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In this work, a double-layered three-dimensional (3D) microfluidic paper-based analytical device (μPAD) with high resolution temporally resolved chemiluminescence (CL) emissions were designed for multiplexed CL analysis. The temporally resolved CL emissions were obtained by virtue of the 3D branched microfluidic channel design, which create time delays for luminol transported from one detection zone to another. The peak intensity and peak shape of the temporally resolved CL emissions were quite stable and base-line separated with resolution as high as 21.2-24.4. Then, the fabricated μPAD was applied to multiplexed determination of glucose, lactate, cholesterol, and choline as model analytes. The sample was added to four detection zone modified with CL catalyst cobalt ion and different oxidase by virtue of chitosan. When luminol flowed to μPAD, four temporally resolved CL peaks were successively generated from the cobalt ion catalyzed CL reactions between luminol and generated H 2 O 2 from the specific enzymatic reactions between the oxidase and the analytes. The generated four CL emission peaks in the CL kinetic curve increased in proportion to the concentrations of glucose, lactate, cholesterol, and choline, respectively. Finally, four linear calibration curves were obtained for the detection of glucose (0.01-1.0 mmol/L), lactate (0.02-5.0 mmol/L), cholesterol (0.01-0.4 mmol/L), and choline (0.001-1.0 mmol/L). The detection limits were as low as 8 μmol/L, 15 μmol/L, 6 μmol/L, and 0.07 μmol/L for glucose, lactate, choline, and cholesterol detection, respectively. The present work provides a new strategy for the fabrication of simple and sensitive 3D μPAD with high resolution temporally resolved CL emissions for multiplexed CL analysis, which holds great application potential for point-of-care diagnosis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Developing green and simple methods for the preparation of cellulose nanofibrils (CNFs) is of great significance. Herein, a green deep eutectic solvent (DES) system based on choline chloride (ChCl) and citric acid (CA) is employed to pretreat cellulose fibers for the preparation of CNFs. The effect of the pretreatment temperature on the chemo-physical properties of the CNFs is comprehensively investigated. A high CNFs yield of up to 84.19% can be achieved under optimized conditions. The optimal CNFs show a narrow diameter distribution and length up to several microns, high crystallinity and thermal stability, as well as excellent dispersibility in water. Furthermore, semi-transparent and flexible cellulose nanopaper (CNP) was fabricated through a facile vacuum filtration process. The optimal CNP shows high tensile strength (175.15 MPa) and toughness (7.51 MJ/m 3 ). Therefore, this work provides a sustainable and facile approach to fabricate CNFs and CNP, which can be potentially used for various high-tech applications., (Copyright © 2021. Published by Elsevier Ltd.)

Treating ground bagasse or Southern yellow pine in the biodegradable ionic liquid (IL), choline acetate ([Cho][OAc]), at 100°C for 24h led to dissolution of hemicellulose and lignin, while leaving the cellulose pulp undissolved, with a 54.3% (bagasse) or 34.3% (pine) reduction in lignin content. The IL solution of the dissolved biopolymers can be separated from the undissolved particles either by addition of water (20 wt% of IL) followed by filtration or by centrifugation. Hemicellulose (19.0 wt% of original bagasse, 10.2 wt% of original pine, containing 14-18 wt% lignin) and lignin (5.0 wt% of original bagasse, 6.0 wt% of original pine) could be subsequently precipitated. The pulp obtained from [Cho][OAc] treatment can be rapidly dissolved in 1-ethyl-3-methylimidazolium acetate (e.g., 17 h for raw bagasse vs. 7h for pulp), and precipitated as cellulose-rich material (CRM) with a lower lignin content (e.g., 23.6% for raw bagasse vs. 10.6% for CRM)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Graphical abstract Highlights • A double-layered μPAD with multiple colorimetric indicators was fabricated. • Simultaneous detection of four biomolecules including glucose, uric acid, lactate, and choline was achieved. • The proposed μPAD exhibited effectively improved colorimetric performance, enhanced sensitivity and extended detection range. Abstract In this work, a double-layered microfluidic paper-based device (μPAD) with multiple colorimetric indicators was presented for the sensitive simultaneous detection of four kinds of small biomolecules, including glucose, uric acid, lactate, and choline in mixture. The double-layered μPAD were composed of the top detection layer and the bottom auxiliary layer to construct 3D microfluidic channels. The detection zones on the top detection layer were modified with various colorimetric reagents, different kinds of oxidase (glucose oxidase, uricase, lactate oxidase or choline oxidase) and horseradish peroxidase (HRP). The immobilized chromogenic reagents could be oxidized by the generated H 2 O 2 from the specific enzymatic reactions between the oxidases and their corresponding substrates to form different colored products with co-immobilized HRP as catalyst. As a result, four linear calibration curves were obtained for the determination of glucose (0.01–10.0 mmol/L), uric acid (0.01–5.0 mmol/L), lactate (0.04–10.0 mmol/L), and choline (0.04–24.0 mmol/L), respectively. The proposed double-layered μPAD with multiple colorimetric indicators exhibited good colorimetric performance, effectively improved sensitivity, and extended linear range, which was further applied to the simultaneously determination of glucose, uric acid, lactate, and choline in serum samples. [ABSTRACT FROM AUTHOR]

