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PubMed1999

Analysis of periprosthetic capsular tissue from women with silicone breast implants by magic-angle spinning NMR.

The amount of silicone (polydimethylsiloxane [PDMS]) in capsular tissue surgically removed from women with breast implants was measured by using (29)Si and (1)H magic-angle spinning solid-state NMR spectroscopy. Twelve women having smooth surface silicone gel-filled implants, including a subject with "low-bleed" double-lumen implants, had detectable levels of PDMS ranging from 0. 05 to 9.8% silicon in wet tissue (w/w). No silicon-containing compounds other than PDMS were detected. No correlation was found between the amount of PDMS measured in the capsular tissue and the length of implantation time (Pearson correlation coefficient, r = 0. 22). The results showed no relationship between higher amounts of PDMS and capsular contracture (p = 0.74) or other symptoms (p = 0. 53). Magn Reson Med 42:436-441, 1999.

Breast↗
PubMed2001

Self-sterilizing and self-cleaning of silicone catheters coated with TiO(2) photocatalyst thin films: a preclinical work.

TiO(2) photocatalysts were successfully coated on silicone catheters or medical tubes by pretreatment of the silicone surface with a sulfuric acid solution (5 M) for 3 h. The TiO(2) film adhered to the silicone substrate strongly against tensile and bending stresses. On the TiO(2)-coated silicone-catheters under UV illumination, both the bleaching of methylene blue dye and the photocatalytic bactericidal effect on Escherichia coli (E. coli) cells were confirmed. Thus, this type of catheter can be sterilized and cleaned simply by irradiation with low-intensity UV light and can, therefore, be useful in the protection from catheter-related bacterial infections.

Coated Materials, Biocompatible↗
PubMed2001

A hydroxyapatite coating covalently linked onto a silicone implant material.

A novel composite consisting of hydroxyapatite (HAp) microparticles covalently coupled onto a silicone sheet was developed. Initially, an acrylic acid (AAc) -grafted silicone sheet with a 16.7 microg/cm(2) surface graft density was prepared by corona-discharge treatment. The surface of sintered, spherical, carbonated HAp particles with an average diameter of 2.0 microm was subsequently modified with amino groups. The amino group surface density of the HAp particles was calculated to be approximately one amino molecule per 1.0 nm(2) of particle surface area. These samples were characterized with Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. After the formation of ammonium ionic bonds between both samples under aqueous conditions, they were reacted at 180 degrees C for 6 h in vacuo to form covalent bonds through a solid-phase condensation. The HAp particles were coupled to the AAc-grafted silicone surface by a covalent linkage. Further improvements in the adhesive and bioactive properties of the HAp-coated silicone material are expected.

Acrylates↗
PubMed2001

Do silicone breast implants cause rheumatologic disorders? A systematic review for a court-appointed national science panel.

OBJECTIVE: To assist in evaluating expert testimony and scientific evidence presented in law suits brought against silicone breast implant manufacturers, a US District Court Order established a National Science Panel to assess whether existing studies provide scientific evidence of an association between silicone breast implants and systemic classic/accepted connective disease, atypical connective disease, and certain signs and symptoms identified by plaintiffs in the law suits. Local disorders potentially associated with these implants were not addressed in this review. Therefore, we performed a systematic review of published studies on the association between silicone breast implants and systemic connective tissue disorders. METHODS: Data from relevant studies (human cohort, case-control, or cross-sectional studies with > or = 10 participants and appropriate controls) were identified through literature searches of Medline, Current Contents, HealthStar, Biological Abstracts, EMBase, Toxline, and Dissertation Abstracts. Two independent reviewers, using standard collection forms, extracted data from the included studies. Adjusted relative risks (RRs) in cohort studies and odds ratios (ORs) in case-control and cross-sectional studies were reported if provided; otherwise, unadjusted RRs and ORs were calculated. RESULTS: Twenty-four studies meeting inclusion criteria were identified. No association was evident between breast implants and any established or atypical connective tissue disorder. There was discordance among studies in reports of arthralgias, lymphadenopathy, myalgias, sicca symptoms, skin changes, and stiffness. CONCLUSION: The panel found no evidence to support expert testimony suggesting an association between silicone breast implants and connective diseases. Discordance for symptoms may reflect differences in symptoms included in various categories, the small number of cases, and the effect of having single subjects with > 1 symptom represented in analyses of each symptom reported. The process presented here is an early example of the use of independent scientific panels to help courts clarify scientific evidence in legal proceedings.

