Role of micellar interface in the synthesis of chitosan nanoparticles formulated by reverse micellar method

Chitosan nanoparticles (Ch-NPs) have been extensively studied due to their wide applicability. The reverse micellar method has attracted special attention as a way to synthesize them, since it makes it possible to obtain size-controlled particles. This procedure involves the chitosan crosslinking reaction into polar cores of reverse micelles (RMs). Previous studies using sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) RMs as nanoreactors showed that by changing the reagent concentration and RM water content, the final particle size can be adjusted. To gain insight into this method, we studied the effect of the micellar interface on the synthesis of Ch-NPs. Both benzyl-n-hexadecyldimethylammonium chloride (BHDC) and AOT RMs were assessed, since there are remarkable differences between their interfacial water entrapped structure. Ch-NPs were characterized by FT-IR spectroscopy, Dynamic Light Scattering, and Scanning Electron Microscopy. Simulation studies by molecular theory were also performed. On the other hand, Ch-NPs obtained under different conditions were assessed in terms of their ability to solubilize curcumin, whose numerous therapeutic properties are somewhat countered by its poor solubility in water. The results show that Ch-NPs can be obtained from AOT and BHDC RMs by the reverse micellar method. The crosslinking reaction takes place in the micellar interface, and is more effective in AOT RMs. This difference in effectiveness can be attributed to the different positions Ch acquires in each of the two RMs tested. Finally, the NPs notably enhance the water solubility of curcumin, and particle size is the main determining factor for encapsulation efficiency.