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

1. General Introductionthe subject of extensive research. Some of these studies have been conducted with theintention of targeting drugs selectively to the lung (171). However, the biodegradability, lackof toxicity and immunogenicity, ready availability and capability to undergo chemicalmodification could render them suitable as a carrier for inhalation of drugs. The possibility ofusing drug-containing albumin microspheres (172) as an inhaled dry powder was alsoinvestigated, employing similar preparation and in vitro evaluation procedures (173).Tetrandrine, an antisilicotic alkaloid, was entrapped in albumin microspheres and factorialdesign employed to optimise particle size and drug entrapment. The tetrandrine recoveredfrom the lower stage of a twin-stage liquid impinger operated under the pharmacopoeialconditions was 13.83 ± 2.58% (n = 6) and such levels were considered sufficient fortherapeutic efficiency. Thus, albumin microspheres have the potential to deliver tetrandrine tothe alveolar region where they may be metabolised to incorporate the drug in alveolarmacrophages, which are thought to be the main site of action of tetrandrine.Also PGL microspheres as a successful drug delivery system, have been used for targetingand controlled release of a wide range of drugs, including peptides and proteins (174). Theirpotential use in pulmonary delivery has also been explored. Masinde and Hickey (175) wereable to prepare poly(lactic acid) (PLA) microspheres with particle sizes between 1 and 11µmby a solvent evaporation technique. After suspending the microspheres in a non-surfactantsolution this was subsequently atomised by a jet nebulizer, particles were generated whichwere suitable for drug delivery to the lower airways, having a median diameter of 2 µm andgeometric standard deviation of 2.4/zm. Sustained bronchodilation was reported by Lai et al.(176) after PGL microspheres with a mean diameter of 4.5/zm containing entrappedisoproterenol (7% w/w) were intratracheally administered to Long-Evans rats. Even though70% of the incorporated isoproterenol had been released from the MS into the instillationmedium prior to administration, the drug still significantly ameliorated serotonin-inducedbronchoconstriction for more than 12 h at a dose of 0.1 mg kg -1.The use of polymeric microparticles to deliver anti-tubercular drugs (ATDs) by differentroutes (injectable, oral and aerosol) has been reported by several investigators. In recent years,one of the best ways to achieve higher drug levels in the lungs has been the development ofnew formulations (microparticle-based) that are directly delivered to the lungs via the aerosolroute.For example, several groups have investigated respiratory delivery of microsphereencapsulatedantibiotics for the local treatment of tuberculosis (177, 178). It has been32