Microbead design for sustained drug release using four natural gums

sodiuma b s t r a c tFour natural gums, namely albizia, cissus, irvingia and khaya gums have been characterized and evaluatedas polymers for the formulation of microbeads for controlled delivery of diclofenac sodium. The naturalgums were characterized for their material properties using standard methods. Diclofenac microbeadswere prepared by ionotropic gelation using gel blends of the natural gums and sodium alginate at differentratios and zinc chloride solution (10%w/v) as the crosslinking agent. The microbeads were assessed usingSEM, swelling characteristics, drug entrapment efficiencies and release properties. Data obtained fromin vitro dissolution studies were fitted to various kinetic equations to determine the kinetics and mech-anisms of drug release, and the similarity factor, f2, was used to compare the different formulations. Theresults showed that the natural gum polymers varied considerably in their material properties. Sphericaland discrete microbeads with particle size of 1.48–2.41 m were obtained with entrapment efficienciesof 44.0–71.3%w/w. Drug release was found to depend on the type and concentration of polymer gumused with formulations containing gum:alginate ratio of 3:1 showing the highest dissolution times. Con-trolled release of diclofenac was obtained over for 5 h. Drug release from the beads containing the polymerblends of the four gums and sodium alginate fitted the Korsmeyer–Peppas model which appeared to bedependent on the nature of natural gum in the polymer blend while the beads containing alginate alonefitted the Hopfenberg model. Beads containing albizia and cissus had comparable release profiles to thosecontaining khaya (f2> 50). The results suggest that the natural gums could be potentially useful for theformulation controlled release microbeads.