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Chitosan (CS) is often used in hydrogels due to its natural origin, sustainability, non-toxicity, and biodegradability. However, the physicochemical properties of CS hydrogels generated via physical cross-linking are relatively poor. CS hydrogels were prepared by cross-linking with glutaraldehyde (GA) at different ratios ranging from 1% to 10% (w/w), using two different molecular weight CS. The swelling degree of hydrogels was investigated at pH 2.0, 5.6, and 7.4. The structure, morphology, and thermal characteristics of hydrogels were examined using Fourier transform infrared, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis, respectively. Compression tests were conducted using Zwick/Roell universal testing equipment following ASTM D695. In vitro degradation studies were performed in enzyme and enzyme-free mediums at pH 7.4. The study demonstrated that low molecular weight CS (L-CS) hydrogels have a lower sol content and higher swelling values than medium molecular weight CS (M-CS) hydrogels. Both L-CS and M-CS hydrogels cross-linked with 1% GA showed maximum swelling degrees at pH 2.0. Thermal analysis concluded that M-CS hydrogels have higher thermal stability than L-CS hydrogels. It was also found that the M-CS hydrogels have higher compressive moduli. The degradation experiments in both enzyme and enzyme-free media showed that L-CS hydrogels have higher degradation rates. Highlights * Chemically cross-linked hydrogels synthesized using low and medium molecular weight chitosan. * The mechanical and physical properties of medium and low molecular weight chitosan hydrogels were compared. * Degradation experiments were performed in both enzyme and enzyme-free media. * Swelling values decreased noticeably with the increasing molecular weight. * Low molecular weight chitosan improved the biodegradability of hydrogels. KEYWORDS chitosan, compressive strength, degradation, molecular weight, sol content, swelling, 1 | INTRODUCTION Hydrogels are a type of polymeric material with a hydrophilic character that allows them to retain enormous volumes of water within their matrix. (1) Chitosan (CS) is [...]

Optimization of chitosan nanoparticles (ChNs) production process employing a [2.sup.(5-2)] fractional factorial design was performed to analyze the influence of viscosity average molecular weight (40-120 kDa), the initial concentration of chitosan (2-5 g/L), the initial tripolyphosphate (TPP) concentration (0.8-1.2 g/L), the ratio chitosan/TPP (4/1-10/1) (VIV), and the stirring speed (300-700 rpm), on final nanoparticles size and zeta potential. The measured responses of average particle size and surface charge were determined on Zetasizer Nano ZS. ChNs were prepared using ionotropic cross-linking of chitosan and TPP and were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The experiments showed that the size of synthesized nanoparticles depended on initial concentration and molecular weight of chitosan, TPP concentration and stirring speed within the chosen levels. However, the zeta potential was significantly influenced by chitosan molecular weight, chitosan concentration and stirring speed. The FTIR analysis confirmed the interaction between negative charge of TPP with positive charge of chitosan through the appearance of new peaks at 1222 and 895 [cm.sup.-1] in produced ChNs. XRD and DSC analysis were used to evaluate the effect of crosslinking of chitosan on crystal structure of ChNs. KEYWORDS average size (AS), chitosan nanoparticles, zeta potential (ZP), 1 | INTRODUCTION Chitosan (Ch) is a natural, non-toxic, biocompatible, and biodegradable polysaccharide, [1,2] obtained by deacetylation of chitin, one of the most abundant natural polymers. [3] Nanoparticles prepared from [...]

