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Focused ultrasound influence on calcein-loaded thermosensitive stealth liposomes.

International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group (2015-02-14)
Anthony Novell, Chantal Al Sabbagh, Jean-Michel Escoffre, Cédric Gaillard, Nicolas Tsapis, Elias Fattal, Ayache Bouakaz
ABSTRACT

Focused ultrasound (FUS) is a versatile technology for non-invasive thermal therapies in oncology. Indeed, this technology has great potential for local heat-mediated drug delivery from thermosensitive liposomes (TSLs), thus improving therapeutic efficacy and reducing toxicity profiles. In the present study we evaluated the influence of FUS parameters on the release of calcein from TSLs used to model a hydrophilic drug. Quantitative calcein release from TSLs (DPPC/CHOL/DSPE-PEG2000: 90/5/5) and non-thermosensitive liposomes (NTSLs) (DPPC/CHOL/DSPE-PEG2000: 65/30/5) was measured by spectrofluorimetry after both water bath and FUS-induced in vitro heating. The heating of TSLs at 42 °C in a water bath resulted in a maximum calcein release of 45%. No additional calcein release was observed at temperatures above 42 °C. A similar percentage of calcein release was achieved when TSLs were exposed to 1 MHz sinusoidal waves at peak negative pressure of 1.5 MPa, 40% duty cycle, for 10 min (i.e. above 42 °C). No release was detected when NTSLs were heated in a water bath. For both TSLs and NTSLs, the calcein release was increased by more than 10% for acoustic pressures ranging from 1.5 MPa to 2 MPa. This additional release was attributed to the mechanical stress generated by FUS, which was sufficient to disrupt the liposomal membrane. Furthermore, analysis of cryo-TEM images showed a significant decrease in liposome size (14%) induced by the thermal effect, whereas the liposome diameter remained unaffected by the FUS-triggered non-thermal effects.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1,2-Dipalmitoyl-sn-glycero-3-phosphocholine, ≥99% (TLC)
Sigma-Aldrich
Calcein, Used for the fluorometric determination of calcium and EDTA titration of calcium in the presence of magnesium.
Sigma-Aldrich
Triton X-100, laboratory grade
Sigma-Aldrich
1,2-Dipalmitoyl-sn-glycero-3-phosphocholine, semisynthetic, ≥99%
SAFC
Cholesterol, Plant-Derived, SyntheChol®, NF, Ph. Eur., JP
Sigma-Aldrich
1,2-Distearoyl-sn-glycero-3-phosphoethanolamine, ≥99%
Sigma-Aldrich
Cholesterol, from sheep wool, ≥92.5% (GC), powder
Sigma-Aldrich
Cholesterol, Sigma Grade, ≥99%
Sigma-Aldrich
Cholesterol, powder, BioReagent, suitable for cell culture, ≥99%
Sigma-Aldrich
SyntheChol® NS0 Supplement, 500 ×, synthetic cholesterol, animal component-free, sterile-filtered, aqueous solution, suitable for cell culture
SAFC
Cholesterol, from sheep wool, Controlled origin, meets USP/NF testing specifications