Technique enables development of viable diagnostic tests and instruments in fight against cancer
Cancer is the second leading cause of death in the U.S., making early, reliable diagnosis and treatment a priority for researchers. Genomic biomarkers offer great potential for diagnostics and new forms of treatment, such as immunotherapy. Miniaturized lab-on-chip approaches are prime candidates for developing viable diagnostic tests and instruments because they are small, need only limited test volumes, and can be cost-effective.
A team of scientists and engineers from the University of California, Santa Cruz and Brigham Young University have developed just such an approach capable of processing biomolecular samples from blood. Their method can analyze and identify multiple targets on a silicon-based molecular detection platform and is described this week in Biomicrofluidics, from AIP Publishing.
Laboratory–on-a-chip describes the miniaturization of laboratory functions such as blood testing on a chip. Instead of transferring relatively large (micro- to milliliters) samples between test tubes or using bulky analytical equipment, samples and reagents are handled on chip-scale devices with fluidic microchannels. This requires much smaller test volumes, and multiple functions can be integrated on a single device, improving speed, reliability and portability of these lab processes.
“Our approach uses optofluidic chips where both fluid processing and optical sensing are done on a chip, allowing for further miniaturization and performance enhancements of the chip system,” said Holger Schmidt, a Narinder Kapany professor of electrical engineering at the University of California, Santa Cruz.
The entire process of testing was a challenge for the team, led by Schmidt and Aaron Hawkins, a physics professor at Brigham Young University. Each of the chips had to be developed and tested for multiple functions, from filtering of blood cells without clogging the filter to reliably analyzing optical data to create the right excitation patterns on the silicon chip. However, the process worked as envisioned, and the team was pleasantly surprised to see just how powerful the multi-spot optical excitation method actually was.
The next step to realizing the potential of this research is to move toward real clinical samples and to detect individual DNA biomarkers.
“We have shown single nucleic acid analysis in the context of on-chip Ebola detection and would like to transfer that to this application,” said Schmidt.
Other goals for the team include increasing the speed of the analysis process, and integrating more optical elements on the chip. They also want to expand their capabilities to analyzing protein biomarkers in addition to nucleic acids and whole virus particles already demonstrated.
This research is expected to have a wide range of applications because the underlying principle of this kind of on-chip optical analysis and manipulation is very general.
“In the near term, we hope to build new diagnostic instruments for molecular diagnostics with applications in oncology and infectious disease detection, both viruses and (drug-resistant) bacteria,” Schmidt said. “In addition, these chips could be very useful for fundamental research in molecular biology and other life sciences since they can provide analysis of single nano- and microparticles without the need for expensive equipment. And they require a relatively low amount of experimental skills.”
Mass-produced microvalves are the key to scalable production of disposable, plug-and-play microfluidic devices
The elusive ‘lab on a chip’ capable of shrinking and integrating operations normally performed in a chemical or medical laboratory on to a single chip smaller than a credit card, may soon be realized thanks to disposable, plug-and-play microfluidic devices developed by A*STAR researchers1.
Microfluidic systems use networks of channels much narrower than a human hair to control the movement of miniscule amounts of fluids. Recent advances in microfluidics technology have proven invaluable for immediate point-of-care diagnosis of diseases and have greatly improved enzymatic and DNA analysis. High throughput microfluidic systems are also being employed in stem cell studies and for the discovery of new drugs.
A stumbling block for successful miniaturization and commercialization of fully integrated microfluidic systems, however, has been the development of reliable microfluidic components, such as microvalves and micropumps. Zhenfeng Wang and colleagues from the Singapore Institute of Manufacturing Technology (SIMTech), A*STAR have removed that obstacle by developing an efficient and scalable method to fabricate disposable plug-and-play microfluidic devices.
“Integrating valves and pumps into thermoplastic devices is usually challenging and costly because the fabrication process is very complicated,” says Wang. “Mass-producing the microvalve module separately from the main device, however, makes the fabrication of the main device relatively simple and robust.”
Scientists at the U.S. Department of Energy’s Argonne National Laboratory have discovered a way to use a microscopic swirling flow to rapidly clear a circle of tiny bacteria or swimming robots.
“This discovery offers a new approach for control and manipulation of microscopic swimmers,” said Argonne physicist and co-author Igor Aronson, and it could be useful in tiny microfluidic (“lab-on-a-chip”) devices that can quickly run chemical or biological analyses or perform tasks.
In the study, published in Nature Communications, the researchers placed a magnetic particle in the center of a liquid film filled with swimming bacteria.
Normally the bacteria swim randomly; but when scientists spun the particle by applying a rotating magnetic field, the swimmers shot away from the center, like a school of fish that suddenly realized there’s a shark in their midst.
What’s actually happening is that the particle is rotating, creating a small vortex around itself. The bacteria swim parallel to the stream lines and are quickly pushed outward — except for a few that get sucked in right next to the particle.
They’re not pushed out by centrifugal force, said Argonne scientist Andrey Sokolov, who co-authored the paper; dead bacteria, which aren’t swimming, are not pushed out with their living companions.
“Because of the curvature of the flow, some swim in and are trapped on the rotating particle, and others are forced to swim out of the curved flow,” Sokolov said.
This technique could separate live from dead bacteria, or different species, bacterial strains or mutants from one another. “The shape and swimming rates of different species would mean they separate,” Aronson said.
“At certain frequencies of rotation, the bacteria self-organize into a spiral-shaped halo, creating a microscopic galaxy — similar to our galaxy Milky Way, but trillions of trillions (1024) of times smaller,” Sokolov said.
In addition to new understanding of the forces governing microswimmers and their environments, the vortex technique could help prevent biofilms from forming and disrupting microfluidic devices, the authors suggested.
They are particularly interested in creating systems in which microswimmers could assemble gears to build a tiny machine and then power it, Aronson said.
Aronson and Sokolov also modeled the results theoretically and saw good alignment between computer models and observed results, they said.
Learn more: Moving microswimmers with tiny swirling flows