FACS-style detection for real-time cell viscoelastic cytometry.

Cell mechanical properties have been established as a label-free biophysical marker of cell viability and health; however, real-time methods with significant throughput for accurately and non-destructively measuring these properties remain widely unavailable. Without appropriate labels for use with fluorescence activated cell sorters (FACS), easily implemented real-time technology for tracking cell-level mechanical properties remains a current need. Employing modulated optical forces and enabled by a low-dimensional FACS-style detection method introduced here, we present a viscoelasticity cytometer (VC) capable of real-time and continuous measurements. We demonstrate the utility of this approach by tracking the high-frequency cell physical properties of populations of chemically-modified cells at rates of ~ 1 s-1 and explain observations within the context of a simple theoretical model.

A simple microfluidic dispenser for single-microparticle and cell samples.

Non-destructive isolation of single-cells has become an important need for many biology research laboratories; however, there is a lack of easily employed and inexpensive tools. Here, we present a single-particle sample delivery approach fabricated from simple, economical components that may address this need. In this, we employ unique flow and timing strategies to bridge the significant force and length scale differences inherent in transitioning from single particle isolation to delivery. Demonstrating this approach, we use an optical trap to isolate individual microparticles and red blood cells that are dispensed within separate 50 µl droplets off a microfluidic chip for collection into microscope slides or microtiter plates.

Single-cell isolation using a DVD optical pickup.

A low-cost single-cell isolation system incorporating a digital versatile disc burner (DVD RW) optical pickup has been developed. We show that these readily available modules have the required laser power and focusing optics to provide a steady Gaussian beam capable of optically trapping micron-sized colloids and red blood cells. Utility of the pickup is demonstrated through the non-destructive isolation of such particles in a laminar-flow based microfluidic device that captures and translates single microscale objects across streamlines into designated channel exits. In this, the integrated objective lens focusing coils are used to steer the optical trap across the channel, resulting in the isolation of colloids and red blood cells using a very inexpensive off-the-shelf optical component.