Biomaterials: Role of surface modifications (original) (raw)
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Surface Modification of Polymeric Materials and its Effect on Blood Compatibility
MRS Proceedings, 1987
The surfaces of commercially available polymeric materials have been modified through two techniques, the chemical infusion process and physical vapor deposition. The surfaces of poly(methylmethacrylate) (PMMA) have been modified through a chemical infusion process by treatment of the sample with a solution containing varying amounts of titanium(IV)isopropoxide and polyvinylpyrrolidone (PVP). The surfaces of silicone rubber samples have been coated with a thin coating of titanium dioxide with an ion beam sputtering technique. The treated samples were characterized by scanning electron microscopy, optical microscopy, and neutron activation analysis. The infused samples were evaluated for blood compatibility using two biological assays: 1) an adherence assay in which the adherence of human polymorphonuclear leukocytes to the samples was determined, and 2) a hemolysis assay using rat blood erythrocytes to determine the hemolytic activity of the samples. Based on the results of these as...
Improving blood-compatibility of polymeric surface
Trends in Biomaterials and Artificial Organs
Biocompatibility has been defined by consensus, but not blood-compatibility. The interactions between blood and a surface depend on the blood composition, the blood flow and the surface of the material defined by its physicochemical features. Blood response is sensitive to surface features such as surface area, crystallinity, hydrophobicity/hydrophilicity, outermost structure and surface chemistry. Material surfaces are not blood-compatible, resulting in triggering of the non-specific self-protection mechanisms of blood. Improving blood-compatibility of polymeric surfaces requires that the surfaces are able to delay, or to control locally the biochemical events implied in these responses. Strategies such as the "repelling brush" or the heparinised and heparin-like surfaces are currently developed to improve blood-compatibility of polymeric surfaces.
Surface properties and processes of the biomaterial-tissue interface
Materials Science and Engineering C
At an implant site, a manmade material meets human tissue, and the manmade material is highly perturbed by the preceeding surgical procedure. The focus of the action, and thus the focus of scientific interest, is the interface between the foreign material and the tissue. The primary interaction occurs on a molecular scale, and involves adsorption and reactions of biomolecules, water and inorganic ions respectively from the bioliquid as well as dissolution of atomic, ionic or molecular fragments from the biomaterial. Successively changing conditions in the tissue, owing to the ongoing healing process and concerted modifications of the surface properties of the biomaterial, make the material-tissue interface a dynamic, non-reversible system in space and time. Secondary processes, induced by the primary processes, may occur far from the interface in the surrounding tissue or as systemic effects.
2001
This thesis describes a new in vitro slide chamber model that makes it possible to conduct studies of molecular and cellular interactions between whole blood and biomaterials. The model proved to be a suitable tool for detection of cell and platelet binding to a biomaterial surface. It was possible to monitor activation of the blood cascade systems and cells in the fluid phase and detect surface-bound molecules. One finding was that thrombin generation is primarily triggered by FXII on a biomaterial surface since corn trypsin inhibitor, inhibited thrombin generation in blood. Another finding was that thrombin generation was dependent on variety types of blood cells, since thrombin generation was almost negligible in platelet-rich plasma. When various preparations of blood cells were used to reconstitute platelet-rich and platelet-poor plasma, erythrocytes were shown to be the most efficient cell type in triggering thrombin generation. Inhibition of platelet aggregation with aspirin and Ro44-9883 was associated with a decrease in thrombin generation, confirming that platelet activation is necessary for normal coagulation activation. These findings suggest that the central events consist of an initial low-grade generation of thrombin that involves erythrocytes and possibly leukocytes which leads to activation of platelets; and a second platelet-dependent amplification loop that produces most of the thrombin. Titanium exposed to whole blood produced high amounts of thrombin. Stainless steel and PVC, generated lower amounts. This indicates that titanium might be less suitable as a biomaterial in devices that are in direct contact with blood for prolonged time. Considering the superior osteointegrating properties of titanium and titanium's response to blood, a correlation between high thrombogenicity and good osteointegration seems to exist. Compstatin, that binds to complement component C3, effectively inhibited the generation of C3a and sC5b-9 and the binding of C3/C3 fragments to the surface. Our results suggest that a biomaterial is able to activate complement through both the classical and alternative pathways and that the classical pathway alone is able to maintain a substantial bioincompatibility reaction. The results show that complement activation is a prerequisite for activation and binding of PMNs to the surface in the in vitro model.
