silicon and Foreign-Body-Reaction

Neural interface technologies including recording and stimulation electrodes are currently in the early phase of clinical trials aiming to help patients with spinal cord injuries, degenerative disorders, strokes interrupting descending motor pathways, or limb amputations. Their lifetime is of key importance; however, it is limited by the foreign body response of the tissue causing the loss of neurons and a reactive astrogliosis around the implant surface. Improving the biocompatibility of implant surfaces, especially promoting neuronal attachment and regeneration is therefore essential. In our work, bioactive properties of implanted black polySi nanostructured surfaces (520-800 nm long nanopillars with a diameter of 150-200 nm) were investigated and compared to microstructured Si surfaces in eight-week-long in vivo experiments. Glial encapsulation and local neuronal cell loss were characterised using GFAP and NeuN immunostaining respectively, followed by systematic image analysis. Regarding the severity of gliosis, no significant difference was observed in the vicinity of the different implant surfaces, however, the number of surviving neurons close to the nanostructured surface was higher than that of the microstructured ones. Our results imply that the functionality of implanted microelectrodes covered by Si nanopillars may lead to improved long-term recordings.

Topics: Animals; Cell Death; Cell Proliferation; Central Nervous System; Foreign-Body Reaction; Gliosis; Nanostructures; Neuroglia; Neurons; Optical Imaging; Prostheses and Implants; Prosthesis Implantation; Rats, Wistar; Silicon

The effect of the living organism on the polymer materials used for the manufacture of grids for implants. It is shown that the recipient's body is actively working to exogenous material , destroying its surface layer and forms around the implant insulating fibro-connective tissue capsule, the thickness of which depends on the severity of the organism's reaction to a foreign body. Proposed instrumental method of determining compatibility before surgery implant material with the recipient using an atomic force microscope (AFM).

Topics: Animals; Biocompatible Materials; Connective Tissue; Foreign-Body Reaction; Materials Testing; Microscopy, Atomic Force; Polypropylenes; Polytetrafluoroethylene; Rabbits; Silicon; Surface Properties; Surgical Mesh

In this study we employed a quantitative immunohistochemical approach to compare the brain tissue response to planar silicon microelectrode arrays that were conformally coated with Parylene-C to uncoated controls at 2, 4, and 12 weeks following implantation into the cortex of adult male Sprague-Dawley rats. We did not find any difference in the relative intensity or the spatial distribution of neuronal or glial markers over the indwelling period, even though Parylene-C-coated substrates supported significantly less cell attachment, indicating that the foreign body response to planar silicon microelectrode arrays has little to do with the composition or decomposition of the silicon electrode. Moreover, our results suggest that changes in microelectrode surface chemistry do not have a strong influence on the cytoarchitectural changes that accompany the brain foreign body response to planar silicon microelectrode arrays. Our quantitative comparison over the indwelling period does not support progressive increases in astrocyte encapsulation and/or progressive neuronal loss in the recording zone as dominant failure mechanisms of the type of chronic recording device. Finally, we found evidence of two potentially new failure mechanisms that were associated with CD68 immunoreactivity including demyelination of adjacent neurons and BBB breakdown surrounding implanted electrodes at long indwelling times.

Topics: Animals; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Astrocytes; Cells, Cultured; Cerebral Cortex; Demyelinating Diseases; Electrodes, Implanted; Foreign-Body Reaction; Male; Microelectrodes; Neurons; Polymers; Rats; Rats, Sprague-Dawley; Silicon; Xylenes

Capsular fibrosis is one of the most severe complications that can occur in connection with silicone breast implants. Should this case arise, a periprosthetic deposition of fibroid tissue may evolve. Transforming growth factor (TGF)-beta is one of the most important mediators in relation to such processes.. The chinazolinone derivative halofuginone is a type I collagen synthesis inhibitor that interferes with the TGF-beta signaling pathway. The work at hand examines the local antifibrotic effectiveness of halofuginone lactate, which has been biotechnologically bound to the silicone implant's surface. The experiments in relation to this were conducted in vivo on two groups of seven Sprague-Dawley rats. Group I received untreated silicone implants, and group II received halofuginone-coated silicone implants.. Submusculary embedded halofuginone-coated silicone implants have shown no systemic side effects. The histologic and immunohistologic examinations of the periprostatic capsules revealed a significant decrease of CD68 histiocytes, TGF-beta, fibroblasts, collagen type I and type III, and capsular thickness after a 3-month period.. The results confirmed a decrease in foreign body responses to halofuginone surface-modified silicone implants and mark their potential for obtaining a lessened capsular fibrosis by way of a local antifibrotic effect.

