Investigations of gas and particle dynamics in first generation needle-free drug delivery devices |
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Authors: | NJ Quinlan MAF Kendall BJ Bellhouse RW Ainsworth |
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Institution: | (1) PowderJect Centre for Gene and Drug Delivery Research, University of Oxford, Oxford OX2 6PE, UK , GB;(2) Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK , GB |
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Abstract: | Abstract. Transdermal powdered drug delivery involves the propulsion of solid drug particles into the skin by means of high-speed gas-particle
flow. The fluid dynamics of this technology have been investigated in devices consisting of a convergent-divergent nozzle
located downstream of a bursting membrane, which serves both to initiate gas flow (functioning as the diaphragm of a shock
tube) and to retain the drug particles before actuation. Pressure surveys of flow in devices with contoured nozzles of relatively
low exit-to-throat area ratio and a conical nozzle of higher area ratio have indicated a starting process of approximately
200 s typical duration, followed by a quasi-steady supersonic flow. The velocity of drug particles exiting the contoured nozzles
was measured at up to 1050 m/s, indicating that particle acceleration took place primarily in the quasi-steady flow. In the
conical nozzle, which had larger exit area ratio, the quasi-steady nozzle flow was found to be overexpanded, resulting in
a shock system within the nozzle. Particles were typically delivered by these nozzles at 400 m/s, suggesting that the starting
process and the quasi-steady shock processed flow are both responsible for acceleration of the particle payload. The larger
exit area of the conical nozzle tested enables drug delivery over a larger target disc, which may be advantageous.
Received 12 March 2000 / Accepted 8 June 2000 |
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Keywords: | : Needle-free drug delivery Transdermal powdered drug delivery Powder injection Biolistics Supersonic nozzle Shock tube Doppler global velocimetry |
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