Aqueous Solutions Of Methylcellulose Research Articles

Swallowing hydrodynamics visualization and aspiration quantification in a patient-specific pharyngolaryngeal model with varying epiglottis inversions

Impaired swallowing, or dysphagia, significantly affects patients' well-being and health. Nearly half of the patients with head and neck cancers experience dysphagia or aspiration following radiation therapy or surgery. However, current dysphagia management approaches are primarily symptom-based rather than etiology-specific, owing to a lack of clear understanding of aspiration mechanisms. This study aimed to understand the mechanisms of aspiration in an anatomically accurate pharyngolaryngeal model at different epiglottis angles. A biomechanical swallowing model was developed using transparent casts, and liquid flow dynamics were visualized using fluorescent dye from side and back views. Two liquids and two dispensing conditions were evaluated for their roles in aspiration. The results demonstrated distinct flow dynamics between water and a 1 ​% w/v methylcellulose aqueous solution and, to a lesser extent, between fast and slow dispensing for the same liquid. Three frequent aspiration sites were identified, including the interarytenoid notch, the cuneiform tubercular recess, and the vallecula, corresponding to aspiration mechanisms of notch overflow, recess overflow, and creeping flow, respectively. The angle of the epiglottis influenced flow dynamics in at least three ways: by facilitating gravity-assisted fluid movement, redistributing flow through the gap between the epiglottis tip and pharyngeal wall, and affecting creeping flow via the angle between the epiglottis base and hypopharynx. Slow dispensing of water to the anterior oropharynx resulted in a significantly high aspiration rate with a downward tilted epiglottis due to concurrent tubercle-recess overflow and vallecular creeping flow. The biomechanical model can serve as a testing platform for better understanding aspiration mechanisms and developing etiology-based strategies before and after treatments for head and neck cancers.

Sol-Gel Transition of a Thermo-Responsive Polymer at the Closest Solid Interface.

Thermo-responsive polymers are applied as surface modifications for the temperature switching of hydrophilic and hydrophobic properties through adsorption and grafting on solid substrates. The current understanding of the influence of polymer chains bound to the solid surface on the transition behavior of thermo-responsive polymers is rather restricted. In this study, we aim to elucidate the effect of the bound polymer chains at the interface on the thermo-responsive sol-gel transition behavior of aqueous methylcellulose (MC) solutions by employing a quartz crystal microbalance (QCM) to evaluate the shear modulus near the solid interface. When the sample thickness was thinner on the order of the millimeter scale, the sol-gel transition temperature evaluated by the cloud point decreased because the condensation of MC near the solid interface promoted the sol-gel transition. On the other hand, focusing on the closest solid interface on the nanometer scale by QCM, the sol-gel transition temperature increased when approaching the solid interface. Adsorption and interfacial interactions reduced the chain mobility and restrained the sol-gel transition by preventing MC chain aggregation. We demonstrated the physical properties evaluation at the closest interface between the thermo-responsive polymer and solid substrate by combining a simple analytical model of QCM and controlling the analytical depth of the QCM sensors. In conclusion, the mobility change of the bound polymer chains at the solid interface caused by adsorption and interfacial interactions must be considered when a thermo-responsive polymer is applied as in adsorbed or thin films on solid substrates for the functionalization of biomaterials.

Rapeseed oleogels based on monoacylglycerols and methylcellulose hybrid oleogelators: Physicochemical and rheological properties

In this study, we investigated the combined impact of monoacylglycerol (MAGs) and methylcellulose (MC) on the production of hybrid oleogels. Since cellulose derivatives are inherently hydrophilic substances, they require dissolution in oil through an emulsion-coating method. Therefore, we developed a hybrid oleogel utilizing MAGs and MC. Initially, a hybrid oleogelator was created by blending an aqueous MC solution into fully melted MAGs to form MC in water-in-MAGs emulsions with varying MC/MAG ratios, followed by drying. Subsequently, the resulting oleogelator was mixed with rapeseed oil to produce oleogels, and their properties were compared with oleogels produced solely with MAG oleogelator. The findings indicated that the obtained oleogelator did not significantly impact the oxidation of the oleogels. Additionally, there was no notable difference observed in the induction period of crystallization and the crystallization rate of the oleogels. Microscopic images revealed that the hybrid oleogel structured with a 30:70 ratio of MAGs and MC contained the lowest liquid phase percentage. In terms of rheological assessment, the hybrid oleogels exhibited solid-like behavior, consistent with polarized light microscopy (PLM) images. Furthermore, based on the three-interval thixotropic test (3-ITT), the hybrid oleogels displayed higher recovery compared to the control sample.

