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PubMed1991

Emulsification of silicone oils with specific physicochemical characteristics.

To determine the exact role of various factors in silicone-oil emulsification, we investigated eight different silicone oils with specific physicochemical characteristics in terms of their rate of emulsification. The silicone oils were defined by viscosity, volatility, amount of low-molecular components, electrical resistivity, degree of purification and chemical composition. The viscosities differed between the ranges of 1000 and 10,000 cs. The silicone oils included purified polydimethylsiloxane (PDMS), hydroxyl-enriched PDMS and trimethylsiloxy-terminated polydiphenylsiloxane (PDPS). As emulsifiers we used 0.1% solutions of fibrinogen, fibrin, gamma globulins, acidic alpha-1-glycoprotein, very-low-density lipoprotein and serum dissolved in sterile, distilled water as well as in balanced salt solution. The group of low-viscosity silicone oils (1000 cs) was least stable. The greatest difference in stability was found among purified PDMS, having viscosities between 1000 and 5000 cs. The most stable oil was purified PDMS, whose emulsification rate was almost identical at 5000 and 10,000 cs. High contents of hydroxyl end groups enhanced silicone-oil emulsification to a greater extent than did phenyl side groups. The strongest emulsifiers were fibrinogen, fibrin and serum, followed by gamma globulins, very-low-density lipoprotein and acidic alpha-1-glycoprotein. Balanced salt solution accelerated silicone oil emulsification in all cases. For reduction of emulsification in vivo, purified PDMS of high viscosity should be used. Biologically active emulsifiers found in hemorrhages or inflammatory situations might be lowered in vivo by hemostasis and sufficient postoperative anti-inflammatory therapy.

Electrolytes↗
PubMed1987

Peritoneal reaction to liquid silicone: an experimental study.

Silicone oils (polymethylsiloxanes) with different viscosities (200, 1000 and 5000 cSt) and a fluorinated silicone oil (5000 cSt) were injected into the peritoneum of CBA mice. Three weeks after the injection, peritoneal exudates were obtained and investigated using light and electron microscopy. For each silicone-oil type, light-microscopic examination revealed the presence of abundant extracellular lipid-like droplets and a dense cellular infiltrate composed of macrophages, lymphocytes and multinucleated giant cells. Lipid-like inclusions were observed in macrophages and multinucleated giant cells. These intracellular inclusions were revealed to be membrane bound by transmission electron microscopy. We observed no differences with respect to the amount of phagocytotic activity for the different silicone-oil types tested. Purified silicone oils of lower viscosity (OP 200 and OP 1000) resulted in the mildest chronic inflammatory reaction. Our results suggest that emulsification, phagocytosis and granulomatous inflammation are associated with intraocular silicone-oil implantation. The question of which properties would make a silicone oil most suitable for clinical use requires further investigation.

Animals↗
PubMedDate not supplied

Evaluation of silicone as an endovascular stent membrane: in vivo canine studies.

PURPOSE: Comparative evaluation of the biological effects of a silicone-covered stent versus a bare-metal stent, in an animal model. METHODS: Twelve stent implants were placed in the iliac arteries of six adult dogs. Each animal received one 8-mm x 20-mm silicone-covered stent (Permalume; Boston Scientific Vascular, Watertown, MA, USA), in the right iliac artery and one Wallstent (Boston Scientific Vascular) of the same diameter and length in the left iliac artery, during systemic anticoagulation. Angiography was performed before and after implantations. Animals were then allowed to recover and no platelet suppression was given during a 6-week interval, after which the animals were euthanized. The stented arteries were isolated and pressure-fixed in situ with 10% buffered formalin at a pressure of approximately 100 mmHg for a period of 1 hr. Two of 12 stented specimens were opened lengthwise and the luminal surfaces were photographed. Ten of 12 stented arterial segments were encased in methacrylate, then stained with hematoxylin and eosin. Neointimal thickness was quantified on histologic cross-section, for both bare and covered stents. The mean neointimal thicknesses were compared for significant difference using a student t-test. RESULTS: All implants were widely patent at 6-week follow-up angiography. Histologic analysis showed bare metal stents covered by a thin uniform lining of neointima composed of smooth muscle cells in a hyaline matrix (mean thickness of 189 +/- 47 microm). Silicone covered stents were devoid of neointima. There was no chronic thrombus or mature endothelium noted anywhere upon the internal silicone surfaces of any of the specimens. There was no foreign body reaction to the silicone cover. CONCLUSION: Short-term implantation of a silicone-lined Wallstent in canine iliac arteries is well tolerated. Silicone appears to be inert at 6 weeks in this experimental application.

