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PubMed1998

Silicone gel enhances the development of autoimmune disease in New Zealand black mice but fails to induce it in BALB/cAnPt mice.

Anecdotal evidence links silicone gel breast implants with the development of autoimmune connective tissue disease in women. To investigate whether silicone gel is capable of directly inducing and/or enhancing the development of autoimmune disease, female BALB/cAnPt (BALB/c) and New Zealand Black (NZB) mice were injected subcutaneously with silicone gel, pristane, a nonmetabolizable substance that can cause plasmacytomas in BALB/c and NZB mice, or saline and monitored for the development of glomerulonephritis and autoantibody production. NZB, but not BALB/c, mice spontaneously develop autoantibodies and an autoimmune hemolytic anemia by 12 months of age. Over a period of 10 months, biweekly screening for proteinuria revealed increases in urinary protein in NZB mice that received multiple injections of either silicone gel or pristane. In contrast, urinary protein was unaffected in identically treated BALB/c mice. Although, silicone gel had no effect on serum titers of antierythrocyte antibodies in NZB mice, the hematocrits were significantly decreased. Moreover, silicone gel both increased the concentration of IgM anti-type I collagen antibodies and skewed the immunofluorescent staining pattern of serum autoantibodies on HEp-2 cells. In contrast, silicone gel failed to induce the production of anti-erythrocyte or antinuclear antibodies in BALB/c mice and induced only slight increases in IgG anti-type I collagen antibodies. These results suggest that silicone gel can exacerbate the development of autoimmune disease in autoimmune NZB mice, but fails to induce disease in normal BALB/c mice. This is consistent with several epidemiological studies failing to demonstrate an increase in the incidence of autoimmune disease in women with breast implants. However, because silicone gel was able to exacerbate autoimmune disease in NZB mice, it may play a similar role in the development of autoimmune disease in a small percentage of women who are genetically susceptible to such diseases.

Animals↗

PubMed1995

Hydration, not silicone, modulates the effects of keratinocytes on fibroblasts.

Topical silicone gel or silicone cream with occlusive dressing has proved to be an efficacious method for the treatment and prevention of hypertrophic scars and keloids, but how this action is triggered remains unknown. Hydration of the epidermis and/or the cellular effects of the released low-molecular-weight silicone oil have been suggested as possible mechanisms. In order to further elucidate the mechanism, we used an in vitro keratinocyte-fibroblast coculture model to investigate the cellular effects of silicone and hydration. In this model, the condition of clinical usage of topical silicone gel or cream or the condition of hydration exerted by occlusive dressing could be mimicked. The model consisted of two chambers separated by a semipermeable membrane, in which a fully differentiated stratified epithelium is present in the upper chamber and medium and monolayer fibroblasts are located in the lower chamber. The keratinocytes were nourished from the basal side only, while the apical surface was submerged in silicone oil, paraffin, Hanks' balanced salt solution, or medium (hydration); or it was exposed to air (control). In the hydration-treated group, the proliferation of fibroblasts measured as [3H]thymidine incorporation and their collagen, glycosaminoglycan production was significantly inhibited when compared with the controls, but exposure of the keratinocyters to silicone oil or paraffin did not influence fibroblast behavior. The results suggest that hydration, not silicone, modulates the in vitro keratinocyte-fibroblast interaction. This may be one possible mechanism by which topical silicone or occlusive dressing treatment may affect the development of hypertrophic scars and keloids.

Cell Division↗

PubMed1990

Intravitreal silicone oil injection: complications and treatment of 415 consecutive patients.

Silicone oil injection in conjunction with pars plana vitrectomy was carried out by five surgeons in 415 consecutive patients using the same surgical equipment, the same surgical techniques and the same highly purified silicone oil (viscosity, 5000 mPa.s). Indications for silicone oil injection after vitrectomy included advanced stages of proliferative vitreoretinopathy following rhegmatogenous retinal detachment (49%), severe proliferative diabetic retinopathy (38%), and proliferative vitreoretinopathy following retinal detachment due to ocular trauma (13%). Postoperative complications were noted in a 6- to 30-month follow-up period. Cataractous changes of varying degree were seen in all phakic eyes. Silicone oil entered the anterior chamber in 6% of all phakic and pseudophakic eyes. Subretinal silicone oil was noted in 4%. Other complications associated with the use of intravitreal silicone oil included biomicroscopically visible silicone oil emulsification (0.7%), keratopathy (5.5%), glaucoma (6%), closure of the inferior iridectomy (6%), and reproliferation of epiretinal and subretinal fibrous membranes (40%). We anticipate that the physico-chemical characteristics of the highly purified silicone oil (viscosity, 5000 mPa.s) and the routine performance of an inferior iridectomy in all aphakic eyes had a positive impact on the low incidence of silicone-oil-related complications such as emulsification, keratopathy and secondary glaucoma.