Background In Mexico, obesity prevalence among adults increased from 23% in 2000 to 36% in 2018, approximately. Mexico has not defined short- or long-term obesity goals, obscuring the level of effort required to achieve a relevant impact. We aimed to explore potential obesity goals for 2030 and 2040 in Mexico and to estimate the required caloric reductions to achieve them. Methods and findings We obtained anthropometric and demographic information on the Mexican adult population (age [greater than or equal to]20 years) from the Health and Nutrition Surveys conducted in 2000, 2006, 2012, 2016, and 2018 (n = 137,907). Each survey wave is cross-sectional, multistage, and representative of the Mexican population at the national, regional, and urban/rural levels. Obesity prevalence was projected for 2030 and 2040 by combining population projections of energy intake by socioeconomic status (SES) with a weight-change microsimulation model taking into account individual-level information on sex, age, physical activity, and initial body weight and height. If current trends continue, Mexico's obesity prevalence is expected to increase from 36% (95% CI 35% to 37%) in 2018 to 45% (uncertainty interval [UI] 41% to 48%) in 2030 and to 48% (UI 41% to 55%) in 2040. Based on expert opinion, we identified 3 obesity goals scenarios: (1) plausible (38% in 2030 and 36% in 2040); (2) intermediate (33% in 2030 and 29% in 2040); and (3) ideal based on the average prevalence of Organization for Economic Co-operation and Development countries (OECD; 19%). We estimated the caloric reductions needed to achieve the goal scenarios using the microsimulation model. Obesity was projected to increase more rapidly in the low SES (around 34% in 2018 to 48% (UI 41% to 55%) in 2040), than in the middle (around 38% to 52% (UI 45% to 56%)), or high SES group (around 36% to 45% (UI 36% to 54%)). Caloric reductions of 40 (UI 13 to 60), 75 (UI 49 to 95), and 190 (UI 163 to 215) kcal/person/day would be needed to reach the plausible, intermediate, and the ideal (OECD) average scenarios for 2030, respectively. To reach the 2040 goals, caloric reductions of 74 (UI 28 to 114), 124 (UI 78 to 169), and 209 (UI 163 to 254) kcal/person/day would be required, respectively. Study limitations include assuming a constant and sedentary physical activity level, not considering cohort-specific differences that could occur in the future, and assuming the same caloric trends under no intervention and the obesity goal scenarios. Conclusions To reach the 3 obesity goals in 2040, caloric reductions between 74 and 209 kcal/day/person would be needed in Mexico. A package of new and stronger interventions should be added to existing efforts such as food taxes and warning labels on non-nutritious food., Author(s): Francisco Reyes-Sánchez 1, Ana Basto-Abreu 1, Rossana Torres-Álvarez 2, Martha Carnalla-Cortés 1, Alan Reyes-García 1, Boyd Swinburn 3,4, Rafael Meza 2, Juan A. Rivera 1, Barry Popkin 5,6, Tonatiuh [...]

A dispersive liquid-phase microextraction method combined with UV-vis spectrophotometry was utilized to highly selective determination of creatinine in human serum and urine samples. To overcome the interferences in complex matrices, creatinine reacted with 1,4-naphthoquinone-2- potassium sulfonate reagent to produce a red coloured product that could be extracted into a small volume of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF.sub.6]) ionic liquid solvent. To increase the sensitivity of the assay, gluconic acid capped silver nanoparticles (Ag NPs) were used. On addition of Ag NPs to the red coloured extracted product, the solution turned to blue accompanied with a red shift in wavelength around 620 nm that could be detected by the naked eye. The effective variables on the determination of creatinine such as concentration of the reagent, amount of formic and hydrochloric acids, type and volume of the extractant, and concentration of Ag NPs were investigated. Under the optimal conditions, the calibration plot was bimodal with linear ranges from 0.1 to 1.5 [micro]g [mL.sup.-1] and 1.5 to 105 [micro]g [mL.sup.-1] creatinine with a limit of detection 0.1 [micro]g [mL.sup.-1]. The relative standard deviation for five measurements at 35 [micro]g [mL.sup.