Miniaturized devices for creating the world’s smallest vinaigrettes of biological components

Our paper highlights recent advances in the field of microfabricated encapsulating devices, emphasizing the development of emulsifying encapsulations, device design and current assays that are performed using encapsulating droplets on microfluidic chips.

Review by HFSP Program Grant holders Henk Haagsman and Annelise Barron and colleagues
authored on Mon, 10 December 2012

Microfluidic devices are miniaturized machines typically made of glass or a silicone substance with features smaller than the width of a single human hair (see Figure).  In the past 20 years, the field of microfluidic device design has exploded, with an eye towards achieving point-of-care diagnoses of diseases within minutes in a clinical setting.  More recently, scientists have given the adage “oil and water do not mix” a new twist;  they’ve created microfluidic devices that can make micrometer-sized oil-in-water emulsions, much akin to a miniaturized vinaigrette salad dressing with biological components.  Our aim was to review the most recent advances over the last 3 years in emulsion microfluidic devices.

Figure: Example of a microfluidic device.  A.  Chip design, with channels 20 µm deep by 40 µm wide.  B. External chassis that houses the microfluidic chip, used to control flow of samples into the chip.

The microfluidic devices we review in this paper are miniaturized instruments in that they analyze and detect encapsulated drops that are typically water-based, surrounded by a layer of oil.  Because the encapsulated drops are micron-sized, they are termed “droplets.”  These droplets are tiny reaction vessels that can be generated at very fast rates and detected equally as fast, to develop high-throughput reactions. Developing microfabricated devices for biomolecule encapsulation in droplets is important for miniaturizing biological assays to reduce reagent consumption, cost and time of analysis, all of which are currently prohibiting adoption of real-time analyses in the clinical setting.

Biological and chemical components such as cells, microgels, beads, hydrogel precursors, polymer initiators and other droplets can be encapsulated within emulsion drops.  The simplicity of operation and speed of analysis with microencapsulated droplets lends itself well to an array of quantitative biomolecular studies such as directed evolution, single-molecule DNA amplification, single-cell encapsulation, high throughput sequencing, enzyme kinetics and microfluidic cell culture.    As it stands now, fields such as medicine, chemistry, biology, and toxicology can all benefit with implementation of microfabricated devices for biomolecule encapsulation, without much optimization necessary. We look forward to new advances in miniaturizing science made possible by encapsulating on-chip. 

Reference

Microfabricated Devices for Biomolecule Encapsulation. Desmarais SM, Haagsman HP, Barron AE. Electrophoresis 2012, 33, 2639–2649.

Pubmed link