Anterior Chamber↗

PubMed2004

Intraocular inflammation following endotamponade with high-density silicone oil.

BACKGROUND: The use of a mixture of silicone oil and partially fluorinated alkanes (high-density silicone oil) has recently been suggested as intraocular tamponade in complicated retinal detachment of the inferior quadrants. We describe a series of patients who developed a clinical picture resembling anterior granulomatous uveitis following endotamponade with high-density silicone oil. METHODS: We evaluated 19 eyes of 18 patients who underwent pars plana vitrectomy and intraocular tamponade with high-density silicone oil (Oxane HD). The indication for this type of intraocular tamponade was limited to cases with complicated retinal detachment of the inferior quadrants. Oxane HD was removed after a mean period of 3 months. RESULTS: One to eight weeks following vitrectomy with high-density silicone oil, an intraocular inflammation was observed in 7 of 19 eyes (37%). These eyes presented with keratic precipitates (KP), pigmented clumps in the inferior part of the anterior chamber and increased anterior chamber cellular reaction. This inflammatory response did not react to topical steroids. In addition to KP a considerable amount of cellular precipitation was noted on the surface of the oil bubble. Strikingly, the intraocular inflammatory signs completely resolved following removal of the high-density silicone oil. CONCLUSIONS: An inflammatory response, resembling granulomatous uveitis, occurs in a significant number of patients after high-density silicone oil endotamponade. It is likely that this vitreous substitute is an immunogenic agent, given the complete resolution of the inflammation after removal of the high-density silicone oil. The routine use of this newly developed silicone oil should therefore await the outcome of additional controlled clinical trials.

Aged↗

PubMed2004

Influence on membrane-mediated cell activation by vesicles of silicone oil or perfluorohexyloctane.

PURPOSE: This study was conducted to investigate whether macrophage activation through cell membrane attachment might be supported by emulsified tamponade droplets of a certain vesicle size. It has been hypothesized that emulsification of vitreous tamponades might stimulate retinal membrane formation. METHODS: In this laboratory investigation, similarly sized vesicles of silicone oil and the partially fluorinated alkane perfluorohexyloctane (F6H8) were produced by extrusion through polycarbonate membranes. Human neutrophils were obtained from blood donors. Human monocytes were negatively isolated from mononuclear cells by depletion of other cells. Cell activation status of phagocyting blood neutrophils was measured by a chemiluminescence assay. Fluorescent attached or internalized vesicles were monitored by fluorescent microscopy. The main outcome measures were the altered activation status of monocytes after vesicle incubation and the ability of human macrophages to attach and/or internalize vesicles in vitro. RESULTS: Extruding silicone oil through a polycarbonate membrane resulted in the production of vesicles that remained stable for at least 2 days. F6H8 vesicles had to be stabilized with an emulsifier, in this case Pluronic PE6800 or Lipoid EPC. The mean vesicle diameter was similar with both components (F6H8: 13.08+/-2.95 microm, silicone oil: 10.05+/-4.6 microm). Neutrophil activation was not influenced by either emulsifier alone or by silicone oil vesicles without emulsifier. Stabilized F6H8 vesicles had a dose-dependent influence on blood neutrophil activation. Only silicone oil vesicles together with Lipoid EPC, not Pluronic PE6800, had a comparable influence on neutrophil activation. Neutrophil activation was influenced neither by 0.125% human serum albumin (HSA) alone nor by vesicles of F6H8 or silicone oil prepared with 0.125% HSA. Monocyte cell membrane attachment of silicone fluid was two times higher than that of F6H8 fluid. F6H8/Pluronic PE6800 vesicles enhanced this process 20-fold, whereas silicone oil vesicles did not enhance cell membrane attachment significantly. CONCLUSIONS: These in vitro data do not support the hypothesis that emulsification of the tamponades silicone oil or F6H8 in the microenvironment of the eye might easily activate neutrophils or stimulate phagocytosis by monocytes. A prerequisite is the combination of a vesicle shape of the tamponades with specific stabilizing or modifying surfactants. Emulsified tamponades stabilized by artificial surfactants, but not by the naturally occurring protein HSA, favor cell activation by cell membrane attachment.

