The encapsulation of drugs inside polymeric nanoparticles/microparticles is a strategy currently employed in the search for new and more effective therapies. The use of biocompatible and biodegradable polymers gives several advantages to these formulations. Protection of the active principals against the action of environmental and physiological agents, the reduced number of doses and a subsequent decrease in drug-related adverse effects, and increased bioavailability are some of these advantages. Several methods and materials are now used to synthesize nanoparticles/microparticles for biomedical applications, from carbon-derived structures to metallic and lipid particles. However, among the methods using polymers, ionotropic gelation is one of the more affordable and easier procedures to perform in daily laboratory work. In this mini-review, we address relevant characteristics of ionotropic gelation, beginning with basic aspects of the technique, which reagents and conditions are commonly used, the factors affecting the stability of the formulation, the advantages and disadvantages of the method and some principal characterization techniques for the nanoparticulate/microparticulate formulation. Finally, we conclude with a few important considerations.

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The capability of some polymers, such as chitosan, to form low cost gels under mild conditions is of great application interest. Ionotropic gelation of chitosan has been used predominantly for the preparation of gel beads for biomedical application. Only in the last few years has the use of this method been extended to the fabrication of chitosan-based flat structures. Herein, after an initial analysis of the major applications of chitosan flat membranes and films and their usual methods of synthesis, the process of ionotropic gelation of chitosan and some recently proposed novel procedures for the synthesis of flat structures are presented.

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