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Cellulose-Based NanoBioMaterials
Published in Bhupinder Singh, Om Prakash Katare, Eliana B. Souto, NanoAgroceuticals & NanoPhytoChemicals, 2018
Michael Ioelovich, Sumant Saini, Teenu Sharma, Bhupinder Singh
Other cellulose derivatives, ethers, esters, and oxycelluloses find diverse applications in biomedicine, pharmaceutics, cosmetics, and personal care. Cellulose acetate phthalate (CAP) is one of the most effective aids used as a protective coating for enteric capsules or tablets to impart them resistance to the acidic environment of the stomach (Edgar, 2007; Rowe et al., 2009). Carboxymethyl cellulose (CMC) is used as a binder for tablets, coating agent, thickener, and suspending aid (Kamel et al., 2008). Methylcellulose (MC) serves mainly as thickener and emulsifying and suspending agent in various flowable remedies (Glass and Haywood, 2006; Rowe et al., 2009). Some other soluble ethers — hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropylmethyl cellulose—also find application in cosmetics, hygiene, and medicine (Kamel et al., 2008).
Forming of Ceramics
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
The powders of advanced ceramics, when mixed with water, do not possess the desirable plastic characteristics found in the clay–water system. For this reason, they are often mixed with a viscous solution containing a few weight percent of an organic binder to achieve the desired plastic characteristics. The solvent is commonly water but nonaqueous solvents (e.g., alcohols and mineral spirits) can also be used. As the extruded body must have sufficient green strength, the binder is generally selected from the medium to high-viscosity grades, e.g., methylcellulose, hydroxyethyl cellulose, poly(acrylimides), or poly(vinyl alcohol). Methylcellulose undergoes thermal gelation, a property that offers considerable benefits for extrusion of ceramics [59]. At higher temperatures, methylcellulose forms a gel, reflected by a sharp rise in viscosity, but returns to its original consistency at lower temperatures. Examples of compositions used in extrusion are given in Table 7.8. Clay-based systems are often slightly flocculated using a small concentration of a flocculant, such as MgCl2, AlCl3, or MgSO4. A lubricant, such as a stearate, silicone, or petroleum oil, is commonly used to reduce die–wall friction.
Polysaccharides used for Microencapsulation Processes
Published in Akhilesh Vikram Singh, Bang-Jing Li, Polysaccharides in Advanced Drug Delivery, 2020
Leilane Costa de Conto, Gustavo Henrique Santos Flores Ponce
Cellulose is the main constituent of plant cell walls. It consists of glucopyranosyl residues joined by ß-(1→4) linkages. Native cellulose is insoluble in water owing to the high level of intramolecular hydrogen bonding in the cellulose polymer. As an edible film for coatings, the permeability of cellulose can be modified by combining it with other coating materials via etherification. The procedure consist in reacting cellulose with aqueous caustic and then with methyl chloride, propylene oxide or sodium monochloroacetate to yield methylcellulose, hydroxypropyl methylcellulose, hydroxypropylcellulose and sodium carboxymethycellulose[89].
Flurbiprofen-loaded interpenetrating polymer network beads based on alginate, polyvinyl alcohol and methylcellulose: design, characterization and in-vitro evaluation
Published in Journal of Biomaterials Science, Polymer Edition, 2020
In vitro release studies of FBP from beads was carried out in pH 1.2 HCl solution for the initial 2 h, then in pH 7.4 phosphate buffer solution for 4 h. Figures 7 and 8 display the cumulative FBP release of beads in different NaAlg/PVA/MC ratios (with 1/2 and 1/4, FBP/polymer ratios and exposure time to GA of 30 min). As shown in Figure 7 (for the FBP/polymer ratio of 1/2, exposure time to GA of 30 min) and in Figure 8 (for the FBP/polymer ratio of 1/4, exposure time to GA of 30 min) release rate of FBP increased with increment of NaAlg amount in the bead formulations. Among NaAlg/PVA/MC formulations (A1, A2, B1 and B2), the highest release rate was obtained from B2 formulation with cumulative FBP release of ∼100% in 6 h, while the lowest release rate was obtained from A1 formulation with cumulative release 84.8% at the end of the 6 h. Methylcellulose is a natural water-soluble polymer and contains methyl groups as well as a lesser number of residual –OH groups. PVA is virtually a linear polymer with –OH groups. On the other hand, alginate, a natural water-soluble polymer, contains hydroxyl and carboxyl groups, which impart hydrophilicity to the molecule. Therefore, penetration of liquid molecules through blend beads and then diffusion of FBP to external medium increases as the amount of NaAlg in the formulations increases. Similar observations have been observed in some studies [20,43]. Güncüm et al. [43] prepared amoxicillin–loaded poly(vinyl alcohol)/sodium alginate (PVA/NaAlg) nanoparticles as a polymer-based controlled release system and reported that as the amount of the NaAlg in the formulations increases, the drug release rate increases. The equilibrium swelling degrees were performed in buffer solution of different pH values (pH: 1.2 and 7.4) for various empty bead formulations and are displayed in Table 2.