Microspheres embedded in microbeads: A novel approach to improve various controlled release characteristics of highly water soluble drug through ionic gelation method

Abstract

The major hindrance behind the preparation of gellan microbeads by simple ionic gelation technique with aqueous soluble drugs is their low entrapment efficiency and sometimes its faster dissolution characteristics. This limits the employment of such a simple method for the preparation of microbeads of water-soluble drugs like stavudine. In the present study a novel attempt has been undertaken by embedding stavudine loaded Eudragit RSPO microspheres into gellan microbeads by ionotropic gelation method with an aim to improve its controlled drug delivery characteristics. The prepared microbeads were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and optical microscopy for surface topography, drug polymer interaction and particle size analysis respectively. Other studies like drug content, encapsulation efficiency and drug release studies were also carried out. The resulting microspheres embedded in microbeads were free flowing in nature with mean particle size ranging from 544.2-564.2 µm. SEM photomicrographs distinctly shows the microspheres embedded within the microbeads effectively with a smooth surface topography and the gellan microbeads containing D4T only are spherical in nature with rough surface. The FTIR study ascertained the compatibility of the drug within the formulation. The microspheres embedded in microbeads had enhanced percentage of drug content, drug entrapment efficiency and controlled release characteristics as compared to beads containing stavudine only. The mechanism of drug release from the formulations were found to follow non Fickian type diffusion with “n” value between 0.5 to 1but in case of stavudine loaded Eudragit RSPO microspheresit was found to be Fickian type.