Polymeric colloidal systems containing ethionamide: preparation and physico-chemical characterization

The association of ethionamide with different colloidal systems was evaluat ed. Nanocapsules (NC), nanospheres (NS), and nanoemulsions (NE) were prepar ed by interfacial deposition and spontaneous emulsification techniques. Eth ionamide was incorporated before (B) and after (A) preparation of nanoparti cles. Ethionamide was assayed by HPLC, the particle size was determined usi ng a Nanosizer(R), and the zeta potential using a Zetasizer(R) 4. Free ethi onamide was determined using a combined ultrafiltration-centrifugation tech nique. The drug release was determined by direct dilution of the nanopartic le dispersion in phosphate-buffer pH 7. All preparations retained acceptabl e particle size distribution (+/-300 nm), except the NE. The zeta potential of all formulations was between -36.6 mV and -46.1 mV. Percentages of ethi onamide associated were: NC (B: 62.4%, A: 56.2%), NS (B: 53.0%, A: 43.2%), and NE (B: 38.5%). After 45 days, the percentage of drug association with N C increased (B: 66.8%, A: 60.6%). The release profiles demonstrated that as sociated ethionamide was more readily released from the NC and NS prepared by procedure A rather than B. The ethionamide amount not released (B) was g reater in NS than NC. The drug is mainly adsorbed onto the surface of nanop articles. However, approximately 10% of ethionamide is encapsulated into NC and 20% entrapped into NS, respectively.