The present work characterizes the formation of free radicals in an implantable human acellular dermal tissue (Alloderm, LifeCell Corp., Branchburg, NJ) upon irradiation. The tissue was preserved in a vitreous carbohydrate matrix by freeze-drying. Freeze-dried samples were irradiated using a synchrotron light source, and free radicals generated were investigated using the electron paramagnetic resonance (EPR) technique. At least two free radical populations, with g factors of 1.993 (approximately 43%) and 2.002 (approximately 57%), respectively, were identified in the irradiated tissue. The transformation (reaction) kinetics of free radicals produced was investigated in the presence of nitrogen, oxygen and moisture. The reaction kinetics of free radicals was extremely slow in the nitrogen environment. The presence of oxygen and moisture greatly accelerated free radical reactions in the tissue matrix. The reaction of free radicals could not be described by traditional reaction kinetics. A dispersive kinetics model and a diffusion model were developed to analyze the reaction kinetics in the present study. The dispersive model took into consideration molecular mobility and dispersivity of free radicals in the heterogeneous tissue material. The diffusion model described the radical reaction kinetics as two parallel and simultaneous processes: a first-order fast kinetics mainly on tissue surface and a diffusion-limited slow kinetics in deeper layers of the tissue matrix. Both models described quantitative experimental data well. Further investigation is needed to verify whether any of these two models or concepts describes the inherent radical reaction kinetics in the solid tissue matrix.
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ACS Chem Neurosci
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Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
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January 2025
State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Tianjin 300353, People's Republic of China.
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Devising advanced protocols to avoid harsh oxidants is of paramount interest in gold catalyzed redox reactions. To address this issue, electrochemical oxidation of precatalytic Au complexes to catalytically active Au in situ species has started to emerge as a potential alternative. Such endeavours not only unlocked the possibility of direct anodic oxidation of Au to Au, but also enables stepwise oxidation of Au to Au to Au through the mediation of electro-generated organic radicals.
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