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PubMed2005

Surface morphology dependent photoluminescence from colloidal silicon nanocrystals.

Monodisperse 1-2 nm silicon nanocrystals are synthesized in reverse micelles and have their surfaces capped with either allylamine or 1-heptene to produce either hydrophilic or hydrophobic silicon nanocrystals. Optical characterization (absorption, PL, and time-resolved PL) is performed on colloidal solutions with the two types of surface-capped silicon nanocrystals with identical size distributions. Direct evidence is obtained for the modification of the optical properties of silicon nanocrystals by the surface-capping molecule. The two different surface-capped silicon nanocrystals show remarkably different optical properties.

Allylamine↗
PubMedDate not supplied

A silicon neuron.

By combining neurophysiological principles with silicon engineering, we have produced an analog integrated circuit with the functional characteristics of real nerve cells. Because the physics underlying the conductivity of silicon devices and biological membranes is similar, the 'silicon neuron' is able to emulate efficiently the ion currents that cause nerve impulses and control the dynamics of their discharge. It operates in real-time and consumes little power, and many 'neurons' can be fabricated on a single silicon chip. The silicon neuron represents a step towards constructing artificial nervous systems that use more realistic principles of neuronal computation than do existing electronic neuronal networks.

Animals↗
PubMed2000

Visual outcome after silicone oil removal and recurrent retinal detachment repair.

PURPOSE: Prospective analysis of the effect of removal of silicone oil (ROSO) in eyes with complicated retinal detachments and evaluation of the visual outcome following recurrent retinal detachment after silicone oil removal. METHODS: We evaluated 62 consecutive cases of ROSO over a 12 month period. All eyes had previously undergone silicone oil placement for complicated retinal detachments. All eyes undergoing scheduled ROSO over the time period of the study were entered and were reviewed post-operatively. RESULTS: Sixty-two eyes were entered into the study. Twenty-one of 62 (34%) developed recurrent retinal detachment following ROSO; 18 of these 21 recurrent detachments were reattached with one additional procedure and only 5 required replacement of the silicone oil. Ten of these 21 eyes (48%) had improvement or stabilisation in final visual acuity compared with the presenting visual acuity. Overall, 39 eyes (63%) had improvement in vision following ROSO and 76% of all eyes had ambulatory visual acuity at the end of the follow-up period. Fourteen eyes required cataract extraction with ROSO to attain this final visual acuity. CONCLUSIONS: Overall, ROSO has a significant rate of recurrent retinal detachment, with a high reattachment rate with one additional procedure. Few of these eyes need the silicone oil replaced. Most eyes will retain ambulatory visual acuity even with multiple procedures in cases of complicated retinal detachments following ROSO even with recurrent retinal detachment.

Adolescent↗
PubMed2002

Macular hole surgery with silicone oil.

PURPOSE: Macular hole surgery usually involves gas tamponade which necessitates a variable period of postoperative posturing in a face-down position. A number of patients find this difficult or impossible for medical or social reasons. This study reviews our experience of macular hole surgery using silicone oil tamponade with no restriction of posturing. METHODS: Sixteen consecutive cases of macular hole (stage III/IV) surgery where silicone oil was used for tamponade were reviewed. Group A patients were unable for medical or social reasons to maintain a face-down posture and Group B patients had previous failed surgery with gas tamponade. RESULTS: Anatomical closure of hole was achieved in 81% (13/16) of all cases and 88% (7/8) of cases with no previous surgery (Group A) with a mean follow-up of 7.5 months (range 4-24 months). Mean visual improvement (log(MAR) value of visual acuity) for Group A and Group B were 0.41 and 0.03, respectively. CONCLUSIONS: The success rate of macular hole surgery using silicone oil as tamponade, in cases with no previous surgery, is comparable to that achieved when gas is used as tamponade. Although good anatomical success can be achieved in cases with previous failed surgery, the visual outcome is less rewarding. Silicone oil is an alternative to gas tamponade for macular hole surgery in patients who are unable or unwilling to posture. However, it has to be borne in mind that silicone oil tamponade is not without risks.

