BIOM 4730 / MECH 4365: Biomaterials (Syllabus)

Course Description: Synthetic materials and their interaction with the physiological environment; methods to design and study materials that are compatible with natural tissue

BIOM 4730 / MECH 4365: Biomaterials

Course Description: Synthetic materials and their interaction with the physiological environment; methods to design and study materials that are compatible with natural tissue

In vitro biocorrosion of Co-Cr-Mo implant alloy by macrophage cells

We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect Co-Cr-Mo alloy\u27s corrosion properties and that alloy corrosion products change macrophage cell behavior. A custom cell culture corrosion cell was used to evaluate how culture medium, cells, and RCS altered alloy corrosion in 3-day tests. Corrosion was evaluated by measuring total charge transfer at a constant potential using a potentiostat and metal ion release by atomic emission spectroscopy. Viability, proliferation, and NO (nitric oxide) and IL-1β (interlukin-1β) release were used to assess cellular response to alloy corrosion products. In the presence of activated cells, total charge transfers and Co ion release were the lowest (p\u3c0.05). This was attributed to an enhancement of the surface oxide by RCS. Cr and Mo release were not different between cells and activated cells. Low levels of metal ions did not affect cell viability, proliferation, or NO release, though IL-1β released from the activated cells was higher on the alloy compared to the controls. These data support the hypothesis that macrophage cells and their RCS affect alloy corrosion. Changes in alloy corrosion by cells may be important to the development of host responses to the alloy and its corrosion products. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved

In vitro biocorrosion of Ti-6A1-4V implant alloy by a mouse macrophage cell line

Corrosion of implant alloys releasing metal ions has the potential to cause adverse tissue reactions and implant failure. We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect the alloy\u27s corrosion properties. A custom cell culture corrosion box was used to evaluate how cell culture medium, macrophage cells and RCS altered the Ti-6A1-4V corrosion behaviors in 72 h and how corrosion products affected the cells. There was no difference in the charge transfer in the presence (75.2 ± 17.7 mC) and absence (62.3 ± 18.8 mC) of cells. The alloy had the lowest charge transfer (28.2 ± 4.1 mC) and metal ion release (Ti \u3c 10 ppb, V \u3c 2 ppb) with activated cells (releasing RCS) compared with the other two conditions. This was attributed to an enhancement of the surface oxides by RCS. Metal ion release was very low (Ti \u3c 20 ppb, V \u3c 10 ppb) with nonactivated cells and did not change cell morphology, viability, and NO and ATP release compared with controls. However, IL-1β released from the activated cells and the proliferation of nonactivated cells were greater on the alloy than the controls. In summary, macrophage cells and RCS reduced the corrosion of Ti-6A1-4V alloys as hypothesized. These data are important in understanding host tissue-material interactions. © 2004 Wiley Periodicals, Inc

Biomaterial and antibiotic strategies for peri-implantitis

Dental implants have 89% plus survival rates at 10-15 years, but peri-implantitis or dental implant infections may be as high as 14%. Peri-implantitis can limit clinical success and impose health and financial burdens to patients and health providers. The pathogenic species associated with periodontitis (e.g., Fusobacterium ssp, A. actinomycetemcomitans, P. gingivalis) are also associated with peri-implantitis. Incidence of peri-implantitis is highest within the first 12 months after implantation, and is higher in patients who smoke or have poor oral health as well as with calcium-phosphate-coated or surface-roughened implants. Biomaterial therapies using fibers, gels, and beads to deliver antibiotics have been used in the treatment of Peri-implantitis though clinical efficacy is not well documented. Guided tissue regeneration membranes (e.g., collagen, poly-lactic/glycolic acid, chitosan, ePTFE) loaded with antimicrobials have shown success in reosseointegrating infected implants in animal models but have not been proven in humans. Experimental approaches include the development of anti-bioadhesion coatings, coating surfaces with antimicrobial agents (e.g., vancomycin, Ag, Zn) or antimicrobial releasing coatings (e.g., calcium phosphate, polylactic acid, chitosan). Future strategies include the development of surfaces that become antibacterial in response to infection, and improvements in the permucosal seal. Research is still needed to identify strategies to prevent bacterial attachment and enhance normal cell/tissue attachment to implant surfaces. © 2008 Wiley Periodicals, Inc

