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PubMed1997

Development of polyarthritis after insertion of silicone breast implants followed by remission after implant removal in 2 HLA-identical sisters bearing rheumatoid arthritis susceptibility genes.

We describe 2 HLA-identical sisters who both received silicone breast implants and subsequently developed polyarticular arthritis and neurologic symptoms. In both patients, HLA typing revealed 3 alleles typically associated with rheumatic diseases: HLA-DRB1*0405 and HLA-DQB1*0302 (associated with RA), and HLA-DRB4*01 (associated with mixed connective tissue disease and autoimmune reactions in patients with silicone breast implants. After removal of the implants, rheumatic as well as neurologic symptoms improved dramatically in both patients. One patient achieved complete remission. The other patient, who initially had more progressive disease, retained mild residual symptoms, but had significant improvement in radiological erosions. We believe that our cases support the theories that silicone may act as a triggering factor in genetically susceptible individuals, and that silicone may represent an adjuvant for the development of autoimmune disease. We discuss the possibility that a manifested spectrum of symptoms after silicone exposure might be more specific for a patient's genetic background than unique for silicone.

Arthritis, Rheumatoid↗
PubMed1998

Optimal imaging protocol after intraocular silicone oil tamponade.

PURPOSE: Our purpose was to define the optimal protocol for imaging of the orbits after vitreous humor replacement with silicone oil. METHODS: Eleven eyes in 10 patients with tractional and/or rhegmatogenous retinal detachment were studied. Five CT scans and 18 high-field (1.5 T) MR images were obtained. Standard T1-weighted, T1-weighted with fat and silicone saturation, fast spin density-weighted, and T2-weighted orbital MR sequences were performed. Unique pulse sequences included fast spin density-weighted and T2-weighted imaging with and without fat saturation or silicone saturation, gradient-echo imaging, and short-tau inversion recovery imaging. RESULTS: The T1-weighted MR and CT studies were comparable in displaying the silicone. However, the fat- or silicone-saturated fast T2-weighted sequences always showed the fibrous bands and subretinal fluid to best advantage. In one case, the eye also contained inadvertently retained perfluorocarbon liquid, which blended with silicone oil on both saturated images, requiring companion T1-weighted sequences without saturation to demonstrate its presence. CONCLUSION: Simple, commonly available fat-saturated fast T2-weighted MR images supplemented by standard T1-weighted images are all that are needed to evaluate the eye efficiently after vitrectomy and tamponade.

Adult↗
PubMed1998

Effects of silicon-insole socks on pressure distribution and shear force of the foot.

BACKGROUND: Many problems of the foot are due to abnormal plantar pressure and shear force, but until now shear force could not be accurately measured. Different methods can be used to reduce foot pressure, such as foot orthosis or shoe modification. The purposes of our study were to propose a method for measuring the maximum shear force of the foot and also to investigate the effect of silicone-insole socks in reducing the peak plantar pressure and shear stress of the foot. METHODS: Twenty-two healthy subjects were included in this study, each subject underwent 2 kinds of experiments to study the peak plantar pressure, the horizontal shear reaction force, and the maximum shear force under 3 conditions: barefoot, wearing 100% cotton socks, and wearing silicone-insole socks. RESULTS: Our results showed a significant decrease in midfoot peak plantar pressure while walking, and a decrease in horizontal shear reaction force and maximum shear force while wearing cotton socks and silicone-insole socks in walking and pulling. Silicone-insole socks were more significant in decreasing horizontal shear reaction force than cotton socks. CONCLUSION: Silicone-insole socks are better than cotton socks in reducing horizontal shear reaction forces and their friction coefficients. Because only normal subjects have been tested, further study is required to prove the efficacy of silicone-insole socks on different kinds of foot pathology.

Adult↗
PubMed1998

[Silicone and autoimmune diseases].

