Effect of crystallinity on electrostatic charging in dry powder inhaler formulations.
OBJECTIVE
This study aimed to characterize inherent charge generated by micron-sized drug-only formulations of amorphous and crystalline salbutamol sulfate (SS).


METHODS
Amorphous SS was produced by spray-drying whilst crystalline SS was produced by conditioning spray-dried SS with supercritical CO2 and menthol. Electrostatic charge of the powders was characterized in two ways. Firstly, the charge profile of the aerosols dispersed from an Aerolizer® was measured using a modified Electrostatic Low Pressure Impactor (ELPI™). Secondly, the net charge of the bulk powders generated from tumbling in containers composed of different materials (polyethylene, polyvinyl chloride, Teflon, nylon and stainless steel) was measured by a Faraday pail.


RESULTS
Following aerosolization, crystalline SS appeared to show more consistent charging and mass deposition than amorphous SS. In the tumbling experiment crystalline SS had a significant correlation between net charge and work function, which was absent in amorphous SS. This may be due to the long-range crystal packing which was reflected as more predictable charging. In addition, the polarity of charging was attributed to the arrangement of SS molecules in the crystal lattice.


CONCLUSIONS
The effect of crystallinity on the electrostatic charge behavior of inhalable micron-sized spherical drug particles with well-defined particle size distribution was investigated for the first time. The knowledge gained may assist in the development of optimized inhaled pharmaceutical products.
Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney, Sydney, New South Wales, Australia.
Jennifer
J
Wong
Philip Chi Lip
PC
Kwok
Tim
T
Noakes
Ali
A
Fathi
Fariba
F
Dehghani
Hak-Kim
HK
Chan
D000280:Administration, Inhalation; D000336:Aerosols / Q000008:administration & dosage / Q000737:chemistry; D000420:Albuterol / Q000008:administration & dosage / Q000737:chemistry*; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000737:chemistry*; D003460:Crystallization; D058995:Dry Powder Inhalers; D010316:Particle Size; D011208:Powders; D055672:Static Electricity
D000336:Aerosols; D001993:Bronchodilator Agents; D011208:Powders; D000420:Albuterol