PubMed · 11217331
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
T Wehr, M Zhu, D T Mao. 2001. Sieving matrix selection.. https://doi.org/10.1385/1-59259-055-1%3A167
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
This work studies the application of a 2(3) factorial design to a cosmetic gel with the aim of simplifying the analysis of the influence of the concentration of Carbopol ETD 2020 (cb), of ethanol (et) and of glycerin (gl) on the viscoelastic parameters: equilibrium modulus (Gn), critical molecular weight (Mc), degree of structuring (logG'/lognu) and viscous modulus (G"). We have obtained high linear polynomial correlations among the components and the response factors determined. The results obtained evidence the usefulness of this type of technique in detecting interactions among the components that would be difficult to foresee otherwise. Mc, logG'/lognu and G" depend on the interaction cb-et. Gn depends on the interaction of cb-et-gl. That is, an increase in gl can increase or decrease the elasticity (Gn) of the gels, depending on the concentrations of cb and et.
A factorial design (2(3)) is applied to study the influence of three of the components of a cosmetic gel (the concentrations of Carbopol ETD 2020, ethanol and glycerine) on flow parameters (Casson's yield value (tau(c)), Casson's viscosity (eta(c)) and apparent viscosity at 125 s-1 (eta(ap.) 125 s-1), spreadability, and transparency. The first-order polynomial equation allowed by the model suitably accounts for the tau(c) and spreadability. Both depend on the concentrations of Carbopol and ethanol, and tau(c) also depends on the ethanol-glycerine interaction. The model explains to a certain extent the complex relationships that are established between the components and that influence eta(c) y eta(ap.) 125 s-1. Transparency is independent of the Carbopol concentration and it is also thought to be independent of the ethanol concentration. In addition, a high linear correlation has been found between the tau(c) and spreadability and other viscoelastic parameters of the gels that were previously determined (Int. J. Pharm. (2001)). The application of the technique of experimental design has been shown to be a very useful tool for formulating gels.
In the present study, the features of two new thiolated polymers--the so-called thiomers--were investigated. Mediated by a carbodiimide cysteamine was covalently attached to sodium carboxymethylcellulose (Na-CMC) and neutralised polycarbophil (Na-PCP). Depending on the weight-ratio polymer to cysteamine during the coupling reaction, the resulting CMC-cysteamine conjugate and PCP-cysteamine conjugate showed in maximum 43 +/- 15 and 138 +/- 22 micromole thiol groups per g polymer (mean +/- S.D.; n=3), respectively, which were used for further characterisation. Tensile studies carried out with the CMC-cysteamine conjugate on freshly excised porcine intestinal mucosa displayed no significantly (P<0.01) improved mucoadhesion, whereas, the mucoadhesive properties of the PCP-cysteamine conjugate were increased 2.5-fold compared with the unmodified polymer. The swelling behaviour of the CMC-cysteamine conjugate was uninfluenced by the covalent attachment of the sulfhydryl compound. In contrast the swelling behaviour of the PCP-cysteamine conjugate was improved significantly (P<0.01) versus unmodified PCP. Furthermore, in aqueous solutions the disintegration time of tablets based on the CMC- and PCP-cysteamine conjugates was prolonged 1.5 and 3.2-fold, respectively, in comparison to tablets containing the corresponding unmodified polymers. According to these results, especially the PCP-cysteamine conjugate represents a promising new pharmaceutical excipient for various drug delivery systems.