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PubMed1990

In vitro alterations in human fibroblast behavior secondary to silicone polymers.

The etiology of fibrous capsular contractures in patients with silicone prostheses is unclear. However, cellular responses to the silicone polymers of the prostheses have not been examined. The exposure of human dermal fibroblasts to the components of the silicone gel prosthesis results in a significant change in cellular configuration and a progressive reduction in cell proliferation as determined by total matrix protein assays and hemocytometer cell counts. Transmission electron microscopy, however, documents a twofold increase in the rough endoplasmic reticulum when cells are exposed to the silicone gel. These findings suggest significant alterations in the behavior of human fibroblast subpopulations in response to silicone polymers.

Cell Line↗

PubMed1991

Proliferation of normal human keratinocytes on silicone substrates.

Several polydimethylsiloxane elastomers and gels were tested as culture substrates for proliferating normal human epidermal keratinocytes. Growth kinetics of normal human keratinocytes (NHK) and dermal fibroblasts were compared on 'very soft', 'soft' and 'hard' silicone gels, as well as on standard cell culture polystyrene dishes. Water contact angles and chemical compositions (IRFT-HATR) of the different silicone surfaces were found to be equivalent, although very different from standard cell culture polystyrene. The topography of the surfaces as well as the shape of the keratinocytes and fibroblasts grown on the different substrates were visualized by scanning electron microscopy, and compared. Although the surface softness and topography of the substrates differed markedly, dermal fibroblasts proliferated in serum-containing medium in equivalent manner on all substrates. Again no correlation could be found between the characteristics and the attachment of the substrates and rapid proliferation of the epidermal keratinocytes in defined medium. The epidermal keratinocytes spread, secreted a structured extracellular matrix network and grew up to confluence on all silicone substrates (elastomers and gels), except the relatively 'hard' silicone gel; this could be due to a direct interference by the waves observed on the silicone gel surfaces.

Biocompatible Materials↗

PubMed2005

AFM study of hippocampal cells cultured on silicon wafers with nano-scale surface topograph.

The rat hippocampal cells were selected as model to study the interaction between the neural cells and silicon substrates using atomic force microscopy (AFM). The hippocampal cells show tight adherence on silicon wafers with nano-scale surface topograph. The lateral friction force investigated by AFM shows significant increase on the boundary around the cellular body. It is considered to relate to the cytoskeleton and cellular secretions. After ultrasonic wash in ethanol and acetone step by step, the surface of silicon wafers was observed by AFM sequentially. We have found that the culture leftovers form tight porous networks and a monolayer on the silicon wafers. It is concluded that the leftovers overspreading on the silicon substrates are the base of cell adherence on such smooth inert surfaces.

Acetone↗

PubMedDate not supplied

Safely re-integrating silicone breast implants into the plastic surgery practice.

In the early 1990s, it was reported that silicone breast implants were possibly responsible for serious damage to women's health. In January 1992, the Food and Drug Administration issued a voluntary breast implant moratorium and, in April, issued a ban on the use of silicone gel-filled implants for cosmetic breast augmentation. Since that time, silicone gel-filled breast implants have been available to women only for select cases: women seeking breast reconstruction or revision of an existing breast implant, women who have had breast cancer surgery, a severe injury to the breast, a birth defect that affects the breast, or a medical condition causing a severe breast deformity. Since the ban on the use of silicone gel-filled breast implants for cosmetic breast augmentation, numerous scientific studies have been conducted. To ensure patient safety, the American Board of Plastic Surgery believes that these scientific studies and the Food and Drug Administration's scrutiny of silicone gel-filled breast implants have been appropriate and necessary.

Breast Implantation↗

PubMed2003

Silicon chemistry as a novel source of chemical diversity in drug design.

The use of organosilicon chemistry in drug design is reviewed. The field of bioorganosilicon chemistry, which sprung up in the 1970s to exploit the opportunities of silicon for drug design, is currently being developed into a practical and commercial enterprise. This review is mainly focused on two different approaches: (i) synthesizing a silicon analog of a known drug in which one carbon atom has been replaced by a silicon atom, with the rest of the molecule being identical (carbon/silicon switch, sila-substitution); (ii) synthesizing completely new silicon-based classes of compounds (the carbon analogs of which do not exist) that exploit specific features of silicon chemistry to address a well-validated target.