Breast Implants↗
PubMedDate not supplied

Imaging of chemiluminescent reactions in mesoscale silicon-glass microstructures.

Chemiluminescent reactions in mesoscale analytical structures (chips) containing micrometre-sized interconnecting channels and chambers (pL-nL total volume) were imaged. The chips were fabricated by bonding Pyrex glass to etched pieces of silicon using a high-temperature diffusive bonding technique. In initial experiments light emission from an enhanced chemiluminescent horseradish peroxidase reaction and from a peroxyoxalate reaction contained in straight channels (300 microns wide x 20 mu deep; volume 70.2 nL) and open chambers (812 microns wide, 400 microns deep, 5.2 mm long) linked by channels (100 microns wide, 20 microns deep) to an exit and entry port were studied using a specially modified microplate holder and an Amerlite microplate luminometer. Light emission from more complex structures (two chambers interconnected by a branching channel 100 microns wide, 20 microns deep) filled with a solution containing alkaline phosphatase, Emerald, and CSPD was imaged using a Photometrics Star 1 CCD camera. Detailed investigation of the detection and spatial resolution of the signal was performed on a Berthold Luminograph LB 980 using both the enhanced chemiluminescent horseradish peroxidase reaction and a peroxyoxalate reaction. We successfully resolved light emission from silicon structures with dimensions 100 microns wide and 20 microns deep. These simple silicon structures served as models for more complex designs that will be used for simultaneous multi-analyte assays in which an imaging system resolves and quantitates light emission from different locations on a silicon-glass analytical device.

Glass↗
PubMed2006

Nanoscale investigation on adhesion of E. coli to surface modified silicone using atomic force microscopy.

Bacterial adhesion on biomaterial surfaces is the initial step in establishing infections and leads to the formation of biofilms. In this study, silicone was modified with different biopolymers and silanes, including: heparin, hyaluronan, and self-assembled octadecyltrichlorosilane (OTS), and fluoroalkylsilane (FAS). The aim was to provide a stable and bacteria-resistant surface by varying the degree of hydrophobicity and the surface structure. The adhesion of Escherichia coli (JM 109) on different modified silicone surfaces was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Mica, an ideal hydrophilic and smooth surface, was employed as a control specimen to study the effect of hydrophobicity and surfaces roughness on bacterial adhesion. AFM probes were coated with E. coli and the force measurements between the bacteria-immobilized tip and various materials surfaces were obtained while approaching to and retracting from the surfaces. A short-range repulsive force was observed between the FAS coated silicone and bacteria. The pull-off force of bacteria to FAS was the smallest among coated surfaces. On the other hand, heparin exhibited a long-range attractive force during approach and required a higher pull-off force in retraction. Both AFM and SEM results indicated that FAS reduced bacterial adhesion whereas heparin enhanced the adhesion compared to pure silicone. The work demonstrates that hydrophobicity cannot be used as a criterion to predict bacterial adhesion. Rather, both the native properties of the individual strain of bacteria and the specific functional structure of the surfaces determine the strength of force interaction, and thus the extent of adhesion.

Bacterial Adhesion↗
PubMed1981

Structural deterioration of prosthetic oesophageal tubes: an in vitro comparison of latex rubber and silicone rubber tubes.

In a series of 100 patients with carcinoma of the oesophagus or cardia undergoing palliative intubation at endoscopy using a latex rubber or a silicone rubber tube 2 cases of tube fragmentation were encountered and are described. The effects of hydrochloric acid, bile and irradiation on the tubes have been studied in vitro. After incubation in hydrochloric acid (0.1 mol/l), the breaking force of latex rubber tubes fell by 31 per cent (48 N) (but did not change significantly for silicone rubber tubes. The addition of bile to the hydrochloric acid (0.1 mol/l) did not further influence the breaking force of either type of tube. Megavoltage irradiation with 7500 rad did not affect the breaking strength of silicone rubber tubes but caused a reduction of breaking strength of latex rubber tubes. These findings suggest that silicone rubber has advantages over latex rubber as a material for prosthetic oesophageal tubes.

