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At least 19 recordsLinked to original sources
PubMed1995

Thyroplasty using a silicone elastomer implant.

Silicone has been used in a variety of forms as a replacement for soft tissue for more than three decades in the United States. The safety of this practice has come under scrutiny recently as our knowledge of the local, systemic, and immune effects of silicone has expanded. Contrary to what was once thought, silicone is not biologically inert. Silicone elastomer, however, has not been implicated in the development of systemic immune disease or carcinogenesis. The evidence to date supports the continued use of silicone elastomer implants in the larynx. It is clear, however, that continued investigation into the basic biologic properties and mechanisms of the host-silicone implant interaction is warranted.

Humans↗
PubMed1996

In vivo inflammatory response to silicone elastomer particulate debris.

Silicone elastomer particles (Silastic silicone elastomer, Dow Corning, Midland, MI), polymethylmethacrylate particles, and monosodium urate particles smaller than 10 microns were injected into a rat subcutaneous air pouch lined with synovial membrane-like cells. Inflammatory exudate from the air pouch was retrieved at 6 hours, 24 hours, 48 hours, and 72 hours after injection. White blood cell count, tumor necrosis factor, and prostaglandin E2 were measured in the exudate. White blood cell and tumor necrosis factor levels in the exudate were the highest for the silicone group at 6 and 24 hours. Prostaglandin E2 was also significantly higher in the silicone group at 24 hours. We conclude that the acute inflammation is particle-type specific and that Silicone elastomer particles are acutely inflammatory.

Animals↗
PubMed2000

Exhaustive soxhlet extraction for the complete removal of residual compounds to provide a nonleaching silicone elastomer.

All commercially available silicone devices contain freely diffusible silicone oils, uncured oligomers, and other impurities (such as catalysts). These residuals have been found in quantities as high as 20% by weight in commercially available silicone medical devices. The fate and effects of these residuals have been the topic of much debate recently. In this study, a method for complete removal of these residual compounds was investigated. The total amount of extractable residuals was determined through exhaustive Soxhlet extraction of 5 silicone elastomers. LIM 6030 had 6.29%, LIM 6070 had 5.74%, Q7-4750 had 3.02%, Q7-4780 had 3.22%, and SE1935 had 0.13% extractables by weight. The amount of silicon containing residuals leaching from both the extracted and nonextracted samples was also evaluated for 3 and 18 days by inductively coiled plasma (ICP) analysis. A significant amount of leachable compounds, reported as microg Si/mg solid sample, was found in all nonextracted elastomers with the exception of SE1935 compared to blanks. The amount of leachable compounds found in the extracted elastomers was not found to be significantly higher than the amount found in the blanks. The residual compounds in silicone elastomers may be completely removed by exhaustive Soxhlet extraction and the resulting polymer does not leach silicon-containing compounds in vitro.

Biocompatible Materials↗
PubMed1992

Polarographic oxygen permeability measurement of silicone elastomer contact lens material.

The flexible silicone elastomer is a contact lens material of substantial potential, primarily because of its high theoretical oxygen permeability (Dk). Review of the previous literature indicates some difficulty in precisely determining the Dk of the silicone elastomer, and quantification of this permeability value ranges from 50 to 340 x 10(-11) cm2 ml 02/sec ml mmHg by various techniques. (The exponential term 10(-11) and the units of Dk will be omitted hereafter in this text). We herein report use of the single-chamber polarographic technique, with edge and boundary corrections, to arrive at a value of 190 with a standard deviation (SD) of 79 for the Dk of one silicone elastomer contact lens material. The excessive SD suggests that an improved method to evaluate contact lens materials with Dk values in excess of 30-50 should be determined.

Contact Lenses↗
PubMed1998

Silicone elastomer cerebrospinal fluid shunt systems. Council on Scientific Affairs, American Medical Association.

A 1995 resolution of the American Medical Association House of Delegates, introduced by the American Academy of Neurology, the American Association of Neurological Surgeons, and the Congress of Neurological Surgeons, asked the American Medical Association Council on Scientific Affairs to add the use of hardened silicone shunts to its study of the effects of silicone gel used in breast implants. On consideration of the important differences between the two materials, silicone elastomer ("hardened silicone") and silicone gel, the Council on Scientific Affairs elected to address the subject of silicone elastomer shunt systems separately. This report describes the different types of medical-grade silicone used in medical devices, the incidence of hydrocephalus and its causes and treatment, and the use of cerebrospinal fluid shunt systems made of silicone elastomer. Published case reports of possible immunological disease in patients who have had silicone elastomer cerebrospinal fluid shunt systems implanted are reviewed. The Council on Scientific Affairs concluded that the evidence presented does not support the occurrence of immune-mediated systemic reactions to implanted silicone elastomer cerebrospinal fluid shunt systems. The local granulomatous or inflammatory responses observed in some patients with silicone shunt systems have not been shown to be immunologically mediated; similar reactions have been described with other implanted foreign bodies.

