Enzyme histochemistry of the tissue response to pure metal implants

IL-1alpha, IL-1beta and TNF-alpha secretion during in vivo/ex vivo cellular interactions with titanium and copper

Titanium (Ti) and copper (Cu) were used to evaluate cytokine secretion around materials with different chemical properties. Ti disks were coated with Cu or left uncoated. The disks were inserted subcutaneously in rats for 1, 3, 12, 18, 24 and 48 h. Interleukin-1alpha (IL-1alpha), IL-1beta and tumor necrosis factor-alpha (TNF-alpha) concentrations were measured in vivo around the materials, in sham operated sites, and after ex vivo incubation of surface adherent cells. Ti and Cu revealed distinct cytokine expression patterns. Cu recruited cells showed higher and prolonged release of IL-1alpha than Ti at longer times (>24 h), whereas Ti exhibited a transient IL-1alpha response at earlier periods (<24 h). An early enhanced secretion of TNF-alpha characterized Ti. Low amounts of IL-1beta were found around both materials. Sham site recruited cells produced lower levels of cytokines. The results after ex vivo incubations were similar to those in vivo. This study shows that material chemical properties influence early cytokine production. The Ti-associated transient rise of IL-1alpha and TNF-alpha may be of importance for the early tissue response around biocompatible materials, while a delayed high IL-1alpha expression could be a marker of inflammation induced by toxic materials.

Relating nickel-induced tissue inflammation to nickel release in vivo

Nickel has a number of adverse biological effects that have made the use of nickel in biomedical implants controversial. Yet information about the distribution of nickel in tissues around nickel-containing implants is scarce. The purpose of the current study was to use a laser ablation technique, combined with inductively coupled mass spectroscopy, to assess the spatial distribution of nickel around nickel-containing implants in vivo. Polyethylene, pure nickel wire, or a nickel-containing alloy (Ni-Cr) were implanted subcutaneously into rats for 7 days. The tissues were analyzed for Ni content and inflammation at 1-mm intervals up to 5 mm away from the implants. The sham surgery sites and the polyethylene caused mild to moderate inflammation 1-2 mm from the implant site with no detectable nickel in the tissue. The nickel wire caused severe inflammation up to 5 mm away from the implant site with necrosis for 1 mm around the implant. Nickel concentrations reached 48 microg/g near the implants, falling exponentially to undetectable levels at 3-4 mm from the implants. The Ni-Cr wire caused inflammation equivalent to polyethylene, with less than 4 microg/g of nickel present in the tissue for 1-2 mm around the implants. The current study showed that the laser-ablation technique was well suited for the analysis of soft tissues for metal-ion content, and that the nickel distribution in tissues correlated well with overt tissue inflammation.

Chemical cleaning of titanium tray for reconstructive surgery

AIMS

To find out the extent of chemical contamination on the surface of titanium wrought mesh before and after swaging, and to assess the effectiveness of cleaning off these contaminants by various chemical methods.

MATERIALS AND METHODS

Qualitative analysis of the surfaces of 6 wrought titanium meshes by scanning electron microscopy (EM) and radiological microanalyser. One of these meshes was subjected to experimental cleaning by different methods. Qualitative chemical analysis of 20 titanium trays fabricated for clinical use before and after acid cleansing.

RESULTS

All 6 titanium meshes had surface contaminants, with silicon being the most common. The effective cleaning methods were chemical cleaning with Titaclean, mechanical trimming, or polishing with diamond paste. The 20 swaged titanium trays were effectively cleaned with either Titaclean or Chemi-Polish solution.

CONCLUSION

Previously unknown surface contamination was common on wrought titanium mesh. Ultrasonic cleansing with Titaclean or Chemi-Polish effectively removed most of the contaminants on the titanium trays before they were implanted.

Inflammatory cell recruitment, distribution, and chemiluminescence response at IgG precoated- and thiol functionalized gold surfaces

