chitosan and plga microspheres as drug delivery ... - UniCA Eprints

7. RFP Loaded PLGA Coated Chitosan Microspheres Obtained by WSD Method7.1.3.5. Nebulization of MicrospheresA compressor nebuliser system (Medel Aerofamily, Italy) was used in the study. A volume of3 ml of sample was used for the nebulization. The aerosols containing RFP-loaded PLGAcoated chitosan microspheres were collected in water using a modified 3 stages glassimpinger. The impinger device was utilized with the collecting flask containing 3 ml of waterto which the aerosol was introduced through a calibrated glass tube and critical orificedelivering the jet of aerosol 5mm above the bottom of the flask.After aerosolization (10 min.), the impinger contents were assayed in order to evaluate theeffect of nebulization on drug leakage of microspheres. It was also important to determine thetotal amount of formulation nebulised into the apparatus. The nebulization efficiency (N.E%)of microsphere formulations is defined as the total output of drug collected on the impinger asa percentage of the total submitted to nebulization.NE% = (Aerosolised drug /Total drug placed in nebuliser) x 100Because nebulization can lead to drug leakage, it is important also to determine thenebulization efficiency of the encapsulated drug (NEED%). This parameter is defined as thepercentage of aerosolised drug that remains encapsulated after nebulization. A portion ofnebulised sample was purified by centrifugation and the amount of drug in the sample afterand before centrifugation was assayed.After nebulization particle size distribution was measured in order to ervaluate the effect ofthis process on this parameter.7.1.4. Release Studies/Stability StudiesIn vitro release of RFP from PLGA coated chitosan microspheres was determined using as therelease mediums, phosphate buffer pH 7.4 and acetate buffer pH 4.4, in order to simulate thecondition in lungs and in particular the conditions inside lysosomes and phagosomes. Freezedriedformulations were suspended in 500 ml of the dissolution medium, and the amount ofmicrospheres was varied in order to kept constant the amount of drug (25 mg). Theexperiments were carried out at 37 ± 0.3°C at a rotation speed of 100 ± 2 rpm. A measure of 1ml samples was withdrawn at appropriate time intervals and centrifuged at 10000 rpm.Supernatants were diluted suitably with acetonitrile and absorbance of the resulting solutionwas measured at 485 nm. The residue (after centrifugation) was redispersed in 1 ml of thefresh dissolution medium and replaced back into the dissolution apparatus. The cumulativeamount of RFP was obtained from the calibration curves of RFP in acetonitrile. The stock105