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Abdul Soumphonphakdy
Abstract:The utilization of cellulose to its full potential is constrained by its recalcitrance to dissolution resulting from the rigidity of polymeric chains, high crystallinity, high molecular weight, and extensive intra- and intermolecular hydrogen bonding network. Therefore, pretreatment of cellulose is usually considered as a step that can help facilitate its dissolution. We investigated the use of microwave oxygen plasma as a pre-treatment strategy to enhance the dissolution of cotton fibers in aqueous NaOH/Urea solution, which is considered to be a greener solvent system compared to others. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Powder X-ray Diffraction analyses revealed that plasma pretreatment of cotton cellulose leads to physicochemical changes of cotton fibers. Pretreatment of cotton cellulose with oxygen plasma for 20 and 40 min resulted in the reduction of the molecular weight of cellulose by 36% and 60% and crystallinity by 16% and 25%, respectively. This reduction in molecular weight and crystallinity led to a 34% and 68% increase in the dissolution of 1% (w/v) cotton cellulose in NaOH/Urea solvent system. Thus, treating cotton cellulose with microwave oxygen plasma alters its physicochemical properties and enhanced its dissolution.Keywords: cotton fiber; cellulose; oxygen plasma; molecular weight; surface modification
Due to the limited amount of compound stocks, we decided to implement the screening of chemical boxes in singlet, with primary evaluation of all compounds at a fixed dose and further dose-response analysis of unconfirmed hits in a secondary screening. As expected, given the error-prone nature of the single-well (single dose, single replicate) measurements used in primary screening, significant discrepancies in inhibition were observed for some compounds in comparison to secondary dose-response evaluation. These discrepancies are common and may be due to a variety of factors [25]. Besides intrinsic compound-specific and experimental data variability [26], these factors may include solubility issues (given that in primary and secondary screenings both the final concentration and serial-dilution protocol were different), differential stability of compounds in stock (10 mM) and working (2 mM) solutions [27], unintended absorption of the compounds to different containing materials during storage, moderate dose-dependent quenching effects of compounds on fluorescence readouts, among others [28]. In addition, although we included 0,01% Triton X-100 in assay buffer, compound-specific aggregate formation was not tested and thus, cannot be dismissed.
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