Preparation and Evaluation of Novel pH‐Sensitive Poly(butyl acrylate‐co‐itaconic acid) Hydrogel Microspheres for Controlled Drug Delivery

In this study, a series of novel pH-sensitive copolymeric butyl acrylate-co-itaconic acid (p(BA-co-IA)) hydrogel microspheres were prepared by modified suspension polymerization of butyl acrylate and itaconic acid with the addition of 5% ethylene glycol dimethacrylate as a cross-linker and 1% benzoyl peroxide as an initiator. Nifedipine, an antihypertensive drug, was successfully encapsulated into these hydrogel microspheres by the equilibrium swelling method. Prepared hydrogel micropsheres were evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The chemical stability of the nifedipine after being encapsulated into prepared hydrogel microspheres was confirmed by FTIR, DSC, and XRD analysis. TGA indicates that prepared samples showed much better thermal stability than pure drug nifedipine. SEM images showed that prepared p(BA-co-IA) hydrogel microspheres are spherical in shape. The size distribution of prepared samples was found between 4.145 to 10 μm using a Malvern nanosize ZS instrument. The maximum percentage entrapment efficiency of nifedipine was found 67%, and % yield was about 72%. The maximum in vitro release studies of drug-loaded microspheres, which is 94.4% for the pH 7.4 buffer solution, demonstrated the pH sensitivity of prepared hydrogel microspheres. The cumulative drug release data were analyzed by using the Korsmeyer–Peppas equation to calculate a value of diffusion exponent (n), which follows non-Fickian diffusion.