The biosynthesis of acetylcholine and the fate of intravenously administered choline [methyl- 3-H] were studied in guinea pigs anesthetized with pentobarbital. Choline and acetylcholine were isolated by paper electrophoresis and estimated by use of a specific enzymatic (choline kinase) - radioisotopic assay. The concentration of acetylcholine ranged from 25.5 to 1.1 nmol/g in the following tissues (in order of decreasing concentration): duodenum, corpus striatum, stomach, cerebral cortex, spinal cord, abdominal fat, submaxillary gland, kidney, adrenal gland, spleen, liver, lung, heart and diaphragm. Choline [methyl- 3-H] was converted in the tissues to acetylcholine within 3 minutes after intravenous administration of the precursor. Virtually all the radioactivity in plasma at that time was present as free choline, suggesting that free choline from plasma is the immediate precursor for acetylcholine synthesized in the tissues cited. The concentration of free choline in tissues ranged from 344 nmol/g in adrenals to 40 nmol/g in heart, while that in plasma was 15 nmol/g. The initial half-life of choline in plasma, estimated from the rate of disappearance of choline after intravenous administration of either a tracer dose of choline [methyl- 3-H] (0.031 mumol/kg) or a high dose of choline chloride (200 mumol/kg), was less than 1 minute. This rapid removal of choline from plasma resulted from uptake (or binding) by tissues, with kidney and liver removing about 50% of the administered dose of choline [methyl- 3-H] within 3 minutes after its administration. Uptake of choline occurred in all tissues cited above, but there was a 20-fold difference in the uptake by the most active tissues (kidney and adrenals), as compared to that of the least active (central nervous system). Within 60 minutes after administration of choline [methyl- 3-H], most of the radioactive choline taken up by tissues had been converted to organic-soluble metabolites and to water-soluble metabolites that behaved like either phosphorylcholine or betaine during paper electrophoresis and chromatography. Betaine was the principal metabolite of choline in plasma. Radioactivity was excreted slowly into urine, which contained primarily free choline, betaine and a large amount of an unidentified metabolite. These findings indicate that the principal mechanism for the rapid removal of choline from plasma is uptake into tissues followed by metabolism.