Design of High-Energy HMX-Based Composite ink and Research on Micro-Detonation Performance

ABSTRACT Using hydroxypropyl methylcellulose (HPMC) aqueous solution and polyethyleneimine (PEI) ethanol solution as the composite bonding system, adding a certain amount of silicone defoamer and toluene diisocyanate (TDI), studied the micro-size charge forming effect of sub-micron Octogen (HMX)-based composite ink under the 3D direct writing printing process and the detonation performance and safety of sub-micron Octogen (HMX) under micro-size charges. The results show that the explosive ink with a solid content (quality score) of 90% has the best rheological properties, excellent printability, and the surface of the molded sample is smooth. The impact energy and friction of the molded sample are 7 J and 324 N, respectively, which are lower than those of the raw material HMX 100% and 237.5%, showing excellent mechanical sensitivity safety performance. In addition, XRD and FTIR show that the HMX crystal form in the composite ink remains β-type, the measured density of the molded sample is 1.432 g·cm−1, the detonation velocity is 6982 m·s−1, and the critical detonation size is 1 × 0.0771 mm, showing excellent microchannel detonation performance.

Effects of Nozzle Retraction Elimination on Spray Distribution in Middle-Posterior Turbinate Regions: A Comparative Study.

The standard multi-dose nasal spray pump features an integrated actuator and nozzle, which inevitably causes a retraction of the nozzle tip during application. The retraction stroke is around 5.5 mm and drastically reduces the nozzle's insertion depth, which further affects the initial nasal spray deposition and subsequent translocation, potentially increasing drug wastes and dosimetry variability. To address this issue, we designed a new spray pump that separated the nozzle from the actuator and connected them with a flexible tube, thereby eliminating nozzle retraction during application. The objective of this study is to test the new device's performance in comparison to the conventional nasal pump in terms of spray generation, plume development, and dosimetry distribution. For both devices, the spray droplet size distribution was measured using a laser diffraction particle analyzer. Plume development was recorded with a high-definition camera. Nasal dosimetry was characterized in two transparent nasal cavity casts (normal and decongested) under two breathing conditions (breath-holding and constant inhalation). The nasal formulation was a 0.25% w/v methyl cellulose aqueous solution with a fluorescent dye. For each test case, the temporospatial spray translocation in the nasal cavity was recorded, and the final delivered doses were quantified in five nasal regions. The results indicate minor differences in droplet size distribution between the two devices. The nasal plume from the new device presents a narrower plume angle. The head orientation, the depth at which the nozzle is inserted into the nostril, and the administration angle play crucial roles in determining the initial deposition of nasal sprays as well as the subsequent translocation of the liquid film/droplets. Quantitative measurements of deposition distributions in the nasal models were augmented with visualization recordings to evaluate the delivery enhancements introduced by the new device. With an extension tube, the modified device produced a lower spray output and delivered lower doses in the front, middle, and back turbinate than the conventional nasal pump. However, sprays from the new device were observed to penetrate deeper into the nasal passages, predominantly through the middle-upper meatus. This resulted in consistently enhanced dosing in the middle-upper turbinate regions while at the cost of higher drug loss to the pharynx.

Understanding Self-Assembly and Molecular Packing in Methylcellulose Aqueous Solutions Using Multiscale Modeling and Simulations.

