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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 (A) and lnk2 (B) versus 1/T for estimating the positive reaction and negative reaction.Abbreviation: T, temperature.
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f4-dddt-8-945: lnk1 (A) and lnk2 (B) versus 1/T for estimating the positive reaction and negative reaction.Abbreviation: T, temperature.

Mentions: The results of ΔS0 could provide some information on the ion-exchange mechanism. This value should be positive in an ionic reaction because the randomness in the (solid + liquid) interface is increased, attributed to the release of sodium and chlorine ions, which have a smaller radius; meanwhile, the value of the adsorption process should be negative due to the decrease in the particle number. In Table 4, the ΔS0 for atenolol was negative, while that for the other four hydrochlorides was positive, which might suggest that the exchange of atenolol in ion-exchange fibers is apt to physical adsorption, while the others are more apt to ion reactions. High linearity is shown in Figure 4, in which the positive and negative reaction activation energies were calculated from the slope of lnk versus 1/T. Wang et al pointed out that the value of Ea depicted the type of adsorption: when its value is between 8 and 16 kJ/mol, it is a chemisorption, while it is a physisorption process when Ea is lower than −40 kJ/mol.23 Nollet et al also reported that low activation energies (5–40 kJ/mol) are characteristic for physisorption, while higher activation energies (40–800 kJ/mol) suggest chemisorptions.24 The Ea1 of atenolol was below 8 kJ/mol, while the Ea1 for the other drugs were all above it. The positive center of atenolol is a secondary amine while the others are tertiary amines. The secondary amine is much harder to ionize in solutions than the tertiary amine, so a coordination complex might be formed between it and hydrochloric acid instead of the ionic compound, resulting in atenolol being absorbed in the molecular form. Similarly, Borodkin et al25 reported that greater affinity existed between the resin and tertiary amines than with secondary amines.


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 (A) and lnk2 (B) versus 1/T for estimating the positive reaction and negative reaction.Abbreviation: T, temperature.
© Copyright Policy
Related In: Results  -  Collection

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

f4-dddt-8-945: lnk1 (A) and lnk2 (B) versus 1/T for estimating the positive reaction and negative reaction.Abbreviation: T, temperature.
Mentions: The results of ΔS0 could provide some information on the ion-exchange mechanism. This value should be positive in an ionic reaction because the randomness in the (solid + liquid) interface is increased, attributed to the release of sodium and chlorine ions, which have a smaller radius; meanwhile, the value of the adsorption process should be negative due to the decrease in the particle number. In Table 4, the ΔS0 for atenolol was negative, while that for the other four hydrochlorides was positive, which might suggest that the exchange of atenolol in ion-exchange fibers is apt to physical adsorption, while the others are more apt to ion reactions. High linearity is shown in Figure 4, in which the positive and negative reaction activation energies were calculated from the slope of lnk versus 1/T. Wang et al pointed out that the value of Ea depicted the type of adsorption: when its value is between 8 and 16 kJ/mol, it is a chemisorption, while it is a physisorption process when Ea is lower than −40 kJ/mol.23 Nollet et al also reported that low activation energies (5–40 kJ/mol) are characteristic for physisorption, while higher activation energies (40–800 kJ/mol) suggest chemisorptions.24 The Ea1 of atenolol was below 8 kJ/mol, while the Ea1 for the other drugs were all above it. The positive center of atenolol is a secondary amine while the others are tertiary amines. The secondary amine is much harder to ionize in solutions than the tertiary amine, so a coordination complex might be formed between it and hydrochloric acid instead of the ionic compound, resulting in atenolol being absorbed in the molecular form. Similarly, Borodkin et al25 reported that greater affinity existed between the resin and tertiary amines than with secondary amines.

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