Toward a Droplet-Based Single-Cell Radiometric Assay

Area of Science:

• Biomedical Engineering
• Molecular Imaging
• Cell Biology

Background:

• Radiotracers are crucial for in vitro and in vivo molecular tracking.
• Current radionuclide detection lacks spatial resolution for single-cell analysis.
• Existing single-cell methods are limited by stochastic decay and low throughput.

Purpose of the Study:

• To develop a new method for translating stochastic radioactive decays in single cells into a stable fluorescence signal.
• To enable high-throughput measurement and sorting of single cells based on radiotracer uptake.

Main Methods:

• Encapsulating single cells in radiofluorogenic droplets containing probes sensitive to radiation byproducts (ROS).
• Evaluating dihydrorhodamine 123 (DHRh 123) as a sensitive and reproducible probe.
• Utilizing fluorescence imaging of microfluidic droplets containing radiolabeled cells.

Main Results:

• DHRh 123 fluorescence intensity increased linearly with X-ray radiation (54%/Gy) and [18F]FDG concentration (15%/MBq/ml).
• Droplets demonstrated a linear response but had a higher detection limit (3 Gy) than bulk measurements.
• Successfully detected [18F]FDG radiotracer uptake in single cancer cells via fluorescence activation in droplets.

Conclusions:

• This novel radiofluorogenic droplet technology enables single-cell detection of radiotracer uptake.
• The method translates stochastic radioactive decays into a quantifiable fluorescence signal.
• Future improvements could lead to quantitative measurement and selective sorting of single cells based on radiotracer uptake.