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

PEGDA acted as a polymerization template for the polymerization of acrylic acid monomers at both ends, resulting in copolymers where PEG became entangled within the polyacrylate polymeric network. PEGDA is hydrophilic, so with the increase in the ratio of PEGDA in copolymeric structures, the hydrophilicity of the hydrogels increased. This study is different from studies that use the usual other small molecular cross-linkers that are not hydrophilic. These cross-linkers cannot impart any hydrophilicity and at the same time can only increase the compactness of the hydrogel mass by a sewing-like action for end-to-end polymeric compaction with an increase in its amounts within the polymeric networks.The trend in the present study showed that as the hydrophilic nature of PEG decreases with the increase in molecular weight, the hydrophilicity of these copolymeric hydrogels decreased with the increase in molecular weight. For the same weight ratio, the molar percentage of PEGDA decreases with the increase in molecular weight, reducing the hydrophilicity and water-absorbing capacity and swelling tendency of such copolymeric polyacrylates.

Water-diffusion study . The release of a drug from a matrix system usually is governed by diffusion, so determining the diffusion coefficient of the hydrogels is essential. The diffusion coefficient of the swollen hydrogel can be measured fairly easily by either the membrane permeation method or the sorption and desorption method. The membrane permeation time–lag experiment has been widely used; however, it is not always the most practical method (30). In the present work, therefore, desorption phenomenon (32) was used to determine the diffusion coefficient of the prepared hydrogels.

Table III: In vitro characterization of different hydrogel formulations (n* = 3).
The hydrogels showed good diffusion property, with diffusion coefficients of the order 10–6 (see Table III). As the molecular weight of the PEGDA was increased, its molar percentage decreased for the same weight percent. The cross-linking density of the system, therefore, decreased with the increase in the molecular weight of PEGDA, thereby increasing the diffusion coefficient. This is evident from the diffusion coefficient of formulation B15, which was 3.32 10–6 cm2 /s, whereas that of B60 was 4.57 10–6 cm2 /s. With the increase in molecular weight of PEGDA, the porosity might have increased because of the increase in chain length of the PEG cross-linker. Also, the hydrophilicity of PEGs decrease with the increase in molecular weight (33), so the diffusion of water became easier from systems containing PEGs of higher molecular weight. The diffusion coefficient, however, decreased with an increase in the amount of PEGDA(e.g., that for C15 was found to be 2.24 10–6 cm2 /s and that for D15 was 1.86 10–6 cm2 /s). This decrease may be attributed to the increase in the amount of hydrophilic PEG, which causes an increase in the difficulty of water diffusion out of the hydrogel matrix.


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