RESUMEN
<p><b>AIM</b>To study the stability of insulin-loaded polybutylcyanoacrylate nanoparticles (IPN) in an oily medium (soybean oil containing 0.5% (v/v) Tween-20 and 5% (v/v) Vitamin E) along with the hypoglycemic effect following their oral administration to streptozotocin (STZ) induced diabetic rats.</p><p><b>METHODS</b>The stability of IPN in the process was appraised by measurement of the amount of undegraded insulin associated to nanoparticles, the average size and the span of IPN, as well as the release of insulin from IPN. IPN in an aqueous medium (containing 0.5% (v/v) Tween-20) at pH 2.0 was also investigated as control.</p><p><b>RESULTS</b>The study showed that IPN in the oily medium was more stable than that in the aqueous medium over one year of storage in the dark at (25 +/- 2) degrees C and the in vitro stability of IPN in the oily medium against degradation by proteolytic enzymes was much better than that in the aqueous medium. The apparent bioavailability of an oral administration of IPN (50 u x kg(-1)) in the oily medium versus an (sc) injection of insulin (2 u x kg(-1)) was 22.4%, much higher than that of IPN in the aqueous medium (15.5%), based on decreased areas above curve (AAC) determination for the blood glucose depression from time zero to 144 h of a single oral administration of IPN to STZ-diabetic rats.</p><p><b>CONCLUSION</b>IPN in soybean oil containing Tween-20 (0.5% v/v) and Vitamin E (5% v/v) could be considered as an effective and stable delivery system for oral insulin.</p>