Preparation of polyacrylamide based microgels with different charges for drug encapsulation

The unique physicochemical properties of hydrogels have attracted considerable attention in their drug storage and delivery applications. Herein, a series of acrylamide based hydrogels with different charges (cationic, neutral, and anionic) under different pH (1, 7, and 13) were prepared via an inverse emulsion polymerization process. The effects of pH and aqueous to organic phase (w/o) ratio on the size of the produced hydrogels were studied. Fluorescein was used as the model drug to assess and optimize the encapsulation efficiency of the hydrogels. Optical microscopy and confocal fluorescence microscopy were carried out to examine the existence and distribution of fluorescein inside the hydrogels. It was found that the hydrogels were swollen to the greatest extent at pH = 13 and their size increased with decreasing w/o ratio. Fluorescein was molecularly dispersed within the cationic and anionic hydrogels at pH = 13 with an encapsulation efficiency of ∼45 wt%. This study provides a convenient method to prepare hydrogels with the required properties and demonstrates the potential of using hydrogels to store and stabilize therapeutics.