-1] concentration level was 3.8%. The newly developed assay was used for the determination of creatinine in human serum and urine specimens with satisfactory results. Key words: creatinine, dispersive liquid phase microextraction, gluconic acid, silver nanoparticles, colorimetric method. Nous avons employe une methode de microextraction liquide-liquide dispersive couplee a la spectrophotometrie UV-visible pour doser de facon hautement selective la creatinine dans des echantillons de serum et d'urine humains. Pour resoudre le probleme des interferences dans les matrices complexes, nous avons fait reagir la creatinine avec le 1,4-naphtoquinone-2-sulfonate de potassium afin de former un produit de couleur rouge pouvant etre extrait dans un faible volume du liquide ionique hexafluorophosphate de 1hexyl-3-methylimidazolium ([HMIM][PF.sub.6]) comme solvant. Pour augmenter la sensibilite de l'essai, nous avons utilise des nanoparticules d'argent (NPAg) recouvertes d'acide gluconique. Lorsque nous avons ajoute les NPAg au produit rouge ainsi extrait, la solution a vire au bleu avec un deplacement des longueurs d'onde vers le rouge a environ 620 nm visible a l'ceil nu. Nous avons etudie les variables influencant le dosage de la creatinine, telles que la concentration du reactif, la quantite d'acide formique et chlorhydrique, le type et le volume de l'agent d'extraction ainsi que la concentration des NPAg. Dans les conditions optimales, la courbe d' etalonnage etait bimodale, avec des domaines de linearite allant de 0,1 a 1,5 [micro]g [mL.sup.-1] et de 1,5 a 105 [micro]g [mL.sup.-1] de creatinine et une limite de detection de 0,1 [micro]g [mL.sup.-1]. Le coefficient de variation (CV en %) de cinq mesures a une concentration de 35 [micro]g [mL.sup.-1] etait de 3,8 %. Nous avons mis a l'epreuve ce nouvel essai pour doser la creatinine dans des echantillons de serum et d'urine humains et nous avons obtenu des resultats satisfaisants. [Traduit par la Redaction] Mots-cles : creatinine, microextraction liquide-liquide dispersive, acide gluconique, nanoparticules d'argent, methode colorimetrique., Introduction Creatine is a compound found naturally in skeletal muscle tissue as phosphocreatine, which is responsible for producing a high-energy molecule called ATP inside cells. Excess creatine that is not [...]

Poly (lactic acid) (PLA) and PLA/nanohydroxyapatite (nHA) composites, containing 2 wt% and 5 wt% of nHA were subjected to in vitro hydrolytic degradation tests in saline phosphate solution at different temperatures (37[degrees]C, 48[degrees]C, 60[degrees]C, and 72[degrees]C) to accelerate degradation. Samples were characterized by water uptake, weight loss tests, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and visual analyses. Arrhenius equation was used to describe the behavior of weight loss as a function of time. The PLA activation energy of weight loss showed to be lower than that of the PLA/nHA composites, indicating that the incorporation of nHA retarded the hydrolytic degradation. The rate and percentage of weight loss increased with increasing temperature. All samples presented a decrease in [T.sub.g] and an increase in degree of crystallinity as a function of time. Incorporation of nHA retarded this behavior that showed to be more expressive in PLA containing 5 wt% nHA. KEYWORDS in vitro hydrolytic degradation tests, nanohydroxyapatite, poly (lactic acid), 1 | INTRODUCTION Poly (lactic acid) (PLA) is a biodegradable, bioresorbable, and biocompatible aliphatic thermoplastic polyester produced from renewable resources. [1] This polymer has been used in packaging and technical [...]

A reinforced double network (DN) hydrogel as a candidate for skin scaffold was prepared. It consists of Ocarboxymethyl chitosan, polyvinyl alcohol, honey, Ca[Cl.sub.2], and graphene oxide. The various concentrations of Ca[Cl.sub.2], namely, 30, 45, and 60 wt% were investigated. Besides, the GO content was studied as 3, 5, and 10 wt%. The structure of the DN was characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, energy dispersive X-ray and Brunauer-Emmett-Teller were evaluated. The mechanical properties were studied, too. It showed that the DN with 45 wt% Ca[Cl.sub.2] was optimized. Also, swelling mechanism was investigated. Moreover, with the increase in GO content, the mechanical strength was increased. The cytotoxicity was evaluated and it was indicated that DN with 45% Ca[Cl.sub.2] and 5% GO had an acceptable level of biocompatibility. Moreover, scanning electron microscopy images showed the porous structure of the DN nanocomposite. Thus, the DN has the potential to be applied in tissue engineering as a skin scaffold., INTRODUCTION Organs and tissues may be injured during an accident or sickness. To treat the injured organ, one strategy is to use tissue engineering, in which the new organ is [...]

