A novel approach for encapsulating cells into monodisperse picolitre droplets actuated by microfluidic pulse inertia force

Abstract

Encapsulation of few cells into monodisperse picolitre droplets is an extremely critical step in the process of the droplet based single cell analysis. This paper presents a novel approach, not based on micro-fluidic chips fabricated by standard soft lithography technique, for encapsulating cells into droplets actuated by microfluidic pulse inertia force. The principle of the encapsulating process is to actuate a hollow PZT stack by a signal generator and a voltage amplification to provide an enough pulse inertia force for a tapered glass capillary and the cell suspension inside to eject droplets in mineral oil and a certain number of the cells will be randomly encapsulated in monodisperse picolitre droplets. The tapered glass capillary was fabricated by a glass heating process without complicated microfabrication technology.Therefore, it has the advantages of good chemical resistance, low friction, easy to manufacture and low cost. The minimum size of the spherical cell droplets that can be reached is 20 mm in diameter and about 4 picolitres in volume. The percentage of the droplets with single HL60 cell can reach 42% when the droplet size is 40 mm and the concentration of the cell suspension is 1 Â 10 8 cells per milliliter since the alternate changed pulse inertia force can make the cells well dispersed in the tapered capillary. The percentage of viable cells that can be reached is 82% as determined by trypan blue staining, when the cell droplet size is 120 mm. The experiment results present a novel strategy for droplet-based single cell analysis.

The Poisson distribution and beyond: methods for microfluidic droplet production and single cell encapsulation

“…For example, Collins et al, utilized a focused travelling SAW to both concentrate particles in solution at a water-oil interface and subsequently create a droplet encapsulating those particles (Fig. 130 By pulsing the actuator, one or more droplets containing a number of cells could be ejected. 134 In an alternative approach, Wang et al fixed a piezoelectric actuator to the end of a glass capillary.…”

“…134 In an alternative approach, Wang et al fixed a piezoelectric actuator to the end of a glass capillary. 130 By pulsing the actuator, one or more droplets containing a number of cells could be ejected. Other novel methods for encapsulation include the formation of hydrodynamically-thinned bridges, which then segregate into droplets (some of which contain cells), as shown in Fig.…”

Active single cell encapsulation using SAW overcoming the limitations of Poisson distribution

“…Some novel non-deterministic, active encapsulation methods have been described in the literature, including: the use of a capillary tube with a fixed piezoelectric transducer which expels droplets from the tube exit, with some drops containing cells; 17 and the use of traveling surface acoustic waves to concentrate particles in solution at the drop producing region, before ultimately producing droplets containing such particles. 18 Generally, however, such nondeterministic, active methods have limited throughput, failing to exceed encapsulation rates in excess of 1 kHz and with low efficiencies of single cell encapsulation.…”

A portable culture chamber for studying the effects of hydrostatic pressure on cellular monolayers

“…8 Such complex correlation, like the direct implication of shear stress on live cells, is an interesting field of research for computational medicine and has been studied widely using mathematical simulations 9 in conjunction with experimental studies. [10][11][12][13][14] As such, the kidney is a sensitive, soft tissue organ that shows serious adverse reactions to external irritants like mechanical strain fields. To evaluate the constituent parenchyma and stroma's response to these diverse types of stimuli, several kinds of instruments and facilities were utilized to study the behavior of live cells.…”