The role of complement activation by artificial surfaces relative to inflammatory response is not well understood. This study was performed to evaluate the inflammatory cell recruitment, distribution, and ex vivo metabolic activation of surfaces with different plasma protein adsorption and complement activation properties in vitro. The implants were (1) pure gold (reference), (2) albumin-precoated (3) IgG-precoated gold, and (4) 3-mercapto-1, 2-propanediol [mercaptoglycerol (MG)] and (5) glutathione (GSH) immobilized to gold. The implant disks were inserted subcutaneously in rats for 24 h, and the number of inflammatory cells that were recruited to the implant adjacent to the surrounding fluid phase (exudate) and the surfaces were quantified by DNA measurements. The oxidative burst was analyzed ex vivo using spontaneous and phorbol myristate acetate (PMA)-stimulated, luminol-enhanced chemiluminescence (CL). The in vitro surface-induced anti-rat C3 binding was evaluated by ellipsometry and antibody techniques after plasma incubations for 1 and 30 min. The ellipsometric results showed that immobilized mercaptoglycerol and IgG-coated, but not the immobilized glutathione or the reference Au, bound anti-C3. The in vivo results revealed that the largest amount of cells was associated with the IgG-coated surfaces, followed by immobilized GSH and MG, albumin-coated, and gold surfaces, respectively. No spontaneous ex vivo luminol-enhanced CL was recorded from the cells irrespective of surface functionality or localization. A down-regulation of surface-associated and exudate leukocyte CL was observed ex vivo, irrespective of surface functionality. The results do not indicate a clear relationship between the degree of complement activation in vitro and leukocyte recruitment and adhesion in vivo for differently functionalized surfaces.

In vitro IL-1 beta and TNF-alpha release from THP-1 monocytes in response to metal ions

OBJECTIVES

Previous studies have shown that biomaterials can activate macrophages to produce cytokines and promote an inflammatory response. Although the toxicity of many metal ions has been extensively investigated, little is known about the ability of these ions to alter cytokine release from macrophages. Yet the release of these ions from biomaterials has been well documented. Previous studies indicated that alterations in cytokine release might be expected because metal ions alter protein production in macrophages at sub-toxic concentrations. Thus, the hypothesis of this study was that metal ions can alter the secretion of cytokines from macrophages at sub-toxic concentrations.

METHODS

The release of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) from macrophages was investigated when the macrophages were exposed to metal ions, with or without lipopolysaccharide (LPS), a component of dental plaque. Human THP-1 macrophages were exposed to ions of Ag, Au, Cu, Hg, and Ni for 24 h. In half of the cultures, LPS was added for the last 4 h. The release of IL-1 beta and TNF-alpha into the medium was measured using enzyme-linked immunosorbent assays. ANOVA and Tukey multiple comparison intervals were used to compare the various experimental conditions.

RESULTS

None of the metal ions elevated the IL-1 beta or TNF-alpha levels after 24 h, but Ni ions significantly elevated the IL-1 beta and TNF-alpha levels after 72 h. With LPS added, Ag, Cu, and Ni significantly amplified the LPS-induced production of IL-1 beta but only Ni amplified the TNF-alpha response. These alterations in cytokine response occurred with metal ion concentrations which have been previously shown to be released from dental alloys in vitro and in vivo.

SIGNIFICANCE

It appeared plausible that macrophage-cytokine mediated inflammatory responses may be altered by the presence of some metal ions in tissues, particularly Ni.

Titanium-induced enzyme activation on murine peritoneal macrophages in primary culture

The biological performance of titanium (Ti) particles has been investigated in vitro on murine peritoneal macrophages in a primary culture system. The ultrastructural study revealed an unchanged morphology with respect to controls and the presence of numerous phagocytic vacuoles containing Ti particles as confirmed by X-ray microprobe analyses. The activities of beta-glucuronidase, acid phosphatase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase were determined. All of the enzymes were found to be activated after different exposure times to various Ti concentrations. These activations are qualified as the consequence of cell defence rather than a significant cytotoxic effect. Nevertheless, they indicate a possible inflammatory action of short duration. This investigation provides new arguments for the high biological performance of Ti.

Acute toxicity of metal ions in cultures of osteogenic cells derived from bone marrow stromal cells

The effects of metal ions released from orthopedic implants on nearby bone cells remain largely unknown. The purpose of this study was to examine the acute toxicity of metal ions on osteogenic cells derived from bone marrow. Bone marrow stromal cells were cultured with metal ions found in commonly used orthopedic implants, that is, Ti-6Al-4V, Co-Cr-Mo, and 316L stainless steel. Solutions of individual ions and combinations representing the alloy composition were prepared from atomic absorption standards and added to the cultures to give concentrations ranging from 50 ppb to 50 ppm. After a 48-h period of exposure to ions, the bone marrow cultures were examined for effects of cytotoxicity by measuring total cell number, total cell protein, and mitochondrial activity. Cr6+ was grossly cytotoxic; Co2+, Mo6+, Fe3+, and Ni2+ were moderately cytotoxic; and Ti4+, Al3+, V5+, and Mn2+ were minimally toxic, as determined by the assays used. Ion solutions representing Co-Cr-Mo and 316L stainless steel were moderately toxic; solutions representing Ti-6Al-4V were toxic at only the highest concentrations used. The observed cytotoxicity was time-dependent, with irreversible toxic effects being initiated following as short as a 3- to 6-hour exposure. These results show that metal ions associated with Co-Cr-Mo and 316L stainless steel are toxic to osteogenic cells at concentrations approximating those measured in the fibrous membrane encapsulating orthopedic implants.