There exists controversy surrounding the potential relationship between silicone implants and autoimmune diseases. Indeed, silicone is not an inert substance and microparticles from the prosthesis can migrate causing localised or generalised reactions. Most notably, silicone has been associated with sclerodermia and human adjuvant disease. Sclerodermia has been observed within 50% patients suffering from autoimmune diseases linked with silicone. For patients with symptoms, the removal of the prosthesis achieves a favourable response in 50% of the cases. Before a patient undergoes a silicone implant, it is essential that personal and family history of autoimmune disorders are ascertained and evaluated. Also, the patient should undergo regular check ups after having received the implant. In spite of the fact that certain epidemiological studies have not demonstrated a relationship between silicone implants and autoimmune disease, the continual appearance of new cases means that the physician should have an open attitude and be aware of the possibility.

Autoimmune Diseases↗
PubMed1998

[The importance of silicone oil removal in prophylaxis of the late complications of internal tamponade].

PURPOSE: To present the functional and anatomical results after silicone oil removal. MATERIAL: Covers 32 patients (34 eyes), age 29-77 years. Silicone oil removal was performed between February 1993 and December 1994. The indication for silicone oil tamponade was: PDVR (17/34), rhegmatogenous retinal detachment (12/34), trauma (4/34) and vitreous haemorrhage (1/34). METHODS: The conditions of silicone oil removal were complete retinal attachment within at least 3 months, visual acuity not worse than 1/50, no proliferations, laser photocoagulation of peripheral retina. RESULTS: In postoperative period retina was attached in 30 cases (88%). Retinal detachment was observed in 4 cases (12%). Visual acuity remains unchanged in 27 cases. CONCLUSIONS: We found that silicone oil removal leads in the majority of eyes to a stabilisation of visual acuity and reduces the progress of silicone oil-related complications.

Adult↗
PubMed1995

High resolution solid-state 29Si NMR spectroscopy of silicone gels used to fill breast prostheses.

We have used 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy to study the chemical structure of the silicone gels in virgin and explanted breast prostheses. Despite evidences of alteration in the morphological appearance of the silicone gel inside the breast prosthesis, our results do not reveal changes in the chemical nature and structure of the silicone gels after implantation. In addition to the main 29Si resonance peak at -22.26 ppm that corresponds to the resonance frequency of the D repeat unit of the polysiloxane chains, the high sensitivity of our NMR technique allows the detection of very low concentrations of silicone compounds. Within our experimental detection limit of 0.2%, no signal between -90 ppm and -150 ppm are observed. This indicates that no silica products are present inside the gel of the prostheses. Furthermore, our 29Si NMR spectra indicate differences in the chemical compositions of the silicone gels from different manufacturers.

Breast Implants↗
PubMed2006

Platinum in silicone breast implants.

Silicone elastomers are widely used in implantable devices, including silicone breast implants. These rubbers are generally formed/cured using platinum-catalyzed hydrosilylation. The current scientific literature on the chemistry of platinum is reviewed, as it applies to the use of platinum catalysts for cure of silicone elastomers destined for use in silicone breast implants. These discussions serve as a basis to examine the recent literature describing release of platinum into tissues adjacent to silicone breast implants, the chemical nature of the platinum present in breast implants and the possible association between platinum and clinical outcomes.

Breast Implants↗
PubMed1996

Chip PCR. I. Surface passivation of microfabricated silicon-glass chips for PCR.

The microreaction volumes of PCR chips (a microfabricated silicon chip bonded to a piece of flat glass to form a PCR reaction chamber) create a relatively high surface to volume ratio that increases the significance of the surface chemistry in the polymerase chain reaction (PCR). We investigated several surface passivations in an attempt to identify 'PCR friendly' surfaces and used those surfaces to obtain amplifications comparable with those obtained in conventional PCR amplification systems using polyethylene tubes. Surface passivations by a silanization procedure followed by a coating of a selected protein or polynucleotide and the deposition of a nitride or oxide layer onto the silicon surface were investigated. Native silicon was found to be an inhibitor of PCR and amplification in an untreated PCR chip (i.e. native slicon) had a high failure rate. A silicon nitride (Si(3)N(4) reaction surface also resulted in consistent inhibition of PCR. Passivating the PCR chip using a silanizing agent followed by a polymer treatment resulted in good amplification. However, amplification yields were inconsistent and were not always comparable with PCR in a conventional tube. An oxidized silicon (SiO(2) surface gave consistent amplifications comparable with reactions performed in a conventional PCR tube.