Changes in surface composition of the Ti-6Al-4V implant alloy by cultured macrophage cells

In this study, X-ray photoelectron spectroscopy (XPS) was used to evaluate the hypothesis that macrophage cells and their released compounds change Ti-6Al-4V surface oxide composition. Ti-6Al-4V surfaces, prepared to simulate clinical conditions, were exposed for 3 days to cell culture medium, macrophage cells, or macrophage cells activated to release inflammatory reactive chemical species (RCS). The as-polished samples were used as controls. The as-polished samples exhibited typical TiO 2 surface oxides. After samples were exposed to medium, only C, O and N peaks from absorbed proteins were observed. When cultured with cells or activated cells, the Ti peaks reappeared and there was a significant shift in the O 1s peak to lower metal oxide binding energies (∼530 eV). This shift was associated with a significant increase in total metal oxides on sample surfaces as compared to medium only surfaces. With activated cells, the enhancement of the surface oxides was attributed to oxidation of the surface by the RCS released by activated macrophage cells (e.g. O 2 + NO → NO 3- and M + NO 3- → M6;O + NO 2- ). These data support the hypothesis that macrophage cells and released RCS affect Ti-6Al-4V surface oxides. Changes in surface oxides are important since they may affect alloy-tissue interactions. © 2003 Elsevier B.V. All rights reserved

Changes in the surface oxide composition of Co-Cr-Mo implant alloy by macrophage cells and their released reactive chemical species

We hypothesized in this study that macrophage cells and their released reactive chemical species (RCS) alter the surface oxide composition of Co-Cr-Mo alloys in vitro. Alloys were prepared to simulate the clinical conditions and incubated for 3 days in cell culture medium, medium with macrophage cells and medium with activated macrophage cells. X-ray photoelectron spectroscopy was used to evaluate the elemental and chemical changes of the surface oxide compositions. The as-polished and passivated specimens exhibited typical Cr 2O3 rich surfaces. After 3 days in medium, the major metal peaks were masked by proteins from the culture medium, as indicated by the increase in N and C peaks. When cultured with cells, the Cr peaks reappeared and the O peak increased in intensity. These peak intensities increased further when the cells were activated to release NO and other RCS. We speculated that the cells reduced protein depositions and RCS may have enhanced alloy surface oxides through the oxidation and nitration reactions. These data have demonstrated that surface oxide composition varied with in vitro environments. Changes in the composition of the alloy surface oxides over time by cells are important to the understanding of host-material interactions and in the release of alloy corrosion products. © 2003 Elsevier Ltd. All rights reserved

Galvanic corrosion and cytotoxic effects of amalgam and gallium alloys coupled to titanium

The aim of this study was to examine and compare the galvanic corrosion of a conventional, a dispersed high-copper, and a palladium-enriched spherical high-copper amalgam and a gallium alloy coupled to titanium in saline and cell culture solutions, and to evaluate the effects of the couples on cultured cells. The potentials and charge transfers between amalgams and titanium were measured by electrochemical corrosion methods. Cytotoxicity of the couples, as indicated by the uptake of neutral red vital stain, was determined in 24-h direct contact human gingival fibroblast cell cultures. Results of this study indicated that before connecting the high-copper amalgams to titanium, the amalgams exhibited more positive potentials svhich resulted in initial negative charge transfers, i.e. corrosion of titanium. However, this initial corrosion appeared to cause titanium to passivate, and a shift in galvanic currents to positive charge transfers, i.e. corrosion of the amalgam samples. Lower galvanic currents were measured for the amalgam-titanium couples as compared to the gallium alloy-titanium couple. Coupling the conventional or the palladium-enriched high-copper amalgams to titanium did not significantly affect the uptake of neutral red as compared to cells not exposed to any test alloy. However, significant cytotoxic effects were observed when the dispersedtype high-copper amalgam and the gallium alloy were coupled to titanium. Even though the corrosion currents measured for these couples were less than gold alloys coupled to amalgam, these results suggest there is the potential for released galvanic corrosion products to become cytotoxic. These data warrant further investigations into the effects of coupling amalgam and gallium alloys to titanium in the oral environment. © Munksgaard, 1996