Background/Objective Evidence from non-human species indicate that hydration and arginine vasopressin (AVP) influence fuel selection, energy expenditure (EE), and food intake, but these relationships are unclear in humans. We sought to assess whether hydration biomarkers [24-h urine volume (UVol) and urine urea nitrogen concentration (UUN)] and copeptin (a surrogate for AVP) are associated with 24-h EE, respiratory quotient (RQ), and daily energy intake (DEI). Subjects/Methods In a secondary analysis of collected data, we selected healthy adults (Group 1, n = 177) who had 24-h whole-room indirect calorimetry measurements in energy balance with 24-h urine collection and fasting copeptin measurements (n = 117), followed by 3 days ad libitum food intake. A separate group (Group 2, n = 284) with hydration markers and calorimetry measurements was also studied. The main outcome measures were 24-h RQ, 24-h EE, DEI, substrate oxidation. Results In Group 1, lower 24-h UVol and higher 24-h UUN, indicating lower hydration, were correlated with lower 24-h RQ (r = 0.35, p < 0.0001, and r = -0.29, p = 0.0001, respectively; results similar in Group 2) and predicted subsequent reduced DEI (r = 0.20, p = 0.01, and r = -0.27, p = 0.0003, respectively), adjusted for confounders. Copeptin was independently associated with 24-h lipid oxidation (r = -0.23, p = 0.01). In Group 2, lower hydration was associated with reduced 24-h EE (24-h UVol: r = 0.29, p < 0.0001; 24-h UUN: r = -0.25, p < 0.0001). Conclusions Hydration biomarkers were associated with metabolic differences characterized by altered food intake, fuel selection, and possibly EE. Independently, copeptin was associated with higher lipid oxidation., Author(s): Douglas C. Chang [sup.1], Alessio Basolo [sup.1], Paolo Piaggi [sup.1], Susanne B. Votruba [sup.1], Jonathan Krakoff [sup.1] Author Affiliations: (1) Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and [...]

A new activity model for Fe-Mg-Al biotites is formulated, which extends that of Mg-Al biotites (Dachs and Benisek, Contrib Mineral Petrol 174:76, 2019) to the K.sub.2O-FeO-MgO-Al.sub.2O.sub.3-SiO.sub.2-H.sub.2O (KFMASH) system. It has the two composition variables X.sub.Mg = Mg/(Mg + Fe.sup.2+) and octahedral Al, and Fe-Mg and Mg-Al ordering variables resulting in five linearly independent endmembers: annite (Ann, K[Fe].sup.M1[Fe].sub.2.sup.M2[Al.sub.0.5Si.sub.0.5].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2, phlogopite (Phl, K[Mg].sup.M1[Mg].sub.2.sup.M2[Al.sub.0.5Si.sub.0.5].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2, ordered Fe-Mg biotite (Obi, K[Fe].sup.M1[Mg].sub.2.sup.M2[Al.sub.0.5Si.sub.0.5].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2, ordered eastonite (Eas, K[Al].sup.M1[Mg].sub.2.sup.M2[Al].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2, and disordered eastonite (Easd, K[Al.sub.1/3Mg.sub.2/3].sup.M1[Al.sub.1/3Mg.sub.2/3].sub.2.sup.M2[Al].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2. The methods applied to parameterize the mixing properties of the model were: calorimetry, analysis of existing phase-equilibrium data, line-broadening in powder absorption infrared (IR) spectra, and density functional theory (DFT) calculations. For the calorimetric study, various biotite compositions along the annite-phlogopite, annite-siderophyllite (Sid, K[Al].sup.M1[Fe].sub.2.sup.M2[Al].sub.2.sup.T1[Si].sub.2.sup.T2O.sub.10(OH).sub.2), and annite-eastonite joins were synthesized hydrothermally at 700 °C, 4 kbar and logf.sub.O2 of around - 20.2, close to the redox conditions of the wüstite-magnetite oxygen buffer at that P-T conditions. The samples were characterised by X-ray powder diffraction (XRPD), energy-dispersive scanning electron microprobe analysis, powder absorption IR spectroscopy, and optical microscopy. The samples were studied further using relaxation calorimetry to measure their heat capacities (C.sub.p) at temperatures from 2 to 300 K. The measured C.sub.p/T was then integrated to get the calorimetric (vibrational) entropies of the samples at 298.15 K. These show linear behaviour when plotted as a function of composition for all three binaries. Excess