Animals↗
PubMed2004

[Unusual complication of silicon synovitis in the rheumatoid wrist].

Silicone synovitis is an important clinical entity recognized in rheumatoid patients after arthroplasties with silicone implants. It is a foreign body reaction to particulate material (silicone elastomer) characterized clinically by the re-occurrence of pain, stiffness and swelling at the site of arthroplasty after initial relief of symptoms. Whereas silicone synovitis is a rare complication in metacarpophalangeal implants, it is an important one in the wrist implant. Long-term follow-up studies have revealed that the rates of fracture and subsidence are high and that the implants deteriorate with time necessitating operative revisions in up to 50% of cases. Indications should therefore be restricted to a painful wrist in the elderly, very low demand patient with insufficient bone stock to permit total wrist arthroplasty with a metal-on-plastic design. Severe preoperative deformity and the need for use of ambulatory aids may further limit the indication. The unusual case of direct perforation of silicone particles from the wrist into the tendon sheath of the M. flexor pollicis longus inducing a tumor-like synovitis and a secondary carpal tunnel syndrome is presented. The importance of silicone synovitis and the indication at present for implantation of a silicone wrist spacer in the rheumatoid patient are discussed.

Arthritis, Rheumatoid↗
PubMed2003

Pitfalls in assessment of progesterone production by granulosa cells cultured in contact with silicone rubber or paraffin oil.

BACKGROUND: The influence of silicone templates, used for compartmentalization of culture dishes, on progesterone accumulation in granulosa cell cultures is studied and compared with the effect of paraffin oil, which is frequently used to cover oocyte/embryo cultures. METHODS: Human granulosa-lutein cells were cultured in culture dishes compartmentalized by silicone templates, or in polystyrene plates under paraffin oil. Progesterone concentrations in the culture supernatant were compared with controls cultured in polystyrene plates. RESULTS: The progesterone concentration in culture supernatant was grossly reduced in silicone template cultures (2+/-0.7% of control). No inhibitory activity was identified in medium conditioned by preincubation with silicone rubber, but progesterone was absorbed from spiked medium incubated in silicone templates (recovery <2%). Progesterone concentration in culture supernatant was also reduced by a paraffin oil overlay (38+/-3% of control). From steroid spiked microdrops under oil, <2% of progesterone and 85+/-4% of estradiol was recovered. CONCLUSION: The steroidogenesis of cells cultured in silicone templates or under oil cannot be assessed correctly. It has to be considered that the concentration of lipophilic compounds may be grossly changed due to absorption by silicone rubber or paraffin oil.

Cell Culture Techniques↗
PubMed2007

Rejection of injectable silicone "Bioplastique" used for vocal fold augmentation.

