BMC Cancer BioMed Central 2BR2M0e0Cs2eC,aanrccerh article x Investigating the mechanism of acoustically activated uptake of drugs from Pluronic micelles Ghaleb A Husseini1, Christopher M Runyan2 and William G Pitt*1 Address: 1Department of Chemical Engineering, Brigham Young University, Provo, Utah, USA 84602, USA and 2Department of Microbiology, Brigham Young University, Provo, Utah 84602, USA E-mail: Ghaleb A Husseini - ghaleb_husseini@hotmail.com; Christopher M Runyan - cmr22@email.byu.edu; William G Pitt* - pitt@byu.edu *Corresponding author Published: 30 August 2002 BMC Cancer 2002, 2:20 Received: 18 April 2002 Accepted: 30 August 2002 This article is available from: http://www.biomedcentral.com/1471-2407/2/20 © 2002 Husseini et al; licensee BioMed Central Ltd. This article is published in Open Access: verbatim copying and redistribution of this article are permitted in all media for any non-commercial purpose, provided this notice is preserved along with the article's original URL. Abstract Background: This paper examines the mechanism of ultrasonic enhanced drug delivery from Pluronic micelles. In previous publications by our group, fluorescently labeled Pluronic was shown to penetrate HL-60 cells with and without the action of ultrasound, while drug uptake was increased with the application of ultrasound. Methods: In this study, the amount of uptake of two fluorescent probes, Lysosensor Green (a pH- sensitive probe) and Cell Tracker Orange CMTMR (a pH-independent probe), was measured in HL-60 and HeLa cells. Results: The results of our experiments show that the increase in drug accumulation in the cells as a result of ultrasonication is not due to an increase in endocytosis due to ultrasonication. Conclusions: We hypothesize that sonoporation plays an important role in the acoustically activated drug delivery of chemotherapy drugs delivered from Pluronic micelles. Background In order to overcome the unwanted effects associated with conventional chemotherapy, the use of molecular vehi- cles to sequester the therapeutic drug in a package and re- lease it to the tumor site at the appropriate time is a topic of vigorous investigation. Such a vehicle would protect healthy cells in the host body from interaction with the chemotherapeutic agents and therefore would help to al- leviate unwanted side effects. The main challenge is to completely sequester the drug, but yet be able to release it upon demand in both time and space. Ultrasound is an ideal mediator of drug delivery because it provides both temporal and spatial control over irradiation of tissue and subsequent delivery of the drug. Results of the comet (DNA degradation) assay presented in a previous publication [1] show that Doxorubicin (Dox) released from Pluronic micelles eventually binds to the DNA and causes it to fragment. In another publica- tion, our group reported that Dox and Ruboxyl (Rb) are released from the core of Pluronic P105 micelles upon ex- posure to ultrasound at frequencies below 100 kHz [2]. Ultrasonic release of Dox and Rb from these micelles is ev- ident. However, the question remains as to if and how ul- trasound enhances uptake of Dox by the cell. This paper probes and discusses possible mechanisms by which the P105 micelles and the ultrasound drug delivery system in- duce drug uptake by cancer cells. Three postulated mech- anisms are presented and discussed below. They are 1) ultrasound releases drug from the micelle and also per- turbs the cell membrane which increases the permeability of the cells toward the drug and Pluronic; 2) ultrasound releases drug from micelles and the drug is taken into the cells by normal passive modes; 3) ultrasound induces an Page 1 of 6 (page number not for citation purposes)