Sol-Gel Behavior of Hydroxypropyl Methylcellulose (HPMC) in Ionic Media Including Drug Release

Abstract

Sol-gel transformations in HPMC (hydroxypropyl methylcellulose) are being increasingly studied because of their role in bio-related applications. The thermo-reversible behavior of HPMC is particularly affected by its properties and concentration in solvent media, nature of additives, and the thermal environment it is exposed to. This article contains investigations on the effects of salt additives in Hofmeister series on the HPMC gelation. Various findings regarding gelation with salt ions as well as with the ionic and non-ionic surfactants are presented. The gel formation in physiological salt fluids such as simulated gastric and intestine fluids is also examined with the interest in oral drug delivery systems. The processes of swelling, dissolution and dispersion of HPMC tablets in simulated bio-fluids are explored and the release of a drug from the tablet affected by such processes is studied. Explanations are provided based on the chemical structure and the molecular binding/association of HPMC in a media. The test results at the body or near-body temperature conditions helped in understanding the progress of the gelation process within the human body environment. The detailed interpretation of various molecule level interactions unfolded the sol-gel mechanisms and the influence of a few other factors. The obtained test data and the established mathematical models are expected to serve as a guide in customizing applications of HPMC hydrogels.

Experimental Studies and Modeling of the Drying Kinetics of Multicomponent Polymer Films

“…S1 supplementary information). These results are in agreement with those reported in the literature (31)(32)(33). Endothermic peaks representing water evaporation appeared in approximately the same regions for the HPMC films, and eventually disappeared with increasing drying times (Fig.…”

The rheological anomaly in water-silicate systems: a possible thermodynamic explanation

“…[9,10]. However, in all these cases the anomaly has a completely different mechanism that is not associated with the polymerization of ions [6,9,11].…”

“…A similar effect was observed in other silicate systems, namely in aqueous solutions of lithium silicates [4] and sodiumtetramminezinc silicate [5]), as well as in several non-silicate organic systems. The latter include aqueous solutions of methylcellulose [6,7], of hydroxypropyl methylcellulose [6,8], of some block copolymers based on polyalkylene glycols, N-substituted polyacrylamides, polyphosphazenes, etc. [9,10].…”

HPMC as Capsule Shell Material: Physicochemical, Pharmaceutical and Biopharmaceutical Properties

“…It is said to undergo cold-set gelation, where cooling results in enthalpicallystabilized inter-chain helix to form segments of individual chains leading to a three dimensional network. On the other hand, aqueous solution of methyl and hydroxypropyl methylcellulose are known to gel upon heating i.e., heat-set gelation [25]. These gels are completely reversible in that they are formed upon heating yet will liquefy upon cooling.…”