Amino Acids↗

PubMedDate not supplied

The effect of silicone gel on basic fibroblast growth factor levels in fibroblast cell culture.

BACKGROUND: Topical silicone gel has shown promise in the treatment of hypertrophic and keloid scars. However, its mechanism of action remains undetermined. OBJECTIVE: To investigate whether the presence of silicone alters the secretion of basic fibroblast growth factor (bFGF), a key cytokine involved in the scar formation process. DESIGN: Serum-free fibroblast cell cultures were established from normal, keloid, and fetal skin, which heals without scarring, and exposed to silicone gel. Serial cell counts were performed, and supernatants were collected for bFGF quantification by enzyme-linked immunosorbent assay at 4, 24, 72, and 120 hours. RESULTS: Growth curves were similar and no statistically significant differences in population doubling times were observed between treated and untreated specimens. Statistically significant differences in bFGF levels between treated and untreated normal fibroblasts were observed at 24, 72, and 120 hours after cell culture initiation. Differences in bFGF levels between treated and untreated fetal fibroblasts that approached statistical significance were observed at 72 and 120 hours. CONCLUSIONS: These results suggest that silicone gel is responsible for increased bFGF levels in normal and fetal dermal fibroblasts. We postulate that silicone gel treats and prevents hypertrophic scar tissue, which contains histologically normal fibroblasts, by modulating expression of growth factors such as bFGF. Our data support the hypothesis that substances that favorably influence wound healing do so by correcting a deficiency or overabundance of the growth factors that orchestrate the tissue repair process.

Adolescent↗

PubMed1998

Accommodation amplitude after lens refilling with injectable silicone by sealing the capsule with a plug in primates.

OBJECTIVE: To restore accommodation in primate eyes by refilling the lens capsule with injectable silicone compounds. MATERIALS AND METHODS: Eight eyes of 8 monkeys (Macaca fascicularis) were treated by the lens refilling procedure. To prevent leakage of the injected liquid silicone before it polymerized in the capsule in vivo, a silicone plug for sealing the capsular opening was developed. After endocapsular phacoemulsification following an upper minicircular capsulorhexis, the plug was introduced into the capsulorhexis opening. A silicone mixture was injected into the capsular bag through the delivery tube of the plug. Automated refractometry was performed 1 week and 3 months after surgery. Accommodation amplitude was determined as the difference between the refractions before and 1 hour after topical application of 4% pilocarpine chloride. RESULTS: Five of 8 eyes could be refilled. In 4 of 5 eyes, refraction could be measured. Accommodation amplitude ranged from 1.0 to 4.5 diopters, with a mean of 2.3 +/- 1.3 diopters (8.0 +/- 2.0 preoperative values). At 3-month examination, thick posterior capsule opacification precluded refractometry in all eyes. CONCLUSIONS: The lens refilling procedure with the use of a silicone plug for sealing the capsular opening was feasible in primate eyes. The accommodation amplitude attained was a small fraction of the value before surgery. This may result from the loss of so-called intracapsular accommodation, ie, active participation of lens fiber cells in accommodation. However, since the obtained accommodation may be sufficient for near vision after cataract surgery, this lens refilling procedure warrants further study. Elucidation of the mechanism of intracapsular accommodation may also be necessary.

Accommodation, Ocular↗

PubMed1983

Ocular findings following intravitreal silicone injection.

In three cases of intraocular silicone oil injection in which the histologic picture is observed at different time intervals, emphasis is given to the fact that fibrous tissue formation around silicone vesicles is a rather constant complication and of early occurrence. Thus, we believe that the removal of liquid silicone from the eye should not take place later than two or three months after the injection. In our first reported case, there was an association of silicone oil injection and vitrectomy with retinal detachment procedures and sympathetic ophthalmia. In the absence of evident histologic or clinical proof, we do not consider silicone oil injection itself as having induced the mechanisms of sympathetic ophthalmia.

Adolescent↗

PubMed1986

The effect of intraocular silicone oil on anterior chamber oxygen pressure in cats.

