Co-processing as a tool to improve aqueous dispersibility of cellulose ethers

Abstract

Cellulose ethers are important materials with numerous applications in pharmaceutical industry. They are widely employed as stabilizers and viscosity enhancers for dispersed systems, binders in granulation process and as film formers for tablets. These polymers, however, exhibit challenge during preparation of their aqueous dispersions. Rapid hydration of their surfaces causes formation of a gel that prevents water from reaching the inner core of the particle. Moreover, the surfaces of these particles become sticky, thus leading to agglomeration, eventually reducing their dispersion kinetics. Numerous procedures have been tested to improve dispersibility of cellulose ethers. These include the use of cross-linking agents, alteration in the synthesis process, adjustment of water content of cellulose ether, modification by attaching hydrophobic substituents and co-processing using various excipients. Among these, co-processing has provided the most encouraging results. This review focuses on the molecular mechanisms responsible for the poor dispersibility of cellulose ethers and the role of co-processing technologies in overcoming the challenge. An attempt has been made to highlight various co-processing techniques and specific role of excipients used for co-processing.

Thermal Behavior of Polymers in Solid-State

“…The original nature of intramolecular that form hydrogen bonds also influences hydrophilicity. Therefore, many cellulose modifications have been made physically or chemically to improve cellulose deficiencies, one of which is making esters derivatives (43). Something that needs to be considered when applying cellulose as a polymer in active substances is that thermal stability depends on molecular weight because cellulose is complex; the level of cellulose used; and environmental humidity (44).…”

Viscometric analysis of the hydration of a surface cross-linked EM-HEC polymer

“…On a practical level, however, addition of the polymer powder to water can often be problematic if the hydration process begins before the powder has been adequately dispersed; under these conditions incomplete dissolution and particle agglomeration (lump formation) can be unwanted consequences. These problems, and possible means by which they can be overcome, have largely been confined to the patent literature for around 50 years, with Sharma et al recently summarising the various mitigation approaches [2].…”

“…This modifies the particle wettability which delays hydration [6], thereby prolonging the dispersion time in water [7]. The resultant effect is that more effective dispersion of the particles can occur before the formation of sticky surface gel layers which are responsible for the unwanted effects described above [2,7].…”

Formulation development of extended and immediate release tablets using extrusion-based 3d printing technology

“…Cellulose esters and ethers are of particular important for producing amorphous solid dispersions because of their physicochemical properties such as high molecular weight and resistance to hydrolysis which protects the absorption of most cellulose ethers and esters in the GI tract(81,82). The adaptable properties of cellulose ethers are their aqueous solubility, enhanced viscosity, and water retention ability have been widely employed for various applications(83).…”