entropies of mixing are thus zero for the important biotite joins. Excess volumes of mixing are also zero within error for the three binaries Phl-Ann, Ann-Sid, and Ann-Eas. KFMASH biotite, therefore, has excess enthalpies which are independent of pressure and temperature (W.sup.G.sub.ij = W.sup.H.sub.ij). A least-squares procedure was applied in the thermodynamic analysis of published experimental data on the Fe-Mg exchange between biotite and olivine, combined with phase-equilibrium data for phlogopite + quartz stability and experimental data for the Al-saturation level of biotite in the assemblage biotite-sillimanite-sanidine-quartz-H.sub.2O to constrain enthalpic mixing parameters and to derive enthalpy of formation values for biotite endmembers. For Fe-Mg mixing in biotite, the most important binary, this gave best-fit asymmetric Margules enthalpy parameters of W.sup.H.sub.AnnPhl = 14.3 ± 3.4 kJ/mol and W.sup.H.sub.PhlAnn = -8.8 ± 8.0 kJ/mol (3-cation basis). The resulting asymmetric molar excess Gibbs free energy (G.sub.ex) departs only slightly from ideality and is negative at Fe-rich and positive at Mg-rich compositions. Near-ideal activity-composition relationships are thus indicated for the Ann-Phl binary. The presently used low value of - 2 kJ/mol for the enthalpy change of the reaction 2/3 Phl + 1/3 Ann = Obi is generally confirmed by DFT calculations that gave - 2 ± 3 kJ/mol for this âH.sub.Fe-Mg order, indicating that Fe-Mg ordering in biotite is weak. The large enthalpy change of âH.sub.Mg-Al disorder = 34.5 kJ/mol for the disordering of Mg and Al on the M sites in Eas (Dachs and Benisek 2019) is reconfirmed by additional DFT calculations. In combination with W.sup.H.sub.PhlEas = 10 kJ/mol, which is the preferred value of this study describing mixing along the Phl-Eas join, Mg-Al disordering over the M sites of biotite is predicted to be only significant at high temperatures > 1000 °C. In contrast, it plays no role in metamorphic P-T settings., Author(s): Edgar Dachs [sup.1], Artur Benisek [sup.1] Author Affiliations: (1) grid.7039.d, 0000000110156330, Fachbereich Chemie und Physik der Materialien, Abteilung Mineralogie, Universität Salzburg, , Jakob-Haringerstrasse 2a, 5020, Salzburg, Austria Introduction Numerous [...]

Purpose We assessed the effects of early goal-directed nutrition (EGDN) vs. standard nutritional care in adult intensive care unit (ICU) patients. Methods We randomised acutely admitted, mechanically ventilated ICU patients expected to stay longer than 3 days in the ICU. In the EGDN group we estimated nutritional requirements by indirect calorimetry and 24-h urinary urea aiming at covering 100% of requirements from the first full trial day using enteral and parenteral nutrition. In the standard of care group we aimed at providing 25 kcal/kg/day by enteral nutrition. If this was not met by day 7, patients were supplemented with parenteral nutrition. The primary outcome was physical component summary (PCS) score of SF-36 at 6 months. We performed multiple imputation for data of the non-responders. Results We randomised 203 patients and included 199 in the intention-to-treat analyses; baseline variables were reasonably balanced between the two groups. The EGDN group had less negative energy (p < 0.001) and protein (p < 0.001) balances in the ICU as compared to the standard of care group. The PCS score at 6 months did not differ between the two groups (mean difference 0.0, 95% CI -5.9 to 5.8, p = 0.99); neither did mortality, rates of organ failures, serious adverse reactions or infections in the ICU, length of ICU or hospital stay, or days alive without life support at 90 days. Conclusions EGDN did not appear to affect physical quality of life at 6 months or other important outcomes as compared to standard nutrition care in acutely admitted, mechanically ventilated, adult ICU patients. Clinicaltrials.gov identifier no. NCT01372176., Author(s): Matilde Jo Allingstrup [sup.1], Jens Kondrup [sup.2], Jørgen Wiis [sup.1], Casper Claudius [sup.1], Ulf Gøttrup Pedersen [sup.1], Rikke Hein-Rasmussen [sup.1], Mads Rye Bjerregaard [sup.1], Morten Steensen [sup.1], Tom Hartvig [...]