Cerebrospinal Fluid Shunts↗
PubMed1997

Effect of saline exposure on the surface and bulk properties of medical grade silicone elastomers.

Medical-grade silicone elastomers were subjected to accelerated aging in saline to verify the hydrolytic stability of the elastomer. Tensile strength, elongation at break, and the elastomer stress measured at 100% or 200% elongation did not change significantly for peroxide-cured sheeting aged in 37 degrees C or 100 degrees C saline for 45 h. Under similar condition, hydrosilylation cured sheeting behaved similarly; however, increases in stresses measured at 100% and 200% elongation were observed after the first hour of treatment. After the first hour, the physical properties remained relatively constant. On either elastomer, initial liquid drop advancing contact angles for water ranged from 110 degrees to 115 degrees, and in no case was a change of > 6 degrees observed as a result of aging in saline for 45 h at temperatures up to 97 degrees C. The high advancing angles indicated that the surface remained largely hydrophobic. Initial liquid drop receding contact angles ranged from 48 degrees to 64 degrees, with receding contact angles being more sensitive to accelerated aging, in one case decreasing to 14 degrees. Similar decreases in receding contact angle were observed on polyethylene subjected to the same accelerated aging conditions. Decreases in receding contact angle were not considered to be indicative of extensive hydrolysis. The observed contact angle phenomena are consistent with current views of contact angle hysteresis being caused by surface heterogeneity. There was no evidence of significant surface or bulk siloxane hydrolysis under these accelerated aging conditions.

Hydrolysis↗
PubMedDate not supplied

Beyond rheology modification: hydrophilically modified silicone elastomers provide new benefits.

The development of silicone elastomers with hydrophilic functionality in the form of PEG substituents provides benefits beyond the rheology modification (thickening) that can be achieved with silicone elastomers that lack functional substituents. We have shown that PEG-modified dimethicone crosspolymer (PEG-DCP) is an effective emulsifier for water-in-silicone (w/s) emulsions where the continuous phase is cyclopentasiloxane. The utility of PEG-DCP for producing simple antiperspirant gels and also multiple emulsions (w/s/w) was demonstrated. Additional benefits for PEG-DCP such as improved compatibility with polar organic oils and reduced syneresis in anhydrous antiperspirants were also shown to be associated with the addition of hydrophilic groups to the silicone elastomer. The performance and physical properties of a series of PEG-DCP samples from a two-level factorial design were evaluated. The variables studied were the level of PEG substitution, the length of the PEG chains, and crosslink density. All of the PEG-DCP samples were synthesized and tested in the form of dispersions in cyclopentasiloxane. Variations in the composition of PEG-DCP such as the level of PEG substitution and the length of the PEG chain were shown to have a significant effect on the viscosity of the PEG-DCP and its emulsification performance in a simple w/s emulsion. Variation of a process parameter that affects the crosslink density of the elastomer also changed the emulsification properties of the PEG-DCP.

Elastomers↗
PubMedDate not supplied

Analysis of MRI images of a silicone elastomer under different axial loading conditions.

Silicone elastomers have been used as implants in orthopaedics for replacements of small joints such as the metacarpophalangeal joint. A series of experiments was conducted an axially tensioned silicone elastomer tendon spacer samples to determine whether there is a relationship between stress in the material and image intensity. With increasing load, reduced image intensities were observed using spin echo (SE), gradient echo (GE) and magnetic resonance imaging (MRI) snapshot techniques. MR attenuation was accentuated in the GE experiment. The T1 and T2 snapshot images were dim and showed a low signal-to-noise ratio, so analysis was limited. Changes in magnetic susceptibility are suggested as the mechanism causing reduced image intensity, due to the more pronounced attenuation in the GE image. An alternative mechanism is the alteration of crystallinity during loading, whereby molecular realignment modifies nuclear relaxation. The changes in spin lattice (T1) and spin spin (T2) relaxation times, which would support this, were not, however, satisfactorily demonstrated.

Image Processing, Computer-Assisted↗
PubMed2002

A dynamic mechanical method for determining the silicone elastomer solubility of drugs and pharmaceutical excipients in silicone intravaginal drug delivery rings.