Base Sequence↗
PubMed2007

Stability of and inflammatory response to silicon coated with a fluoroalkyl self-assembled monolayer in the central nervous system.

A self-assembled monolayer (SAM) of fluoroalkyl silane (FAS) (CF(3)(CF(2))(5)(CH(2))(2)SiCl(3)) was deposited on the surface of silicon wafers, aiming to enhance its stability and to reduce the inflammatory response in the central nervous system. Following implantation of the FAS SAM coated silicon in rat brains, the FAS SAM coating failed to reduce the inflammatory response of silicon, because it could not prevent the corrosion of the underlying silicon. The corrosion was hindered for the initial 10 days by the FAS SAM coating, but there was nearly no difference when compared to the uncoated silicon when the implantation periods were extended to 28 and 90 days. The FAS SAM coating was completely removed within 28 and 90 days. Meanwhile, on all the extracted uncoated and FAS SAM coated silicon wafers, there were proteinaceous substances deposited on the surfaces, and the amount of the deposits increased with exposure time.

Animals↗
PubMed1999

Role of Silicone Surfactant in Flexible Polyurethane Foam.

Grafted copolymers which consist of a polydimethylsiloxane backbone and polyethylene oxide-co-propylene oxide pendant groups are used as surfactants to stabilize the foam cells in the flexible polyurethane foaming process. The mechanical properties of the cured polyurethane foam such as air permeability and foam cell size are affected significantly by the structure of the silicone surfactant used in the formulation. It is shown that silicone surfactant has an important impact on both the bubble generation and the cell window stabilization stage. A series of silicone surfactants with different structures was tested. Surfactants with higher silicone content will provide lower surface tension and thus help increase the number of air bubbles introduced during mixing. These air bubbles serve as the starting point for foam cell growth. As a result, the cured polyurethane foam made with higher silicone content surfactant has a smaller bubble size. It is also shown that silicone surfactant can reduce the cell window drainage rate due to the surface tension gradient along the cell window. The Gibbs film elasticity, the dynamic film elasticity, and the film drainage rate were measured for the first time versus surfactant composition. Surfactants with longer siloxane backbones are shown to give higher film elasticity. Using the vertical film drainage and foam column tests, it is shown that surfactants with higher film elasticity will yield slower drainage rate and better foam cell stability. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Characterization of a silicon transporter gene family in Cylindrotheca fusiformis: sequences, expression analysis, and identification of homologs in other diatoms.

The transport of silicon is an integral part of the synthesis of the silicified cell wall of diatoms, yet knowledge of the number, features, and regulation of silicon transporters is lacking. We report the isolation and sequence determination of five silicon transporter (SIT) genes from Cylindrotheca fusiformis, and examine their expression patterns during cell wall synthesis. The encoded SIT amino acid sequences are highly conserved in their putative transmembrane domains. Nine conserved cysteines in this domain may account for the sensitivity of silicon uptake to sulfhydryl blocking agents. A less conserved C-terminal domain is predicted to form coiled-coil structures, suggesting that the SITs interact with other proteins. We show that SIT gene expression is induced just prior to, and during, cell wall synthesis. The genes are expressed at very different levels, and SIT1 is expressed in a different pattern from SIT 2-5. Hybridization experiments show that multiple SIT gene copies are present in all diatom species tested. From the data we infer that individual transporters play specific roles in silicon uptake, and propose that the cell regulates uptake by controlling the amount or location of each. The identification of all SIT genes in C. fusiformis will enhance our understanding of the mechanism and control of silicon transport in diatoms.

Amino Acid Sequence↗
PubMed2005

Evaluation of polymer and self-assembled monolayer-coated silicone surfaces to reduce neural cell growth.

