Chondroitin sulfate-capped gold nanoparticles for the oral delivery of insulin

Chondroitin sulfate (CS)-capped gold nanoparticles (AuNPs) were synthesized and its feasibility for oral insulin (INS) delivery was investigated in vivo. CS was used as both reducing and stabilizing agent in the synthesis of AuNPs with around 48 nm mean diameter, narrow size distribution, and negative zeta potential. After loading INS into CS-capped AuNPs structure, NPs with about 123 nm mean diameter, narrow size distribution, and negative zeta potential were successfully fabricated. By surface plasmon resonance (SPR) measurement, 0.5% (w/v) CS was chosen for the synthesis of AuNPs. Stability of AuNPs and AuNPs/INS was maintained for 7 weeks according to SPR study. Cytotoxicity of AuNPs/INS in Caco-2 cells was measured and no significant cytotoxicity was observed in tested AuNPs concentration range. In the streptozotocin-induced diabetic rat model, the oral administration of AuNPs/INS exhibited an efficient regulation of glucose level, compared to INS solution-treated group. The mean INS concentration in plasma at 120 min after oral administration of AuNPs/INS was 6.61-fold higher than that of INS solution-administered group. All of these findings indicate the successful application of CS-capped AuNPs for oral delivery of INS to the therapy of diabetes.