Quantitative microinjection using fluorescence calibration of streaming microdroplets on a superhydrophobic surface

Christopher L Moore; Erin M Taylor; Kelly K Ball; Laura J Bernock; Robert J Griffin; Seunghyun Jung; Amal Shoeib; Michael J Borrelli

doi:10.1016/j.yexcr.2018.07.006

Quantitative microinjection using fluorescence calibration of streaming microdroplets on a superhydrophobic surface

Exp Cell Res. 2018 Sep 15;370(2):426-433. doi: 10.1016/j.yexcr.2018.07.006. Epub 2018 Jul 4.

Authors

Christopher L Moore¹, Erin M Taylor², Kelly K Ball³, Laura J Bernock⁴, Robert J Griffin⁵, Seunghyun Jung⁶, Amal Shoeib⁷, Michael J Borrelli⁸

Affiliations

¹ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: Christopher.Moore@fda.hhs.gov.
² Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: EMTaylor@uams.edu.
³ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: BallKellyK@uams.edu.
⁴ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: LJBernock@uams.edu.
⁵ Departments of Radiation Oncology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: RJGriffin@uams.edu.
⁶ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: SHJung@uams.edu.
⁷ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: AMShoeib@uams.edu.
⁸ Departments of Radiology, Center for Advanced Surface Engineering, Arkansas Nanomedicine Center, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA. Electronic address: MJBorrelli@uams.edu.

PMID: 29981341
DOI: 10.1016/j.yexcr.2018.07.006

Abstract

A simple and reproducible procedure was developed to measure the volume of liquid microinjected into cells. A calibration curve of droplet fluorescence intensity versus volume was constructed by injecting a fluorescent dextran solution through a 125-150 µm diameter micropipette into an oil-filled culture dish to create a spray of varied-sized droplets. The droplets retained a spherical shape because they were in an oil medium and they settled onto a glass surface coated with a superhydrophobic surface. Fluorescent micrographs of the droplets were obtained and analyzed with Image-J software to quantify the fluorescence intensity and radius of each spherical droplet to produce the calibration curve. Subsequently, Dut-145 human prostate carcinoma cells were microinjected with the same fluorescent dextran solution and fluorescent micrographs of the cells were obtained using the identical exposure conditions used to photograph the droplets. The measured fluorescence intensity of the microinjected cells was entered into the formula for the regression line that was fit to the calibration curve allowing determination of the volume of solution injected into each cell. Thus, a mixture consisting of known concentrations of a test material of test material (macromolecules, drugs, etc.) and a fluorescent dextran, volumetric, tracer can be used to quantify the relationship between the amount of a microinjected material and subsequent effects on cells.

Keywords: Cells; Fluorescence; Microdroplets; Microinjection; Quantitative; Superhydrophobic.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Calibration*
Cell Line, Tumor
Dextrans
Fluorescence
Fluorescent Dyes / metabolism
Humans
Hydrophobic and Hydrophilic Interactions
Microinjections*
Microscopy, Fluorescence* / methods
Surface Properties

Substances

Dextrans
Fluorescent Dyes