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Current Trends in Biotechnology and PharmacyVol. 5 (2) 1084-1097 April 2011. ISSN 0973-8916 (Print), 2230-7303 (Online)1091increased cell viability from 148.55% to 199.61%as the concentration of insulin increased from 7.5to 12 µg/ml, respectively. The same behavior wasobserved when preparing nanoparticles by ESE(ET-Ac) technique. Also, Nanoparticles preparedby MM method increased cell viability from168.56% to 191.4% as insulin content increasedfrom 7.5 to 12 ìg/ml, respectively.In vivo effects of nanoparticles loaded withinsulin on diabetic ratsIn contrast to the in vitro release results,where about 60% to 70% of insulin was releasedin the first 30 minutes, insulin nanoparticles haveprolonged the hypoglycemic effect of the drugmore than 24 hours compared to control insulinsolution of the same dose (Figure 7). This clearlyshowed lack of in vitro/in vivo correlation forinsulin containing nanoparticles . After thesubcutaneous administration of 10 IU of insulininto diabetic rats as solution (in PBS, pH 7.4) andencapsulated in nanoparticles prepared by ESE(DCM), ESE (Et-Ac), and MM methods, theblood glucose levels decreased by 14.44%,35.50%, 19.70% and 22.12%, respectively after30 minutes. However, only nanoparticles of ESE(DCM) showed significantly lower blood levelscompared to the remaining formulations and thecontrols (p0.05). At 3 hours, blood glucose levelsdecreased by 69.30%, 63.81%, 56.33%, and77.54% using insulin solution, nanoparticles ofESE (DCM), ESE (Et-Ac), and MM methods,respectively, and the differences between thegroups are not statistically significant (P>0.05).Blood glucose levels were significantly lower(p
Current Trends in Biotechnology and PharmacyVol. 5 (2) 1084-1097 April 2011. ISSN 0973-8916 (Print), 2230-7303 (Online)1092that R was proportional to the size of the PLGAnanoparticles, while χ was inversely proportionalto it (28). The size distributions of the PLGAnanospheres prepared with different waterimmiscible, water miscible and partially watermiscible solvents when PVA (1%) was used asthe stabilizer were also studied (29). There wasno significant difference in particle size betweenpartially water soluble like ET-AC or fully watersoluble solvent like acetone. Also, the studyconcluded that the larger particle size ofnanoparticles prepared using DCM was due toits immiscibility with water causing significantaggregation of emulsion droplets.The zeta potential results showed thatinsulin nanoparticles were negatively charged. Itis well known that insulin above its PI (5.5)acquires a partial negative charge and becauseinsulin’s relatively smaller molecular size (6 kDa)when compared to other peptides, it might diffuseto the nanoparticle surface and impart negativecharge to nanoparticles at the pH of 7.4 (30,31).The drug present on the surface of thenanoparticles gets released quickly upon exposureto media, resulting in the initial burst of insulin(32). Previous studies have shown that the particlesize of microparticle did not significantly affectthe drug in-vitro release profiles (33). Hence, thevariability in the release profiles may not be dueto variability in the nanoparticle size.The release of insulin was found to besimilar from nanoparticles prepared by aqueousMM method and by ESE (DCM) method. Bothmethods showed lower burst release of insulincompared to ESE (ET-AC) method. A plausibleexplanation is that an increase in the hydrophilicityof ET-Ac enhanced the migration of insulinmolecules to the surface of nanoparticles andinsulin subsequently adsorbs to the nanoparticlessurface after the evaporation of the solvent(34,35). On the other hand, higher viscosity ofMPEG, resulted in the accumulation of smallerinsulin molecules on the nanoparticle surface byMM method. Thus, the drug release is largelycontrolled by the weak affinity between the insulinand the polymer, which resulted in a higher burstrelease (36).The solubility of insulin varies at differentpH conditions: >10 mg/ml,
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(December 7-9, 2011)Venue: Karunya
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