Stability, defined as the reproducible behavior of a device upon its storage, is an important issue in pharmaceutical formulation. Silica xerogels obtained through the sol-gel route are relatively ...new as matrices for the controlled release of drugs. In some cases, it was observed that their behavior changes upon storage, so that they cannot always be defined as "stable". This occurs especially when gel processing is performed at mild temperatures, a procedure that may have to be used to prevent degradation of the embedded drug. This work investigated the use of inorganic catalysts as potential xerogel stability inducers when gel curing by heating is not applicable. Three compounds known to accelerate sol-gel polymerization, namely ammonia, sodium fluoride and sodium carbonate, were introduced during the polymerization of low-temperature processed inorganic and organically modified gels, and the effect of each compound on xerogel stability and drug release was monitored. The use of carbonate leads to formulations with good retention properties, as opposed to ammonia and NaF, which lead to poorly retentive xerogels in accordance with their known ability to increase porosity. Ammonia was shown to be a poor stability promoter independently of gel composition, as opposed to fluoride and carbonate, which both displayed stabilizing properties in a dose-dependent manner. No correlation was found between xerogel stability and drug release properties. An attempt was also made to correlate stability data with polymerization rates and wet gel syneresis time evolution with the purpose of identifying one or more synthesis parameters that could act as stability predictors for pre-formulation studies. No correlation was found between stability and syneresis data. A similar trend in the curve of gel time vs. catalyst concentration was observed for the two stabilizing catalysts, which was different for the non-stabilizing ammonia. It was concluded that the trend of this curve could potentially provide an indicator of catalyst stabilizing efficacy.
Stability, defined as the reproducible behavior of a device upon its storage, is an important issue in pharmaceutical formulation. Silica xerogels obtained through the sol–gel route are relatively ...new as matrices for the controlled release of drugs. In some cases, it was observed that their behavior changes upon storage, so that they cannot always be defined as “stable”. This occurs especially when gel processing is performed at mild temperatures, a procedure that may have to be used to prevent degradation of the embedded drug. This work investigated the use of inorganic catalysts as potential xerogel stability inducers when gel curing by heating is not applicable. Three compounds known to accelerate sol–gel polymerization, namely ammonia, sodium fluoride and sodium carbonate, were introduced during the polymerization of low-temperature processed inorganic and organically modified gels, and the effect of each compound on xerogel stability and drug release was monitored. The use of carbonate leads to formulations with good retention properties, as opposed to ammonia and NaF, which lead to poorly retentive xerogels in accordance with their known ability to increase porosity. Ammonia was shown to be a poor stability promoter independently of gel composition, as opposed to fluoride and carbonate, which both displayed stabilizing properties in a dose-dependent manner. No correlation was found between xerogel stability and drug release properties. An attempt was also made to correlate stability data with polymerization rates and wet gel syneresis time evolution with the purpose of identifying one or more synthesis parameters that could act as stability predictors for pre-formulation studies. No correlation was found between stability and syneresis data. A similar trend in the curve of gel time vs. catalyst concentration was observed for the two stabilizing catalysts, which was different for the non-stabilizing ammonia. It was concluded that the trend of this curve could potentially provide an indicator of catalyst stabilizing efficacy.
Stability, defined as the reproducible behavior of a device upon its storage, is an important issue in pharmaceutical formulation. Silica xerogels obtained through the sol-gel route are relatively ...new as matrices for the controlled release of drugs. In some cases, it was observed that their behavior changes upon storage, so that they cannot always be defined as "stable". This occurs especially when gel processing is performed at mild temperatures, a procedure that may have to be used to prevent degradation of the embedded drug. This work investigated the use of inorganic catalysts as potential xerogel stability inducers when gel curing by heating is not applicable. Three compounds known to accelerate sol-gel polymerization, namely ammonia, sodium fluoride and sodium carbonate, were introduced during the polymerization of low-temperature processed inorganic and organically modified gels, and the effect of each compound on xerogel stability and drug release was monitored. The use of carbonate leads to formulations with good retention properties, as opposed to ammonia and NaF, which lead to poorly retentive xerogels in accordance with their known ability to increase porosity. Ammonia was shown to be a poor stability promoter independently of gel composition, as opposed to fluoride and carbonate, which both displayed stabilizing properties in a dose-dependent manner. No correlation was found between xerogel stability and drug release properties. An attempt was also made to correlate stability data with polymerization rates and wet gel syneresis time evolution with the purpose of identifying one or more synthesis parameters that could act as stability predictors for pre-formulation studies. No correlation was found between stability and syneresis data. A similar trend in the curve of gel time vs. catalyst concentration was observed for the two stabilizing catalysts, which was different for the non-stabilizing ammonia. It was concluded that the trend of this curve could potentially provide an indicator of catalyst stabilizing efficacy.
