microns. Examples of biochemical modifications include mono- or lipid membranes and protein coatings on different surfaces. A new method to evaluate, e.g., biomaterial-protein and biomaterial-cell interactions--the Quartz Crystal Microbalance--is described briefly.

The interaction of human serum albumin with titanium studied by means of atomic force microscopy

“…[1] The adsorption of proteins in this early stage strongly influences the biocompatibility of a material. [2] During the adsorption process, the proteins may undergo conformational changes. [3] In some cases the interaction between the surface of the biomaterial and proteins, such as osteointegration, promotes the integration of a biomaterial in the human body.…”

Evaluation of the in vitro cell-material interactions and in vivo osteo-integration of a spinal acrylic bone cement

“…In the present work, the cement topography showed some R a and R m values of about 5 and 30 lm, respectively. Previous studies have shown that surface topography features at the cell scale affect the behaviour of cells [26]. For example, looking at the BMSC behaviour on rough titanium surfaces compared to smoother ones with identical surface chemistry, Deligianni [27] found an increased cell adhesion, a slightly higher proliferation and similar ALP activity on rougher surfaces.…”

Determination of the Adsorption Free Energy for Peptide−Surface Interactions by SPR Spectroscopy

“…The concentration of the peptide at the surface (C s ) can be expressed as (2) where q is the excess amount of peptide per unit area adsorbed on the surface compared to that under bulk solution conditions (i.e., C b ) and δ is the thickness of the adsorbed layer.…”