Another approach to delivery of inhaled anticancer agents is to employ 1-5 pm particles in the dry state that swell to form larger particles in the warm and humid environment of the lung, are able to evade being engulfed by alveolar macrophages, and could be employed as carriers for drug-loaded NPs (El-Sherbiny et al. 2010).
Amphipathic surfactant molecules self-assemble to a core-shell nanostructure in aqueous solution at a certain concentration and temperature to form polymeric micelles. Micelles represent colloidal dispersions with particle size from 5 to 50-100 nm. At low concentrations, these amphiphilic molecules exist separately as unimers; however, at a critical micelle concentration, they aggregate to form micelles, which are close to spherical in shape. The hydrophobic fragments of amphiphilic molecules form the core of a micelle, and poorly soluble pharmaceuticals can be carried in the core. The structure of these micelles can be chemically altered to improve drug stability, provide controlled drug release, and provide targeted drug delivery (Lavsanifar et al. 2002).
Aerosol Delivery Devices
Traditionally, pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs), and nebulizers have been employed as aerosol generators, but pMDIs and DPIs are rarely employed for delivery of anticancer agents. More modern technologies generate aerosols by passing a solution through a vibrating mesh (e.g., Aeroneb® or eFlow®), by producing a soft mist from a drug solution (e.g., Respimat® and AERx®), or by evaporative condensation of a drug powder (e.g., Staccato® inhaler) (Dolovich and Dhand 2011). Other DPIs utilize compressed air (e.g., Exubera®) or electrical vibration (e.g., Microdose®) to disperse powder formulations. Aerosols generated by the Microsprayer® could be targeted to specific intrapulmonary sites.