We present a multiscale molecular dynamics (MD) simulation study on self-assembly in methylcellulose (MC) aqueous solutions. First, using MD simulations with a new coarse-grained (CG) model of MC chains in implicit water, we establish how the MC chains self-assemble to form fibrils and fibrillar networks and elucidate the MC chains' packing within the assembled fibrils. The CG model for MC is extended from a previously developed model for unsubstituted cellulose and captures the directionality of H-bonding interactions between the -OH groups. The choice and placement of the CG beads within each monomer facilitates explicit modeling of the exact degree and position of methoxy substitutions in the monomers along the MC chain. CG MD simulations show that with increasing hydrophobic effect and/or increasing H-bonding strength, the commercial MC chains (with degree of methoxy substitution, DS, ∼1.8) assemble from a random dispersed configuration into fibrils. The assembled fibrils exhibit consistent fibril diameters regardless of the molecular weight and concentration of MC chains, in agreement with past experiments. Most MC chains' axes are aligned with the fibril axis, and some MC chains exhibit twisted conformations in the fibril. To understand the molecular driving force for the twist, we conduct atomistic simulations of MC chains preassembled in fibrils (without any chain twists) in explicit water at 300 and 348 K. These atomistic simulations also show that at DS = 1.8, MC chains adopt twisted conformations, with these twists being more prominent at higher temperatures, likely as a result of shielding of hydrophobic methyl groups from water. For MC chains with varying DS, at 348 K, atomistic simulations show a nonmonotonic effect of DS on water-monomer contacts. For 0.0 < DS < 0.6, the MC monomers have more water contacts than at DS = 0.0 or DS > 0.6, suggesting that with few methoxy substitutions, the MC chains are effectively hydrophilic, letting the water molecules diffuse into the fibril to participate in H-bonds with the MC chains' remaining -OH groups. At DS > 0.6, the MC monomers become increasingly hydrophobic, as seen by decreasing water contacts around each monomer. We conclude based on the atomistic observations that MC chains with lower degrees of substitutions (DS ≤ 0.6) should exhibit solubility in water over broader temperature ranges than DS ∼ 1.8 chains.

How does Poly(ethylene glycol) with varied chain length affect the thermo-responsive behavior of methyl cellulose in aqueous solutions?

In this study, by using a set of narrowly distributed polyethylene glycol (PEG) samples with varied average molar mass (PEGn, 9 <n < 454), we have systematically studied how PEG molar mass and solution concentration influence the thermal response behavior of methyl cellulose (MC) aqueous solutions (Mw = 4.3 × 105 g/mol, <Rg> = 71 nm) by a combination of isothermal titration calorimetry (ITC), rheometer, UV–vis spectroscopy, laser light scattering (LLS) and atomic force microscopy (AFM). At room temperature, ITC result clarifies the existence of extremely weak hydrophobic interactions between MC and PEG chains. In addition, for MC/PEG mixed solution with shorter PEGs (PEG22 and PEG90), experimentally measured zero-shear viscosity (ηexp) is confirmed to be 5–10% higher than the theoretical values (ηcalc), further supporting the interchain association. Whereas for MC/PEG454, insoluble aggregates are formed, which results in ηexp < ηcalc. Further, dynamic laser scattering (DLS) results further reveal how the percentage of peak area of aggregates depends on the chain length of PEG. During the heating process from T = 20 to 70 °C, a combination of UV, LLS and AFM results clearly illustrates that the shorter PEG chains can effectively stabilize the formed MC fibers and prevent the fiber extension; whereas for longer PEG chains, they can not only promote the nucleation process, but also destabilize the formed fibers and promote the fiber extension. Our result unambiguously reveals the macromolecular effect of PEGs on the thermal response behavior of MC in solutions.

Interfacial Selective Study on the Gelation Behavior of Aqueous Methylcellulose Solution via a Quartz Crystal Microbalance.

It is important to understand the interfacial structure and physical properties of a polymer material to improve its function. In this study, we used a quartz crystal microbalance (QCM) and neutron reflectivity (NR) measurements to evaluate the viscoelasticity and structure of an aqueous methylcellulose solution near the gold interface. The apparent shear modulus, which was calculated from the complex frequency, was used to assess gelation behavior. The apparent shear modulus determined via the QCM suggested high-frequency rheological properties that reflected the relaxation of skeletal stretching and rotational motion of polymer segments, as well as cooperative motion of the various functional groups. The gelation temperature was found to be lowered at the interface in comparison with that of the bulk. It is suggested that the QCM can evaluate the shear modulus accompanying the gelation near the interface. The interfacial segregation on the gold substrate caused by the surface free energy and long-range van der Waals interaction was observed from NR measurements.

