Copolymerized PEGlyated Acrylate Hydrogels for Delivery of Dicolofenac Sodium - Pharmaceutical Technology

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Copolymerized PEGlyated Acrylate Hydrogels for Delivery of Dicolofenac Sodium
Hydrogels are biocompatible drug delivery systems by which the physical properties can be controlled by the cross-linking density. Hydrogels were prepared by copolymerization of acrylic acid monomers in the presence of poly(ethylene glycol)(PEG) to form polyethylene diacrylate (PEDGA). Various molecular weights of PEGs were used for the synthesis of PEGDA to study the effect of molecular weight of PEG on the properties of hydrogels. These hydrogels were further characterized for free water, swelling..

Pharmaceutical Technology

A small burst release initially was observed from all the formulations, approximately 3–4% of the loaded drug was released during the first hour, which may have resulted from the adsorption of some of the drug molecules on the surface of the hydrogels. In the later phase, the release of the drug in the hydrogel matrix was assisted by the diffusion of water through the matrix. The release rate, therefore, decreased after the initial burst release because diffusion through the cross-linked polymer matrices is a time-consuming phenomenon. In each case, however, the release rate was faster for hydrogels made of higher molecular weight PEG, which might be as a result of the decrease in cross-linking density with the increase in molecular weight as the molar composition of PEGDA decreases for the same weight composition. The release rate is slower for higher molar percentages of PEGDA. As with the increase in hydrophilicity, the ease of drug release decreases because the drug diffuses out along with water as solution. For example, after 96 h, 80.38% of the loaded drug was released from B60 whereas 33.23% diclofenac was released from formulation D60 .

Table IV (a): Cumulative percentage of drug released by various hydrogel formulations.

Table IV (b): Cumulative percentage of drug released by various hydrogel formulations.

Drug release from matrix systems generally takes place by diffusion. As the diffusion of water in the present case increased with an increase in molecular weight of PEGDA (as found by the diffusion coefficient studies), the drug-release profile also followed similar trends (see Tables IV[a]) and IV [b]) as the drug was released from the hydrogels in the form of an aqueous solution. In the case of the same weight percentage of PEGDA, an increase in the molecular weight of PEGDA led to an increase in the release rate. For example, after 96 h, 35.24% of the loaded drug was released from B10 , whereas 59.35% diclofenac was released from formulation B40 within the same time period.

The data of release profiles for each formulation further were analyzed by model fitting using the following equations:

Table V: Results of data-fitting analysis of release profiles of the hydrogel formulations.
in which, % R is the percent of drug release; K is the release rate constant; t is the time of release; and e is the logarithmic exponent.


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