Intraocular silicone oil has been observed to lessen the incidence of neovascular glaucoma in patients with a high risk of anterior segment neovascularization. In order to test the hypothesis that the presence of silicone oil in the vitreous cavity acts as a diffusion/convection barrier to oxygen and prevents the decrease in anterior chamber oxygen tension that occurs after lensectomy and vitrectomy, we measured anterior chamber oxygen pressure in six cats that had undergone lensectomy-vitrectomy in one eye and lensectomy-vitrectomy with silicone oil placement in the other eye ten to 21 days previously. The anterior chamber oxygen tension was 17.8 +/- 6.9 mm Hg (mean +/- SD) in the eyes that had undergone lensectomy-vitrectomy and 34.8 +/- 3.5 mm Hg in the silicone oil-treated eyes (P less than .001). Silicone oil does appear to act as a diffusion/convection barrier to oxygen and may alter the stimulus for anterior segment neovascularization.

Animals↗

PubMed1987

Effect of silicone oil on experimental traction retinal detachment.

The use of silicone oil as a retinal tamponade in the treatment of proliferative vitreoretinopathy is often complicated by membrane reproliferation. We studied the development of traction retinal detachments following the intravitreal injection of 15,000 retinal pigment epithelial cells in silicone-, perfluoropropane-, and fluid-filled rabbit eyes. By 28 days a higher proportion of silicone-filled eyes (83%) had severe proliferative vitreoretinopathy than either the perfluoropropane-filled (30%) or fluid-filled (10%) eyes. An in vitro proliferation assay using the vitreous samples showed that the silicone-filled vitreous had increased mitogenic activity for retinal pigment epithelial cells compared with the gas-filled or fluid-filled vitreous. Silicone oil appears to increase proliferation by stimulating the release of more or different mitogenic factors as well as by concentrating active factors into a smaller volume near the retina.

Animals↗

PubMed1994

Autogenous tissue breast reconstruction in the silicone-intolerant patient.

BACKGROUND: Concerns regarding the safety of silicone gel breast implants have motivated many patients with complications from their silicone breast implants to search for alternatives for breast reconstruction. Although autogenous tissue has been used for primary breast reconstruction after mastectomy, few studies have described its use in the patient in whom silicone-implant breast reconstruction has failed. METHODS: Between 1988 and 1993, 33 patients who had previous unsuccessful breast reconstruction with silicone breast implants underwent implant removal and autogenous tissue reconstruction. Preoperative evaluation included implant-related problems, such as capsular contracture, pain, and loss of implant shell integrity. Systemic symptoms that developed after implantation also were evaluated. Three types of myocutaneous flaps were used for breast reconstruction: the latissimus dorsi pedicle flap, the transverse rectus abdominis free flap, and the superior gluteus maximus free flap. Follow-up evaluation was done for both implant-related problems and issues related to patient satisfaction after autogenous tissue reconstruction. RESULTS: The overall flap survival rate for 33 women who underwent flap reconstruction was 94%. All flap losses occurred in the first nine flaps. Ninety-two percent of patients felt their autogenous tissue reconstructions were aesthetically superior to their previous implant reconstruction. All but one patient felt complete resolution in their chest wall discomfort and pain. Eighty-one percent of patients with systemic symptoms also felt improvement in their systemic symptoms. CONCLUSIONS: Autogenous tissue reconstruction from multiple areas of the body is an effective and aesthetically superior alternative for the patient who no longer desires the silicone implant option.

Adult↗

PubMed2005

Disproving a silicon analog of an alkyne with the aid of topological analyses of the electronic structure and ab initio molecular dynamics calculations.

A silicon compound has recently been synthesized that was claimed to exhibit the first realization of a silicon-silicon triple bond. We debate this classification on the basis of a thorough investigation of the nature of the chemical bond, using the rigorous topological analysis of the electron density as developed in Bader's atoms-in-molecules theory, that of the electron localization function and the related orbital-independent definitions of the bond order. Our results refer both to the ground-state geometry and to nonequilibrium configurations, which are accessed by the system in a room-temperature ab initio molecular dynamics simulation. We also use the reciprocal compliance force constant as an independent chemical descriptor. All the above procedures are in agreement and do not support the classification of the silicon-silicon central bond as triple. The characterization which consistently emerges from the present study is one in which two electron pairs participate in the bonding and the other pair belongs mainly to nonbonding regions.

Alkynes↗

PubMed2002

Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion.

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon-plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface-modified silicone after 1 h. C. albicans exhibited very low adherence to all silane-treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion that incorporated long-chain functional groups were inhibiting the adherence of the yeast, possibly by the formation of a barrier between the surface of the material and the yeast. In conclusion, silane surface treatment of an experimental silicone rubber has been successful in reducing candidal adherence.