HPMC Hydrogel Formation Mechanisms Unveiled by the Evaluation of the Activation Energy.

Aqueous solutions of hydroxypropyl methylcellulose (HPMC) show inverse thermoreversible gelation, i.e., they respond to small temperature variations exhibiting sol–gel transition during heating, and reversibly gel–sol transition during cooling. According to the pertinent literature on HPMC aqueous systems, at room temperature, the loss modulus (G”) is higher than the storage modulus (G’). During the heating ramp, the viscoelastic response follows a peculiar path: initially, G” and G’ smoothly decrease, then drop to a minimum and finally increase. Eventually, G’ overcomes G”, indicating the gel formation. A recent explanation of this behaviour considers a two-step mechanism: first, phase separation occurs, then fibrils form from a polymer-rich phase and entangle, leading to a three-dimensional network. Based on this, our research focuses on the rheological analysis of the different steps of the sol–gel transition of an HPMC aqueous solution. We perform different viscoelastic tests: thermal ramps, time sweeps, and frequency sweeps at selected characteristic temperatures. We couple classical analysis of the SAOS experiments with an innovative approach based on the evaluation of the activation energy (Ea), made possible by the instrument intrinsic temperature oscillations around the target value. Results show that Ea can be a valid tool that contributes to further clarifying the peculiar microstructural evolution occurring in this kind of thermoreversible gel.

Temperature-dependent dynamic light scattering studies on dilute aqueous solution of methylcellulose

Temperature-dependent dynamic light scattering studies on dilute aqueous solution of methylcellulose

A methylcellulose/agarose hydrogel as an innovative scaffold for tissue engineering.

In situ crosslinked materials are the main interests of both scientific and industrial research. Methylcellulose (MC) aqueous solution is one of the representatives that belongs to this family of thermosensitive materials. At room temperature, MC is a liquid whereupon during temperature increase up to 37 °C, it crosslinks physically and turns into a hydrogel. This feature makes it unique, especially for tissue engineering applications. However, the crosslinking rate of MC alone is relatively slow considering tissue engineering expectations. According to these expectations, the crosslinking should take place slowly enough to allow for complete injection and fill the injury avoiding clogging in the needle, and simultanously, it should be sufficiently fast to prevent it from relocation from the lesion. One of the methods to overcome this problem is MC blending with another substance that increases the crosslinking rate of MC. In these studies, we used agarose (AGR). These studies aim to investigate the effect of different AGR amounts on MC crosslinking kinetics, and thermal, viscoelastic, and biological properties. Differential Scanning Calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements proved that AGR addition accelerates the beginning of MC crosslinking. This phenomenon resulted from AGR's greater affinity to water, which is crucial in this particular crosslinking part. In vitro tests, carried out using the L929 fibroblast line and mesenchymal stem cells (MSCs), confirmed that most of the hydrogel samples were non-cytotoxic in contact with extracts and directly with cells. Not only does this type of thermosensitive hydrogel system provide excellent mechanical and biological cues but also its stimuli-responsive character provides more novel functionalities for designing innovative scaffold/cell delivery systems for tissue engineering applications.