The silicone elastomer solubilities of a range of drugs and pharmaceutical excipients employed in the development of silicone intravaginal drug delivery rings (polyethylene glycols, norethisterone acetate, estradiol, triclosan, oleyl alcohol, oxybutynin) have been determined using dynamic mechanical analysis. The method involves measuring the concentration-dependent decrease in the storage modulus associated with the melting of the incorporated drug/excipient, and extrapolation to zero change in storage modulus. The study also demonstrates the effect of drug/excipient concentrations on the mechanical stiffness of the silicone devices it 37 degrees C.

Biocompatible Materials↗
PubMed1998

Biomedical silicone elastomers as carriers for controlled release.

Biomedical silicone elastomers have been studied for their potential application as carriers for controlled release of drugs, since these materials display a unique combination of properties, which might be favorable to the above use. A two component silicone gel system was used and various cross-linker ratio was applied, in order to produce networks with varying crosslink density. Swelling experiments in toluene were run in order to evaluate the network characteristics. The silicone elastomer was loaded with salicylic acid and propranolol hydrochloride and their delivery in distilled water was followed. The results showed that release is almost of zero order for high loading of salicylic acid, while delivery seems to be diffusion controlled up to a certain limit. The administered drug concentrations are relatively low if silicone discs are used, due to the hydrophobic nature of this material. On the other hand, when membranes are used with a thickness of 0.1-0.2 mm, then the delivery rate is much higher depending of course on the hydrophilic character of the drug.

Biocompatible Materials↗
PubMed1995

An in-vitro evaluation of silicone elastomer latex for topical drug delivery.

A silicone elastomer latex was evaluated as a topical drug-delivery system. With the addition of a fumed silica and the removal of water, the latex produced elastomeric solid films. The water vapour permeability of the solid film was found to be a function of the film composition. An increase in silica content and the incorporation of a water-soluble component, PEG 3350, rendered the silicone elastomer-free film even more permeable to water vapour. The release of hydrocortisone from the elastomer film can be described by a matrix-diffusion-controlled mechanism. Drug diffusion is thought to occur through the hydrophobic silicone polymer network and the hydrated hydrophilic silica region in the film matrix. Silicone elastomer film with a higher silica content exhibited a faster drug-release rate. The addition of PEG 3350 to the film further enhanced the drug-release rate.

Administration, Topical↗
PubMedDate not supplied

Ultrastructure of collapsed metatarsophalangeal silicone elastomer implant.

The use of silicone elastomer implants in podiatric surgical practice is presently a well accepted treatment modality. However, there are instances of failure, and the present study describes a total collapse and fragmentation of a metatarsophalangeal joint prosthesis. Defects are demonstrated by scanning electron microscopy, while physical and chemical reasons for the occurrence as stated in the current literature are reviewed.

Biomechanical Phenomena↗
PubMed1988

Use of silicone elastomer for improvement of intestinal clamp.

An intestinal clamp was improved by application of a silicone elastomer measuring 3, 4 and 5 millimeters in thickness to the nip surfaces to reduce nip force or to make pressure distribution more uniform. For the 1 kilogram weight, the output from the pressure sensor, which was placed on the blade, was decreased as the thickness of the silicone elastomer was increased. Pressures loaded on central and marginal regions of the large intestine were more than seven times greater than that on the mesenteric region with use of a conventional clamp. In contrast, pressures on all of the mesenteric, central and marginal regions were relatively low and uniform with use of clamps equipped with silicone elastomer. These results indicate that the clamp equipped with the silicone elastomer damages tissues only to a small extent because of the dispersion effect of the pressure and the uniformity of the pressure distribution.

Anastomosis, Surgical↗
PubMed1998

Development of a new silicon-based transdermal system. I. Study of silicone elastomers and effect of liquid ingredients.

The polarities of four elastomers made of silicon oligomers of different viscosities were investigated by measuring the uptake of swelled solvent in different polarity solvents after 24, 48, and 72 hr of treatment. The solvent uptake provides a good characterization for the polarity of the inside of the matrix. On the basis of the results the oligomers were divided into two groups. The same method has been used for the investigation of the change of the inner polarity of samples containing various amounts of polar and apolar liquid ingredients. It was shown that the polarity of the inside of the matrix is related to the swelling properties. The ingredients used changed the matrix framework, which was also influenced by the type of oligomers. The solvent uptake shows large dependence on the timing of the measurement. Measurements carried out after 48 hr of polymer production showed constant solvent uptakes, indicating that the final structure of the polymer was formed.

