Entrapment of unstable active compounds by chitosan nanocapsules

Abstract

In this work, mPEG-phthaloylchitosan and mPEG-4-methoxycinnamoyl-phthaloylchitosan nanoparticles were synthesized. The synthetic processes involved 1) reacting of chitosan with phthalc anhydride to give phthaloylchitosan which was soluble in organic solvent 2) esterifying of mPEG-COOH (and 4-methoxycinnamic acid) with the phthaloylchitosan and 3) preparing nanopaticles from the chitosan derivatives by solvent displacement method. Grafting of mPEG-COOH onto chitosan gave mPEC-phthaloylchitosan with 7% degree of substitution. The obtained product is negatively charged (-30.3 mV) nanoparticles with an average sizes of 40-150 nm. Studying of patch test and photopatch test of the particles showed no sign of irritation to the human skin. Furthermore, encapsulation of 2-ethylhexyl-p-methoxycinnamate (EHMC), ascorbyl palmitate and astaxanthin into the particles gave the particles with 45, 39 and 94% (w/w) of the actives in the particles at encapsulation efficiency (EE) of more than 97% (w/w). Photostabilitys tudy indicated that the EHMC that was encapsulated into the prepared particles was more photostable than the free EHMC. Grafting of mPEG-COOH and 4-methoxycinnamic acid onto phthaloylchitosan gave mPEG-4-methoxycinnamoyl-phthaloylchitosan with degree of substitution of 0.313 and 5.7%, respectively. The product is negatively charged (-31.53) nanoparticles with the average sizes of 100-450 nm. Encapsulation of astaxanthin and ascorbyl palmitate into the particles gave product with 22 and 69% (w/w) of the actives at 100% EE.