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Allergic Contact Dermatitis from Rubber and Plastic Gloves
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
Epoxy resin monomers are strong skin sensitizers known to cause occupational allergic contact dermatitis. Diglycidyl ethers of bisphenol A and F (DGEBA and DGEBF) are widely used as components in epoxy resin products. Alternative compounds have been designed, synthesized, and assessed for sensitizing potency using in vivo murine local lymph node assay. Studies have shown that the allergenic effects of diglycidyl ethers of bisphenol F (DGEBF) depend on the absence of oxygen in the side chain of the molecule, known as the “terminal epoxide groups.”75 Thus, an epoxy resin that lacks oxygen in the side chain was considered promising and was synthesized. As predicted, the sensitizing potency was reduced by a factor of ten with the removal of the oxygen molecule. The technical properties of the newly synthesized polymer were not considered sufficient. Developing an alternative epoxy material is a delicate balance between allergenic activity and polymerization properties. The use of improved epoxy resin monomers with less skin sensitizing effects is one way to address contact allergy to epoxy resin.76
Ultrastructural Immunocytochemistry
Published in Joan Gil, Models of Lung Disease, 2020
Samuel S. Spicer, Bradley A. Schulte
The physicochemical nature of epoxy resins poses obstacles to immunostaining. First, the epoxy medium resists penetration by most staining reagents, particularly those of high molecular weight, because a medium sufficiently inelastic to yield ultrathin sections lacks the porosity needed to allow diffusion of reagents into it. Hydrophobicity of the medium presumably also plays a part in the impenetrability to reagents in aqueous solution. In addition, chemical reagents in the medium, including the oxidants effecting polymerization, adversely affect the antigenicity of cell constituents. The prolonged high temperature required for polymerization of the resin also contributes to denaturation of the antigen.
Environmental toxicants on Leydig cell function
Published in C. Yan Cheng, Spermatogenesis, 2018
Leping Ye, Xiaoheng Li, Xiaomin Chen, Qingquan Lian, Ren-Shan Ge
Bisphenols are a group of compounds with two hydroxyphenyl groups. The most abundantly produced bisphenol is bisphenol A (BPA). BPA is used to make certain plastics and epoxy resins. A human can be exposed to BPA via various sources such as indoor air, dust ingestion, and food.129 Human urine samples had significant levels of BPA with 95% detection.130–132 Men had higher BPA levels (1.49 ng/mL) than women (0.64 ng/mL), possibly because of androgen-related metabolism of BPA.133
Antimicrobial effectiveness of root canal sealers against Enterococcus faecalis
Published in Biomaterial Investigations in Dentistry, 2022
Paola Castillo-Villagomez, Elizabeth Madla-Cruz, Fanny Lopez-Martinez, Idalia Rodriguez-Delgado, Jorge Jaime Flores-Treviño, Guadalupe Ismael Malagon-Santiago, Myriam Angelica de La Garza-Ramos
Complete removal of microorganisms from the root canal system in all patients is impossible; therefore, filling materials with antimicrobial activity for the root canal are used to reduce microorganisms and prevent infections. On the other hand, many endodontic failures occur after removing necrotic or inflammatory tissue with microorganisms. These tissues need to be retreated and managed with apical surgery; however, filtration failure occurs in 15% to 22% [4]. These complications are attributed to the lack of root canal sealing after endodontic treatment due to the high hydrophobicity and water absorption caused by the solubility of the cement. The development of new ceramic-type materials has improved sealing to reduce this problem. Epoxy resin is widely used as a gold standard, although it still has limitations, such as mutagenicity, cytotoxicity, inflammation, and hydrophobicity. Calcium silicate-based sealers with high biocompatibility and hydrophilicity have also been introduced. Both cements reduce microfiltration thanks to properties in their dynamic environment and being biocompatible in this application [5].
The effect of 4.5 G (LTE Advanced-Pro network) mobile phone radiation on the optic nerve
Published in Cutaneous and Ocular Toxicology, 2021
Erkin Özdemir, Ülkü Çömelekoğlu, Evren Degirmenci, Gülsen Bayrak, Metin Yildirim, Tolgay Ergenoglu, Banu Coşkun Yılmaz, Begüm Korunur Engiz, Serap Yalin, Dilan Deniz Koyuncu, Erkan Ozbay
After VEP recordings, the animals were sacrificed by overdose ketamine. Following sacrifice, the optic nerves 2.5 mm proximal to the globes were isolated. Optic nerve samples were fixed to 2.5% glutaraldehyde solution for four hours. At the end of this period, the fixed tissues were washed with phosphate buffer. After application of standard electron microscope procedures, tissues were embedded in epoxy resin. From these blocks, 50–70 nm thick sections were taken with ultra-microtome (Leica UCT125, Leica GmbH, Germany), and these ultra-thin sections were contrasted with uranyl acetate and lead citrate solutions. Contrasted sections were examined by transmission electron microscopy (JEOL JEM1011, JEOL Corp., Tokyo, Japan). Later, they were photographed with a digital camera (Mega view III, Olympus GmbH, Germany) attached to the electron microscope.
Modified self-healing cementitious materials based on epoxy and calcium nitrate microencapsulation
Published in Journal of Microencapsulation, 2021
Fahimeh Farshi Azhar, Aylin Ahmadinia, Alireza Mohammadjafari Sadeghi
Epoxy resin because of its excellent chemical, physical, mechanical and thermal properties, is an effective candidate for healing agent. A wide variety of curing agents such as amines and anhydrides can be used for curing of epoxy resin at different temperatures (Reaz Chowdhury et al. 2015). Also, epoxy resin has the most matches with urea–formaldehyde in microencapsulation. Blaiszik et al. (2009) synthesised microcapsules containing PUF shell containing reactive epoxy resins core with different diluents. The prepared capsules meet the requirements for use in self-healing composites, containing processing survivability, thermal stability and efficient in situ rupture for delivery of the healing agents. Jin et al. (2012) studied the microcapsules comprise of hollow PUF shell and epoxy-amine healing agent. Yuan and Liang (2008) evaluated some effective factors in size and surface morphology of PUF microcapsules containing epoxy resins, such as type and concentration of surfactant, adjusting time for pH value and heating rate. But, in these studies, healing behaviour of the host matrix was not reported. On the other hand, the PUF-epoxy microcapsules have been studied mostly for self-healing in polymer-based composites by now, and few researches have been reported on its utilisation in cementitious materials (Dong et al.2016, Perez et al.2015).