Aged↗
PubMed1979

Mechanical properties of antibacterial silicone rubber for hydrocephalus shunts.

In an effort to find a solution to the serious problem of bacterial colonization of cerebrospinal-fluid shunting devices, room-temperature and heat-vulcanizing silicone rubbers were impregnated with gentamicin sulphate. The effects on the mechanical properties of the two rubbers were studied. Results show that the tensile strength and extensibility of the room-temperature-vulcanizing silicone rubber reduced with increasing concentration of the drug. For the heat-vulcanizing silicone rubber, the tensile strength was also found to decrease with increasing drug content. The extensibility after an initial reduction at low concentrations was found to increase at drug concentrations in excess of 10 mg/g. Nevertheless, the changes in mechanical properties measured are considered not to be so great as to preclude the application of drug-impregnated silicone rubbers to cerebrospinal-fluid shunting devices.

Bacteria↗
PubMedDate not supplied

Characterization of plasma polymerized silicone coatings useful as biomaterials.

Plasma polymerization techniques were used to deposit a layer of filler-free silicone rubber on a variety of substrate materials. The thickness of the deposited film was 0.5-0.8 micron. As it is the surface of the biomaterial that comes in direct contact with the body fluids, the surface of the biomaterial is of paramount importance. In this study, the plasma polymerized biomaterials were characterized. Thus, the scanning electron microscope (SEM) showed the surfaces to be smooth. To study the surface layer of the deposited polymer, Fourier-transform infrared spectrometry in the attenuated total reflection (ATR) mode was used. The deposited material was indeed silicone polymer with adsorption bands at 1262, 1020, and 802 cm-1 for the Si-CH3 bending, Si-0-Si stretching, and Si-CH3 bending, respectively. To find the bonding nature of the polymer, electron spectrometry for chemical analysis (ESCA) was used. The silicone polymer was shown to be highly cross-linked. To find the molecular weight between cross-links, swelling studies were done. Thus the results of the study show that the plasma polymerization could produce a filler-free silicone layer on a variety of substrate materials.

Biocompatible Materials↗
PubMedDate not supplied

Evaluation of in vivo adsorption of blood elements onto hydrogel-coated silicone rubber by scanning electron microscopy and fourier transform infrared spectroscopy.

Three hydrogel formulations consisting of 2-hydroxyethyl methacrylate (HEMA) copolymerized with N-vinyl pyrrolidone (NVP) were incorporated into silicone rubber by irradiation-induced polymerization. These coatings were chosen to represent different degrees of hydrophilicity, and they changed the hydrophobic character of the silicone rubber surface to that of hydrophilic. These composite materials and the silicone rubber comparison material were used as femoral artery-to-vein (A-V) shunts and were removed at 15 min, an approximate time representative of an initial buildup stage of blood elements on test surfaces. Data obtained by scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells and fibrin at the time interval described. One-half of each specimen was used for Fourier Transform Infrared (FT-IR) analysis to provide a direct comparison of the relative amounts of protein present on the silicone rubber and the three hydrogel composite samples. The combined SEM and FT-IR analyses were performed on A-V samples from three dogs. Differences in the response of blood to the surfaces were found by the combined SEM and FT-IR analyses. The more hydrophilic a hydrogel grafted surface, the less fibrin and cellular elements were seen deposited on it. This is not interpreted as an indication of less reactivity, but is more likely due to thrombus buildup and a degree of subsequent embolization (a tearing of sections of the platelet matting away from a surface, revealing an area that again can be covered.

Acrylates↗
PubMed1994

Splenic response to silicon drain material following intraperitoneal implantation.