Concentrations and specific radioactivities of choline, acetylcholine, phosphorylcholine, lipid choline, and sn-glycero-3-phosphorylcholine after i.v. injection of methyl-14C-choline were measured in the brain of untreated controls and of rats anesthesized with urethane. The specific activity was found to be decreased during deep anesthesia by 40% in acetylcholine, 20-30% in phosphorylcholine, 50-75% in lipid choline, and 30-40% in sn-glycero-3-phosphoryl-choline. No significant change was detected in the specific activity of choline. The brain concentration of acetylcholine was increased by 40%, the concentration of sn-glycero-3-phosphorylcholine, however, was diminished by 10% during anesthesia. No change was found in the concentration of the other choline containing compounds investigated. Measuring choline incorporation into 4 subcellular fractions of brain tissue specific activities were found to be decreased by the same percentage, although 2 fractions (nuclei and microsomes) were higher labelled than the 2 other fractions (crude mitochondria with synaptosomes and lysosomes). A correlation between the biochemical and the functional alterations is supported by the dose-effect relationships on both parameters. It is suggested that urethane reduces turnover of lipids and by that mechanism inhibits the exocytotic release of the transmitter from presynaptic nerve endings.

1. Labelled precursors of choline, namely ethanolamine, dimethylaminoethanol and methionine and also labelled choline itself were injected intraperitoneally into the adult female rat and the incorporation into lipids and water-soluble fractions was traced in liver, blood and brain. 2. No significant free choline was detected and no labelling of the phosphorylcholine of blood. There was, however, considerable labelling of the phosphorylcholine of brain and liver. 3. After intracerebral injection, [1,2-(14)C]dimethylaminoethanol was rapidly phosphorylated and converted into phosphatidyldimethylaminoethanol, presumably by the cytidine pathway. 4. In view of the pattern of labelling and the amount of phosphatidylcholine in the tissues examined, it seems highly likely that choline is transported to the brain by the blood in a lipid-bound form.

Phosphorylcholine-1,2-(14)C and choline-1,2-(14)C-labeled cytidine diphosphate choline are incorporated into lecithin by whole homogenates and particulate fractions of rat retina with optimal incorporation of label by the microsomal fraction. The soluble fraction contains a factor(s) which stimulates incorporation of label with release of inorganic phosphate. Mg(++) is required for optimal incorporation of intermediates into lecithin in the presence of added diglycerides; without added diglycerides, incorporation of phosphorylcholine or cytidine diphosphate choline was moderately stimulated by preincubating the system in the absence of Mg(++) with added phosphatidic acid and by adding this mixture to fresh enzyme and the complete incubation mixture (including Mg(++)). The results show that the retina is capable of de novo synthesis of phosphatides and suggest that the rod outer segments depend on the pigment epithelium and(or) the inner rod segments for a source of phospholipids. Coenzyme A and ATP added to whole homogenate of retina did not significantly increase the incorporation of CDP-choline-1,2-(14)C into lecithin but slightly increased the radioactivity found in lysolecithin and sphingomyelin. Rats with hereditary retinitis pigmentosa have an abnormally high lipid phosphorus content of the retina, but they do not incorporate labeled CDP-choline into lecithin of retina at a higher rate than do normal animals.

Permeability of the cardiac cell membrane to choline ions was estimated by measuring radioactive choline influx and efflux in cat ventricular muscle. Maximum values for choline influx in 3.5 and 137 mM choline were respectively 0.56 and 9 pmoles/cm(2).sec. In 3.5 mM choline the intracellular choline concentration was raised more than five times above the extracellular concentration after 2 hr of incubation. In 137 mM choline, choline influx corresponded to the combined loss of intracellular Na and K ions. Paper chromatography of muscle extracts indicated that choline was not metabolized to any important degree. The accumulation of intracellular choline rules out the existence of an efficient active pumping mechanism. By measuring simultaneously choline and sucrose exchange, choline efflux was analyzed in an extracellular phase, followed by two intracellular phases: a rapid and a slow one. Efflux corresponding to the rapid phase was estimated at 16-45 pmoles/cm(2).sec in 137 mM choline and at 1.3-3.5 pmoles/cm(2).sec in 3.5 mM choline; efflux in 3.5 mM choline was proportional to the intracellular choline concentration. The absolute figures for unidirectional efflux were much larger than the net influx values. The data are compared to Na and Li exchange in heart cells. Possible mechanisms for explaining the choline behavior in heart muscle are discussed.