full issue - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and PharmacyVol. 5 (2) 1084-1097 April 2011. ISSN 0973-8916 (Print), 2230-7303 (Online)1089Insulin release (%)PLGA 50:50 (EtAc:ESE)PLGA 50:50 (DCM:ESE)PLGA 50:50 (MPEG:MM)Insulin release (%)pH 1.2pH 5.6pH 7.4Time (hr)Fig. 2. Insulin release (%) from nanoparticles prepared bydifferent methods in phosphate buffer pH 7.4 at 37 0 C Datarepresented as the mean+SD (n=3)84% entrapment efficiency (EE) as shown inTable 1. Of the different methods of preparation,MM method resulted in lower EE%. However,there was no significant difference in Insulin EE%compared to nanoparticles prepared by ESEmethods (p>0.05). All nanoparticles prepared bydifferent methods showed negative zeta potentialat pH 7.4.Insulin Release from nanoparticles preparedby different methods : The release of insulinfrom nanoparticles prepared by different methodswas found to be biphasic (Fig. 2). The initial rapidrelease (burst effect) was high, where, 52%, 52.4,and 54.2% of the entrapped insulin was releasedfrom nanoparticles prepared by ESE (DCM),MM, ESE (ET-AC), respectively. This burstrelease in the first 5 minutes was followed byabout 8% release of insulin after 30 minutes incase of ESE (DCM) and MM methods. On theother hand, about 16% of insulin was releasedfrom nanoparticles of ESE (ET-AC) methodfollowing the burst release. After the first 30minutes, very slow release of minute amounts ofinsulin was observed over 24 hours.To use nanoparticles via the oral route, itis important to test the release of insulin atdifferent pH range. Insulin release fromnanoparticles of ESE (DCM) method wasselected for the test as they show no significantdifferences in release compared to MM method(P>0.05). The release of insulin was significantlyFig. 3. Effect of release medium pH on insulin release fromPLGA (50:50) nanoparticles prepared using ESE (DCM)method. Data represented as the mean+ SD. (n=3).affected by the external pH. Complete releaseof insulin occurred in 5 minutes at pH 1.2 asshown in Figure 3. However, the initial burstrelease was only 8% at pH 5.6 and 52% at pH7.4. After 24 hours, only 42.5% of insulin wasFig. 4. MALDI-TOF Mass spectra of standrd insulin (aand e), insulin extracted from nanoparticles prepared usingMM (b), ESE (ET-AC) (c), and ESE (DCM) (d) methods.Insulin concentration used was 0.2 mg/ml.Insulin immunogenicity (%)Time (hrs)Mass/ChargeESE (DCM) ESE (ET-AC) MMFig. 5. Immunogenicity of insulin, determined as the ratioof insulin detected by ELISA test to insulin detected byBCA protein assay kit.Mahmoud et al