Gautam J, Schott H
School of Pharmacy, Temple University, Philadelphia, PA 19140.
J Pharm Sci. 1994 Mar;83(3):316-21. doi: 10.1002/jps.2600830310.
The interaction of gelatin with four monosulfonated or monocarboxylated azo dyes was investigated by measuring the surface tension and intrinsic viscosity of gelatin solutions containing the dyes at different concentrations, the rigidity and melting point of their gels, and the moisture regain of their films. The dyes, which were used as models for anionic drugs, differed in the size of their aromatic hydrocarbon moieties. Surface tension measurements showed that the gelatin did not affect the critical micelle concentration of the free dyes and that the bound dyes increased the surface activity of the gelatin. The dyes reduced the intrinsic viscosity of gelatin by as much as 2/3. They also lowered the rigidity and the melting point of dilute gelatin gels and reduced the moisture regain of dry gelatin films. These changes became more pronounced with increasing dye concentrations. The effectiveness of the dyes in producing these changes increased with the size of their hydrocarbon moieties because, as had been shown in a previous study, increasingly larger hydrocarbon moieties increased the binding of the dyes to gelatin. At the pH of the measurements, which was 1.9 units below the isoelectric point of the gelatin, the gelatin was a cationic polyelectrolyte. Binding of the dye anions by ion pairing, hydrogen bonds, and other secondary valence forces rendered the gelatin less ionic and less hydrophilic, which accounts for the present observations.
通过测量含有不同浓度染料的明胶溶液的表面张力和特性粘度、其凝胶的刚性和熔点以及其薄膜的回潮率，研究了明胶与四种单磺化或单羧化偶氮染料的相互作用。用作阴离子药物模型的染料，其芳烃部分的大小不同。表面张力测量表明，明胶不影响游离染料的临界胶束浓度，而结合的染料增加了明胶的表面活性。染料使明胶的特性粘度降低多达2/3。它们还降低了稀明胶凝胶的刚性和熔点，并降低了干明胶薄膜的回潮率。随着染料浓度的增加，这些变化变得更加明显。染料产生这些变化的有效性随着其烃部分的大小而增加，因为正如先前研究中所示，越来越大的烃部分增加了染料与明胶的结合。在测量的pH值下，即比明胶的等电点低1.9个单位，明胶是一种阳离子聚电解质。通过离子配对、氢键和其他次价力结合染料阴离子，使明胶的离子性和亲水性降低，这解释了目前的观察结果。
