Ultrasound-mediated release of calcein from echogenic liposomes

Abstract

Echogenic liposomes (ELIP) have been developed for drug encapsulation. The gas contents in ELIP present a potential mechanism for ultrasound-triggered release of drug contents. Calcein, a fluorescent dye, was loaded in ELIP as a drug substitute (C-ELIP) and ultrasound-induced release was quantified with fluorescence spectrophotometry. Pulsed 6.0-MHz color Doppler from a clinical diagnostic ultrasound scanner (CL15-7 transducer, Philips HDI 5000, MI of 1.3, 150 Hz pulse repetition frequency) was applied to samples of C-ELIP in an in vitro flow phantom (2.2 ml/min). For comparison, Triton X-100 was added to C-ELIP to release calcein. Control samples of C-ELIP were not treated with ultrasound or Triton X-100. The echogenicity of C-ELIP (expressed as mean digital intensity in a 0.5 cm2 region of interest) decreased by 9.6±2.1 dB after exposure to ultrasound. The observed calcein concentration (μg/ml) was 3.1±0.1 for the untreated sample, 4.5±0.1 after Triton X-100 treatment, and 4.2±0.2 after ultrasound exposure. 65.6% of encapsulated calcein was released with ultrasound. These results demonstrate that ultrasound-mediated release of drugs from ELIP using a clinical diagnostic ultrasound scanner is feasible. [Work supported by an AIUM Education and Research Grant and NIH 1R01 HL074002, and NIH 1RO1 NS047603-01S1.]

Ultrasound-Triggered Release of 5-Fluorouracil from Soy Lecithin Echogenic Liposomes

“…However, total reliance on membrane permeabilization on cavitation or ultrasound is not yet fully understood. Ultrasound has been explored to trigger the release of therapeutics from various carriers [12,20,21] such as lipospheres, polymer systems or liposomes made from synthetic phospholipids. To the best of our knowledge, the use of crude soy lecithin (CSL) in an echogenic cancer study has not yet been reported.…”