Aged↗
PubMed2004

Reused silicone catheter for clean intermittent catheterization (CIC): is it safe for spinal cord-injured (SCI) men?

STUDY DESIGN: Study of reusable catheter. OBJECTIVE: To investigate whether a silicone cathether reused over years for clean intermittent catheterization (CIC) was safe for spinal cord injured (SCI) men. SETTING: Maharaj Hospital, Chiang Mai, Thailand. METHOD: A cross-sectional study was obtained from SCI men who had used CIC with a reusable silicone catheter for more than a year. Demographic data, urological management and urinary tract complications focusing on the radiologic status of the urethra were reviewed and analyzed. In addition, two reused and one new catheters were studied under electron microscope for catheter morphology (surface and lumen) and stiffness. RESULTS: There were 28 SCI men included in this study. The average duration of CIC use was 4.8 years and the average time of usage for each catheter was 3 years (range 1-7 years). In all, 26 men previously used indwelling catheterization (ID) during the acute phase. In all, 23 men performed self-catheterization. Regarding urinary complications, three reported urethral bleeding, five had episodes of pus per urethra, five had epididymitis, four had passing stones, 18 had occasional foul smelly urine, 10 developed fever and cloudy urine during the past year. Of 17 patients who had ultrasonography done, four had pathologic findings in kidney and one had bladder calculi. Demographic data, urinary management and complications did not have significant relation to the abnormality of the urethrogram or urinary tract infection. However, where the frequency of CIC was higher, the abnormality of the urethra was lower (P<0.05). All had serum Cr level < or =1.3 mg/dl. Electron microscopic findings of reused catheters for 2 years revealed encrustation but no obstruction in the lumens and 20% increase in stiffness. CONCLUSION: The clinical outcome, especially with regard to urethral abnormalities with this reusable silicone catheter is as good as with a disposable one. However, to reuse urinary catheters, one should consider the increasing risk of infection. For SCI patients in developing countries, CIC with a reusable silicone catheter may be a suitable and safe choice if one cleans and applies it properly to reduce infection. In order to answer the question how long a person in a developing country should use the same silicone catheter, further research should be conducted.

Adult↗
PubMed2003

Silicone gel sheeting for the management and prevention of onychocryptosis.

BACKGROUND: Onychocryptosis, commonly referred to as ingrown nails, has many therapeutic alternatives for its management. Although mild cases can be treated conservatively, in severe cases, surgical treatment is preferred. Silicone gel sheeting is found to be effective in the treatment of hypertrophic scars and keloids. OBJECTIVE: To document the effectiveness of silicone gel sheeting in the management of patients with onychocryptosis and in the prevention of the recurrences by breaking the devil's circle, which usually took place after the surgical procedures used in the treatment of the onychocryptosis. METHODS: Fourteen patients were enrolled in the study. Entry criteria required the presence of slight (2 patients), moderate (2 patients), or severe (10 patients) onychocryptosis. The simple technique used in the study was the excision of the one-quarter part of the lesional side of the nail plate without excising the granulation tissue. After 24 hours, the silicone was placed on the granulation tissue and the exposed nail bed. Silicone gel sheet was bandaged loosely without applying any pressure. Patients entering the study were given detailed instructions in applying and using the gel for 12 hours during the daytime. The study lasted for 14 months and was composed of a treatment period of 4 months and a follow-up period of 10 months. The patients were evaluated every 2 weeks in the first month and then monthly. The change in thickness of granulation tissue was evaluated by comparing them with the baseline photographs and those taken at each visit. RESULTS: The management and prevention of onychocryptosis were achieved in 12 of 14 patients (85.71%). The silicone gel sheeting treatment was well tolerated except for an occasional transient exudation, which was resolved when the treatment was withdrawn. CONCLUSION: The results show that the new method that we used for the treatment of onychocryptosis is successful in reducing the thickness of the hypertrophic nail fold and prevents the recurrence of the condition during the regrowth of the nail plate by breaking the devil's circle. The advantage of this method is that it is not destructive to the nail matrix and the adjacent tissue.

