Rapid test uses origami technology

Jun 21, 2012
Rapid Test Uses Origami Technology

(Phys.org) -- Complex laboratory investigations do produce reliable results, but they are not useful for point-of-care diagnostics. This is especially true in developing countries, which must rely on simple, inexpensive test methods that do not require a power source. Biosensors based on paper are an interesting alternative. American researchers from the University of Texas at Austin and the University of Illinois at Urbana-Champaign have now introduced a particularly clever concept in the journal Angewandte Chemie: print on one side of the paper, fold it up origami-style, laminate it, and the test is ready. Test evaluation requires only a voltmeter.

The team of researchers uses chromatography fabricated by wax printing. The printed areas become hydrophobic, while the unprinted remains hydrophilic. On one half of the paper, the researchers led by Richard M. Crooks and Hong Liu created a sample inlet and two hydrophilic channels, each leading from the inlet to a small chamber. The two chambers are connected to each other through a narrow opening. The required are also “printed” onto the paper. On the second half of the paper, a screen-printing process is used to add two electrodes made of conductive carbon ink. When the paper is then folded down the middle according to the principles of origami—no tape or glue—a three-dimensional structure is formed. This causes the electrodes to come into contact with the chambers. Finally, the folded paper is laminated.

When a drop of the sample is put into the inlet, the liquid moves through the two channels. One of the channels contains microspheres coated with an aptamer. An aptamer is a strand of DNA that can be constructed so as to selectively bind nearly any desired analyte molecule. For the purpose of demonstration, the researchers chose an aptamer for adenosine. If adenosine is in the sample, the aptamer binds to it. This releases an enzyme that was coupled to the aptamer. The enzyme continues to flow through the channel and reaches the chamber, which contains glucose and Prussian blue (iron hexacyanoferrate). This complex contains trivalent iron. The enzyme, glucose oxidase, oxidizes the glucose, which causes the iron in the Prussian blue to be reduced to the divalent form.

The second channel contains spheres with no aptamer. In the second chamber, therefore, no iron is reduced. Because the oxidation state of the iron in one chamber has been changed, the two chambers no longer have the same composition and an electric potential builds up. This can be measured by means of a capacitor and a measuring device like those used to test the voltage of a battery.

This principle can be used to easily and inexpensively produce rapid tests for a broad spectrum of different target molecules.

Explore further: Scientists develop 'electronic nose' for rapid detection of C. diff infection

More information: Richard M. Crooks, Aptamer-Based Origami Paper Analytical Device for Electrochemical Detection of Adenosine, Angewandte Chemie International Edition, dx.doi.org/10.1002/anie.201202929

Related Stories

Diagnosis by Patterned Paper

Jan 29, 2007

Testing biological fluids such as blood and urine is essential for both diagnostics and routine checks. In remote, non-industrialized regions or for emergency on-the-spot diagnosis, current methods of laboratory analysis ...

Universal detector made of DNA building blocks

Mar 30, 2011

(PhysOrg.com) -- A method for detecting such diverse substances as antibiotics, narcotics and explosives - a universal detector, so to speak - has been developed by German researchers at the Max Planck Institute ...

Everything flows in rapid diagnostic tests

Apr 12, 2012

(Phys.org) -- Our ability to detect pathogens has become quite good, but it usually requires complex laboratory techniques. Sometimes we need a quick result, or there is no laboratory nearby. Portable and ...

Recommended for you

Faster, cheaper tests for sickle cell disease

10 hours ago

Within minutes after birth, every child in the U.S. undergoes a battery of tests designed to diagnose a host of conditions, including sickle cell disease. Thousands of children born in the developing world, ...

Simulations for better transparent oxide layers

14 hours ago

Touchscreens and solar cells rely on special oxide layers. However, errors in the layers' atomic structure impair not only their transparency, but also their conductivity. Using atomic models, Fraunhofer ...

The chemistry of beer and coffee

17 hours ago

University of Alabama at Birmingham professor Tracy Hamilton, Ph.D., is applying his chemistry expertise to two popular beverages: beer and coffee.

User comments : 0