¹Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080, USA

Correspondence: Dr S Mitragotri, E-mail: samir@engineering.ucsb.edu

Revised 1 November 2004; Accepted 18 November 2004; Published online 1 February 2005.

Abstract

Bioflavonoids, such as quercetin, have recently emerged as a new class of chemotherapeutic drugs for the treatment of various cancer types, but are marred by their low potency and poor selectivity. We report that a short application of low-frequency ultrasound selectively sensitises prostate and skin cancer cells against quercetin. Pretreatment of cells with ultrasound (20 kHz, 2 W cm^-2, 60 s) selectively induced cytotoxicity in skin and prostate cancer cells, while having minimal effect on corresponding normal cell lines. About 90% of the viable skin cancer cell population was lost within 48 h after ultrasound-quercetin (50 M) treatment. Ultrasound reduced the LC₅₀ of quercetin for skin cancer cells by almost 80-fold, while showing no effect on LC₅₀ for nonmalignant skin cells.