Female↗
PubMed2002

Long-term results after silicone prosthesis replacement of the proximal pole of the scaphoid bone in advanced scaphoid nonunion.

The treatment of scaphoid fracture nonunion with a small proximal fragment with disturbed circulation and radioscaphoid arthrosis is difficult, and the result is often unsatisfactory. For this reason, in 1981 the replacement of the proximal fragment by a silicone lunate prosthesis was recommended for such cases. From 1980 to 1984, 11 patients (all male, average age 42 [range, 25-59] years) with the conditions described above were treated by silicone prosthesis partial replacement of the scaphoid. In one patient, the prosthesis had to be removed due to dislocation, and in another patient an arthrodesis of the wrist had to be carried out after 5 years due to increasing pain. All nine remaining patients were followed up after an average of 14 (range, 12-16) years, and were clinically and radiologically re-examined and assessed wing the evaluation scheme proposed by Martini (1999). The overall results were satisfactory. Specifically, the outcome was good in one case, satisfactory in six cases, and poor in two cases. Concerning the individual criteria, the best scores were observed in "subjective overall assessment" and in "work and sports", whilst the worst were found in "movement" ad "X-ray". For all patients, X-ray examination revealed both postoperative arthrosis and extensive multiple cystoid osteolysis, presumably due to silicone synovitis. Nevertheless, most patients were free of symptoms. None of the patients felt that further treatment was necessary. Silicone prosthesis partial replacement of the scaphoid leads to long-term reduction in pain and adequate hand function. However, it is not capable of preventing carpal collapse and carpal arthrosis. Furthermore, since in several cases a progressive silicone synovitis developed, the method was rightly abandoned after 1984.

Adult↗
PubMed2004

[Individual silicon applicator for nasopharyngeal brachytherapy].

BACKGROUND: Beyond surgery, conventional radiation therapy, and chemotherapy brachytherapy may enrich treatment of primary, residual, or recurrent head and neck cancer. Nasopharyngeal cancer is a proper indication for intracavitary brachytherapy which can be performed using a commercial applicator system or an individual applicator. METHODS AND PATIENTS: Technique for manufacturing an individual nasopharyngeal silicon applicator and its experiences in 3 patients (2 times brachytherapy in treatment regime of primary nasopharyngeal cancer, 1 time for nasopharyngeal lymphoma treatment) are presented. RESULTS: Under general anaesthesia in all 3 patients nasopharyngeal imprinting after placement of two suction tubes was performed with shore 12 silicon and followed by manufacturing the individual silicon applicator with two included tubes after plaster cast of the imprinting form has been performed. This silicon applicator enabled safe endocavitary brachytherapy using the high-dose-rate-afterloading-method. Tumor control was achieved in all 3 patients. CONCLUSIONS: The presented individual silicon applicator is suited for intracavitary brachytherapy of the nasopharynx being an valuable contribution in the primary treatment regime of nasopharyngeal cancer.

Adult↗
PubMed2003

Nasal dorsal augmentation with silicone implants.

Silicone rubber has been used safely and effectively for facial augmentation for nearly 5 decades in eastern Asia. We have used silicone rubber nasal implants in primary ethnic rhinoplasty and have found consistent and long-lasting results with low complication rates. Silicone dorsal nasal augmentation in primary rhinoplasty avoids donor site morbidity and implant resorption as seen with autogenous implants. Silicone nasal implants have a low extrusion and infection rate. In the appropriate patient with proper placement, silicone nasal implant is nearly the ideal implant material.

Biocompatible Materials↗
PubMed1994

[Postoperative leakage of silicone oil into the anterior chamber].

