The amount of albumin adsorbed to three dental crown and bridge alloys (high- and low-gold content and silver-palladium), platinum, silver, and stainless steel was quantitated for the as-immersed conditions as well as with anodic and cathodic charge transfers in artifical saliva at a pH = 6.8. A methanolchloroform technique was utilized prior to protein assay which precipitated protein by phase separation. Amido black staining of protein on nitrocellulose filter paper was evaluated for optical density and compared to a standard curve of known quantities of protein. Cathodic charges decreased the quantity of adsorbed protein while anodic charges both increased and decreased adsorbed protein depending upon metal or alloy. Quantities adsorbed ranged from 0.5 to 8 μg/cm2. Interaction of positive oxidized species with the excess negative charges of the albumin molecules is thought to have increased protein adsorption. Formation of corrosion products with inorganic conponents is thought to have masked positive charges from protein thereby decreasing adsorption.

Current interest in the clinical application of alloplastic grafts for treating dental and orthopedic bone defects suggested this investigation on phosphate glasses. Particularly, the calcium phosphate ceramic materials of hydroxyapatite and tricalcium phosphate appear to be promising graft materials. Our interest in amorphous rather than crystalline ceramics centered on the potentially wide compositional variation that may be possible and their concomittant properties such as solubility.

The use of a Vicker's indenter to measure the fracture resistance of dental composite resins was correlated to fracture toughness results obtained by bending of notched bars. There is a fair correlation between the methods, but many dental composites do not form cracks by the indentation technique, thereby limiting its usefulness. SEM micrographs reveal a crack propagation mode which is mostly through the matrix and along the filler/matrix interface, with evidence of particle fracture

A study was made of the adhesion of insulating polymer coatings under long term exposure to electrical bias. Since a common mode of failure in implanted devices is the penetration of water into poorly adhering insulation/conductor interfaces followed by electrolytic degradation, development of processes, primers, and insulators with good adhesion that resist the effects of water were sought. Polyimide coatings were tested for their ion barrier properties by immersion of insulated comb patterns in saline with 9 V D.C. bias between the comb fingers. Leakage currents, measured over three years exposure, increased from several picoamps initially to several nanoamps in surviving specimens. Subsequent studies showed that dramatic improvements in the moisture durability of the adhesion could be obtained using Hitachi's aluminum chelate type primer. Whereas the peel strength of polyimide on unprimed platinum fell more than 90% after several hours of boiling saline exposure, the peel strength of polyimide coatings on primed surfaces remained at over 80% of their initial values. ESCA analysis of the peel interfaces showed that both aluminum oxide and polyimide remain on the substrate after peeling back the polyimide. This suggests a combination of cohesive and adhesive failure at the primer/polyimide interface. The effects of exposure of the polymer/substrate interfaces (edges) to saline and electrochemical stress were examined by patterning circular openings in the polyimide. A 10 V anodic potential was found to damage adhesion to titanium as far as 75 microns away from the edge. Pulsing at 500 Hz, 1 V peak to peak was found to have no measurable effect in the short term.

Many implantable biomedical devices could benefit from a material with a strongly temperature-dependent modulus. Catheters made from such a material could be inserted as a stiff plastic, and upon reaching body temperature, would soften dramatically to minimize erosion of adjacent tissue. Sutures could be stiff during placement in an incision, heated slightly to form a shape to hold the suture in place, and then cooled. A new family of materials known as softenable, shape-memory thermoplastics have a distinct and adjustable thermal transition that produces a dramatic change in modulus at a predetermined temperature (range)

The biocompatibility of Ti and Ti alloys is closely associated with the passivating surface oxide which covers these materials. In this paper results are presented from a broad surface characterization of pure Ti and Ti6A14V alloy surface oxides prepared by thermal oxidation by machining, or by electrochemical procedures (electropolishing and anodic oxidation). The chemical composition of the surface oxide on both materials is mainly TiO2, as shown by XPS, AES, and SIMS analyses. Significant differences exist for both the thermal and anodic oxides, in that the alloying elements are present in the surface oxide of the alloy. TEM and STEM studies show that the microstructure of the anodic oxide films is rather heterogeneous with areas of different porosity which can be correlated with the grain structure of the bulk metals. Oxides on the alloy are even more heterogeneous than on Ti, due to the more complex (two-phase) microstructure of the bulk metal, and also differ in crystallinity. The differences in the surface oxide properties can be expected to lead to differences in the biological response to these two materials. With the alloy, one must consider the risk of Al and/or V dissolution into the biological system.

