Chitosan-clay nanocomposite microparticles for controlled drug delivery: Effects of the MAS content and TPP crosslinking

Chitosan and clays can form nanocomposites via electrostatic interactions, offering an interesting potential as advanced drug delivery systems. Such nanocomposites can be prepared in the form of microparticles using spray-drying. The objective of this study was to produce and characterize spray-dried chitosan-magnesium aluminum silicate (MAS) nanocomposite microparticles, loaded with propranolol HCl. The effects of the MAS content and addition of the crosslinking agent sodium tripolyphosphate (TPP) were investigated. The incorporation of MAS rendered the microparticles less spherical. The spray-dried particles exhibited an intercalated nanocomposite structure, the drug being dispersed in an amorphous form and/or dissolved in the systems. Interestingly, propranolol release was sustained during several hours from all types of microparticles in 0.1 M HCl and phosphate buffer pH 7.4, and no burst release was observed. This is rather surprising, because the particles were in the lower micrometer range, and chitosan is soluble at acidic pH. These results highlight the importance of "drug - chitosan" and "drug - MAS" interactions in this type of nanocomposite microparticles. With increasing MAS content drug release clearly slowed down at low and neutral pH, whereas the incorporation of 1-3% TPP caused only a slight/moderate decrease in the release rate, irrespective of the type of release medium. (C) 2017 Elsevier B.V. All rights reserved.