Cytoplasmic Vesicles↗

PubMed2006

The phenomenon of "sticky" silicone oil.

BACKGROUND: To investigate the reasons for difficulties removing silicone oil from the vitreous cavity due to putative adherence to the retina. METHODS: Gas chromatography-coupled mass spectroscopy of the headspace (GC/MS/HS) and gel permeation chromatography (GPC) were used to detect volatile compounds in silicone oil samples explanted from patients, qualitatively as well as quantitatively. Surface and interfacial tensions of the explanted samples were measured using the pendent-drop technique. To simulate the removal of silicone oil from the vitreous cavity, the contact between silicone oil and differently treated surfaces and various aspiration techniques were tested in vitro. RESULTS: The median concentration of perfluorodecalin in seven "sticky" samples was 2.4 times higher than in 14 non-sticky samples. In the sticky samples, the median surface tension of the aqueous phase was lower. The difficulty of aspirating silicone oil could be reproduced in vitro by reducing the surface tension of the aqueous environment of the silicone oil. CONCLUSION: The observed stickiness of silicone oil seems to be a matter of reduced surface tension of the surrounding aqueous material and/or contamination of silicone oil with perfluorocarbon liquid, which creates interruption of the material flow, giving the impression of adherence of the silicone oil to the retina.

Adhesiveness↗

PubMed1986

Accuracy of addition silicones as a function of technique.

Both addition and condensation silicones produced stone dies that were larger in diameter and shorter in height than the tooth preparation. For both materials, there was little change in the distance between stone die preparations compared with the standard. The most significant difference between types of silicone was that condensation silicones produced significantly shorter dies (-0.24% to -0.37%) than addition silicones (-0.08%). Among addition silicones, Cinch produced more than twice as much vertical change (-0.16%) than the other three products (-0.06%). Since castings made from a short die will not seat completely on the prepared tooth, these results support the use of three of the four addition silicones tested. The same accuracy of impressions was achieved for all techniques (that is, putty/wash, single mix, and double mix) when addition silicones were used, whereas the putty/wash technique produced the most accurate dies for the condensation silicones. The custom tray produced dies that were much more accurate in vertical dimensions (-0.03%) than the stock trays (-0.15% to -0.21%). Thus the custom tray is the impression tray of choice, even for addition silicones, which produce relatively little polymerization shrinkage and are dimensionally stable.

Chemical Phenomena↗

PubMed1987

Silicone and rheumatic diseases.

Silicone generally has been regarded as a biologically inert material. However, recent reports suggest that inflammatory responses to silicone occur. There is some experimental and clinical evidence of a direct inflammatory response to the presence of liquid or particulate silicone. These include granulomatous skin reaction to injected silicone, synovitis around silicone prosthetic joints, and lymphadenopathy proximal to silicone prostheses. There are case reports of systemic rheumatic disease following silicone prostheses, but no definitive proof of a direct relationship between silicone prostheses and systemic disease. The clinical features of the reported cases following breast augmentation include breast tenderness, axillary adenopathy, sclerodermatous skin changes, arthritis, Raynaud's phenomenon, rheumatoid factors, and ANAs. Prior epidemiologic evidence and the number and consistency of our own and others' clinical findings suggest that silicone may indeed be associated with inflammatory processes and rheumatic diseases.

Adult↗

PubMed1994

Autoantibodies in patients with silicone implants.

