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DNA-Based Beacon for Single-Step Fluorescence Detection of Diagnostic Antibodies in Diseases Such As Rheumatoid Arthritis and HIV; Flexible, Modular Nano “Machine” Offers Faster, Cheaper Alternative to Current Approaches

New research may revolutionize the slow, cumbersome, and expensive process of detecting the antibodies that can help with the diagnosis of infectious and auto-immune diseases such as rheumatoid arthritis and HIV. An international team of researchers has designed and synthetized a nanometer-scale DNA "machine" whose customized modifications enable it to recognize a specific target antibody. The researchers’ new approach, which they described online on September 4, 2015 in Angewandte Chemie, promises to support the development of rapid, low-cost antibody detection at the point-of-care, eliminating the the treatment initiation delays and the increasing healthcare costs associated with current techniques. The article is titled “A Modular, DNA-Based Beacon for Single-Step Fluorescence Detection of Antibodies and Other Proteins.” The binding of the antibody to the DNA machine causes a structural change (or switch), which generates a light signal. The sensor does not need to be chemically activated and is rapid (acting within five minutes), enabling the targeted antibodies to be easily detected, even in complex clinical samples such as blood serum. In the abstract of their article, the scientists technically describe their new system as follows. The scientists say they have developed “a versatile platform for the one-step fluorescence detection of both monovalent and multivalent proteins. This system is based on a conformation-switching stem–loop DNA scaffold that presents a small-molecule, polypeptide, or nucleic-acid recognition element, on each of its two stem strands. The steric strain associated with the binding of one (multivalent) or two (monovalent) target molecules to these elements opens the stem, enhancing the emission of an attached fluorophore/quencher pair. The sensors respond rapidly (<10 min) and selectively, enabling the facile detection of specific proteins even in complex samples, such as blood serum.”

The scientists further wrote that “the versatility of the platform was demonstrated by detecting five bivalent proteins (four antibodies and the chemokine platelet-derived growth factor) and two monovalent proteins (a Fab fragment and the transcription factor TBP) with low nanomolar detection limits and no detectable cross-reactivity."

"One of the advantages of our approach is that it is highly versatile," said Professor Francesco Ricci, of the University of Rome, Tor Vergata, senior co-author of the study. "This DNA nanomachine can be, in fact, custom-modified so that it can detect a huge range of antibodies, this makes our platform adaptable for many different diseases."

"Our modular platform provides significant advantages over existing methods for the detection of antibodies," added Professor Vallée-Bélisle of the University of Montreal, the other senior co-author of the paper. "It is rapid, does not require reagent chemicals, and may prove to be useful in a range of different applications such as point-of-care diagnostics and bioimaging."

"Another nice feature of our this platform is its low-cost," said Professor Kevin Plaxco of the University of California, Santa Barbara. "The materials needed for one assay cost about 15 cents, making our approach very competitive in comparison with other quantitative approaches."

"We are excited by these preliminary results, but we are looking forward to improving our sensing platform even more," said Simona Ranallo, a Ph.D. student in the group of Professor Ricci at the University of Rome and first-author of the paper.

"For example, we could adapt our platform so that the signal of the nanoswitch may be read using a mobile phone. This will make our approach really available to anyone! We are working on this idea and we would like to start involving diagnostic companies."

The image here illustrates the light-generating DNA antibody-detecting nano "machine" described here, in action, bound to an antibody. (Credit: Marco Tripodi).

[English press release] [French press release] [Angewandte Chemie abstract]