Administration, Cutaneous↗
PubMed1993

A new approach to combatting iodine deficiency in developing countries: the controlled release of iodine in water by a silicone elastomer.

OBJECTIVES: Four hundred million people or more may be exposed to iodine deficiency worldwide, in developing countries in particular. Because of the practical problems with existing methods for the large-scale prevention of iodine deficiency, the authors developed a new approach to collective prophylaxis. METHODS: This approach relies on the controlled diffusion of iodine into water from a silicone elastomer. Silicone matrices installed in a bore well released iodine at a rate sufficient to permit the daily per capita intake of at least 100 micrograms of iodine, the amount recommended by the World Health Organization. The matrices were tested over 1 year in a village in Mali, West Africa, an area in which goiter was highly endemic. The effects on the well water and population were compared with those of a placebo system in a control village. RESULTS: An increase in urinary iodine levels was observed in the treated population, and after 12 months the incidence of goiter had fallen from 53.2% to 29.2%. CONCLUSIONS: This new concept, adaptable to all sources of water supply, may contribute to the eradication of iodine deficiency.

Adult↗
PubMed2004

DNA attachment chemistry at the flexible silicone elastomer surface: toward disposable microarrays.

This paper describes the preparation and surface characterization of maleimide-activated silicone elastomer (PDMS(MCC)) followed by covalent functionalization using thiol-terminated DNA sequences (primary oligo). The stability of this attachment chemistry was demonstrated by the retention of the primary oligo through the process of hybridization with a labeled complementary DNA sequence. In these studies, the hybridized labeled DNA oligomers were detected using confocal fluorescence microscopy. We have employed a vapor deposition technique in which a plasma-treated silicone elastomer (PDMS(OH)) was exposed to vapors of 3-(aminopropyl)triethoxysilane (APTS) under vacuum, to yield the amine-functionalized silicone elastomer (PDMS(NH)(2)). PDMS(NH)(2) was further coupled with a heterofunctional cross-linker, sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate to obtain PDMS(MCC). The surface functionalities of the elastomers were characterized using contact angle measurements and X-ray photoelectron spectroscopy. Surface-modified silicone elastomers appear to be promising substrates for use as substrates for disposable microarrays.

Chemical Phenomena↗
PubMed1996

The adjuvant effect of silicone gel and silicone elastomer particles in rats.

This study examines the adjuvant properties of silicone oil, silicone gel and silicone elastomer using a foreign antigen, bovine serum albumin (BSA). Seventy male Harlan Sprague-Dawley rats, approximately 250 grams each, were divided into 7 groups: A- incomplete Freund's adjuvant (IFA) with BSA; B- silicone oil with BSA; C- IFA/silicone oil with BSA; D- 50% silicone gel/50% silicone oil with BSA; E- silicone oil/1000 microns elastomer particles with BSA; F- silicone oil/500 microns elastomer particles with BSA; G- saline with BSA. Rats were implanted intramuscularly with mixtures or emulsions of the above described treatment materials. Cardiac punctures were performed on days 0, 14, 28, 42, and 55. Serum IgG antibody response to BSA was determined by enzyme-linked immunosorbent assay (ELISA). Rats were sacrificed on day 55 and sections of the injection sites were collected and stained for histopathologic evaluation. The results demonstrated that silicone gel functions as a potent immunologic adjuvant as measured by a heightened IgG antibody response to BSA. In contrast silicone elastomer particles have no apparent adjuvant effect as determined by the low anti-BSA antibody levels in these treatment groups throughout the course of the study. Histologically, silicone gel and silicone elastomer elicit a moderate to severe "foreign body" granulomatous inflammatory response at the injection site. Silicone oil elicits mild or no local inflammatory response.

Adjuvants, Immunologic↗
PubMed1992

Antibodies to silicone elastomers and reactions to ventriculoperitoneal shunts.

Silicone elastomers used to make medical implants and prostheses are generally believed to be biologically inert. However, we have seen two patients who showed severe, apparently immunemediated, reactions to ventriculoperitoneal (VP) shunts. We used an enzyme-linked immunosorbent assay in which Silastic tubing served as the solid-phase antigen to test serum from the two patients, five other VP shunt patients without inflammatory reactions, and nine healthy adults. IgG binding to Silastic tubing was consistently higher in the two patients than in the healthy or patient controls. The IgG seemed to be binding specifically, since IgG Fab fragments also bound to the tubing, and preincubation of serum with Silastic or silylated proteins removed most of the activity. These findings show that specific immune reactivity to elastomers of polydimethylsiloxane can develop in human beings.

Adolescent↗