BACKGROUND: One reason for complications after silicone oil application is the postoperative entrance of silicone oil into the anterior chamber. In a retrospective study, we tried to define risk factors for oil entrance into the anterior chamber. METHODS: 159 Eyes of 148 patients, vitrectomized and filled with silicone oil between 1988 and 1992 were analysed. In 22 eyes (13.8%) silicone oil entered the anterior chamber postoperatively. Eyes with emulsified oil in the anterior chamber and eyes, where the oil entered the anterior chamber during cataract extraction were not included in this group. Diagnoses, postoperative fundus findings and lens status, intraocular pressure, depth of the anterior chamber and time of the oil entrance were analysed. RESULTS: Risk factors in the first 10 postoperative days (14 eyes = 63.6%) seem to be aphakia and choroidal effusions, especially if combined with buckling procedures (encircling bands). In the late postoperative period, i.e. up to 6.5 months (8 eyes = 36.4%), proliferative vitreoretinopathy was responsible for the entrance of silicone oil into the anterior chamber in all cases. The decreased production of aqueous humour combined with hypotony seems also to play an important role in this process. CONCLUSIONS: It seems that in the early postoperative period the frequency of oil entrance into the anterior chamber can only be lowered by a subtotal oil filling in aphakic eyes with accompanying encircling procedures. It remains open if radical amputation of the vitreous base can avoid peripheral reproliferations.

Anterior Chamber↗
PubMed1990

[Does silicone oil improve the prognosis of severe proliferative diabetic retinopathy?].

We report on a series of 135 consecutive cases of pars plana vitrectomy for proliferative diabetic retinopathy (average period of observation was 13 months). BSS was used in 69 eyes and silicone oil was used in 66 eyes as a vitreous substitute, the indications for silicone oil in these cases were the presence of several retinotomies or retinectomies as well as sharply increased risk for rebleeding. Postoperatively and after a minimum follow up of 6 months (55 eyes) the two groups with BSS or silicone oil achieved comparable functional results despite the different anatomical preoperative situation. Thus 18 out of 23 eyes of the silicone oil group, originally with detached macula and visual acuity of HM or FC, achieved a visual outcome of greater than = 0.02, showing the best postoperative result. In the BSS-group, with attached macula prior to the operation and same visual acuity, this result is attained by 27 out of 35 eyes. We interpret these figures as meaning, that silicone oil in proliferative diabetic retinopathy reduces some of the problems connected with more advanced retinal changes like retinal detachment and rebleeding thereby allowing a visual outcome which corresponds to the macular condition.

Adult↗
PubMed1986

[Temporary silicone oil implantation following vitrectomy in proliferative diabetic retinopathy].

Report on 23 patients with proliferative diabetic retinopathy who underwent silicone oil implantation due to recurrent intravitreal hemorrhages following pars plana vitrectomy. Postoperatively, it was possible to perform panretinal laser photocoagulation without difficulty or haste. After an average period of 4 months, silicone oil was removed from 10 eyes. Subsequent hemorrhages in 4 of these eyes are due to diabetic retinopathy, not to silicone oil. In 6 cases, silicone oil removal is planned for the near future; in a further 7 cases, silicone oil removal has been postponed because of the potential danger of further traction retinal detachment.

Diabetic Retinopathy↗
PubMed1995

Silicone breast implants and the risk of connective-tissue diseases and symptoms.

