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Active Membranes (active + membrane)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

A New Generation of Catalytic Poly(vinylidene fluoride) Membranes: Coupling Plasma Treatment with Chemical Immobilization of Tungsten-Based Catalysts ,

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006
C. Lopez
Abstract A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low-temperature plasma-modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH3 radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten-based heterogeneous catalysts. Particular attention has been focused on tungstate, WO42,, and decatungstate, W10O324,, which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma-modified membranes surface-tailored with WO42, have been used in catalytic membrane reactors to activate hydrogen peroxide for oxidizing secondary amines to nitrones; membranes modified with W10O324, have been used for the complete degradation of phenol. The obtained results, in terms of amine,nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W-based catalysts on plasma-treated membranes. [source]

Reduction of Active Elastase Concentration by Means of Immobilized Inhibitors: A Novel Therapeutic Approach

BIOTECHNOLOGY PROGRESS, Issue 3 2004
Valentina Grano
The inhibitory power of three different active Nylon membranes, separately loaded with three different protease inhibitors, was studied with the aim of reducing the increased elastase concentration occurring during hemodialysis or extracorporeal blood circulation in patients undergoing cardiopulmonary bypass. Chemical grafting was carried out to make the inert Nylon membrane suitable for the immobilization of the inhibitors. The behavior of immobilized ,1 -antitrypsin, bovine pancreatic trypsin inhibitor (BPTI), or elastatinal was separately studied. ,1 -Antitrypsin and BPTI were covalently immobilized by means of a diazotization process, whereas elastatinal was covalently attached via a condensation process mediated by glutaraldehyde. The inhibitory power of each membrane type was studied as a function of the amount of immobilized inhibitor and temperature. All active membranes have shown good inhibitory power. The most efficient membrane was that loaded with ,1 -antitrypsin, the less efficient that with BPTI. [source]

Circulating bone marrow-derived endothelial precursor cells contribute to neovascularization in diabetic epiretinal membranes

ACTA OPHTHALMOLOGICA, Issue 2009
A ABU EL ASRAR
Purpose Role of vasculogenesis, recruitment and differentiation of circulating bone marrow-derived endothelial precursor cells into mature endothelium, in proliferative diabetic retinopathy (PDR) remains undefined. We investigated the presence of bone marrow-derived endothelial precursor cells and the expression of the chemotactic pathway SDF-1/CXCL12?CXCR4 in PDR epiretinal membranes. Methods Membranes from 8 patients with active PDR and 9 patients with inactive PDR were studied by immunohistochemistry using antibodies against CD133, vascular endothelial growth factor receptor-2 (VEGFR-2), CD14, SDF-1 and CXCR4. Results Blood vessels expressed CD133, VEGFR-2, CD14, SDF-1 and CXCR4 in 10, 10, 10, 7 and 7 out of 17 membranes, respectively. There were significant correlations between number of blood vessels expressing CD34 and number of blood vessels expressing CD133 (rs=0.646; p=0.005), VEGFR-2 (rs=0.704; p=0.002), CD14 (rs=0.564; p=0.018), and SDF-1 (rs=0.577; p=0.015). Stromal cells in close association with blood vessels expressed CD133, VEGFR-2, CD14, and CXCR4 in 10, 12, 13, and 14 membranes, respectively. Number of blood vessels expressing CD133 (p=0.013), VEGFR-2 (p=0.005), CD14 (p=0.008) and SDF-1 (p=0.005), and stromal cells expressing CD133 (p=0.003), VEGFR-2 (p=0.013) and CD14 (p=0.002) was significantly higher in active membranes than in inactive membranes. Conclusion Bone marrow-derived CD133+ endothelial progenitor cells and CD14+ monocytes may contribute to vasculogenesis in PDR. [source]

Expression of advanced glycation end products and related molecules in diabetic fibrovascular epiretinal membranes

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 1 2010
Ahmed M Abu El-Asrar MD PhD
Abstract Purpose:, To investigate associations between expressions of advanced glycation end products (AGEs), transforming growth factor-, (TGF-,), tumour necrosis factor-, (TNF-,) and integrins and correlations between their expression and level of vascularization and proliferative activity in diabetic fibrovascular epiretinal membranes. Methods:, Membranes from eight patients with active proliferative diabetic retinopathy and nine patients with inactive proliferative diabetic retinopathy were studied by immunohistochemistry. Results:, Blood vessels expressed AGEs, TGF-,, TNF-, and ,v,3 integrin in 5, 13, 8 and 8 membranes, respectively. Stromal cells expressed AGEs, TNF-, and ,v,3 integrin in 15, 13 and 3 membranes, respectively. There was no immunoreactivity for ,v,5, ,5,1 and ,2,1 integrins. There were significant correlations between number of blood vessels expressing CD34 and number of blood vessels expressing AGEs (rs = 0.496; P = 0.043), TGF-, (rs = 0.777; P < 0.001) and TNF-, (rs = 0.699; P = 0.002). There were significant correlations between number of blood vessels expressing AGEs and number of blood vessels expressing TGF-, (rs = 0.532; P = 0.028) and TNF-, (rs = 0.626; P = 0.007). The correlation between number of blood vessels expressing TNF-, and ,v,3 integrin was significant (rs = 0.617; P = 0.008). Number of blood vessels expressing CD34 (P = 0.001), TGF-, (P = 0.006) and TNF-, (P = 0.002) and stromal cells expressing AGEs (P = 0.001) and TNF-, (P = 0.004) were significantly higher in active membranes than in inactive membranes. Conclusion:, Interactions of AGEs, TGF-,, TNF-, and ,v,3 integrin might be involved in pathogenesis of proliferative diabetic retinopathy fibrovascular proliferation. [source]