Application of flow cytometry to determine the cytotoxicity of urethane dimethacrylate in human cells

The effects of an oligomer, urethane dimethacrylate (UDMA), on two human cell lines were studied using flow cytometry (FCM). Untreated and treated cultures of propidium iodine-stained KB (epidermal oral carcinoma cells) and human foreskin fibroblast (HFF) cells were analyzed for cellular DNA content. Concentrations of 10 and 25 microM of UDMA slightly perturbed the KB cell cycle progression at 24 and 48 h of incubation. However, the effect of 50 microM was more pronounced at the latter incubation time period. In cell growth experiments, the sublethal concentrations (10 and 25 microM) produced inhibition of KB cell growth rate at a moderate level, which resulted in the prolongation of cell population doubling time. Significant inhibition of cell growth occurred when 50 microM (lethal concentration) was used. Data obtained from the cell cycle perturbation analysis, evidenced by FCM, correlated with the extent of inhibition in KB cell growth rates. The effects of sublethal concentrations were reversible during a 24 h period of oligomer withdrawal from culture medium. In contrast, the effects of 50 microM were not reversible. In HFF cells the depletion of S phase in the cell cycle was the major effect of 50 microM of UDMA. It was concluded that FCM technology is an ideal and practical approach for studying the cytotoxicity of components of dental composites.

The early host and material response of bone-bonding and non-bonding glass-ceramic implants as revealed by scanning electron microscopy and histochemistry

The interface of bone-bonding and non-bonding glass-ceramics in the femur of of rats with the concomitant material and host response has been investigated by scanning electron microscopy (SEM) and histochemistry after transverse fractures in the interface level. During wound healing around these implants, four overlapping phases could be distinguished: (1) blood clot formation, (2) formation of organization tissue, (3) formation of primary bone and calcification, and (4) remodelling which lasts from months to years. This sequence of healing was disturbed around metal ions containing non-bonding implants, as shown by a longer settlement of acid phosphatase positive macrophages and a disturbed calcification at the surface of the material. Only bone-bonding implants developed considerable changes in surface morphology due to leaching and corrosion phenomena. A preferential leaching of the glass moiety, starting at the phase transition between glass and ceramic, contributes to the production of surface elevations which provide adhesion points for fibres and fibrils. Subsequent mineralization of inserting fibres contributes to a tensile strength at the interface. These findings are essential for further understanding of bone-bonding mechanisms and for further development of surface-reactive materials.

Evaluation of connective tissue cell responses to orthopaedic implant materials

We have developed an in vitro cell culture model to examine the interaction between connective tissue cells and orthopaedic implant biomaterials. Human connective tissue cells grown on different materials exhibit distinct responses in terms of attachment, morphology, proliferative capacity and matrix biosynthesis. Our results closely complement in vivo observations concerning biocompatibility and demonstrate the usefulness of this in vitro system for evaluating biomaterials. More importantly, this model can be used to define the specific cellular and biochemical processes that are responsible for the local tissue responses to orthopaedic implant materials.

Alteration of retrieved implants in vitro by processing and infiltrating fluids

Undecalcified histology has proved of immense value in the examination of the interface membrane between the prosthesis and bone. However, to provide such histological sections, dehydrating and clearing fluids as well as plastic infiltrating fluids must be used. This study investigates the possibility that some of these commonly used fluids may alter the biomaterial after removal from the body and be misinterpreted as an in vivo product. Ten different routinely used fluids were tested on 11 different biomaterials that are commonly used in prosthetic devices. The nonmetal biomaterials were placed in glass tubes containing the different fluids at room temperature for 5 days. The biomaterials were assessed for changes each day. After 5 days the biomaterial was examined and discarded and the glass tube was centrifuged. The pellet was examined using polarized light microscopy. Polysulfone and bone cement was found to be considerably altered in vitro by most of these fluids. While the components (plasticizer and catalyst) of the plastic fluids caused some changes to the biomaterial. Spurr's and GMA did not cause any alterations to any of the biomaterials that were examined.