Immune disorders are characterized by development of autoantibodies. Autoantibodies, particularly antinuclear antibodies, are detected in the majority of patients with connective tissue diseases such as systemic lupus erythematosus and scleroderma. Recent reports have described persons with silicone implants who have developed scleroderma and systemic lupus erythematosus. Since autoantibodies are suspected to play an important role in the pathogenesis of the connective tissue disease, the nature of the autoantibodies produced in patients with silicone-associated rheumatic disease is important to understand. A review of the English literature and abstracts from the 1992 American College of Rheumatology meeting showed that immunofluorescent testing for antinuclear antibody was positive in a wide range (7% to 68%) of patients with silicone implants. When examining only those patients with silicone implants and clinical evidence of connective tissue disease, the proportion of patients with a positive immunofluorescent test was less than commonly found in a series of patients with idiopathic connective tissue disease. Sensitive testing by Western blot technique revealed autoantibodies in 10% of patients with silicone implants and negative immunofluorescent test results. Patients with silicone implants and scleroderma-like illness were characterized by anticentromere and anti-PM-Scl antibodies, whereas patients with silicone implants and SLE or undifferentiated connective tissue disease were characterized by antibodies to small nuclear ribonucleoproteins, specifically B'/B polypeptide. In addition, antibodies to a high molecular weight protein have been discovered by Western blot in more than 50% of persons with silicone implants. Differences in autoantibody production between patients with silicone-associated rheumatic disease and patients with idiopathic rheumatic disease may be a distinguishing feature. Further characterization of these autoantibodies is needed.

Antibodies, Antinuclear↗

PubMed2005

Reference values for serum silicon in adults.

Silicon is an essential nutrient of fundamental importance to human biology. It has been shown that silicon is required for bone, cartilage, and connective tissue formation. However, the assessment of silicon concentration is difficult as reference values are lacking. The aim of the present study was to establish reference values for apparently healthy individuals. Silicon concentrations were determined in serum of 1325 healthy subjects 18-91 years of age using atomic absorption spectrometry. Medians for serum silicon concentrations showed a statistically significant age and sex dependency. In men 18-59 years of age the median was 9.5 micromol/L and decreased to 8.5 micromol/L at 60-74 years of age. In women there was an increase in the median from age 18-29 years (10.00 micromol/L) to 30-44 years (11.10 micromol/L) followed by a decrease in the age group of 45-59 years (9.23 micromol/L). In subjects aged over 74 years the median serum silicon values were 7.70 micromol/L for men and 8.00 micromol/L for women. The most important findings in this study are the decrease of silicon and the course of the silicon concentrations with age, especially in women. The present study is an important prerequisite for studies that aim to identify the health effects and medical implications of silicon.

Adolescent↗

PubMed2006

Modification of chemical properties of cell walls by silicon and its role in regulation of the cell wall extensibility in oat leaves.

Effects of silicon on the mechanical and chemical properties of cell walls in the second leaf of oat (Avena sativa L.) seedlings were investigated. The cell wall extensibility in the basal region of the second leaf was considerably higher than that in the middle and subapical regions. Externally applied silicon increased the cell wall extensibility in the basal region, but it did not affect the extensibility in the middle and subapical regions. The amounts of cell wall polysaccharides and phenolic compounds, such as diferulic acid (DFA) and ferulic acid (FA), per unit length were lower in the basal region than in the middle and subapical regions of the leaf, and silicon altered these amounts in the basal region. In this region, silicon decreased the amounts of matrix polymers and cellulose per unit length and of DFA and FA, both per unit length and unit matrix polymer content. Silicon treatment also lowered the activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) in the basal region. In contrast, the amount of silicon in cell walls increased in response to silicon treatment in three regions. These results suggest that in the basal region, silicon reduces the net wall mass and the formation of phenolic acid-mediated cross-linkages between wall polysaccharides. Such modifications of wall architecture may be responsible for the silicon-induced increase in the cell wall extensibility in oat leaves.

Ammonia-Lyases↗

PubMed2005

Comparison of safety and efficacy between silicone and polypropylene Ahmed glaucoma valves in refractory glaucoma.

