[Preparation of nanoparticles for sustained insulin release using poly (ethylene glycol) -poly (ε-caprolactone)-poly (N, N-diethylamino-2-ethylmethaerylate)].

OBJECTIVE: To prepare an insulin-loaded nanoparticle assembled using pH-sensitive poly(ethylene glycol)-poly(e-caprolactone)-poly(N,N-diethylamino-2-ethylmethaerylate) (mPEG-PCL-PDEAEMA) and investigate its performance of sustained insulin release in vitro and its hypoglycemic effects in diabetic rats. METHDOS: mPEG-PCL-PDEAEMA triblock copolymers with different hydrophobic lengths were synthesized by ring opening polymerization (ROP) combined with atom transfer radical polymerization (ATRP). The copolymers were characterized using Fourier-transform Infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance spectroscopy (1H-NMR). Insulin-loaded nanoparticles were prepared by nanoprecipitation technique, in which the reversible swelling of the pH-sensitive material was used for insulin loading and release. The obtained nanoparticles were further confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The entrapment efficiency (EE%), drug loading (DL%) and in vitro release characteristics of the insulin- loaded nanoparticles were assessed using BCA protein assay kit. The hypoglycemic effects of the nanoparticles were evaluated by monitoring the glucose levels. RESULTS: The size of the nanoparticles decreased as pH value increased within the range of 1.2 to 7.4. Using copolymers mPEG5k-PCL13k- PDEAEMA10k and mPEG5k-PCL10k-PDEAEMA10k as the drug carriers, the nanoparticles prepared with an optimal insulin-coplymer mass ratio of 90% had an average size of 181.9∓6.67 nm and 169∓7.1 nm, maximal EE% of (81.99∓1.77)% and (53.12∓0.62)%, and maximal DL% of (42.46∓0.53)% and (32.34∓0.26)%, respectively. Compared with free insulin, the insulin-loaded nanoparticles was capable of sustained insulin release and the release rate was lowered as the hydrophobic length increases. In diabetic rats, the insulin-loaded nanoparticles based on mPEG5k-PCL13k- PDEAEMA10k maintained a sustained hypoglycemic effect for 48 h, which was significantly longer than the time of free insulin. CONCLUSION: The pH-sensitive triblock copolymer mPEG-PCL-PDEAEMA can serve as a promising candidate of carrier for sustained release of insulin.