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 assays, the PMMA samples treated with PVP alone resulted in an improvement in reactivity with the blood cells.

When blood comes in contact with a foreign surface, protein adsorption occurs within seconds and precedes the arrival of blood cells. Since a layer of plasma proteins is laid down on any surface in contact with blood before the platelets arrive, differences in platelet reactivity with different surfaces must result from variations in the nature of the protein-surface interactions. These interactions may vary in terms of which proteins bind to the surfaces, the amounts bound, and the various changes in protein conformation induced by surface contact.

A study has been made on the surface wettability, atomic ratio, chemical structure, chemical bonding states and plasma protein adsorption of ion implanted silicone rubbers. C+-, N2+-, 02+-, Ar+- and Na+-ion implantations were performed at an energy of 150 keV at room temperature. The doses ranged from 1x1012 to 1x1017 ions/cm2. Ion implantation caused the surface roughness to increase by 1–5 times. Surface wettability was estimated by means of a sessile drop method using water. With increasing ion dose, the contact angle of water decreased from 98.9° to 48.5°. However, if the sample was in the air, the contact angle of water returned to its initial valve in time elapsed. The results of XPS measurements showed that implanted elements were incorporated in a gaussian like distribution and host elements were redistributed in the polymer matrix. No change of binding energies of 01s, CIS, Si2p and Si2p can be observed upon ion implantation. Results of FT-IR-ATR showed that C+-, N2+-, 02+-, and Ar+-ion implantation decomposed the original chemical bonds to form the new radicals. The amounts of new radicals are related to doses of implanted ions. In contrast, Na+-ion implantation hardly formed new radicals. The amount of albumin adsorbed onto 02+-, Ar+-, N2+-, and C+- ion implanted silicone is less than that on unimplanted specimens, but more fibrinogen is adsorbed. Na+-ion implantation produced an increase in the amount of adsorbed albumin as the dose increased. In summary, Na+ion implantation produces effects that are attributable to the additional implanted constituent in the surface of the silicone, and 02+-, N2+-, C+-, and Ar+-ion implantations primarily cause radiation effects on silicone rubber.

Comparative wear data for unimplanted and implanted (50 keV, 5 × 1015 N+ cm−2) glassy carbon (GC) and pyrolytic carbon (PC) are reported. The implanted GC is about 120 times more resistant to diamond abrasion than unimplanted GC and at least 10 times more resistant than PC. In sliding tests, using a ruby ball as the abrader, the implanted GC is almost unaffected for the conditions employed (50 g load, 30,000 revs) compared with the unimplanted GC and unimplanted PC each of which endured measurable wear. The reasons for the enhancement of wear resistance and the ease with which 1–2 μm thick layers may be produced are discussed.

Concern continues over the possible long-term biological effects of corrosion products released by degradation of metallic surgical implant materials in the human body. One approach to improve long-term biological performance involves surface modifications to significantly reduce degradation rates. Fundamentally, the elements with lowest driving forces (lowest ΔG functions) for corrosion in aqueous solutions over a wide pH range are the noble metals. With regard to surface-modifications, one of the most effective methods is through ion implantation.