Metal release from plates used in jaw fracture treatment. A pilot study

This study investigated the occurrence of corrosion associated with the use of metallic implants to stabilize jaw fractures. Three different types of plates, Co-Cr and Ni-Cr alloys and Titanium, were connected in vivo to the mandibular bone surface of monkeys (Cercopithecus aethiops). The animals were killed after 3 and 6 months. The mucous membrane and bone tissue were analysed for concentrations of Co, Cr, Ni, Mo, Al, and Ti by atomic absorption spectrophometry and a radiochemical neutron activation technique. With the exception of Ti, higher concentrations of all the above elements were found in the tissue near the implants when compared with contralateral controls. However, no signs of corrosion, macroscopic or microscopic, were observed on the surface of the implants.

Albumin adsorption on metal surfaces

Studies of adsorption kinetics, desorption and adsorption isotherms concerning the interaction between albumin and a range of metal and metal oxides were undertaken in vitro. Three distinct types of behaviour concerning the adsorption of albumin on to metal surfaces were identified. Some metals adsorb considerably greater amounts of protein than might be expected from surface energy alone and it is suggested that electrostatic forces could be responsible for this phenomenon.

In vitro testing of dental materials by means of macrophage cultures: II. Effects of particulate dental amalgams and their constituent phases on cultured macrophages

It is known that macrophages play an important role in the removal of foreign particulate matter from tissue. When powdered dental amalgam is introduced into the soft tissues an amalgam tattoo is formed due to the intracellular degradation of amalgam by macrophages and their polykaryons. It was therefore feasible to study the effects of particulate amalgams as well as their individual phases on macrophages in vitro. The parameters compared were rate of the phagocytosis, changes of cellular morphology, and release of lactate dehydrogenase (LDH) to demonstrate plasma membrane permeability. It was shown that all the alloys except the Sn8Hg particles (gamma 2-phase) and gamma 2-containing Revalloy were effectively phagocytized by macrophages, and the alterations in cellular morphology were slight during the first day. Prominent cellular damage was seen in cultures treated with particulate Ag2Hg3 (gamma 1-phase) and Revalloy for 1 week. A slight increase in LDH activity in the medium was seen one hour after the alloy treatment. The LDH activities due to the amalgam treatment increased in the order Dispersalloy less than Revalloy less than Sybraloy. Intraperitoneal phagocytosis did not cause any morphological changes in macrophages, but the per cent of phagocytosis was diminished.

In vitro and in vivo biological responses to some dental alloys tested separately and in combinations

Biocompatibility of dental alloys has been tested both in vivo and in vitro. In addition, combinations of dissimilar alloys were investigated in relation to possible enhanced corrosion by galvanic effects. Implantation tests, cytotoxicity tests on epithelial cells, macrophages and erythrocytes were performed, and the results compared. The severity of tissue response in implantation tests corresponded to the nobleness of the casting alloys joined to amalgam. Similar results were obtained in the in vitro macrophage test. All the alloys except the high-gold alloy (LM-Hard) had a toxic effect on epithelial cells. The combination of the casting alloys with amalgam diminished the toxic effect. Three of the alloys (amalgam, LM-Hard and Midi low-gold alloy) caused a slight haemolysis. Poor correlation was obtained between the agarose overlay tests, the haemolysis tests and the implantation tests.

Protein absorption and desorption phenomena on clean metal surfaces

The noncompetitive adsorption of the proteins albumin and fibrinogen onto 17 different metal surfaces has been studied in vitro using 125I-labeled proteins. Although many of the metals showed very similar adsorption characteristics to polymers, several of them adsorbed considerably greater amounts. Copper, gold, and silver were the most significant in this respect, all three being face-centered cubic, group 1B metals known to bind to many types of protein in vitro and in vivo. The desorption of the proteins was studied in an in vivo model in which preproteinized metals were implanted in rats. There was considerable variations in the amounts of the proteins removed from the various metal surfaces. Generally those metals onto which protein is most readily adsorbed tend to lose the protein quickly, whereas others, such as iron, with only moderate adsorbed amounts, may retain a large part of the adsorbed layer for a long time.

Scanning electron microscopy of the metal-tissue interface. II. Observations with lead, copper, nickel, aluminium, and cobalt

The nature of the metal-tissue interface following the implantation of five pure metals, lead, copper, nickel, aluminium and cobalt, in rats has been observed by scanning electron microscopy. The general conclusion, derived from light microscopy that the tissue response to pure metals is characteristic of and specific to individual pure metals has been confirmed in this study. However, far more detailed observations of factors such as the extent of metallic corrosion, the distribution of red blood cells, platelets and other cells in the capsule and adherent to the metal surface, have been possible with SEM.