Liposome Delivery to the Respiratory System
A significant volume of our research has focused on the development of nanosystems which are both stable and can be manufactured on a large scale.
Novel proliposome formulations have been developed for nasal and pulmonary drug delivery. Our recent studies have utilised vibrating mesh nebulisers in delivery of liposomes. These devices have a vibrating plate with multiple apertures through which liquid is passed to form an aerosol. Our studies have shown that these nebulisers are highly suitable for delivering liposomes using proliposome technologies.
The novel mechanism of aerosol generation using this type of nebulisers offers advantages over established nebulisers which destabilise liposomes by shearing or thermal degradation. In collaboration with Aerogen, Ireland, micropump nebulisers with various mesh sizes were developed permitting optimisation of formulation delivery in terms of aerosol droplet size and liposome stability. Large mesh nebulisers (8 μm) enhanced liposome stability to nebulisation as higher amounts of the originally entrapped drug was retained in liposomes after nebulisation to a two-stage impinger.
The use of liposomes in nasal delivery provides a means for the entrapped drug to cross the epithelial barrier in order to treat systemic diseases. Using an ethanol-based proliposome technology, mucoadhesive liposomes were developed for protein delivery. Moreover, the ability of liposomes to solubilise poorly soluble drugs and enhance the permeability of macromolecules (e.g. gene and protein) has been exploited and novel strategies of mucosal vaccination using the nasal delivery route are being investigated. Studies in the field of drug delivery to the respiratory system are ongoing using surface-based systems, mucoadhesive formations , cochleates and niosomes.
The thermal behaviour of liposomes prepared using different technologies and excipients is being investigated. For instance, we have found that liposomes prepared by proliposome methods exhibited different modes of phase transition compared to vesicles prepared by the conventional thin-film method. Moreover, the extent and mode of liposome bilayer interaction with the model antiasthma steroid beclometasone dipropionate was different when such different preparation methods were used.