Using methods to produce “bio-inks”, researchers can use conventional office ink-jet printers to print man-made DNA molecules with very high molecular weight on paper.
The size of the DNA—which produces a signal when a specific disease biomarker is present—is enough to ensure it remains immobilized and stable and solves previous movement issues.
The paper sensor emerges from the printer ready to use, like pH paper.
Aptamer creation
Biochemist Yingfu Li and graduate student Carmen Carrasquilla also worked on the research.
“Aptamers can be created for any target molecule. If the target is present there will be a higher level of fluorescence then if it is not present,” Li told FoodQualityNews.
“We are identifying the needs of the market and seeing what practical uses this hand-held sensor could have,” he said.
“We could imagine it being used in restaurants or by food health inspection agencies related to onsite inspections.
“It can be scaled up for mass production. We recently received provisional funding to create the set-up to engineer the sensors to a level where we can move closer to the market.”
Researchers said a major challenge was finding suitable bioinks amenable to high-speed printing and that remained functional.
They made an aqueous ink composed of megadalton-sized tandem repeating structure-switching DNA aptamers (concatemeric aptamers) to create patterned paper sensors on filter paper by inkjet printing.
These concatemeric aptamer reporters remain immobilized during printing through strong adsorption but retain sufficient segmental mobility to undergo structure switching and fluorescence signaling to provide qualitative and quantitative detection of small molecules and protein targets.
Two different concatemeric structure-switching aptamer reporters were produced, using model aptamers for adenosine triphosphate (ATP) and platelet-derived growth factor (PDGF).
Paper-based sensors
Paper-based screening technologies let users generate an answer in the form of letters and symbols that appear on the test paper to indicate the presence of infection or contamination in people, food or the environment.
The main techniques to make paper-based biosensors involve conjugating the biological sensing elements to the paper surface by chemical modification of paper fibers, entrapping these biomolecules within sol–gel derived inks, or localizing adsorbed biomolecules using hydrophobic barriers to define channels created by photolithography, etching, plasma treatment, flexographic or screen-printing methods.
However, these can be laborious, prone to nonspecific binding, and may require complex reactions, which can make fabrication inconvenient and increase cost, said the study.
John Brennan, director of McMaster’s Biointerfaces Institute, said the simplicity of the system makes it cheap and easy to implement in the field.
“Imagine being able to clearly identify contaminated meat, vegetables or fruit. This method can be extended to virtually any compound, be it a small molecule, bacterial cell or virus.”
Source: Chemistry – A European Journal, volume 21 Issue 20
Article online ahead of print, DOI: 10.1002/chem.201500949
“Patterned Paper Sensors Printed with Long-Chain DNA Aptamers”
Authors: Carmen Carrasquilla, Jessamyn R. L. Little, Prof. Dr Yingfu Li and Prof. Dr John D. Brenna