Characterization of serum proteins attached to distinct sol-gel hybrid surfaces : Characterization of serum proteins attached to distinct sol-gel hybrid surfaces

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

A goal of current implantology research is to design devices that induce controlled, guided, and rapid healing. In addition to acceleration of normal wound healing phenomena, endosseous implants should result in formation of a characteristic interfacial layer and bone matrix with adequate biomechanical properties. To achieve these goals, however, a better understanding of events at the interface and of the effects biomaterials have on bone and bone cells is needed. Such knowledge is essential for developing strategies to optimally control osseointegration. This paper reviews current knowledge of the bone-biomaterial interface and methods being investigated for controlling it. Morphological studies have revealed the heterogeneity of the bone-implant interface. One feature often reported, regardless of implant material, is an afibrillar interfacial zone, comparable to cement lines and laminae limitantes at natural bone interfaces. These electron-dense interfacial layers are rich in noncollagenous proteins, such as osteopontin and bone sialoprotein. Several approaches, involving alteration of surface physicochemical, morphological, and/or biochemical properties, are being investigated in an effort to obtain a desirable bone-implant interface. Of particular interest are biochemical methods of surface modification, which immobilize molecules on biomaterials for the purpose of inducing specific cell and tissue responses or, in other words, to control the tissue-implant interface with biomolecules delivered directly to the interface. Although still in its infancy, early studies indicate the value of this methodology for controlling cell and matrix events at the bone-implant interface.

We have merged four different views of the human plasma proteome, based on different methodologies, into a single nonredundant list of 1175 distinct gene products. The methodologies used were 1) literature search for proteins reported to occur in plasma or serum; 2) multidimensional chromatography of proteins followed by two-dimensional electrophoresis and mass spectroscopy (MS) identification of resolved proteins; 3) tryptic digestion and multidimensional chromatography of peptides followed by MS identification; and 4) tryptic digestion and multidimensional chromatography of peptides from low-molecular-mass plasma components followed by MS identification. Of 1,175 nonredundant gene products, 195 were included in more than one of the four input datasets. Only 46 appeared in all four. Predictions of signal sequence and transmembrane domain occurrence, as well as Genome Ontology annotation assignments, allowed characterization of the nonredundant list and comparison of the data sources. The "nonproteomic" literature (468 input proteins) is strongly biased toward signal sequence-containing extracellular proteins, while the three proteomics methods showed a much higher representation of cellular proteins, including nuclear, cytoplasmic, and kinesin complex proteins. Cytokines and protein hormones were almost completely absent from the proteomics data (presumably due to low abundance), while categories like DNA-binding proteins were almost entirely absent from the literature data (perhaps unexpected and therefore not sought). Most major categories of proteins in the human proteome are represented in plasma, with the distribution at successively deeper layers shifting from mostly extracellular to a distribution more like the whole (primarily cellular) proteome. The resulting nonredundant list confirms the presence of a number of interesting candidate marker proteins in plasma and serum.