Evaluation of Antibacterial and Antifungal Activity of Moringa Concanensis

In today’s scenario, fungal and bacterial infections are one of the most challenging pestilential diseases for the health-care professional which is increasing with a very high rate in the growing population, especially among the immune compromised people.The present work involved the study to extract active principles of Moringa concanensis and perform antibacterial and antifungal activity for various extracts. The leaves were dried powdered unexpected using solvents petroleum ether, chloroform, ethanol and water. Chemical tests were performed to ascertain presence of various classes of phyto-constituents like alkaloids, glycosides, saponins, carbohydrates, proteins, amino acids tannins, flavonoids and phenolic substances. All four extracts showed the presence of various phytochemicals responsible for multiple pharmacological activities. The extracts were reconstituted using 1% aqueous solution of carboxy methyl cellulose and were tested for antibacterial and antifungal activity against six microorganisms, namely Bacillus subtilis, Enterobacter aerogenes, Bacillus cereus, Aspergillus Flavus, Aspergillus Niger and Helminthosporium, using well diffusion method. The results of the activity are promising with chloroform extract showing highest inhibitory activity against most of the organisms. All the extracts were able to demonstrate significant activity compared to control inhibition of microorganisms tested and hold key to discover lead molecules after further scientific investigation.

Particle coating with composite shell in a pan granulator

In this study, the coating of urea granules with a composite shell was performed in a laboratory-scale pan granulator. The composite shell of coated particles consisted of a filler and a binder. Aqueous solutions of sodium silicate, methylcellulose, and polyacrylamide were used as the binders. Powdery calcium carbonate was used as the filler. The influence of the pan rotation speed, the pan-tilt angle, and the binder type on coating performance and the product properties was investigated. The pan rotation speed varied in the range from 30–70 rpm and the pan-tilt was changed from 30° to 75°. The relative shell mass, crushing strength, moisture content of the coated particles, and particle size distribution (PSD) were determined. A mathematical model was developed based on the population balance equation with the main purpose of predicting PSD. Particles’ weight gain was assumed to be proportional to the ratio of the surface area of the given size particles and the surface area of all particles in the coater. A comparison of calculated and experimental cumulative distributions of particle size was performed. Good agreement was observed between the modeling and the measurements.

Nanocellulose-containing cellulose ether composite films prepared from aqueous mixtures by casting and drying method

A TEMPO-oxidized cellulose nanofibril (TEMPO-CNF)/water dispersion was mixed with an aqueous solution of hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), methyl cellulose (MC), or carboxymethyl cellulose sodium salt (CMC). The mixtures were converted into TEMPO-CNF/cellulose ether composite films containing 0–5% TEMPO-CNFs by casting and drying of the aqueous mixtures. All the composite films had high light transparency. However, the tensile properties of the composite films of a given TEMPO-CNF content differed for the HPC and HEC, MC, and CMC matrices. The nano-reinforcing effect owing to TEMPO-CNFs was evident in the TEMPO-CNF/HPC composite films, which became strong but brittle. In contrast, the TEMPO-CNF/HEC composite films did not exhibit this nano-reinforcing effect. Transmission electron microscopy observation of the film cross-sections revealed that the TEMPO-CNF elements were homogeneously distributed in the 5% TEMPO-CNF/HPC composite film. In contrast, the TEMPO-CNF elements were densely present on the top and bottom surfaces of the 5% TEMPO-CNF/HEC composite film; the TEMPO-CNFs were heterogeneously distributed in the HEC matrix. The low gelation or aggregation concentrations of TEMPO-CNFs in water may have resulted in the different distribution states of TEMPO-CNFs, depending on the cellulose ether matrix used, and hence the different tensile behaviors.

Evaluation of Local Gelation Behavior of Aqueous Methylcellulose Solution Using Quartz Crystal Microbalance

Evaluation of Local Gelation Behavior of Aqueous Methylcellulose Solution Using Quartz Crystal Microbalance

A study to enhance the oral bioavailability of s-adenosyl-l-methionine (SAMe): SLN and SLN nanocomposite particles