A rare case of repeated granulomatous inflammation after silicone injection laryngoplasty for vocal fold immobility as well as its treatment by endoscopic approach is reported. The patient presented a right-sided vocal fold immobility after laryngeal trauma and remained dysphonic despite of logopedic voice therapy because of severe glottal insufficiency. An endoscopic transoral intrafold silicone injection was applied to improve the vocal function. Silicone granuloma inflammation was observed 8 days after the vocal fold augmentation. Oral broad-spectrum antibiotics and corticosteroids did not improve the inflammation. A cordotomy was performed to remove the silicone implant. After 3 months, a second endoscopic surgical intervention was necessary to remove a recurrent silicone granuloma. Eight months after the second surgical intervention, the inflammation had disappeared. An autologous fat injection to restore the glottal closure was performed successfully. Type IV contact allergy was excluded with an epicutaneous patch and scratch test with components of the silicone implant. Clinical and treatment observations are reported and the literature on complications of intrafold injected silicone for vocal fold augmentation is reviewed.

Adult↗
PubMed2003

Partially fluorinated alkanes as wash out solutions after removal of silicone oil used as an ocular endotamponade.

BACKGROUND: The partially fluorinated alkanes perfluorohexyloctane (F(6)H(8)) and perfluorobutylbutane (O(44 V)) were investigated as wash out solutions after routine silicone oil removal. METHODS: Eleven eyes were rinsed twice with F(6)H(8) immediately after passive silicone oil removal. The silicone oil concentration in both F(6)H(8) samples was measured quantitatively using optical emission spectroscopy (OES). Nine eyes were rinsed twice with O(44 V) immediately after passive silicone oil removal. The silicone oil concentration in both O(44 V) samples was measured quantitatively using OES (n=5) and/or infrared spectroscopy (IR) (n=8). RESULTS: The mean concentration in the first F(6)H(8) sample was 103.0 ppm, and in the second sample 63.5 ppm using OES. The mean concentration in the first O(44 V) sample was 135.6 ppm, and in the second O(44 V) sample 68.0 ppm using OES. CONCLUSION: Since the solubility of silicone oil in F(6)H(8) or O(44 V) is dependent on the temperature and mixture ratio, their use as a routine washout after silicone oil removal in patients without severe emulsification is inefficient. The degree of washout is strongly influenced by surface phenomena and adhesion forces.

Diabetic Retinopathy↗
PubMed2003

Tamponade properties of double-filling with perfluorohexyloctane and silicone oil in a model eye chamber.

BACKGROUND: The use of perfluorohexyloctane as a heavier-than-water tamponade for long-term use is limited by its tendency to dispersion and associated intraocular inflammation. Double-filling with silicone oil and F6H8 produces a united, two-layer bubble, appearing as a single bubble. This has been proposed as a method of improving the utility of F6H8 as a tamponade. METHODS: A surface modified polymethylmethacrylate model eye chamber was double-filled with perfluorohexyloctane and silicone oil to approximate a 90% fill. The proportion of silicone oil was increased in a stepwise fashion. A qualitative comparison of surface contact at each stage was made. Chambers with one, two or no indent were used. Dispersion by agitation of the chamber was assessed. RESULTS: With less than 20% silicone oil it was difficult to force the two liquids to make contact. With more oil they united in the form of a single bubble joined at an interface. Once joined, the sides of the single bubble were drawn away from the wall of the chamber. As the proportion of silicone oil increased the area of lost contact increased and progressed inferiorly. Compared to F6H8 alone the double-fill reduced dispersion. CONCLUSION: Silicone oil and F6H8 can unite to form a single bubble that changes the effectiveness of either tamponade agent on their own. The double-fill needs to have enough silicone oil to form a single bubble, but this needs to be kept as low as possible to avoid progressive loss of lateral tamponade. It does not provide good simultaneous superior and inferior tamponade. The double-fill reduces dispersion.

Drug Therapy, Combination↗
PubMed2007

Confocal microscopy imaging of the cornea in patients with silicone oil in the anterior chamber after vitreoretinal surgery.