The development of silicone catheters has improved the treatment of hydrocephalus. Unfortunately, the functionality of the catheters used for the treatment of hydrocephalus is compromised by cell obstruction. In this study silicone surfaces coated with biopolymers (heparin and hyaluronan) and self-assembled monolayers (SAM) (octadecyltrichlorosilane-OTS and fluoroalkylsilane-FAS) were employed to investigate the effect of these coatings on astrocyte and choroid plexus cell growth in vitro. Compared to unmodified silicone, FAS surfaces significantly reduced (p<0.05) astrocyte proliferation, heparin (p<0.001) and hyaluronan (p<0.001) surfaces significantly increased astrocyte growth, while no significant difference was observed on OTS surfaces. A similar trend was observed for choroid plexus cell growth on heparin (p<0.05) and hyaluronan (p<0.05) coatings, however, no significant reduction in cell growth was observed on FAS- or OTS-coated surfaces compared to silicone. Low cell growth may be attributed to hydrophobicity of the surfaces (FAS 112.2+/-2.6 degrees , OTS 102.2+/-1.3 degrees). Contact angle measurements confirmed the stability of the hydrophobic and hydrophilic properties of all the coatings on the silicone surfaces for 30 days. Surface roughness did not play an important role on cell growth. Silicone shunts coated with SAMs may be suitable for future clinical applications to improve the treatment of hydrocephalus.

Animals↗
PubMed2006

Water sorption in silicone foam containing diatomaceous earth.

Room temperature vulcanizing (RTV) silicone foams are commonly used for compression sealing, structural support, packaging, and damping applications. The presence of sorbed water in foams can affect the mechanical and chemical properties of these materials. In order to investigate water sorption behavior, a silicone foam containing diatomaceous earth filler was synthesized and studied for water uptake characteristics at 20, 50, and 80 degrees C. Type II equilibrium and bimodal kinetic behavior that was governed by a rapid initial uptake followed by a prolonged sorption over a larger time scale was observed. In order to explain this bimodal behavior, the major components of this foam-the silicone polymer and the diatomaceous earth-were independently studied for their water equilibrium behavior and uptake kinetic characteristics. Type II equilibrium was observed for both components. The kinetic behavior of the silicone polymer was governed by a very rapid uptake of water. The kinetic behavior of the diatomaceous earth was governed by a rapid initial uptake followed by a prolonged sorption over a larger time scale. A physically based and thermodynamically consistent mathematical model describing the water equilibrium and kinetics in diatomaceous earth and silicone polymer components, was employed to characterize the data. This model formed the basis of a predictive model for estimation of water sorption in filled silicone foam. The predictive model was tested against sorption and desorption data yielding favorable results for a range of temperatures.

Journal Article↗
PubMed2000

TEM characterisation of porous silicon

In this work, the results of a structural investigation by transmission electron microscopy of porous silicon and porous silicon-based devices is reported. This investigation covers a wide range of porous silicon materials going from photoluminescent micro- or meso-porous silicon to macro-porous layers as well as some recent applications of this material for the fabrication of porous silicon and Si/SiO2 superlattices, suspended thick membranes and gas sensor devices. It appears that the structural investigation technique here employed, is a fundamental tool for the optimisation of the technological processing of this material. From the results reported in this work, a quite comprehensive view of the potentialities and limitations of the applications of porous silicon in the field of optical and gas sensor devices should also emerge. Finally, some solutions to the problems usually met during the technological processing of this material are proposed.

Journal Article↗
PubMed2001

Porous silicon as a versatile platform for laser desorption/ionization mass spectrometry.

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is a novel method for generating and analyzing gas-phase ions that employs direct laser vaporization. The structure and physicochemical properties of the porous silicon surfaces are crucial to DIOS-MS performance and are controlled by the selection of silicon and the electrochemical etching conditions. Porous silicon generation and DIOS signals were examined as a function of silicon crystal orientation, resistivity, etching solution, etching current density, etching time, and irradiation. Pre-and postetching conditions were also examined for their effect on DIOS signal as were chemical modifications to examine stability with respect to surface oxidation. Pore size and other physical characteristics were examined by scanning electron microscopy and Fourier transform infrared spectroscopy, and correlated with DIOS-MS signal. Porous silicon surfaces optimized for DIOS response were examined for their applicability to quantitative analysis, organic reaction monitoring, post-source decay mass spectrometry, and chromatography.