Topics: Animals; Breast Implants; Coated Materials, Biocompatible; Collagen Type I; Disease Models, Animal; Female; Fibrosis; Foreign-Body Reaction; Mammary Glands, Animal; Piperidines; Protein Synthesis Inhibitors; Quinazolinones; Rats; Rats, Sprague-Dawley; Silicon; Treatment Outcome

Several variations of microelectrode arrays are used to record and stimulate intracortical neuronal activity. Bypassing the immune response to maintain a stable recording interface remains a challenge. Companies and researchers are continuously altering the material compositions and geometries of the arrays in order to discover a combination that allows for a chronic and stable electrode-tissue interface. From this interface, they wish to obtain consistent quality recordings and a stable, low impedance pathway for charge injection over extended periods of time. Despite numerous efforts, no microelectrode array design has managed to evade the host immune response and remain fully functional. This study is an initial effort comparing several microelectrode arrays with fundamentally different configurations for use in an implantable epilepsy prosthesis. Specifically, NeuroNexus (Michigan) probes, Cyberkinetics (Utah) Silicon and Iridium Oxide arrays, ceramic-based thin-film microelectrode arrays (Drexel), and Tucker-Davis Technologies (TDT) microwire arrays are evaluated over a 31-day period in an animal model. Microelectrodes are compared in implanted rats through impedance, charge capacity, signal-to-noise ratio, recording stability, and elicited immune response. Results suggest significant variability within and between microelectrode types with no clear superior array. Some applications for the microelectrode arrays are suggested based on data collected throughout the longitudinal study. Additionally, specific limitations of assaying biological phenomena and comparing fundamentally different microelectrode arrays in a highly variable system are discussed with suggestions on how to improve the reliability of observed results and steps needed to develop a more standardized microelectrode design.

Topics: Action Potentials; Animals; Artifacts; Brain; Brain Injuries; Ceramics; Electric Impedance; Electrodes, Implanted; Electronics, Medical; Electrophysiology; Foreign-Body Reaction; Iridium; Microelectrodes; Neurons; Neurophysiology; Prosthesis Implantation; Rats; Rats, Long-Evans; Signal Processing, Computer-Assisted; Silicon; Time; Time Factors

The in vivo behavior and tissue reaction to tetrahedral amorphous carbon (ta-C) has been evaluated for periods of up to 6 months in SV129 mice. Two sample types were tested--silicon die coated with ta-C (n = 53) and micromachined particles (n = 40). The coated samples were compared to uncoated silicon die (n = 22). Die samples were implanted subcutaneously, and tissue reaction and capsule formation were evaluated at various time points. Micromachined particles of 1, 3, 10, and 30 microm were injected adjacent to the sciatic nerve, and tissue samples were examined histologically at various time points (4 days-6 months). Tissue reaction to ta-C was mild and was localized to the area of the injection or implantation. Samples with a higher ratio of 3-fold bonding appeared to shed material during the experiments; this was not observed on samples with a higher level of 4-fold bonding, nor on uncoated silicon die. The results strongly suggest that films with greater 4-fold bonding character (more diamond-like) are more resistant to in vivo fragmentation than films with higher 3-fold character (more graphitic).

Topics: Animals; Carbon; Coated Materials, Biocompatible; Connective Tissue; Foreign-Body Reaction; Implants, Experimental; Injections, Intramuscular; Macrophages; Materials Testing; Mice; Molecular Structure; Muscle, Skeletal; Particle Size; Sciatic Nerve; Silicon; Spectrum Analysis, Raman

Current retinal prosthetics are designed to stimulate existing neural circuits in diseased retinas to create a visual signal. However, implantation of retinal prosthetics may create a neurotrophic environment that also leads to improvements in visual function. Possible sources of increased neuroprotective effects on the retina may arise from electrical activity generated by the prosthetic, mechanical injury due to surgical implantation, and/or presence of a chronic foreign body. This study evaluates these three neuroprotective sources by implanting Royal College of Surgeons (RCS) rats, a model of retinitis pigmentosa, with a subretinal implant at an early stage of photoreceptor degeneration. Treatment groups included rats implanted with active and inactive devices, as well as sham-operated. These groups were compared to unoperated controls. Evaluation of retinal function throughout an 18 week post-implantation period demonstrated transient functional improvements in eyes implanted with an inactive device at 6, 12 and 14 weeks post-implantation. However, the number of photoreceptors located directly over or around the implant or sham incision was significantly increased in eyes implanted with an active or inactive device or sham-operated. These results indicate that in the RCS rat localized neuroprotection of photoreceptors from mechanical injury or a chronic foreign body may provide similar results to subretinal electrical stimulation at the current output evaluated here.

Topics: Animals; Electric Stimulation; Foreign-Body Reaction; Neuronal Plasticity; Photoreceptor Cells, Vertebrate; Prostheses and Implants; Rats; Recovery of Function; Retinitis Pigmentosa; Silicon

Square-shaped silicon or titanium implants with plane or porous surfaces surrounded by a rim of silicone were implanted in the rat abdominal wall for evaluation of the tissue response after one, six, or 12 weeks. Cell damage was identified as increased membrane permeability using fluorescence microscopy by injection of propidium iodide prior to the killing of the rats. Capsule thickness and immunohistochemical quantification of macrophages were used as a further measure of the foreign-body reaction. There were no significant differences in capsular cell densities for macrophages, total cells (macrophages, fibroblasts, and other cells), or necrotic cells at the different time points for the four surfaces studied. However, significant differences in the kinetics of the response were found between plane surfaces compared with porous ones. Both types of plane surfaces developed a significant increase in capsule thickness over time in contrast to the porous implants. Porous silicon displayed a significant decrease in total cells in the reactive capsule over time. Furthermore, porous silicon and titanium surfaces displayed a significant decrease in total cell numbers at the implant interface between six and 12 weeks. The present study demonstrated that implanted silicon elicited soft-tissue reactions comparable to that of titanium.