OBJECTIVE: Evaluation of corneal morphology by confocal microscopy after vitreoretinal surgery complicated by passage of silicone oil into the anterior chamber. Design Case series (case control study). METHODS: Eight patients (eight eyes) who had undergone vitreoretinal surgery and had silicone oil in the anterior chamber but no clinically evident corneal abnormalities made up the patient group. The control group consisted of eight patients (eight eyes) who had undergone vitreoretinal surgery with application of silicone oil tamponade but who had no silicone oil clinically observable in the anterior chamber. In vivo examination of the cornea using a ConfoScan 3 (Nidek Technologies) confocal microscope equipped with the standard 40x immersion lens was performed. Central, upper, and lower parts of the cornea were assessed separately. High-magnification evaluation of the status of corneal layers and endothelial cell density in upper parts of the cornea directly in contact with silicone oil in the anterior chamber and in parts of the cornea not in direct contact with silicone oil was carried out. RESULTS: Alterations in corneal morphology, especially in endothelium and posterior and medium stroma, were observed. In all cases, changes were more advanced in the upper part of the cornea. Endothelial cell density was significantly decreased in upper parts of the cornea. CONCLUSIONS: In patients with silicone oil in the anterior chamber, confocal microscopy imaging reveals early morphological alterations of the cornea before their clinical manifestation.

Adolescent↗
PubMed1999

Follow-up of functionally lost eyes after vitrectomy and silicone oil tamponade for tractional retinal detachment.

BACKGROUND: Is there any association between, on the one hand, retention or removal of silicone oil or any specific ocular finding in patients with functionally lost eyes after vitrectomy and silicone oil tamponade for tractional retinal detachment and, on the other, a greater chance of preservation of the eye? This information is important in deciding whether to remove silicone oil, as well as in counseling patients about their individual chances of preserving their eye. METHODS: Seventy-three consecutive patients with a functionally lost eye with a minimum follow-up of 3 years were retrospectively studied. The relation between the variables at study entry or the removal of silicone oil during the follow-up period and a subsequent intervention (enucleation, evisceration or conjunctival cover with a scleral shell) were tested for statistical significance with Cox proportional hazards analysis. RESULTS: The absence or removal of silicone oil was not associated with a greater chance of finally preserving the eye. Nor could we identify other factors which predicted better chances of preservation. CONCLUSION: The notion that functionally lost eyes after treatment with vitrectomy and silicone oil tamponade for complicated tractional retinal detachment have better chances of preservation of the eye without silicone oil is not supported by our study.

Blindness↗
PubMed1995

Silicone injection granulomas of the breast: treatment by subcutaneous mastectomy and immediate subpectoral breast implant.

Silicone leakage from silicone breast prostheses with or without rupture of the prostheses is of great concern. Silicone injection for breast augmentation is still common in Asia, even though silicone injection induced granulomas and associated malignancy have been reported. A series of 24 women who had bilateral silicone injection granulomas in their breasts, requiring subcutaneous mastectomies and immediate breast reconstruction, is presented. Most of the patients had had one silicone injection into each breast. The patients' average age was 37.5 years and removal of the granulomas was done 3-20 years (mean 8.4 years) after the silicone injections. All patients had breast lumps and some had mastitis (21%) and dermatitis (16%) but none had palpable axillary lymph nodes. Mammograms showed diffuse, multiple granulomas of various sizes. Subcutaneous mastectomies were done via inframammary incisions. Immediate breast reconstruction was carried out with double-lumen silicone/saline implants or textured saline-filled implants inserted subpectorally via a separate axillary incision. The implants were entirely covered by the pectoralis major muscle and partially dissected serratus anterior fascia. Two cases had wound infections (8%) as early complications, and two cases developed hypertrophic scars (8%). At 6-41 months follow-up (mean 21.4 months), 69% of the patients had Baker II and 31% of the patients had Baker III breast capsular contractures.

Adult↗
PubMed1988

Possible methylation of inorganic mercury by silicones in the environment.

