Designing Advanced Cross-Linked Proton Exchange Membranes with Enhanced Structural Homogeneity and Proton Conductivity via Radiation-Induced RAFT Polymerization.

This study introduces an innovative approach to fabricate well-defined cross-linked proton exchange membranes (PEMs) using radiation-induced reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization on cost-effective ethylene tetrafluoroethylene (ETFE) films. The incorporation of the RAFT mechanism into the cross-linking process significantly enhanced structural homogeneity, providing uninterrupted proton conductivity. Thorough characterizations confirmed the successful grafting of polystyrene (PS) chains onto ETFE films and subsequent sulfonation. Despite a reduction in proton conductivity attributed to restricted chain movements, a notable improvement in chemical stability was observed after cross-linking reactions. Chemical stability of the cross-linked membranes increased approximately 4-fold compared to those synthesized without a cross-linker. The synthesized PEMs with degrees of grafting at 45% and 67% demonstrated superior proton conductivity, outperforming various alternatives, including commercial Nafion samples. Specifically, these cross-linked membranes exhibited promising proton conductivity values of 93.7 and 139.1 mS cm-1, respectively. This work highlights the potential of radiation-induced RAFT-mediated polymerization in carrying out cross-linking reactions as an efficient pathway for designing well-defined high-performance PEMs, offering enhanced homogeneity and conductivity compared to existing literature counterparts.

The Effect of Ascorbic Acid (Vitamin C) on Transepithelial Corneal Cross-Linking in Rabbits.

PURPOSE: To evaluate the effects of ascorbic acid (vitamin C), the main antioxidant agent in the cornea on transepithelial corneal cross-linking (CXL) where the main mechanism is oxidation. METHODS: Twenty eyes of 20 rabbits were divided into 3 groups: Group 1 (7 eyes) had transepithelial corneal CXL after being fed with normal diet; Group 2 (7 eyes) had corneal CXL after once-daily subcutaneous injections of 200 mg of ascorbic acid in addition to normal diet; and the control group (6 eyes) was fed with normal diet but did not have corneal CXL performed. Ascorbic acid levels were measured in aqueous humor and plasma, and biomechanical measurements were applied to the cornea. RESULTS: There was a significant difference in ascorbic acid levels of plasma (P = 0.008) and aqueous humor (P = 0.006) between group 1 and 2. The Young's modulus values of group 1 and 2 were similar (P = 0.741) and were significantly higher than the control group (P = 0.02 and P = 0.01). The increase rate in Young's modulus values was 37.3% in group 1 and 43.9% in group 2 compared to control group. The ultimate strain values in group 1 and 2 were similar (P = 0.632) and were significantly higher than control group (P = 0.04, P = 0.03). The ultimate stress values in group 1 and 2 were similar (P = 0.836) and were significantly lower than control group (P = 0.001, P = 0.001). CONCLUSIONS: Systemic vitamin C does not appear to decrease effectiveness of transepithelial corneal CXL. Therefore, there is no reason to stop or reduce vitamin C supplementation before corneal CXL therapy.

Analysis of CASP8 D302H Gene Variants in Patients with Primary Brain Tumors.

BACKGROUND: Alteration in cell-cycle control and apoptosis pathways play important roles in tumorigenesis. Caspase-8 (CASP8) is a member of the cysteine protease family, that is implicated in apoptosis regulation. The present study was designed to investigate the possible role of CASP8 D302H gene polymorphism in the tumor development. MATERIALS AND METHODS: A total of 91 patients with brain tumors (including 39 meningioma and 52 glioma cases) and 114 healthy controls were included in the study. We investigated CASP8 D302H polymorphism by using polymorphism chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. RESULTS: The CASP8 D302H polymorphism genotypic frequencies were not statistically significantly different between meningioma cases and controls, with frequencies of GG, GC and CC genotypes of 71.2%, 19,2% and 9.6%; and 57.9%, 36.8% and 5.3%, respectively. The GG/CC genotypic frequencies were significantly increased in patients with glioma patients compared to controls (p=0.023) (χ(2)=5.149, odds ratio [OR]=1.27, 95% confidence interval [CI]=1.054-1.551). According to tumor characteristics, there were no statistically significant differences within the groups with astrocytic, oligoastrocytic tumors and oligodentriogliomas. CONCLUSION: D302H polymorphism of CASP8 gene may be associated with increased risk of glioma but larger study groups in different ethnic populations are needed to better elucidate the role of CASP8 gene polymorphism in the pathogenesis of primary brain tumors.