Synthesis and characterization of carboxymethyl chitosan carrying ricinoleic functions as an emulsifier for azadirachtin

An amphiphilic carboxymethyl chitosan with ricinoleic acid (R-CM-chitosan) was synthesized, and was used as a carrier for the botanical pesticide azadirachtin (Aza), which formed a Aza/R-CM-chitosan water dispersion on the nanoscale level. The shape, zeta potential, loading efficiency and outdoor stability of the Aza/R-CM-chitosan nanoparticle were characterized. The relationship between the nanoparticle's performance and the constituents' concentrations in a water-dispersion was discussed. The results indicated that the nanoparticle's size, polydispersity index and zeta potential were all influenced by the concentration ratio of the carrier to the drug, especially for ratios between 5 and 15. The Aza/R-CM-chitosan nanoparticle had a small (200-500 nm) and polydisperse particle size, with a negative charge on the particle surface. R-CM-chitosan efficiently restrained Aza degradation in a natural environment, as the loading efficiency reached up to 56%. Furthermore, Aza/R-CM-chitosan provided a better controlled release of the drug compared to the control groups. (c) 2012 Elsevier Ltd. All rights reserved.