Proteins, platelets, and blood coagulation at biomaterial interfaces
Blood coagulation and platelet adhesion remain major impediments to the use of biomaterials in implantable medical devices. There is still significant controversy and question in the field regarding the role that surfaces play in this process. This manuscript addresses this topic area and reports on state of the art in the field. Particular emphasis is placed on the subject of surface engineering and surface measurements that allow for control and observation of surface-mediated biological responses in blood and test solutions. Appropriate use of surface texturing and chemical patterning methodologies allow for reduction of both blood coagulation and platelet adhesion, and new methods of surface interrogation at high resolution allow for measurement of the relevant biological factors.
Journal of Biomedicine and Biotechnology, 2007
Extended use of cardiopulmonary bypass (CPB) systems is often hampered by thrombus formation and infection. Part of these problems relates to imperfect hemocompatibility of the CPB circuitry. The engineering of biomaterial surfaces with genuine longterm hemocompatibility is essentially virgin territory in biomaterials science. For example, most experiments with the well-known Chandler loop model, for evaluation of blood-biomaterial interactions under flow, have been described for a maximum duration of 2 hours only. This study reports a systematic evaluation of two commercial CPB tubings, each with a hemocompatible coating, and one uncoated control. The experiments comprised (i) testing over 5 hours under flow, with human whole blood from 4 different donors; (ii) measurement of essential blood parameters of hemocompatibility; (iii) analysis of the luminal surfaces by scanning electron microscopy and thrombin generation time measurements. The dataset indicated differences in hemocompatibility of the tubings. Furthermore, it appeared that discrimination between biomaterial coatings can be made only after several hours of bloodbiomaterial contact. Platelet counting, myeloperoxidase quantification, and scanning electron microscopy proved to be the most useful methods. These findings are believed to be relevant with respect to the bioengineering of extracorporeal devices that should function in contact with blood for extended time.
Modern biomaterials: a review—bulk properties and implications of surface modifications
Journal of Materials Science: Materials in Medicine, 2007
This review concerns the importance of length and time on physicochemical interactions between living tissue and biomaterials that occur on implantation. The review provides information on material host interactions, materials for medical applications and cell surface interactions, and then details the extent of knowledge concerning the role(s) that surface chemistry and topography play during the first stage of implant integration, namely protein adsorption. The key points are illustrated by data from model in vitro studies. Host implant interactions begin nanoseconds after first contact and from then on are in a state of flux due to protein adsorption, cell adhesion and physical and chemical alteration of the implanted material. The many questions concerning the conformational form and control of bound proteins and how this may impact on cell adhesion in the first instance and later on cell signalling and implant integration can be answered by systematic investigations using model materials. Only then we will be in a more informed position to design new materials for use in the body.
Preliminary hemocompatibility assessment of an innovative material for blood contacting surfaces
Journal of Materials Science: Materials in Medicine
Over the years, several devices have been created (and the development of many others is currently in progress) to be in permanent contact with blood: mechanical circulatory supports represent an example thereof. The hemocompatibility of these devices largely depends on the chemical composition of blood-contacting components. In the present work, an innovative material (hybrid membrane) is proposed to fabricate the inner surfaces of a pulsatile ventricular chamber: it has been obtained by coupling a synthetic polymer (e.g., commercial polycarbonate urethane) with decellularized porcine pericardium. The hemocompatibility of the innovative material has been preliminarily assessed by measuring its capacity to promote thrombin generation and induce platelet activation. Our results demonstrated the blood compatibility of the proposed hybrid membrane.