OBJECTIVE: To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs) over 1 year of follow-up. DESIGN: Retrospective comparative study. PARTICIPANTS: Fifty consecutive patients with polypropylene and 49 consecutive patients with silicone AGV implantation. METHODS: Our hospital instituted a formulary conversion of the glaucoma aqueous drainage device from polypropylene to silicone AGVs in January 2003. We reviewed the polypropylene AGVs within 7 months before and the silicone AGVs within 7 months after the date of conversion performed on patients with glaucoma refractory to medical treatment and filtering procedures, without previous drainage devices or cyclodestructive procedures, and with a minimum of 12 months' follow-up. Surgical success was defined as an intraocular pressure (IOP) reduction of > or =20% and a final IOP of >5 and <22 mmHg, without additional surgical intervention for IOP control, loss of light perception, or serious complications. MAIN OUTCOME MEASURES: The 2 groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. RESULTS: Significant IOP reductions occurred after polypropylene AGV implantation (from 32.4+/-11.3 mmHg to 16.5+/-6.9 mmHg, P<0.0001) and silicone AGV implantation (from 32.6+/-12.6 mmHg to 14.7+/-6.9 mmHg, P<0.0001). The silicone group had a lower mean IOP than the polypropylene group at all postoperative visits, but the differences were significant only at 3 months postoperatively (P = 0.014). In addition, the silicone group was associated with a rate of insufficient IOP control as the reason of failure (IOP of > or =22 mmHg or IOP reduction of <20%) lower (4.1%) than that of the polypropylene group (20.0%, P = 0.015), but a rate of non-tube related serious complications (16.3%) higher than that of the polypropylene AGV (4.0%, P = 0.042). CONCLUSION: After 1 year of follow-up, the silicone AGV is at least as effective as the polypropylene AGV in IOP reduction but may be associated with a higher rate of complications. These differences are important for surgeons converting to use of the silicone AGV in patients with glaucoma refractory to other forms of treatment.

Aged↗

PubMed1977

Silicon, fibre, and atherosclerosis.

A logical argument can be made for the hypothesis that lack of silicon may be an important aetiological factor in atherosclerosis. As silicic acid or its derivatives, silicon is essential for growth. It is found mainly in connective tissue, where it functions as a cross-linking agent. Unusually high amounts of bound silicon are present in the arterial wall, especially in the intima. Various kinds of dietary fibre have been reported to be effective in preventing experimental models of atherosclerosis, reducing cholesterol and blood-lipid levels, and binding bile acids in vitro. Exceptionally large amounts of silicon (1000 to 25 000 p.p.m.) were found in fibre products of greatly varying origin and chemical composition which were active in these tests. Inactive materials, such as different types of purified cellulose, contained only negligible quantities of the element. It is concluded that silicate-silicon may be the active agent in dietary fibre which affects the development of atherosclerosis. Two out of three samples of bran also had relatively low levels, which could explain why bran does not lower serum-cholesterol. The fact that atherosclerosis has a low incidence in less developed countries may be related to the availability of dietary silicon. Two instances are presented where silicon is reduced by industrial treatment: white flour and refined soy products were much lower in silicon than--their respective crude natural products. The chemical nature of silicon in different types of fibre is not known. It could exist as orthosilic acid, polymeric silicic acid, colloidal silica (opal), dense silica concentrations, or in the form of organically bound derivatives of silicic acid (silanolates). Possible mechanisms of action are discussed.

Anticholesteremic Agents↗

PubMed2001

Surgical management of secondary glaucoma after pars plana vitrectomy and silicone oil injection for complex retinal detachment.

OBJECTIVE: To evaluate the outcomes of surgical intervention for secondary glaucoma after pars plana vitrectomy and silicone oil injection for repair of complex retinal detachment. DESIGN: Retrospective noncomparative interventional case series. PARTICIPANTS: Forty-three eyes of 43 patients who underwent incisional surgery for secondary glaucoma after pars plana vitrectomy and silicone oil injection for repair of complex retinal detachment over a 9-year period. MAIN OUTCOME MEASURES: Intraocular pressure (IOP), intraoperative and postoperative complications, visual acuity, and the need for further surgical intervention for glaucoma. Success was defined as IOP < or =21 mmHg and > or =5 mmHg with or without medication but without surgical reoperation for glaucoma. RESULTS: Findings associated with elevated IOP included emulsified oil in the anterior chamber (n = 14), pupillary block from silicone oil (n = 13), open-angle glaucoma without silicone oil in the anterior chamber (n = 9), and angle-closure glaucoma without pupillary block (n = 7). The mean (+/- standard deviation) IOP was 41.4 +/- 15.1 mmHg before surgery for glaucoma and 17.2 +/- 10.2 mmHg after an average follow-up of 19.6 months (P < 0.001). Cumulative success was 69%, 60%, 56%, and 48% at 6, 12, 24, and 36-months respectively. In patients who underwent silicone oil removal alone for surgical management of glaucoma (n = 32), 11 of 12 IOP failures (92%) were due to uncontrolled IOP, whereas most IOP failures in the group who underwent silicone oil removal plus glaucoma surgery (n = 8) failed because of hypotony (3 of 4, 75%, P = 0.027). Of three patients who underwent glaucoma surgery alone to control IOP, one failed because of hypotony. There was no significant change in visual function at last follow-up (logarithm of the minimum angle of resolution [logMAR] 2.01) compared with preoperative visual function (logMAR 2.07, P = 0.74). CONCLUSION: Surgical management of secondary glaucoma after silicone oil injection for complex retinal detachment may achieve good IOP control and stabilization of visual function in most patients. Patients who undergo silicone oil removal alone to control IOP are more likely to have persistent elevation of IOP and possibly undergo reoperation for glaucoma, whereas patients who undergo concurrent silicone oil removal and glaucoma surgery are more likely to have hypotony.

