Recombinant Human Insulin- PLGA NP Administered Orally after Combination with a Protease Inhibitor (N-Ethylmaleimide) in vivo Results

Based on our published results, insulin PLGA NP composed from human insulin (5 mg) encapsulated in PLGA 2.5% (w/v) mixed with PEG (2 kDa, 5% w/w) and the external aqueous phase contained 1.25% of PVA (%w/v) were prepared by the modified double emulsion solvent evaporation technique [1,2]. The resulting NP have been investigated for oral administration of recombinant human insulin (100 IU/kg) in diabetic rats [3]. Our animal model, Male Sprague–Dawley rats (12-week-old, obtained from National researches center, Cairo, Egypt.) weighing 250-300 gm were fasted for 6 hours prior to the induction of type I diabetes via i.p injection of streptozotocin (50-60 mg.kg-1, pH=4.5). Rats with blood glucose levels >250 mg dl-1 were considered to be in a diabetic state. Three percent sodium bicarbonate solution (500 μL) in phosphate buffer saline (PBS) was administered through an oral gavage to neutralize gastric acid, a protease inhibitor -PI-(NEthylmaleimide, 2 mM) was physically mixed with free insulin or insulin PLGA-NP before oral administration [4,5]. To investigate the effect of PI, other two animal groups of rats were utilized for free insulin and insulin PLGA-NP without PI (Figure 1) [6,7].