Pumpless Microflow Cytometry Enabled by Viscosity Modulation and Immunobead Labeling

Major
challenges of miniaturizing flow cytometry include obviating
the need for bulky, expensive, and complex pump-based fluidic and
laser-based optical systems while retaining the ability to detect
target cells based on their unique surface receptors. We addressed
these critical challenges by (i) using a viscous liquid additive to
control flow rate passively, without external pumping equipment, and
(ii) adopting an immunobead assay that can be quantified with a portable
fluorescence cell counter based on a blue light-emitting diode. Such
novel features enable pumpless microflow cytometry (pFC) analysis
by simply dropping a sample solution onto the inlet reservoir of a
disposable cell-counting chamber. With our pFC platform, we achieved
reliable cell counting over a dynamic range of 9–298 cells/μL.
We demonstrated the practical utility of the platform by identifying
a type of cancer cell based on CD326, the epithelial cell adhesion
molecule. This portable microflow cytometry platform can be applied
generally to a range of cell types using immunobeads labeled with
specific antibodies, thus making it valuable for cell-based and point-of-care
diagnostics.