The endogenous molecule, S-adenosyl-l-methionine (SAMe) is a key factor due to its role in the methylation cycle and modulation of monoaminergic neurotransmission. Since many mental disorders have linked to the monoaminergic system, the level of SAMe in blood and cerebrospinal fluid is important in the treatment of major depression. In this study, solid lipid nanoparticles (SLN) were prepared in order to increase the limited oral bioavailability of SAMe, and SLN based nanocomposite particles (SAMe-SLN-NC) were further developed using an enteric polymer for passive targeting of intestinal lymphatic system. In this manner, it was also aimed to protect SAMe loaded SLN from harsh gastric environment as well as hepatic first-pass metabolism. Dynamic light scattering (DLS) analysis of SLN was performed, drug content was measured, SAMe release patterns were examined and the permeation ability of SAMe was investigated by the Parallel Artificial Membrane Permeability Assay (PAMPA) to characterize SAMe loaded SLN formulation. According to the PAMPA results, SAMe-SLN with the average particle size of 242 nm showed enhanced SAMe permeability in comparison to pure drug. Delayed drug release obtained by SLN nanocomposite particles indicated the protection of drug-loaded SLN in the acidic gastric medium and their intact presence in the intestine. SAMe solution or particle suspensions were prepared using 0.45 (w/v) hydroxypropyl methylcellulose aqueous solution to be applied to groups of animals for pharmacokinetic studies. In vivo pharmacokinetic parameters revealed enhancement in relative bioavailability of SAMe upon oral administration of SLN based formulations. This was attributed to intact absorption of lipid matrix through lymphatic path. A statistically significant increase in SAMe plasma levels was obtained at 15th and 30th minutes with SAMe-SLN and at 2nd and 4th hours with SAMe-SLN-NC.Overall results suggest that SLN is a promising carrier to passive lymphatic targeting of SAMe and novel SLN nanocomposite particles which presented efficient oral bioavailability is a potential way for oral delivery of SAMe and treatment of major depression.

Behavior of bubble plume in shear-thinning crossflowing liquids

The behavior of bubble plume in crossflows was investigated by experimental and theoretical methods. The high-speed photography method was applied to analyze the visualization of bubble plume in tap water and carboxyl methyl cellulose (CMC) aqueous solution. The influence of crossflow velocity, superficial gas velocity and rheology of liquid phase on the inclination trajectory of bubble plume was studied. The results indicated that the trajectories of bubble plumes in tap water and CMC aqueous solutions approximated linearly, while the inclination characteristic of the bubble plume in CMC aqueous solutions were significantly different from those in tap water due to the effect of the rheological properties. The inclination angle of bubble plume in CMC aqueous solution was one-third more than that in tap water at high crossflow velocity. A correlation was developed via dimensional analysis to predict the inclination trajectories of bubble plumes in Newtonian and shear-thinning non-Newtonian fluid system. Considering the non-Newtonian rheology, the modified integral model of bubble plume was applied for theoretical calculation of centroids of bubble plume in crossflow.

Evaluation of Local Gelation Behavior of Aqueous Methylcellulose Solution Using Quartz Crystal Microbalance

Evaluation of Local Gelation Behavior of Aqueous Methylcellulose Solution Using Quartz Crystal Microbalance

Microfluidic filament thinning of aqueous, fibrillar methylcellulose solutions

Filament stretching using a flow-focusing microfluidic device coupled with image analysis has emerged as a promising method to resolve extensional properties of low viscosity, low molecular weight solutions. This method was used to calculate extensional properties of aqueous methylcellulose (MC) solutions at varying NaCl concentrations, where transient changes in filament diameter were used to calculate the flow-driven, apparent extensional viscosity of each solution. The increase in apparent extensional viscosity at room temperature as the NaCl concentration increases is attributed to the presence of a fibrillar MC network formed in solution.

Osmotic-Pressure-Induced Nematic Ordering in Suspensions of Laponite and Carboxy Methyl Cellulose.

Laponite is a synthetic clay that is known to form gels in aqueous suspensions at low concentrations (0.01 g/cm3). Although it is expected to form lyotropic liquid crystals, such phases usually do not form, as a consequence of laponite's tendency to form gels at concentrations below the threshold for liquid crystal formation. Here we show that macroscopic, birefringent phases of laponite can be prepared through osmotic compression of a laponite solution by an aqueous solution of carboxy methyl cellulose (CMC). We present polarization imaging studies showing how the initially dilute, isotropic laponite phase shrinks while developing typical birefringence colors between crossed polarizers. Using the Michel-Lévy interference charts, we were able to extract the refractive index and orientation of the laponite nanodisks in the compressed region. Our observations allow us to propose a tentative state diagram, indicating the concentration regions for which we obtain optically anisotropic gels.