Organosiloxanes (silicones) are being released to the environment in increasing quantities, and there are questions concerning the reactivity of silicones as methylating agents under environmental conditions. Specifically, the interaction of inorganic mercury and polydimethylsiloxanes, and other silicones, to give methylmercury is important in this content. To this end a series of laboratory experiments, in which inorganic mercury, short and long chain silicones, cyclic siloxanes, oxidized silicone gums, and industrial formulations containing silicones, were conducted. In all cases, there was evidence of the production of methylmercury, a finding of potential significance. Analyses for methylmercury and related silicon-containing degradation products were conducted using a combination of gas chromatography, mass spectrometry, and head-space gas analysis.

Environmental Pollution↗
PubMed1994

Silicone toxicology.

Silicone, a man-made polymer containing the element silicon, has been used in a variety of medical devices including breast implants. Silicone was used, in part, because it was suggested to have the property of biological inertness. Inert materials do not affect chemical, physiological, or immunological processes. Silicone is not inert. Silicone from breast implants "bleeds" through the surrounding envelope and is present in the surrounding capsule or migrates to other distant locations. Silicone and/or the multiple chemical contaminants elicit foreign body reactions associated with granulomatous inflammation and fibrosis. Silicone and its contaminants have the potential for significant toxicity in the implant recipient.

Animals↗
PubMedDate not supplied

Response of the human larynx to silicone.

This report is concerned with tissue reaction to silicone and, in particular, long-term foreign body reaction. A histopathologic study was done on the larynx of a patient who had been injected 12 years before in the right vocal fold with room temperature vulcanizing silicone. The examination revealed particles of silicone encapsulated by thin fibrous tissue. There were few giant cells of the foreign body type and little cell infiltration. In addition, a questionnaire was returned by 54 of 90 patients who had vocal fold injected with less than 1.5 mL of either silicone fluid or room temperature vulcanizing silicone in the vocal fold from 1977 to 1984. Of these 54 patients, there was no occurrence of laryngeal disease, carcinoma, and/or connective tissue disease after the silicone injection. These findings attest to the safety of silicone in the small amounts used to treat vocal cord paralysis.

Foreign-Body Reaction↗
PubMed2006

Role of silicon contamination on calcification of hydrophilic acrylic intraocular lenses.

PURPOSE: To verify the presence of the element silicon on hydrophilic acrylic intraocular lenses (IOLs) explanted because of calcification. DESIGN: Interventional case series with clinicopathological correlation. METHODS: Twenty explanted IOLs with surface deposits (MemoryLens), and 20 with deposits mostly within their optic substance (SC60B-OUV and Aqua-Sense; 10 each) were used. After gross, microscopic, and histochemical analyses to confirm the presence of deposits, the lenses underwent scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) for elemental composition, on the external surface of MemoryLens IOLs, and on the surface and internal substance of SC60B-OUV and Aqua-Sense IOLs. The weight percentage of the element silicon was obtained at the level of deposits, and at adjacent deposit-free areas in all lenses. RESULTS: Scanning electron microscopy (SEM) coupled with EDS confirmed that the composition of the deposits was calcium/phosphate in all cases. The element silicon was found in all 40 lenses, on all areas analyzed. The silicon weight percentage was higher at the level of the deposits. The presence of aluminum on five MemoryLens IOLs, and in most of the SC60B-OUV and Aqua-Sense lenses might be related to scattering from the aluminum mounting stubs used for surface analyses. CONCLUSIONS: Silicone compounds have been implicated in the calcification of another hydrophilic acrylic design (Hydroview). They may also have a role in the calcification of other hydrophilic acrylic IOLs. Further investigation on the relationship between the presence of the element silicon and the silicone compounds found on calcified hydrophilic acrylic lenses is necessary.

Acrylic Resins↗
PubMed2005

Phase formation and evolution in the silicon substituted tricalcium phosphate/apatite system.

