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The load and release characteristics on a strong cationic ion-exchange fiber: kinetics, thermodynamics, and influences.

Yuan J, Gao Y, Wang X, Liu H, Che X, Xu L, Yang Y, Wang Q, Wang Y, Li S - Drug Des Devel Ther (2014)

Bottom Line: The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China.

ABSTRACT
Ion-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.

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lnk1 versus molecular weight at 25°C, plotted with the molecular weight of model drugs loading.
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f5-dddt-8-945: lnk1 versus molecular weight at 25°C, plotted with the molecular weight of model drugs loading.

Mentions: The relationships of lnk1 or Ea1 versus molecular weight are exhibited in Figure 5. The activation energy increased and loading rate decreased with increasing molecular weight. Good linearity adequately proved that molecular weight was the most important influence on drug load. The surface of the fibers where the ionic reactions occurred was limited unlike homogeneous reactions; thus, steric hindrance appeared to be a noticeable factor in affecting the loading process. While some parts of the drug ions bonded quickly with the ion-exchange groups, other parts needed more time to rearrange into an appropriate position for the exchange, typically for drug ions with larger molecule weights, which move more slowly. This is why the observed values of the exchange rate were somewhat lower than the predicted rates for sinomenine at lower temperatures. When the load occurred at a higher temperature, the time was shorter because of the acceleration of molecular thermal motion; the loading curve was similar to that of type one (Figure 2B).


The load and release characteristics on a strong cationic ion-exchange fiber: kinetics, thermodynamics, and influences.

Yuan J, Gao Y, Wang X, Liu H, Che X, Xu L, Yang Y, Wang Q, Wang Y, Li S - Drug Des Devel Ther (2014)

lnk1 versus molecular weight at 25°C, plotted with the molecular weight of model drugs loading.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109635&req=5

f5-dddt-8-945: lnk1 versus molecular weight at 25°C, plotted with the molecular weight of model drugs loading.
Mentions: The relationships of lnk1 or Ea1 versus molecular weight are exhibited in Figure 5. The activation energy increased and loading rate decreased with increasing molecular weight. Good linearity adequately proved that molecular weight was the most important influence on drug load. The surface of the fibers where the ionic reactions occurred was limited unlike homogeneous reactions; thus, steric hindrance appeared to be a noticeable factor in affecting the loading process. While some parts of the drug ions bonded quickly with the ion-exchange groups, other parts needed more time to rearrange into an appropriate position for the exchange, typically for drug ions with larger molecule weights, which move more slowly. This is why the observed values of the exchange rate were somewhat lower than the predicted rates for sinomenine at lower temperatures. When the load occurred at a higher temperature, the time was shorter because of the acceleration of molecular thermal motion; the loading curve was similar to that of type one (Figure 2B).

Bottom Line: The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China.

ABSTRACT
Ion-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.

Show MeSH