Abstract
The goal of this paper was to design several sodium carboxymethylcellulose hydrogels containing a BCS class II model drug and to evaluate their flow and thixotropic properties. The rheological measurements were performed at two temperatures (23 °C and 37 °C), using a rotational viscometer. The hydrogels were stirred at different time intervals (10 s, 2, 5, 10 and 20 min at 23 °C, and 10 s, 2 and 5 min at 37 °C), with a maximum rotational speed of 60 rpm, and the corresponding forward and backward rheograms were recorded as shear stress vs. shear rate. For all hydrogels, the rheological data obtained at both temperatures showed a decrease of viscosity with the increase of the shear rate, highlighting a pseudoplastic behaviour. The flow profiles viscosity vs. shear rate were quantified through power law model, meanwhile the flow curves shear stress vs. shear rate were assessed by applying the Herschel-Bulkley model. The thixotropic character was evaluated through different descriptors: thixotropic area, thixotropic index, thixotropic constant and destructuration thixotropic coefficient. The gel-forming polymer concentration and the rheological experiments temperature significantly influence the flow and thixotropic parameters values of the designed hydrogels. The rheological characteristics described have an impact on the drug release microenvironment and determine the stasis time at the application site.
Highlights
Hydrogels are semisolid dosage forms, consisting of three-dimensional networks of water-soluble materials of polymeric, protein, peptidic, colloidal, surfactant, or lipid origin, with a cross-linked structure
The aim of this study was the design of some sodium carboxymethylcellulose hydrogels containing a Biopharmaceutical Classification System (BCS) class II drug model, and the investigation of the rheological behaviour of the resulting experimental hydrogels, in correlation with the formulation variables
The forward and backward rheograms were recorded for eight experimental hydrogels, prepared according to the formulas presented in Section “4.2.1
Summary
Hydrogels are semisolid dosage forms, consisting of three-dimensional networks of water-soluble materials of polymeric, protein, peptidic, colloidal, surfactant, or lipid origin, with a cross-linked structure. They can be formulated in a variety of physical forms, ranging from micro- or nanoparticles to coatings and films applied on solid dosage forms [1,2]. Their applications cover a vast array, both in clinical practice and experimental medicine. One of the major challenges in developing new medicinal products was to improve the aqueous solubility of these poorly water-soluble drugs, especially of Biopharmaceutical Classification System (BCS) class II active ingredients (high permeability, low solubility) with low molecular weight (MW < 1000 Da) [14,15,16]
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