BACKGROUND: Silicone breast implants have been linked to a variety of illnesses, the most controversial of which are connective-tissue diseases and symptoms. To study this relation, we analyzed data from 14 years of follow-up of the Nurses' Health Study cohort. METHODS: Women who were free from connective-tissue disease in June 1976 were followed through May 31, 1990, before there was widespread media coverage of the possible association of breast implants and connective-tissue diseases. Information was collected through biennial and supplementary mailed questionnaires and blinded reviews of medical records with the use of standardized criteria. Relative risk, the measure of association, was defined as the incidence rate of connective-tissue disease among women with breast implants divided by the corresponding incidence rate among women without breast implants. RESULTS: Among 87,501 women who were eligible for follow-up, 516 were confirmed as having definite connective-tissue diseases and 1183 as having breast implants (of which 876 were silicone-gel-filled, 170 saline-filled, 67 double-lumen, 14 polyurethane-coated, and 56 of unknown type). The mean (+/- SD) period of follow-up after surgery was 9.9 +/- 6.4 years (range, 1 month to 40.5 years). Three of the patients with definite connective-tissue disease--all had rheumatoid arthritis--had implants (one silicone-gel-filled, one saline-filled, and one double-lumen). The age-adjusted relative risk of a definite connective-tissue disease among women with any type of implant was 0.6 (95 percent confidence interval, 0.2 to 2.0), as compared with women without implants. For women with silicon-gel-filled implants, the comparable relative risk was 0.3 (95 percent confidence interval, 0 to 1.9). The relative risk of self-reported signs or symptoms of connective-tissue disease for women with implants was 1.5 (95 percent confidence interval, 0.9 to 2.4); the risk of having any 1 of 41 signs, symptoms, or laboratory features of connective-tissue disease was 0.7 (95 percent confidence interval, 0.3 to 1.6). CONCLUSIONS: In a large cohort study, we did not find an association between silicone breast implants and connective-tissue diseases, defined according to a variety of standardized criteria, or signs and symptoms of these diseases.

Adult↗
PubMed2005

Diffusion characteristics of microfabricated silicon nanopore membranes as immunoisolation membranes for use in cellular therapeutics.

OBJECTIVE: Immunoisolating membranes protect transplanted xenogeneic tissue by physically isolating them from the host. However, most are commercial filter membranes that do not possess all the features needed for immunoisolation. Silicon nanopore membranes are thin layers of silicon containing tens of thousands of nanometer-sized channels, which allow passive diffusion of small molecules. They are excellent size-selective barriers, and the objective of this study was to further characterize their immunoprotective properties and make comparisons with commercial filter membranes. METHODS: Diffusion across membranes was studied using molecules of different sizes, including fluorescein isothiocyanate-dextrans (relative molecular sizes of 4.4 kDa, 20 kDa, and 70 kDa), glucose (0.18 kDa), insulin (6.1 kDa), and immunoglobulin G (IgG) (150 kDa). Protection from complement-mediated lysis was analyzed by a hemolysis assay. Comparative studies were done with filter membranes that have been reported as immunoisolation barriers. To evaluate if silicon nanopore membranes changed insulin response patterns for glucose-stimulated islets, macrocapsules were constructed with nanopore membranes and filled with pancreatic islets, and dynamic perifusion studies were performed. RESULTS: Relative to commercial membranes, silicon nanopore membranes showed high rates of diffusion for glucose and insulin, and acted as efficient barriers to complement proteins and IgG. No other commercial membrane showed comparable diffusion and immunoisolating properties. Islets placed within the macrocapsule exhibited glucose-responsive insulin secretion in perifusion studies. CONCLUSIONS: Silicon nanopore membranes possess unique and desirable diffusion properties as immunoisolation membranes and allow rapid response times for the stimulation of islets by glucose. These features are attributed to the physical properties of the membranes, namely, the straight channels, adequate porosity, and the 5 microm thickness.

Animals↗
PubMed1991

Effect of dietary silicon on growth and skeletal development in chickens.

Experiments were conducted to determine the effect of supplementary dietary silicon on weight gain, feed efficiency, percent tibia bone ash and on the development of tibial dyschondroplasia in broiler chickens. Experiments 1 and 2 were conducted with casein/gelatin-based purified diets and Experiments 3 and 4 with corn/soy-based practical diets. All experiments used day-old broiler cockerels and lasted 16 d. Silicon supplementation (250 mg/kg) significantly decreased growth rate and the incidence and severity of tibial dyschondroplasia in Experiment 1 and had no effect on either parameter in Experiments 2-4. Dietary silicon supplementation significantly reduced feed efficiency in Experiments 1 and 3. Tibia bone ash was unaffected by dietary silicon supplementation in any of the experiments conducted. The results of the present studies indicate that dietary silicon supplementation has no effect on growth and skeletal development in broiler chickens.

