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

4. RFP Loaded Chitosan Microspheres Prepared by Precipitation Method4.1.3.4. Measurement of Loading Efficiency of RFP in Chitosan MicrospheresA series of RFP solutions of known concentrations in acetonitrile were prepared, andabsorbances were measured in order to generate a standard curve.The rifampicin content of each lot of microspheres was determined by first extracting the RFPand quantifying the amount of drug spectrophotometrically.The drug encapsulation efficiency was calculated as the percentage of drug entrapped inmicrospheres compared with the initial amount of drug recovered in unpurified samples. Theconcentration of rifampicin contained in each sample was determined by measuring theabsorbance on a spectrophotometer at 485 nm.4.1.3.5 Nebulization Studies 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 chitosanmicrospheres were collected in water using a modified 3 stages glass impinger similar tothose in Figure 4.1. The impinger device was utilized with the collecting flask containing 3 mlof water to which the aerosol was introduced through a calibrated glass tube and criticalorifice delivering the jet of aerosol 5 mm above the bottom of the flask.After aerosolization (10 minutes), and taking into account the dilution (after measuring theexact volume of dispersion collected), the RFP contained in the impinger were assayed inorder to evaluate the effect of nebulization on drug leakage from microspheres and the totalamount of formulation nebulised into the apparatus. The Nebulization Efficiency (NE%) ofmicrosphere formulations is defined as the total output of drug collected on the impinger as apercentage of the total drug submitted to nebulization.NE% = (Aerosolised drug /Total drug placed in nebuliser) x 100Because nebulization can lead to drug leakage, it is important to also 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 beforeand after centrifugation was assayed.56