Female↗

PubMed1997

Comparative study of silicone versus acrylic foldable lens implantation in primary glaucoma triple procedure.

OBJECTIVE: To compare silicone versus acrylic foldable intraocular lens (IOL) implantation in primary glaucoma triple procedure (PGTP). DESIGN: Prospective, randomized. PARTICIPANTS: A total of 79 eyes of 79 primary open-angle glaucoma (POAG) patients in need of combined surgery were randomized to a silicone IOL group (36 eyes) and acrylic IOL group (43 eyes). INTERVENTION: The study eyes underwent PGTP, which consisted of primary trabeculectomy, phacoemulsification, and posterior chamber IOL implantation. Adjunctive mitomycin C (MMC) (0.5 mg/ml for 1 minute) was used selectively only in patients with one or more risk factors for filtration failure of PGTP. MAIN OUTCOME MEASURES: Snellen visual acuity, intraocular pressure (IOP), slit-lamp biomicroscopy, and number of glaucoma medications were measured, performed, or determined preoperatively and at regular intervals postoperatively. RESULTS: There were no significant differences in the mean number of postoperative glaucoma medications at 1, 2, 3, 4-6, and 9-12 months and at last follow-up (P > 0.05); mean change in corrected visual acuity best attained (P = 0.315) or at last follow-up (P = 0.223) between the silicone and acrylic groups. Both groups had significant decreases in mean IOP and mean number of medications postoperatively at all times (P < 0.05). However, the postoperative IOP > 25 mmHg and IOP spike > 5 mmHg above preoperative IOP during the first month were significantly higher in the acrylic group (P = 0.026). The mean postoperative IOP at 1 month in the acrylic group was also significantly higher than the silicone group (14.1 +/- 5.0, 11.2 +/- 3.9, P = 0.005). Conversely, there were no significant differences in mean postoperative IOP at 2, 3, 4-6, and 9-12 months and at last follow-up between the silicone and acrylic groups (P > 0.05). Suture removal or release occurred significantly more frequently in the acrylic IOL group during the first month and the first 2 months (48.8% and 60.5%) than the silicone group (25.0% and 36.1%, P = 0.030 and 0.031, respectively). There were no significant differences in postoperative complications or surgical interventions between the two groups (P > 0.05). CONCLUSIONS: During the first year following the PGTP with selective use of MMC, there were no significant differences in the medical dependency or visual outcomes or complications between the silicone and acrylic groups. Both groups attained significant decreases in IOP postoperatively. However, the mean IOP was significantly higher in the acrylic than the silicone group at 1 month postoperatively, and postoperative IOP > 25 mmHg and IOP spike > 5 mmHg above preoperative IOP were significantly greater in the acrylic group. There were significantly more suture releases in the acrylic IOL group than the silicone IOL group in the first 2 months postoperatively.

Acrylic Resins↗

PubMed2003

Investigation of the release behavior of a covered-rod-type formulation using silicone.

