Rheological Evaluation of Silicon/Carbopol Hydrophilic Gel Systems as a Vehicle for Delivery of Water Insoluble Drugs
Journal Title: The AAPS Journal - Year 2008, Vol 10, Issue 1
Abstract
The present study analyzed the thickening properties of Carbopol 974 and 971 in a 50:50 mixture of water/Silsense™ A-21, a new cationic silicon miscible in any proportion with water. Samples were prepared by simply dispersing different Carbopol amounts (0.5–4%) at room temperature or at 70°C without neutralizing. Temperature sweep and time sweep analysis did not reveal significant structural changes at increasing temperature in the samples prepared following the first procedure. On the other hand systems obtained at 70°C possessed higher elastic character particularly at polymer concentration higher than 2% (w/v). Analysis of the G′ and G″ vs frequency curves by using different fitting equations (linear fitting, power law) gave information about the viscoelastic properties of the systems. The fitting of the frequency spectra and the calculation of the relaxation times from the master curves outlined the structural differences within the samples prepared with the two different procedures, confirming stronger gel-like behaviour for the samples prepared by the heating procedure. High preparation temperature promoted the polymer–solvent interactions, aiding the solvation of Carbopol. Heating facilitated polymer–solvent and polymer–polymer interaction, giving rise to a better organised structure typical of gel-like systems. Furthermore this preparation method provided good stability properties as shown by the stress sweeps tests performed during the three months of storage. The interpretation of the rheological results was supported by statistical analysis. A design methodology (screening and optimisation) was also applied in order evaluate the influence on dynamic rheological moduli of several parameters (polymer type and concentration, preparation method, temperature of the tests). This last method showed the relevance of the interaction of two main factors: polymer concentration and preparation procedure. Thus, statistical analysis confirmed that temperature increased the polymer–solvent interaction and improved the viscoelastic properties of the systems, particularly when Carbopols were present in considerable amounts.
Authors and Affiliations
Giulia Bonacucina, Marco Cespi, Monica Misici-Falzi, Giovanni F. Palmieri
Keywords
Related Articles
- EP ID EP681529
- DOI 10.1208/s12248-008-9008-9
- Views 108
- Downloads 0
Monitoring intracellular pH changes in response to osmotic stress and membrane transport activity using 5-chloromethylfluorescein
Intracellular free H+ concentration (pHi) responds to numerous extracellular stimuli. The use of fluorescent indicator dyes to measure pHi is strongly influenced by the ability of target cells to retain activated dye wit...
Drug–Drug Interaction Studies: Regulatory Guidance and An Industry Perspective
The online version of this article (doi:10.1208/s12248-013-9470-x) contains supplementary material, which is available to authorized users.
Integrated Pharmacokinetic-Driven Approach to Screen Candidate Anticancer Drugs for Brain Tumor Chemotherapy
The online version of this article (doi:10.1208/s12248-012-9428-4) contains supplementary material, which is available to authorized users.
A Report from the Pediatric Formulations Task Force: Perspectives on the State of Child-Friendly Oral Dosage Forms
Despite the fact that a significant percentage of the population is unable to swallow tablets and capsules, these dosage forms continue to be the default standard. These oral formulations fail many patients, especially c...
The composite solubility versus pH profile and its role in intestinal absorption prediction
The purpose of this study was to examine absorption of basic drugs as a function of the composite solubility curve and intestinally relevant pH by using a gastrointestinal tract (GIT) absorption simulation based on the a...