In the present on-going study, static in vitro corrosion properties of noble-metal ion-implanted surgical Ti-6Al-4V and commercially-pure(CP) Ti are being investigated in nonpassivating acid and passivating saline solutions. It was postulated that during the early stages of corrosion (or during a corrosion pretreatment) the implanted noble metal would enrich at the surface and significantly reduce subsequent corrosion rates. Thus far, the effects of ion-implanted Au and Rh have been studied, with mixed results. The Au implanted material yielded early benefits, but the enhanced corrosion resistance deteriorated with time, probably because the Au, during the enrichment stage, was not adequately adherent to the substrate. On the other hand, the observed behavior for the Rh implanted material appeared to follow the postulated mechanism, with both initial and time-dependent improvements in corrosion resistance.

This preliminary investigation evaluates the influence of ion implantation on tissue adhesion by measuring the tendency of fibroblasts to attach to the surface of ion implanted Ti. For this work, polished specimens of commercially pure Ti were implanted with ions of Ti, Ca, C, or N to produce a surface concentration of the implanted element up to about 25 at. %. Unimplanted and ASTM treated Ti, and tissue culture plate specimens were prepared as controls. Specimens were sterilized, then exposed for 15 min. to a culture medium containing about 100,000 fibroblasts. The solution and loose fibroblasts were rinsed away and the fibroblasts counted to determine those left attached. The influence of the different implantation protocols on fibroblast adhesion to Ti will be described. Analysis of the structure and composition of the ion implanted surfaces was obtained by scanning electron microscopy, x-ray photoelectron spectroscopy, and elastic backscattering spectrometry of energetic He ions.

The results of wear tests of various Ti alloys are presented. The N+ implanted alloy, especially after solution treating and aging, shows a better wear resistance. Ti-trace element studies of prosthetic patients' hair or blood show a higher average Ti content after about 10 years of replacement over the control subjects.

Calcium hydroxyapatite has been sputtered on glass and Ti-6Al-4V substrates using a 1.5-kV argon ion beam. The films have been examined by x-ray diffraction analysis, energy dispersive spectroscopy, scanning electron microscopy, and adhesion testing. Results of this experimentation are presented.

Starting with a pure hydroxylapatite sputter target, highly adherent coatings have been produced on metals and polymers by combining rf sputter deposition and ion implantation techniques. Reflection high energy electron diffraction (RHEED) scratch and adhesion tests have been done and more analysis is planned. Comparison of the RHEED data with HA and tricalcium phosphate standards shows the material to be polycrystalline hydroxylapatite rather than the amorphous, hydroxyl-free material usually produced by similar methods. Because of its structure this coating is expected to be nonresorbable. The coating is non-porous, hard and scratch-resistant. Data on the crystallography and mechanical properties of the coating will be presented.

After 40 years of research on various types of artificial organs, artificial organs once considered to be impossible have now become realities. The implantation of total cardiac prostheses is now feasible and many patients have been successfully bridged to transplant with total and partial artificial hearts. The use of the artificial kidney is now widespread all over the world. Various surgical implants such as heart valves, vascular grafts, cardiac pacemakers, and ophthalmologic implants, orthopedic implants are now used routinely. With the current trend of an increasing older population and the extension of the average life span, the need of artificial organ technologies is increasing annually. Because prostheses or artificial organ applications are quite expensive, the expenses involved for these types of application are increasing at an alarming rate annually. In the past, the only traditional medical technologies applied were primarily drugs and surgery. There are still limitations today in preventing end stage organ failure despite the remarkable studies made in surgery, drug therapy and even more recently in biochemistry and immunology. Artificial organ technologies must not only be for end stage organ failure but they can be useful in prophylaxis.

The role of artificial organ technologies in therapeutics is now being recognized. The removal of pathologic macromolecules by plasmapheresis technologies such as in various types of autoimmune diseases has been proven to slow down the disease processes and in some cases stop their progression. Studies on lipoprotein removal by extracorporeal technologies show that the process of atherosclerosis may be slowed or stopped and that regression of atherosclerotic lesions may be possible.

It is believed that the future of artificial organs should not only be focused on the development of replacement organs, but also on the artificial organ technologies for therapeutic or preventative medicine. By applying aggressively these type of technologies, certainly the outcome of early end stage organ failure can be prevented and the needs for artificial hearts, artificial kidneys, orthopedic implants and various implantable artificial organs reduced.