Retinitis pigmentosa is a heterogeneous group of ocular diseases that causes progressive degeneration of the photoreceptor cells mainly affecting the rods of the peripheral retina. The association ...between retinitis pigmentosa and exudative retinopathy was first described in 1956 and has been called “Coats-like retinitis pigmentosa.” Mutations in the Crumbs homolog 1 ( CRB1 ) gene have been reported as a risk factor for developing Coats-like changes in patients with autosomal recessive retinitis pigmentosa. We report the case of a 15-year-old girl affected by CRB1 gene–negative retinitis pigmentosa and Coats-like exudative vasculopathy who was successfully treated with laser photocoagulation.
Purpose
To determine the presence of sickle cell retinopathy and maculopathy and to identify associations between markers of hemolysis and systemic and ocular manifestations in children affected by ...sickle cell disease.
Methods
Eighteen children with sickle cell disease, aged 5–16 years, underwent complete eye examination including best-corrected visual acuity, slit-lamp biomicroscopy, ophthalmoscopy after pharmacological mydriasis, spectral-domain optical coherence tomography (SD-OCT), and optical coherence tomography angiography (OCTA). Blood test results and clinical history information were collected for each child, including fetal hemoglobin (HbF), hemoglobin (Hb), hematocrit (Htc), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), reticulocytes percentage (%ret), lactic dehydrogenase (LDH), total and direct bilirubin, glomerular filtration rate, number of painful crises, acute chest syndromes, and splenic sequestration. Therapeutic regimen and transfusion therapy were also evaluated.
Results
Sixteen of 36 eyes (44.4%) had non-proliferative sickle cell retinopathy on ophthalmoscopic evaluation. No patients had proliferative sickle cell retinopathy. In 13 of 36 eyes (36.1%), SD-OCT and OCTA detected signs of sickle cell maculopathy. Nine eyes (25%) presented sickle cell retinopathy and maculopathy, 7 eyes (19.4%) sickle cell retinopathy alone, and 4 eyes (11.1%) sickle cell maculopathy alone. A statistically significant association was found between sickle cell retinopathy; lower levels of HbF, Hb, and Htc; and higher MCV and percentage of reticulocytes. Sickle cell maculopathy was associated with lower values of H and Htc and higher levels of reticulocytes and total bilirubin.
Conclusions
We identified early signs of sickle cell retinopathy and maculopathy in a pediatric population with SD-OCT and OCTA. These two retinal complications were more frequent in children with higher hemolytic rates.
Fluorescein angiography (FA) has been a pivotal tool to study the pathophysiology of retinopathy of prematurity (ROP) in vivo. We examined the course of ROP using FA in order to assess the predictive ...value of angiographic features.
This is an observational retrospective cohort multi-center study of eyes screened for ROP with binocular indirect ophthalmoscope and with FA. All infants undergoing screening examination for ROP who had retinal vasculature limited to Zone I and posterior Zone II vascularization underwent FA between 31 and 34 weeks postmenstrual age. RetCam fundus imaging and video digital fluorescein angiography were performed in the neonatal intensive care units. Masked grading of the FA images was retrospectively conducted by two ROP expert ophthalmologists. Ten criteria that describe retinovascular and choroidal features on FA were used to assess their predictive value for development of treatment-requiring ROP.
A total of 98 eyes of 56 patients were included for this study. FAs of eyes of premature infants show a wide range of features either at the junction between the vascular and avascular retina and posteriorly to that. Among the angiographic features evaluated, leakage, shunts and hyperfluorescent lesions at the junction between vascular and avascular zone were predictive of the development of treatment-requiring ROP (p < 0.05), but findings in the posterior vascularized retina were not.
FA can add to our understanding of the evolution of vascular abnormalities in the course of ROP and can help predict which eyes will go on to treatment.