Journal Article↗
PubMed2003

Bis-silicon-bridged stilbene homologues synthesized by new intramolecular reductive double cyclization.

A homologous series of bis-silicon-bridged stilbenes has been synthesized on the basis of a new intramolecular reductive cyclization of bis(o-silyl)-diphenylacetylene. Thus, the reaction of bis(o-silyl)-diphenylacetylenes with excess lithium naphthalenide undergoes the two-electron reduction at the acetylene moiety to produce a dianion intermediate, which further undergoes a double cyclization in a 5-exo mode to produce the bis-silicon-bridged stilbenes. This methodology can also be applied to the synthesis of tetrakis-silicon-bridged bis(styryl)benzenes. The silicon-bridged pi-conjugated systems thus prepared show intense fluorescence in the visible region. Comparison of a bis-silicon-bridged stilbene with its carbon analogue demonstrates the substantial effects of the silicon-bridges on the electronic structures and thus on the fluorescence properties.

Journal Article↗
PubMed2006

In situ STM investigation of gold reconstruction and of silicon electrodeposition on Au(111) in the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide.

The electrodeposition of silicon on Au(111) was investigated by cyclic voltammety (CV) and by in situ scanning tunneling microscopy (STM) in the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide with a SiCl(4) concentration of 0.1 mol/L. A main reduction process begins in the cyclic voltammogram at about -1800 mV versus ferrocene/ferrocinium, which is correlated to the electrodeposition of elemental semiconducting silicon. It has been found that at an electrode potential more negative than the open circuit potential (OCP), the Au(111) surface is subject to a restructuring/reconstruction both in the case of the pure ionic liquid and in the presence of SiCl(4). The first STM-probed silicon islands with 150-450 pm in height appear at about -1700 mV versus ferrocene/ferrocinium. Their lateral and vertical growth leads to the formation of a rough layer with silicon islands of up to 1 nm in height. At about -1800 mV the islands merge and form silicon agglomerates. In situ I/U tunneling spectroscopy reveals a band gap of 1.1 +/- 0.2 eV for layers of about 5 nm in height, a value that has to be expected for semiconducting silicon.

Journal Article↗
PubMed2006

Trapping silicon surface-based radicals.

The spontaneous one-electron reduction of diazonium salts on hydride-terminated porous silicon (pSi) and flat silicon produces surface radicals that can be trapped chemically. These silicon radicals react with reagents such as alkyl/arylselenoethers, alkenes, alkynes, and alkylbromide groups to generate covalently bound functionalities in a manner analogous to the chemistry of molecular-based silicon radical species, prepared via different methods. When pSi is exposed to an acetonitrile solution of any of the three diazonium salts examined in this study, aryl groups from the diazonium precursor become covalently bound and significant oxidation is noted; if, however, a reactive trapping agent is added, such as an alkyl/arylselenoether or a carbon-carbon unsaturated bond, no aryl group attachment is observed and oxidation is circumvented due to the efficiency of the trapping chemistry. The reactions proceed rapidly, in less than 3 h to maximum coverage, at room temperature. The diazonium salt-initiated radical reaction with alpha,omega-alkenes and alkynes tolerates various functional groups including aryl, diene, diyne, carboxylic acid, and hydroxyl, reacting exclusively via the carbon-carbon unsaturated bond; alpha,omega-bromoalkenes are not, however, compatible with this chemistry. A silicon-based molecule, tris(trimethylsilyl)silane, in the presence of a diazonium salt initiator and a primary alkyne does not lead to the hydrosilylation product but to tris(trimethylsilyl)silylbromide and the hydrogenated arene, derived from the diazonium. The difference in reactivity between the molecule and the surface is due to the fact that the silicon surface is a source of electrons to reduce the diazonium salts to aryl radicals, whereas a heterolytic pathway is followed in the molecular silane case.

Journal Article↗