Effects of microwave on drug-release responses of spray-dried alginate microspheres

Abstract

Context: Microspheres prepared from rigid guluronic acid- (MG) and flexible mannuronic acid-rich (MC) alginate will undergo different drug release changes with respect to the influence of microwave on the matrix. An in-depth understanding of their differences in drug release changes is attainable through investigating cross-linking agent-free alginate microspheres prepared by spray-drying technique. Objective: The behavior of MG and MC alginate in controlling drug release responses of spray-dried microspheres against microwave was investigated. Sodium diclofenac was used as a model water-soluble drug. The formed microspheres were subjected to drug release, drug content, size, shape, surface morphology, Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffractometry analysis. Results: MC microspheres required a shorter period of microwave irradiation to reduce drug release extent than MG microspheres. In response to microwave, the drug release profiles of 1:1 MG—MC microspheres resembled MC microspheres. Discussion: The state of polymer—polymer and drug—polymer interaction via O–H and/or N–H moiety of microspheres was affected by alginate chain flexibility under the influence of microwave. It then governed the drug release responses of microspheres. Conclusion: The drug release property of alginate microspheres can be modified by microwave irradiation, and its changes are a function of alginate conformation.