Methylcellulose gel

The thermal gelation temperature for methylcellulose decreases as a function of concentration. The presence of additives can increase or decrease the thermal gelation temperature. The presence of drugs can influence the properties of methylcellulose gels. In addition, the viscosity of methylcellulose solutions can be modified by the presence of drugs or other additives. Aqueous solutions of methylcellulose can be frozen and do not undergo phase separation upon freezing. 

Individual components in the formulation of the aqueous phase all contribute to the successful production of a GPC/SEC gel. The stabilizer acts as a protective coating to prevent the agglomeration of the monomer droplets. Polyvinyl alcohol, gelatin, polyacrylic acids, methylcellulose, and hydroxypro-... 

The GBR resin works well for nonionic and certain ionic polymers such as various native and derivatized starches, including sodium carboxymethylcel-lulose, methylcellulose, dextrans, carrageenans, hydroxypropyl methylcellu-lose, cellulose sulfate, and pullulans. GBR columns can be used in virtually any solvent or mixture of solvents from hexane to 1 M NaOH as long as they are miscible. Using sulfonated PDVB gels, mixtures of methanol and 0.1 M Na acetate will run many polar ionic-type polymers such as poly-2-acrylamido-2-methyl-l-propanesulfonic acid, polystyrene sulfonic acids, and poly aniline/ polystyrene sulfonic acid. Sulfonated columns can also be used with water glacial acetic acid mixtures, typically 90/10 (v/v). Polyacrylic acids run well on sulfonated gels in 0.2 M NaAc, pH 7.75. 

Methylcellulose and carboxymethylcellulose are forms of the familiar polysaccharide cellulose that have been treated to make them more soluble in water. Cellulose is a long chain made of the sugar glucose. The long chains mix with water to create a thick syrup or gel. 

Attapulgite adsorbs excess fluid in the stool with few adverse effects. Calcium polycarbophil is a hydrophilic polyacrylic resin that also works as an adsorbent, binding about 60 times its weight in water and leading to the formation of a gel that enhances stool formation. Neither attapulgite nor polycarbophil is systemically absorbed. Both products are effective in reducing fluid in the stool but can also adsorb nutrients and other medications. Their administration should be separated from other oral medications by 2 to 3 hours. Psyllium and methylcellulose products may also be used to reduce fluid in the stool and relieve chronic diarrhea. 

The water-soluble hydroxyethylcellulose has only a limited use as compared to water-soluble methylcellulose, principally because of the difficulty of isolating the product. Aqueous solutions of hydroxyethylcellulose do not gel on heating and the product is about as soluble in hot water as in cold, so that the method used for isolating water-soluble methylcellulose is not applicable. However, by dialyzing the reaction product the alkali and salts may be removed and the product isolated. 

Hydrogel and water-soluble ointment achieve their consistency by means of different gel-forming agents (gelatin, methylcellulose, polyethylene glycol). Lotions are aqueous suspensions of water-insoluble and solid constituents. 

Goodness-of-fit analysis applied to release data showed that the release mechanism was described by the Higuchi diffusion-controlled model. Confirmation of the diffusion process is provided by the logarithmic form of an empirical equation (Mt/ M=ktn) given by Peppas. Positive deviations from the Higuchi equation might be due to air entrapped in the matrix and for hydrophilic matrices due to the erosion of the gel layer. Analysis of in vitro release indicated that the most suitable matrices were methylcellulose and glycerol palmitostearate. 

Bulk-forming laxatives are indigestible, hydrophilic colloids that absorb water, forming a bulky, emollient gel that distends the colon and promotes peristalsis. Common preparations include natural plant products (psyllium, methylcellulose) and synthetic fibers (polycarbophil). Bacterial digestion of plant fibers within the colon may lead to increased bloating and flatus. 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

Figure 2 illustrates the temperature dependence of the swelling degree as a function of precursor polymer type. Methylcellulose (MC), hydroxypropyl-methylcellulose, type E (HPMC-E) and hydroxypropylmethylcellulose, type K (HPMC-K) gels have comparable effective crosslink densities of about 2 x 10 5 mol/cm3 (as determined from uniaxial compression testing), while the crosslink density of the hydroxypropylcellulose (HPC) gel is about half this [52]. The transition temperature for each gel is within several degrees of the precursor polymer lower critical solution temperature (LCST), except for the MC gel, which has a transition temperature 9 °C higher than the LCST. The sharpness of the transition was about 3%/°C, except for the HPC gel transition, which was much sharper - about 8%/°C. 

Mohamadi et al. [96] reported online preconcentration of human serum albumin (HSA) and its immunocomplex with a monoclonal antibody on-chip coupled to isotachophoresis. The sample injection, preconcentration, and separation were carried out continuously and controlled by a sequential voltage switching program. Preconcentration was carried out with on-chip nondenaturing gel electrophoresis in methylcellulose solution. Furthermore, the authors applied this method for immunoassay of HSA. The separation of HSA and its immunocomplex was achieved in 25 seconds in 1 cm of the microchannel with induced fluorescence detection at 7.5 pM. 

The absorptive properties of commonly used powders such as titanium dioxide (TiC>2), zinc oxide (ZnO), kaolin, cornstarch, and methylcellulose were shown to differ considerably when evaluated under standardized conditions (Figure 22.2). The highest water absorption was shown with ZnO and kaolin, followed by cornstarch and Ti02. Methylcellulose formed a gel with water that prevented the entire soaking of the powder, and thus water absorption remained low. 

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