title: Effect of ultrasound parameters on the release of liposomal calcein.
abstract: The ultrasound exposure parameters that maximize drug release from dierucoyl-phosphatidylcholine (DEPC)-based liposomes were studied using two transducers operating at 300 kHz and 1 MHz. Fluorescent calcein was used as a model drug, and the release from liposomes in solution was measured using a spectrophotometer. The release of calcein was more efficient at 300 kHz than at 1 MHz, with thresholds of peak negative pressures of 0.9 MPa and 1.9 MPa, respectively. Above this threshold, the release increased with increasing peak negative pressure, mechanical index (MI), and duty cycle. The amount of drug released followed first-order kinetics and increased with exposure time to a maximal release. To increase the release further, the MI had to be increased. The results demonstrate that the MI and the overall exposure time are the major parameters that determine the drug's release. The drug's release is probably due to mechanical (cavitation) rather than thermal effects, and that was also confirmed by the detection of hydroxide radicals.
authors.affiliation: Department of Physics, The Norwegian University of Science and Technology, Trondheim, Norway. mercy.afadzi@ntnu.no
authors.forename: Mercy
authors.initials: M
authors.lastname: Afadzi
authors.forename: Catharina de L
authors.initials: Cde L
authors.lastname: Davies
authors.forename: Yngve H
authors.initials: YH
authors.lastname: Hansen
authors.forename: Tonni
authors.initials: T
authors.lastname: Johansen
authors.forename: Oyvind K
authors.initials: OK
authors.lastname: Standal
authors.forename: Rune
authors.initials: R
authors.lastname: Hansen
authors.forename: Svein-Erik
authors.initials: SE
authors.lastname: Måsøy
authors.forename: Esben A
authors.initials: EA
authors.lastname: Nilssen
authors.forename: Bjørn
authors.initials: B
authors.lastname: Angelsen
mesh_terms: D003692:Delayed-Action Preparations / Q000737:chemistry* / Q000528:radiation effects*; D004058:Diffusion / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005452:Fluoresceins / Q000737:chemistry* / Q000528:radiation effects; D008081:Liposomes / Q000737:chemistry* / Q000528:radiation effects*; D011829:Radiation Dosage; D013010:Sonication / Q000379:methods*
chemical_list: D003692:Delayed-Action Preparations; D005452:Fluoresceins; D008081:Liposomes; C007740:fluorexon