Fatty acid and quaternary ammonium modified chitosan nanoparticles for insulin delivery

Liver is the major organ where insulin performs its physiological function. In this study, lauric acid and oleic acid were respectively conjugated to quaternized chitosan, and the fatty acid modified chitosan derivatives were used as the carriers to deliver the loaded insulin to liver. The nanoparticles with sizes of about 280 nm were fabricated via the electrostatic and hydrophobic interactions between insulin and the chitosan derivative. Both of insulin loading efficiency and loading capacity of the chitosan derivatives were higher than 98%. The surface hydrophobicity of the nanoparticles increased with the increases of fatty acid hydrophobicity and also fatty acid substitution degree of the chitosan derivative. The nanoparticles with higher surface hydrophobicity displayed higher hepatocyte absorption, more accumulation in the liver and better antidiabetic efficacy. Compared with free insulin treatment group, the relative pharmacological availabilities were 233% and 311% for the groups treated with the nanoparticles having lauric acid and oleic acid, respectively, after subcutaneous injection into diabetic mice. This study demonstrates that the nanoparticles fabricated from fatty acid modified polymer are an effective liver-targeted delivery system of insulin.