title: Fluorescence response of human HER2+ cancer- and MCF-12F normal cells to 200MHz ultrasound microbeam stimulation: a preliminary study of membrane permeability variation.
abstract: Targeted mechanical cell stimulation has been extensively studied for a better understanding of its effect on cellular mechanotransduction signaling pathways and structures by utilizing a variety of mechanical sources. In this work, an ultrasound-driven single cell stimulation method is thus proposed, and a preliminary study is carried out by comparing the fluorescence intensities representing a change in cell membrane permeability between MDA-MB-435 human HER2+ cancer cells (∼40-50μm in diameter) and MCF-12F normal cells (∼50-60μm) in the presence of ultrasound. A 200MHz single element zinc oxide (ZnO) transducer is employed to generate ultrasound microbeam (UM) whose beamwidth and depth of focus are 9.5 and 60μm, comparable to typical cell size. The cells in tetramethyl rhodamine methyl ester (TMRM) are interrogated with 200MHz sinusoidal bursts. The number of cycles per burst is 5 and the pulse repetition frequency (PRF) is 1kHz. The temporal variation of fluorescence intensity in each cell is measured as a function of input voltage to the transducer (16, 32, and 47V), and its corresponding fluorescence images are obtained via a confocal microscope. A systematic method for visualizing UM's focus by adding Rhodamine B to the immersion medium is also proposed to enhance the precision in aiming the beam at an individual cell. Both types of cells exhibit a decrease in the intensity upon UM irradiation. In particular, normal cells show more fluorescence reduction (down to 0.7 in normalized intensity) than cancer cells (∼0.9) under the same excitation condition of the transducer. With UM being turned off, the normalized intensity level in normal cells is slowly increased to 1.1. The cell images taken before and after UM exposure indicate that the intensity reduction is more pronounced in those cells after exposure. Hence the results show the potential of UM as a non-invasive in vitro stimulation tool for facilitating targeted drug delivery and gene transfection as well as for studying cellular mechanotransduction.
authors.affiliation: Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
authors.forename: Jae Youn
authors.initials: JY
authors.lastname: Hwang
authors.forename: Jungwoo
authors.initials: J
authors.lastname: Lee
authors.forename: Changyang
authors.initials: C
authors.lastname: Lee
authors.forename: Anette
authors.initials: A
authors.lastname: Jakob
authors.forename: Robert
authors.initials: R
authors.lastname: Lemor
authors.forename: Lali K
authors.initials: LK
authors.lastname: Medina-Kauwe
authors.forename: K Kirk
authors.initials: KK
authors.lastname: Shung
mesh_terms: D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability; D005240:Feasibility Studies; D005453:Fluorescence; D006801:Humans; D040542:Mechanotransduction, Cellular; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D012235:Rhodamines; D014159:Transducers; D014465:Ultrasonics / Q000379:methods*; D015034:Zinc Oxide
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D012235:Rhodamines; D015034:Zinc Oxide; C401833:tetramethylrhodamine methyl ester