Biocompatible Materials↗

PubMedDate not supplied

Effect of silicone oil on the cornea.

Silicone oil can dissolve about seven times more oxygen that can water. Placed in a depot between a rigid scleral lens and the corneal surface, silicone oil might thus be useful for treating severe dry-eye patients and for preventing exposure keratitis. To explore this possibility, generic (300, 500, 1000, and 12,500 cs) and medical-grade (1000 cs) silicone oils were tested on rabbit eyes. When oxygenated silicone oil was placed in a cup formed by the lids and hanging sutures and allowed to remain for 3 h on the eyes of anesthetized rabbits, the immediate reaction was mild epithelial edema. By 3 to 6 days later, the thickness of the epithelium and of the entire cornea had increased irregularly. The most common histologic finding was intracellular epithelial edema, particularly in the basal cell layer. The reaction was most intense for the generic oils of the lowest viscosities. The medical-grade oil was the best tolerated, but it too affected epithelial and corneal thickness. Ultrastructural studies of treated eyes showed abnormal epithelial surfaces but no major changes within the epithelial cells. Biochemical analysis showed some decrease of glycogen in the corneal epithelium of eyes kept under oxygenated medical-grade silicone oil. A smaller decrease of glycogen level persisted after 2 days exposure of the treated eye to air, suggesting that the corneal epithelium was injured by a mechanism other than hypoxia.

Animals↗

PubMed1991

Improved biocompatibility of silicone rubber by removal of surface entrapped air nuclei.

Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p less than 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p less than 0.001, ANOVA). Surface chemical analysis by x-ray photo-electron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.

Air↗

PubMed1995

Contribution of vascular catheter material to the pathogenesis of infection: the enhanced risk of silicone in vivo.

There is currently very little information to suggest that polymer materials used to make vascular catheters differ in their risk of infection. A rabbit model of subcutaneous Staphylococcus aureus infection was used to determine the relative risk of infection associated with silicone, polyurethane, polyvinylchloride, and Teflon catheters. Seven days after catheter implantation and inoculation with S. aureus, catheters were observed for gross purulence and quantitatively cultured. Silicone catheters were found to have a greater risk of grossly apparent infection (purulence) and a greater number of organisms removed from catheters by quantitative culture than the other three catheter materials (P < .01). The risk of infection associated with silicone catheters decreased (P < .05) if the S. aureus inoculation was delayed for 2 days or if the catheters were preincubated in the subcutaneous space prior to insertion. The histology of the inflammatory response around the four catheter materials was evaluated at either 2 or 7 days after catheter insertion with or without S. aureus inoculation. Silicone catheters had greater associated inflammation (P < .05) with or without S. aureus inoculation. These results suggest that silicone catheter materials may have unique properties that increase the risk of infection after implantation. Further studies should be done to understand the mechanism(s) of these observations.

Animals↗

PubMedDate not supplied

Silicone-fat differentiation in the breast: exploiting the bright-fat phenomenon in fast spin-echo MR imaging.

Selective suppression of silicone or fat with chemical shift-selective (CHESS) pulses is difficult because of the small chemical shift difference between the primary lipid signal and the primary silicone signal at 1.5 T. Differentiation of these chemically distinct species is, however, an important clinical task in assessing implant rupture and silicone migration in breast tissue. A method uniquely suited for silicone-fat differentiation with fast spin-echo (FSE) sequences is reported. It is based on the dependence of fat signal on echo spacing in FSE imaging and results show that it may provide a clinically robust method for silicone-fat differentiation in magnetic resonance imaging of the breast.

Adipose Tissue↗

PubMed2006

Iminodiacetic acid derivatized porous silicon as a matrix support for sample pretreatment and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis.

Iminodiacetic acid (IDA)-1,2-epoxy-9-decene has been synthesized and covalently linked to the surface of porous silicon wafer through a photochemical reaction. The negatively charged carboxylic acid groups on the porous silicon wafer are capable of binding oppositely charged species from sample solutions through electrostatic interactions. This allows the removal of contaminants prior to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) by simply washing the porous silicon surface. The carboxylic acid end groups on porous silicon can be used to selectively bind and concentrate target species in sample solutions. Furthermore, Fe(3+)-IDA-derivatized porous silicon was prepared to specifically and effectively concentrate phosphopeptides from the tryptic digests of phosphoproteins, followed by MALDI-MS analysis.

Caseins↗