MICROENCAPSULATION OF DNA WITHIN ALGINATE MICROSPHERES AND CROSS-LINKED CHITOSAN MEMBRANES FOR IN-VIVO APPLICATION

Calf thymus DNA was microencapsulated within crosslinked chitosan memb ranes, or immobilized within chitosan-coated alginate microspheres. Mi crocapsules were prepared by interfacial polymerization of chitosan, a nd alginate microspheres formed by emulsification/internal gelation. D iameters ranged from 20 to 500 mu m, depending on the formulation cond itions. Encapsulated DNA was quantified in situ by direct spectrophoto metry (260 nm) and ethidium bromide fluorimetry, and compared to DNA m easurements on the fractions following disruption and dissolution of t he microspheres. Approximately 84% of the DNA was released upon core d issolution and membrane disruption, with 12% membrane bound. The yield of encapsulation was 96%. Leakage of DNA from intact microspheres/cap sules was not observed. DNA microcapsules and microspheres were recove red intact from rat feces following gavage and gastrointestinal transi t. Higher recoveries (60%) and reduced shrinkage during transit were o btained with the alginate microspheres. DNA was recovered and purified from the microcapsules and microspheres by chromatography and differe ntial precipitation with ethanol. This is the first report of microcap sules or microspheres containing biologically active material (DNA) be ing passed through the gastrointestinal tract, with the potential for substantial recovery.