Digital microfluidics opening the way for revolution in blood sampling

The days of the blood sample routine - arm out, tie tube, make a fist, find a vein and tap in -- may soon be over, thanks to a new analysis method developed at U of T by Institute of Biomaterials and Biomedical Engineering (IBBME) core professor Aaron Wheelerin which only a pinprick of blood is necessary.

Traditional methods of blood sampling requires intravenous extraction of several millilitres of blood. A phlebotomist then separates serum, which is frozen for transport or storage and later thawed and analyzed. A relatively new alternative to the traditional method uses blood samples stored as dried blood spots (DBSs).

The DBS method requires only a pinprick to extract a few microlitres of blood, which is blotted onto filter paper, where the sample, it has been found, remains stable. While DBSs have been gaining increasing popularity for the ease of sampling and storage for some time, they are still not a standard laboratory technique, and the process for using them remained laborious -- until now.

In a study published in Lab on a Chip last week, Wheeler and colleagues demonstrated the proof-of-principle that digital microfluidics could be used to automate the process of dried blood spot analysis in the case of testing for specific genetic diseases at Newborn Screening Ontario (NSO) in Ottawa. This paper is the result of a collaboration between Wheeler and NSO rsearchers.

NSO regularly screens every baby born in Ontario for genetic diseases - some 140 000 babies a year - and collects DBS samples via heelprick. Each DBS must be manually collected. Technicians must prepare the sample for testing, put it into a centrifugal tube, pipette solvent onto the sample, extract the necessary material by centrifuge, and then use robotics to conduct the chemical analysis.

Wheeler’s digital microfluidic platform automates this process. Droplets are manipulated onto the sample using electrical signals, and the material needed for analysis is extracted - all on a “lab-on-a-chip” with little manual intervention. Wheeler, the Canada Research Chair in Bioanalytical Chemistry, created the prototype for this process in the Bahen Cleanroom, a facility of the Emerging Communications Technology Institute at U of T.

Wheeler’s study quantified particular amino acids that are markers of three metabolic disorders: phenylketonuria, homocystinuria, and tyrosinemia. His next steps will be to evaluate the rest of the 28 diseases that NSO screens for.

Wheeler’s innovation is indicative of the innovative tools for biomedical engineering that IBBME researchers create. “The applications for this process go far beyond newborn screening,” Wheeler stated. “Pharmaceutical companies are moving towards dried blood spot analysis, but they’re still lacking the tools to make widespread use feasible. We’ve demonstrated that digital microfluidics could be that tool. Our system is fast, robust, precise, and compatible with automation.”

While it might be a while before the days of the dreaded blood sample needle are behind us, Wheeler’s digital microfluidics method is the next step in moving to a DBS-based sampling system, said Pranesh Chakraborty, director of NSO. “This approach could save considerable costs as a result of the lower volumes of reagent required,” he affirmed. “An automated system based on this approach would also process samples faster, with higher accuracy, less risk of errors, all while freeing up time for technologists to perform other work.” Charaborty’s team provided the screening and medical perspective in this research.

A patent has been filed, and Wheeler, who also holds appointments in chemistry and Banting and Best Department of Medical Research, is currently exploring commercialization options.

Provided by University of Toronto (news : web)

Nanotechnology: injections or sampling? New 'molecular syringes' under testing

 Which is better, a quick vertical jab on the buttock or the delicately soft entry of a blood sample? Waiting to find out "for what," some are already wondering "how" to use those tiny "molecular syringes" which are carbon nanotubes. With a diameter of less than one millionth of a millimetre (nanometre) and a maximum length of just a few millimetres, the first use that springs to mind when we think of this ethereal tubes -- the smallest ever made by man -- is as potential needles for injecting drugs or genes into sick cells. And if a syringe it is, we had better start thinking about how to use them.

A group of researchers at the Ciamician department of the University of Bologna (Unibo, Italy) has no doubt about it. The easiest and most natural way of penetrating a cell membrane with a carbon nanotube, in its simplest form, is at an angle which is almost flat against the membrane surface. Just as a nurse does to "find" a vein.

Siegfried Höfinger (Unibo) explains: "A flat entry offers the most favourable energy balance." The entry of the nano-needle is in fact twice as easy than at an angle of, say, 45°, and three times easier than vertical penetration. "We can even hypothesise that the nanotube takes on this position of its own free will when placed near the membrane," adds Tommaso Gallo, another of the young authors working on the study, which is in press in the scientific journal Biomaterials.

The scientists' doubts lie in the extreme difficulty in handling such small objects. "Probably no one is able to experimentally verify these phenomena yet," says Höfinger. The chemists from Bologna, part of Francesco Zerbetto's research group, have drawn their conclusions not from physical experiments but from theoretical simulations. Mathematical models which consider all the forces at stake and the physical and chemical properties of the elements involved, predicting their behaviour.

The encouraging aspect of the Unibo research, which also saw the participation of the Michigan Technological University and the Universidade do Porto, is that two independent simulations based on completely different theoretical approaches led to an identical response. Flat entry into the membrane is certainly preferable. The first simulation was based on the system's energy balance and the concept of "environmental free energy." The second simulation, on the other hand, is typically used to describe the behaviour of large molecules in solutions (solvents and polymers). It may be less accurate than the first, but it has the advantage of illustrating the dynamic and temporal evolution of the described phenomenon well.

To simplify the problem, the researchers considered the use of very short tubes, maximum 7 nanometres long, which could be fully included in the cell wall, which is around 5 nanometres thick. It was also seen that, once inside the membrane, the longer tubes tend to lie longitudinally, parallel to the surface. Carrying out the test with bundles of smaller tubes bound together, it was also demonstrated that compact bundles of tubes bound tightly to each other cause less cell damage.

The future that Höfinger sees for the nanotubes is not however that of molecular syringes, but of probes. Their physical properties, including their great electrical and thermal conductivity, make them particularly suited for exchanging information between the inside and outside of the cell. They may therefore also be used to test for certain substances and test certain processes beyond cell membranes. Probes or syringes, the scientist in any case feel comfortable in their role as molecular nurses, and are eager to keep on testing using all the new tools of the trade.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Universita di Bologna, via EurekAlert!, a service of AAAS.

Journal Reference:

Siegfried Höfinger, Manuel Melle-Franco, Tommaso Gallo, Andrea Cantelli, Matteo Calvaresi, José A.N.F. Gomes, Francesco Zerbetto. A computational analysis of the insertion of carbon nanotubes into cellular membranes. Biomaterials, 2011; DOI: 10.1016/j.biomaterials.2011.06.011