Fluorescein isothiocynate-dextran uptake by chinese hamster ovary cells in a 1.5 MHz ultrasonic standing wave in the presence of contrast agent

Uptake of fluorescein isothiocynate-dextran (FITC-dextran) by Chinese hamster ovary cells was studied after exposure to ultrasonic standing wave (USW) in presence of Optison(R), an ultrasound contrast agent. Confluent Chinese hamster ovary cells were harvested and suspended in phosphate-buffered saline + 0.1% bovine serum albumin containing FITC-dextran (10, 40, and 500 kDa) at 10 mu M final concentration. The suspension was seeded with contrast agent (75 mu L/mL) and exposed to a 1.5 MHz USW system at acoustic pressures ranging from 0.98 to 4.2 MPa. Macromolecular uptake was assessed by fluorescent microscopy and quantified by flow cytometry 10 min after exposure. FITC-dextran positive cells, as assessed by flow cytometry, were 1 +/- 0.05% and 2.58 +/- 0.27% for acoustic pressures of 1.96 and 4.2 MPa, respectively (p = 0.006). Fluorescent microscopy indicated a degree of macromolecular loading at 0.98 MPa with 46% of peripherally FITC-dextran- and/or propidium iodide-stained cells coincident with the appearance of significant frequency (f(0)/2 and 2 f(0)) emission signals. At higher pressures, high macromolecular loading with 6% peripherally stained cells at 1.96 MPa was associated with lower order emission signals and white noise. The study conclusively demonstrates macromolecular loading in an USW, a significantly higher macromolecular loading at higher pressures and indicates potential of emission signals for a feedback loop to control the acoustic power outputs and fine-tune the biologic effects associated with sonoporation. (E-mail: AmsoNN@cf.ac.uk) (C) 2006 World Federation for Ultrasound in Medicine & Biology.