Chitosan nanoparticles: a survey of preparation methods

The application of macromolecules in therapy is frequently hindered by stability and/or permeation issues. These limitations have been addressed by the pharmaceutical industry through the development of suitable noninjectable drug carriers. In this context, nanoparticles have emerged as one of the most exciting tools due to the increased surface-to-volume ratio, which provides an intimate interaction with epithelial surfaces. Nanoparticles further enable the encapsulated molecules to retain their biological activity, from the production steps to the final release. Chitosan has reached a prominent position as carrier-forming material, as diverse methods can be applied to produce nanoparticles using that excipient. These involve either hydrophilic or lipophilic environments that generally result in mild conditions or aggressive and time-consuming processes, respectively. In this review, a detailed description of methods used to produce chitosan nanocarriers is provided, accompanied by illustrative schemes of the procedures. The emphasis is on the variables reported to affect the final properties of the vehicles.