The sintering of silicon doped calcium phosphate ceramics prepared from a basic colloidal hydroxyapatite (Ca5(PO4)3OH or HA) precipitate mixed with silica over 800 degrees C yields a phase mixture of tricalcium phosphate phases (TCP) designated Si-TCP, beta-TCP and a silicon substituted dehydrated apatite (Si-Ap). The Si-TCP phase is defined as a combination of a silicon stabilized TCP in which the silicon content attains a saturated value (Ca3(P0.9Si0.1O3.95)2 or Si-TCP(sat)) and alpha-TCP (Ca3(PO4)2). Si-TCP(sat) has the same crystalline space group (P2(1)/a) as alpha-TCP, but with characteristically different lattice parameters due to the substitution of silicon in tetrahedral phosphorus sites. The nucleation and growth kinetics of Si-TCP in samples of composition 0.2 mol SiO2:mol HA (0.2:1) and 1 mol SiO2:mol HA (1:1) can be understood in terms of the initial growth of alpha-TCP at a silica-HA interface followed by a transformation to Si-TCP(sat) or beta-TCP. A thermodynamic model for the formation of Si-TCP(sat) predicts a nucleation temperature of 795 degrees C, in close agreement with experiment. If sufficient silicon is available, the alpha-TCP transforms to Si-TCP(sat) during extended sintering. In the absence of sufficient silicon, the alpha-TCP transforms to beta-TCP.

Apatites↗
PubMed2006

Synthesis and characterization of single-phase silicon-substituted alpha-tricalcium phosphate.

Silicon-substituted calcium phosphate (CaP) powders with a Ca/(P+Si) ratio of 1.50 have been prepared by a wet chemical method, with silicon contents up to 2.16 weight percent (wt%). Sintering for 2 h at 1250 degrees C yields single-phase silicon-substituted alpha tricalcium phosphate (Si-alpha-TCP) for compositions between 0.59 and 1.14 wt% silicon. The sintered powders have been characterized with X-ray fluorescence (XRF) spectrometry, X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy (ATR-IR) and transmission electron microscopy (TEM). Compositions with less than 0.59 wt% silicon result in mixtures of Si-alpha-TCP, beta-TCP, and calcium hydroxyapatite (HA), while compositions with more than 1.14 wt% silicon result in mixtures of Si-alpha-TCP and HA. The lattice parameters of single-phase Si-alpha-TCP prepared with 0.87 wt% silicon are a=12.874(1)A, b = 27.372(2) A, c = 15.225(1) A, and beta = 126.38(1) degrees .

Bone Substitutes↗
PubMed2006

Amphotericin B channels in phospholipid membrane-coated nanoporous silicon surfaces: implications for photovoltaic driving of ions across membranes.

The antimycotic agent amphotericin B (AmB) functions by forming complexes with sterols to form ion channels that cause membrane leakage. When AmB and cholesterol mixed at 2:1 ratio were incorporated into phospholipid bilayer membranes formed on the tip of patch pipettes, ion channel current fluctuations with characteristic open and closed states were observed. These channels were also functional in phospholipid membranes formed on nanoporous silicon surfaces. Electrophysiological studies of AmB-cholesterol mixtures that were incorporated into phospholipid membranes formed on the surface of nanoporous (6.5 nm pore diameter) silicon plates revealed large conductance ion channels ( approximately 300 pS) with distinct open and closed states. Currents through the AmB-cholesterol channels on nanoporous silicon surfaces can be driven by voltage applied via conventional electrical circuits or by photovoltaic electrical potential entirely generated when the nanoporous silicon surface is illuminated with a narrow laser beam. Electrical recordings made during laser illumination of AmB-cholesterol containing membrane-coated nanoporous silicon surfaces revealed very large conductance ion channels with distinct open and closed states. Our findings indicate that nanoporous silicon surfaces can serve as mediums for ion-channel-based biosensors. The photovoltaic properties of nanoporous silicon surfaces show great promise for making such biosensors addressable via optical technologies.

Amphotericin B↗