title: The influence of actuator materials and nozzle designs on electrostatic charge of pressurised metered dose inhaler (pMDI) formulations.
abstract: OBJECTIVE
  To investigate the influence of different actuator materials and nozzle designs on the electrostatic charge properties of a series of solution metered dose inhaler (pMDI) aerosols.
  
  
  METHODS
  Actuators were manufactured with flat and cone nozzle designs using five different materials from the triboelectric series (Nylon, Polyethylene terephthalate, Polyethylene-High density, Polypropylene copolymer and Polytetrafluoroethylene). The electrostatic charge profiles of pMDI containing beclomethasone dipropionate (BDP) as model drug in HFA-134a propellant, with different concentrations of ethanol were studied. Electrostatic measurements were taken using a modified electrical low-pressure impactor (ELPI) and the deposited drug mass assayed chemically using HPLC.
  
  
  RESULTS
  The charge profiles of HFA 134a alone have shown strong electronegativity with all actuator materials and nozzle designs, at an average of -1531.34 pC ± 377.34. The presence of co-solvent ethanol significantly reduced the negative charge magnitude. BDP reduced the suppressing effect of ethanol on the negative charging of the propellant. For all tested formulations, the flat nozzle design showed no significant differences in net charge between different actuator materials, whereas the charge profiles of cone designs followed the triboelectric series.
  
  
  CONCLUSIONS
  The electrostatic charging profiles from a solution pMDI containing BDP and ethanol can be significantly influenced by the actuator material, nozzle design and formulation components. Ethanol concentration appears to have the most significant impact. Furthermore, BDP interactions with ethanol and HFA have an influence on the electrostatic charge of aerosols. By choosing different combinations of actuator materials and orifice design, the fine particle fractions of formulations can be altered.
authors.affiliation: Respiratory Technology Woolcock Institute of Medical Research and Discipline of Pharmacology Sydney Medical School, University of Sydney, Sydney, NSW, 2037, Australia.
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
authors.forename: Paul M
authors.initials: PM
authors.lastname: Young
authors.forename: David F
authors.initials: DF
authors.lastname: Fletcher
authors.forename: Hak Kim
authors.initials: HK
authors.lastname: Chan
authors.forename: Edward
authors.initials: E
authors.lastname: Long
authors.forename: David
authors.initials: D
authors.lastname: Lewis
authors.forename: Tanya
authors.initials: T
authors.lastname: Church
authors.forename: Daniela
authors.initials: D
authors.lastname: Traini
mesh_terms: D000336:Aerosols; D002851:Chromatography, High Pressure Liquid; D004867:Equipment Design; D036501:Metered Dose Inhalers; D055672:Static Electricity
chemical_list: D000336:Aerosols