As a means of selectively removing pathogenic macromolecular substances, an affinity adsorbent or immunoadsorbent has been investigated in experimental and clinical studies on blood purification in the treatment of immune diseases. There are several affinity adsorbents currently available for clinical application. The authors developed physicochemical affinity adsorbents Immusorba IM-TR and IM-PH, whose experimental and clinical evaluations have been satisfactory in several immune diseases, such as rheumatoid arthritis, myasthenia gravis, systemic lupus erythematosus and multiple sclerosis.

Absorptive cell separation, for leucocyte-free blood transfusion or for cytapheresis, has been developed using a leucocyte removal filter, whose container has fine, long fibers of polyester which are densely packed. The filters Sepacell and Cellsorba are used for erythrocyte transfusion and cytapheresis, respectively. In experimental and clinical trials, they provide efficient removal of leucocytes. Erythrocytes can be recovered virtually without loss. Clinical evaluation is now being conducted.

In conclusion, the above-mentioned new methods provide promising immunomodulations for the treatment and for the clearification of pathphysiology of immune diseases.

Exploitation of specific cell membrane receptor molecules is a promising avenue for the separation and purification of particular cell populations for biomedical and biotechnological purposes. Cell affinity chromatography is a technique which uses this principle to separate cells. In it, ligand molecules with a high binding affinity for specific receptors on targeted cell populations are immobilized on surfaces over which mixed cell populations are passed. These targeted populations are preferential retained, affecting a separation.

Often, the resulting separation is not as selective or efficient as the receptor/ligand biochemistry would promise. We present a theoretical analysis which elucidates the role of physical factors, such as van der Waals, electrostatic, and fluid mechanical forces, in affecting cell adhesiveness and hence selectivity. We demonstrate that only fairly narrow ranges of parameters characterizing these forces permit the selectivity inherent in the receptor/ligand biochemistry.

Recently there has been a growing awareness of the importance of the interactions of the human complement system with biomaterials which largely stems from the understanding that complement-materials interactions may result in the production of inflammatory mediators, termed C3a and C5a anaphylatoxins, that can produce significant pathopysiologic alterations in the exposed patient. This presentation will review studies of complement activation produced by various hemodialysis membranes. our current data suggests that hemodialysis membranes may be roughly divided into three categories. The first type of membrane displays a high complement-activating potential as judged by measurements of C3a antigen levels produced during dialysis. These membranes also liberate sufficient quantities of C5a to induce both significant granulocytopenia and cardiopulmonary effects. The second group of membranes exhibits a moderate capacity to activate complement, with the amount of C3a antigen produced by these devices being about half that seen with the highly activating dialyzers. Dialyzers in this intermediate group produce only enough C5a to provoke a modest degree of leukopenia and they generally fail to induce cardiopulmonary manifestations. The third type of device fails to produce significant amounts of either free C3a or C5a and does not produce significant granulocytopenia. Factors that could affect the propensity of a material to activate complement include the density and type of surface nucleophiles, and the presence of surface dcarge which may facilitate the interaction of regulatory components and the adsorbtion of both active and bystander proteins.

Synthetic polymer membranes which have a nominal pore size (NPS) of 0.03 to 10 microns were evaluated at varying filtration temperatures to separate pathologic macromolecules such as immune complexes, cryoprecipitable proteins and low density lipoproteins (LDL) from essential plasma proteins. At low temperatures (4 to 10°C) cryoprecipitable proteins were selectively removed from cryoglobulinemic plasmas with membranes of 3 micron NPS. However, severe membrane plugging occurred with membranes of smaller pore sizes. In addition, decreased albumin sieving occurs. Above 37°C, increased albumin sieving and prolonged membrane plugging occurs. In the selective removal of low density lipoproteins from hypercholesterolemic plasmas, membranes with NPS of 0.03 microns were found to be suitable at high operating temperatures. Given the proper combination of membrane and temperature control, disease related pathological macromolecules can be treated effectively by selective macromolecule removal.