Analysis of Variance↗
PubMed1998

Adherence of Staphylococcus aureus isolated in peritoneal dialysis-related exit-site infections to HEp-2 cells and silicone peritoneal catheter materials.

BACKGROUND: Peritoneal catheter exit-site infections cause a relevant morbidity in peritoneal dialysis patients and are frequently caused by Staphylococcus aureus. We tested the hypothesis that adherence of exit-site-derived S. aureus to epithelial cells and peritoneal catheter silicone tubes discriminates virulent and less virulent strains. METHODS: The binding of isolated S. aureus to an epithelial cell line (HEp-2) and to silicone tubes was analyzed using light-microscopy or radioactive labeling of bacteria. RESULTS: Of 378 exit-site swabs, 99 (26%) were positive for microbial growth. S. aureus was cultured in 25 of 99 positive swabs; three of 13 swabs taken in exit-site infections grade 3 and 4 that had tested positive for S. aureus. Adherence of S. aureus from exit-site infections grade 2, 3 and 4 to Hep-2 cells did not differ from adherence of bacteria isolated from asymptomatic or moderately inflamed catheter exit sites (grade 0-2). However, binding of S. aureus to silicone tubes was enhanced in grade 0/1 compared with grade 2-4 exit-site isolates. CONCLUSIONS: Staphylococcus aureus is an important pathogen in CAPD-related exit-site infection being isolated in about 6.6% of all exit-site swabs (and in 25% of all positive swabs). Silicone-adhesive strains may be of more clinical significance in peritoneal dialysis patients since adhesion to silicone was increased in S. aureus strains isolated in more severe exit-site infections.

Bacterial Adhesion↗
PubMed1988

Silicone lymphadenopathy associated with augmentation mammaplasty. Morphologic features of nine cases.

Silicone lymphadenopathy (SL)--defined as the presence of silicone in a lymph node--is a rare side effect of mammary augmentation either by injection of liquid silicone or by placement of a bag-gel prosthesis. Nine new cases in eight patients are herein reported and compared with six previously well-documented cases. The available data showed that SL was frequently detected as an incidental finding of no clinical significance during mastectomy and nodal dissection for associated breast carcinoma (nine cases), but may present as a painful or nontender enlarged lymph node (six cases). The latter presentation was almost always associated with a history of injection of liquid silicone or rupture of the prosthesis. All or some of the following findings were present in an affected lymph node: coarse vacuoles, fine vacuoles, and multinucleated giant cells. All lymph nodes contained a variable amount of an unstained, nonbirefringent, refractile material that, in seven of our cases, was shown to contain elemental silicon by energy-dispersive x-ray elemental analysis. In 312 lymph nodes collected from 18 routine cases of breast carcinoma, coarse vacuoles probably representing fat were found in 107 lymph nodes (34%); focal fine vacuoles were found in one (0.3%), and a single multinucleated giant cell was found in one (0.3%). In conclusion, SL probably will be encountered more frequently when cancer-prone age is reached by the susceptible population. In most cases, it is an incidental finding of no clinical significance. However, the histologic diagnosis can be made by observing characteristic light-microscopic changes, which may be supplemented in doubtful cases by energy-dispersive x-ray analysis.

Breast↗
PubMed1994

Regional silicone-gel migration in patients with ruptured implants.

The current literature is reviewed, and four clinical cases of silicone-gel migration are reported. All 4 patients reported here had histories of closed capsulotomy, and all were symptomatic. Preoperative magnetic resonance imaging demonstrated the anatomical locations of silicone-gel migration into the chest wall muscles, axillae, and upper extremity. Intraoperative and pathological findings correlated with the presence of silicone-gel migration and granulomas in various anatomical regions. With the recent advances in diagnostic breast imaging of silicone-implant patients, intracapsular rupture can be identified. Implant removal may be indicated for intracapsular ruptures to prevent silicone-gel migration into parenchyma, chest wall muscles, axillae, and the upper extremity.

Adult↗