To study the splenic response to intraperitoneal biomaterials, 100% silicon rubber drain fragments were intraperitoneally implanted in the rat. Four days after implantation, specimens of the spleen and implanted rubber fragment were retrieved and subjected to scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX). In SEM, macrophages with membrane fusion and cytoplasmic spreading were noted on the surfaces of implanted rubber fragments. Specimens of the spleen from animals with implants showed light 3-10-microns structures that were not observed in those without implants. EDX revealed the presence of silicon both in the rubber fragment and in the spleen of the implanted animals. Both light microscopy and transmission electron microscopy showed a large number of particles inside giant cells of the spleen. The present study demonstrated an active transport of rubber fragments containing silicon from the peritoneal cavity to the spleen by adherent macrophages, reflecting a splenic response to intraperitoneal implantation of biomaterials. The modes of silicon rubber degradation and transportation remain to be elucidated.

Animals↗
PubMed2003

Plasma-enhanced chemical vapor deposited silicon carbide as an implantable dielectric coating.

Amorphous silicon carbide (a-SiC) films, deposited by plasma-enhanced chemical vapor deposition (PECVD), have been evaluated as insulating coatings for implantable microelectrodes. The a-SiC was deposited on platinum or iridium wire for measurement of electrical leakage through the coating in phosphate-buffered saline (PBS, pH 7.4). Low leakage currents of <10(-11) A were observed over a +/-5-V bias. The electronic resistivity of a-SiC was 3 x 10(13) Omega-cm. Dissolution rates of a-SiC in PBS at 37 and 90 degrees C were determined from changes in infrared absorption band intensities and compared with those of silicon nitride formed by low-pressure chemical vapor deposition (LPCVD). Dissolution rates of LPCVD silicon nitride were 2 nm/h and 0.4 nm/day at 90 and 37 degrees C, respectively, while a-SiC had a dissolution rate of 0.1 nm/h at 90 degrees C and no measurable dissolution at 37 degrees C. Biocompatibility was assessed by implanting a-SiC-coated quartz discs in the subcutaneous space of the New Zealand White rabbit. Histological evaluation showed no chronic inflammatory response and capsule thickness was comparable to silicone or uncoated quartz controls. Amorphous SiC-coated microelectrodes were implanted in the parietal cortex for periods up to 150 days and the cortical response evaluated by histological evaluation of neuronal viability at the implant site. The a-SiC was more stable in physiological saline than LPCVD Si(3)N(4) and well tolerated in the cortex.

Animals↗
PubMed2006

Human osteoblast response to silicon-substituted hydroxyapatite.

Human osteoblasts were cultured on hydroxyapatite (HA), 0.8 wt % silicon substituted hydroxyapatite (Si-HA) and 1.5 wt % Si-HA discs. The influence of these substrates on cell behaviour in vitro was assessed by measuring total protein in the cell lysate and the production of several phenotypic markers: collagen type I (COL I), alkaline phosphatase (ALP), osteocalcin (OC), and the formation of bone mineral. After 7 days, beta-glycerophosphate and physiological levels of hydrocortisone were added to the culture medium to stimulate cell differentiation and mineral production. There was a significantly higher production of ALP on 1.5 wt % Si-HA at day 7 following which, the addition of hydrocortisone promoted the differentiation of cells on the other two substrates. Hydrocortisone addition also decreased the production of OC. During the period, when hydrocortisone was present, no significant difference in behavior was seen between cells on Si-HA and HA; however, following removal of hydrocortisone, cells responded to 0.8 wt % Si-HA with a significant increase in protein production. Using fluorescence microscopy, nodular structures labeled with tetracycline were observed on the surface of all substrates after 21 days. These structures were deposited on areas of high cell density but were not related to the presence or level of silicon in the substrate. These results indicate that human osteoblasts are affected by the presence of silicon in the HA substrate and that the timing of these effects may be dependent upon the level of silicon substitution.

Cells, Cultured↗
PubMed2006

The nature of platinum in silicones for biomedical and healthcare use.

Silicone is an important biomaterial in many different biomedical and healthcare applications. Network formation in one type of silicone relies upon a chemical crosslinking reaction that typically employs a platinum catalyst. As a consequence, low concentrations of platinum may remain in certain medical devices designed for human use. The characteristics of platinum in silicone before, during, and after the crosslinking reaction have been well described in the literature. This review summarizes the relevant literature on the organometallic and analytical chemistry of platinum in silicone and thus provides a foundation for understanding the effects this platinum may have, if any, in the various biomedical and healthcare applications where it may be present.