Topics: Abdominal Muscles; Animals; Biocompatible Materials; Cell Membrane Permeability; Foreign-Body Reaction; Image Processing, Computer-Assisted; Immunoenzyme Techniques; Male; Microscopy, Fluorescence; Prostheses and Implants; Prosthesis Design; Rats; Rats, Sprague-Dawley; Silicon; Statistics, Nonparametric; Titanium

The ubiquitousness of silicon is well known. Recent work has demonstrated measurable baseline levels of silicon in nonaugmented cadavers, subsequent to numerous reports of significant elevations of such levels within patients with silicone breast implants and even more reports alleging a causal relation between silicone gel prostheses and connective-tissue diseases. Despite the lack of scientifically substantiated data that such a relation exists, the calamitous silicone breast implant controversy has ensued. Saline-filled breast implants are constructed with a silicone elastomer envelope that remains in direct contact with periprosthetic capsular tissue following implantation. Although there is no evidence to link saline implants with any disorders, it is important to know if saline breast implants contribute any silicon to human body baseline silicon levels. The present study measured tissue silicon levels in 28 breasts of 16 patients with saline-filled implants to determine if the silicone envelope of these prostheses can contribute to the elevation of such levels. These data were compared with data from 116 breasts of 65 patients with silicone gel-filled prostheses as well as breast tissue from 17 patients (controls) who had never been exposed to either type of implant. Samples of breast tissue and periprosthetic capsular tissue were obtained from patients with both intact and ruptured implants. Silicon levels of breast tissue specimens from patients with saline-filled implants were within the range of the controls if the implants were intact. Silicon levels in periprosthetic capsular tissue from patients with intact saline-filled implants were significantly higher than controls (p < 0.02); however, they were still 100-fold less than capsular tissue levels from patients with intact gel-filled implants. Silicon levels measured in both types of tissue were significantly elevated in patients with silicone gel-filled implants compared with controls (p < 0.01). In the case of ruptured gel implants, breast tissue demonstrated higher silicon levels than did similar specimens from patients with intact implants (p < 0.054); periprosthetic capsular tissue levels also were elevated, although the differences were not statistically significant (p = 0.54). These findings are independent of the implant brand or length of exposure to the particular prosthesis. The finding of elevated levels of silicon in both breast and periprosthetic capsular tissue in patients with

Topics: Adult; Aged; Breast; Breast Implants; Female; Foreign-Body Reaction; Humans; Middle Aged; Silicon; Sodium Chloride

We describe 2 patients with foreign body synovitis simulating acute septic arthritis. One patient was an 11-year-old boy who developed acute knee swelling due to a penetrating fragment of wood. The other patient was an intravenvous drug abuser in whom silicon was identified in synovial fluid and synovial membrane and whose arthritis improved after complete synovectomy.

Topics: Acute Disease; Adult; Arthritis, Infectious; Child; Diagnosis, Differential; Elbow Joint; Foreign Bodies; Foreign-Body Reaction; Humans; Knee Joint; Male; Silicon; Wood

In 100 consecutive cases in which grossly normal ovaries were removed at the time of pelvic surgery, 9% were found to contain crystalline foreign particles. An additional 9% contained cortical granulomas. In four of six cases, computer-assisted x-ray analysis of the crystalline foreign particles was successful and revealed magnesium and silicon.

Topics: Adult; Electron Probe Microanalysis; Female; Foreign-Body Reaction; Humans; Magnesium; Middle Aged; Ovary; Silicon

Miniature "soft gel" filled breast prostheses were implanted into rats, and half of these were purposefully ruptured upon insertion. At sacrifice of the animals later, the position of the exuded gel, the variability of the capsule thickness, and the extent of the capsule formation were evaluated. The capsule thickness was significantly increased around the ruptured prostheses, in response to the exuded gel. Also, the gel migrated through the fibrous capsule and into the surrounding tissue, eliciting an inflammatory response there to produce capsule thickening.

Topics: Animals; Breast; Female; Foreign-Body Reaction; Gels; Prostheses and Implants; Rats; Silicon; Skin

An investigation, by scanning electron microscopy of the capsules formed around silicone breast implants revealed that they consist almost entirely of connective tissue. In contrast, the capsules around the Y-prostheses (with a polyurethane foam surface) showed a foreign body reaction. We believe that excessive capsule formation around silicone implants is, among other factors, most likely due to discrete or moderate bleeding with subsequent hematoma formation. Therefore, we favor a two-stage procedure for subcutaneous mastectomy with insertion of the implant at 4 to 6 months after the excision.

Topics: Breast; Connective Tissue; Connective Tissue Cells; Female; Foreign-Body Reaction; Humans; Microscopy, Electron, Scanning; Polyurethanes; Prostheses and Implants; Silicon; Silicone Elastomers