The purpose of this study was to investigate the effects of the properties of a drug on its release behavior in a cylindrical sustained-release formulation having a two-component structure, with a silicone matrix containing drug powder as the inner layer component, and with its lateral side covered with an silicone outer layer (CR silicone formulation). In this study, the release profile of a drug from "the lateral side covered with silicone" and from "the cross-sections where the inner layer is exposed to the surface" was examined using a newly designed bi-directional elution cell. The relationships between the release profile and solubility of the drug and its permeability through silicone were also studied. Bovine serum albumin (BSA), antipyrine (ANP), indometacin (IDM) and ketoprofen (KP) were used as model drugs. Each CR silicone formulation containing drug powder consisting of a drug and sucrose (SUC) was investigated, and a satisfactory relationship was observed between drug release from the cross-sections and drug solubility, and between drug release from the lateral side and permeability of the drug through a silicone membrane. For CR silicone formulations containing IDM, the addition of deoxycholate sodium (DOC) improved the solubility of IDM; however, release from the lateral side of the formulation remained unchanged, and IDM release from the cross-sections of the formulation increased. In this study it was found that, for controlled release of a drug from CR silicone formulations, control of drug solubility is effective.

Antipyrine↗

PubMed1999

Quantitative detection of silicone in skin by means of electron spectroscopy for chemical analysis (ESCA).

BACKGROUND: Evaluation of silicone-induced morbidity in skin has been hampered by the difficulty of detecting silicone in tissue because conventional methods are nonquantitative and insensitive. OBJECTIVE: We attempted to determine whether silicone could be identified and quantitated in skin by means of electron spectroscopy for chemical analysis (ESCA). METHODS: Skin biopsy specimens were obtained from the nose, chin, malar region, and inner arm of a patient who had received injections of silicone gel in his nose and chin. Frozen sections were dried under vacuum and examined by means of ESCA. Contiguous sections were examined by light microscopy. RESULTS: The surface concentrations of silicone were as follows: chin, 20.6% +/- 3.6%; nose, 19.0%; malar region, 2.6% +/- 1.6%; inner arm, 0.0% +/- 0.0%. Light microscopy revealed homogeneous "globules" consistent with silicone in the chin and nose sections only; the malar region and inner arm sections showed no evidence of silicone. CONCLUSION: ESCA can be used to detect silicone in skin in a specific, highly sensitive, and quantitative manner. This is the first report of quantification of silicone in skin by means of ESCA.

Arm↗

PubMed2001

Posterior continuous curvilinear capsulorhexis with hydrogel and silicone intraocular lens implantation: development of capsulorhexis size and capsule opacification.

PURPOSE: To evaluate the influence of primary posterior continuous curvilinear capsulorhexis (PCCC) on capsule opacification development and capsular bag changes within the first year after cataract surgery with 2 intraocular lenses (IOLs) of comparable design but different material. SETTING: Department of Ophthalmology, University of Vienna, Medical School, Vienna, Austria. METHODS: Thirty-seven patients with age-related cataract had bilateral small incision cataract surgery with a PCCC performed after capsular tension ring insertion. One eye was randomly assigned to receive a hydrogel IOL and the other eye, a silicone IOL. Standardized digital retroillumination photographs were taken 1 day, 1 week, and 1, 3, 6, and 12 months after surgery to evaluate changes in the dimensions of the anterior and posterior capsulorhexis opening area and the presence of anterior and posterior capsule opacification. RESULTS: The area of the anterior continuous curvilinear capsulorhexis (ACCC) opening was significantly reduced during the first 6 postoperative months. The shrinkage was more pronounced (-25%) in the silicone IOL group than in the hydrogel IOL group. Ten percent of eyes with a silicone IOL had marked shrinkage of the ACCC. The area of the PCCC did not change in eyes with a hydrogel IOL but was larger (+20%) in eyes with a silicone IOL. Anterior ongrowth was observed in 60% in the hydrogel group and in no eye in the silicone group. Anterior capsule fibrosis was observed in 90% in the silicone group and in 20% in the hydrogel group. Total closure of the PCCC was not observed within the first year, but posterior ongrowth was observed in 40% in the hydrogel group and 10% in the silicone group. CONCLUSIONS: Anterior capsulorhexis shrinkage with concomitant posterior capsulorhexis enlargement was observed in eyes with a silicone IOL. The hydrogel IOL induced more ongrowth on the anterior and posterior IOL surfaces, whereas the silicone IOL induced more anterior capsule fibrosis. Total closure of the PCCC was not observed within the first year after surgery.

Aged↗