Biocompatible Materials↗
PubMedDate not supplied

Sonographic features with histologic correlation in two cases of palpable breast cancer after breast augmentation by liquid silicone injection.

Sonography is rarely used to evaluate the breasts in patients who have undergone liquid silicone injections for breast augmentation because strong acoustic shadowing from the resulting silicone granulomas hampers the examination. We report on 2 patients who underwent silicone injection 18 and 20 years earlier and in whom breast cancers (1 invasive ductal carcinoma and 1 carcinosarcoma) were diagnosed by sonographically guided core-needle biopsy. On sonograms, both cancers had a peripheral hypoechoic rim surrounding an echogenic center. The echogenic center corresponded histologically to a silicone granuloma in 1 patient and to a large area of necrosis in the other; the hypoechoic rims corresponded to areas of cancer in both patients.

Biopsy, Needle↗
PubMed2001

Direct assay of Aplysia tissues and cells with laser desorption/ionization mass spectrometry on porous silicon.

Desorption/ionization on porous silicon (DIOS) is a form of laser desorption mass spectrometry that allows for the direct mass analysis of a variety of analytes without the addition of organic matrix. Protocols are described for the direct analysis of exocrine tissue and single neurons using DIOS-MS. The atrial gland of Aplysia californica was blotted on to porous silicon and analyzed with DIOS-MS in the range m/z 1000-4000. The ability to culture invertebrate neurons directly on porous silicon is also presented. Isolated bag cells regenerated neuronal processes in culture on porous silicon. DIOS-MS allowed the direct detection of the peptides contained in individual cultured neurons indicating that with appropriate protocols, DIOS can be used with biological samples with considerable thickness.

Animals↗
PubMed2005

Silicone oil induced aggregation of proteins.

Prior to delivery to the patient, protein pharmaceuticals often come in contact with a variety of surfaces (e.g., syringes and stoppers), which are treated to facilitate processing or to inhibit protein binding. One such coating, silicone oil, has previously been implicated in the induction of protein aggregation. We have investigated the propensity of model proteins to aggregate when silicone oil is present in solution and find significant induction of aggregation in four proteins of various molecular weights and isoelectric points in the presence of 0.5% oil. The ability of silicone oil to induce conformational changes that might be responsible for this aggregation was also examined by a combination of circular dichroism (CD) and derivative UV spectroscopy. Neither method produces evidence of large conformational changes or alterations in thermal stability although in a limited number of cases some small changes suggest the possibility of minor structural alterations. The most probable explanation for silicone oil induced aggregation is that the oil has direct effects on intermolecular interactions responsible for protein association through interaction with protein surfaces or indirectly through effects on the solvent.

Circular Dichroism↗
PubMed1986

Permeation of mouse skin and silicone rubber membranes by phenols: relationship to in vitro partitioning.

A discrepancy has been noted in the relationship between the relative skin permeabilities of phenols and their lipophilicities as expressed in commonly used octanol:water partition coefficients (PCoctanol:water). The lack of correlation between partitioning and permeability is seen with the nitrophenols, particularly 4-nitrophenol. In the present study, the permeability coefficients-of 4-nitrophenol and several other phenols through skin and a model lipophilic membrane made of silicone rubber were found to be independent of concentration, ruling out concentration-dependent molecular aggregation as the cause of the partitioning-permeability incongruity. An unexpectedly low permeation rate was observed for the diffusion of 4-nitrophenol through the synthetic, silicone rubber membrane, confirming the anomalous position of this phenol in permeability relative to the octanol:water partitioning scale. However, when oil:water (o/w) partition coefficients for the phenolic compounds based on either n-hexane, CH2Cl2, CHCl3, or silicone rubber as the water immiscible phase are used, permeability coefficients for the skin and the synthetic membrane followed expected permeation-partitioning dependencies. On this basis, it appears that PCoctanol:water does not properly reflect the lipophilicity of the phenols with respect to partitioning into skin and silicone rubber during mass transfer.

Animals↗