Electrochemical biosensor for antibody detection
The quantitative detection of specific antibodies in complex samples
such as blood can inform on many different diseases but usually requires
a complicated laboratory procedure. A new method for the rapid,
inexpensive, yet quantitative and specific point-of-care detection of
antibodies has now been introduced in the journal Angewandte Chemie
by an Italian research team. It uses an electrochemical cell-free
biosensor that can directly detect antibodies against diseases such as
influenza in blood serum.
© Wiley-VCH, re-use with credit to 'Angewandte Chemie' and a link to the original article.
Influenza is a severe, widespread, epidemic disease that can be fatal
and may also have significant societal and economic consequences. The
clinical evaluation of immune responses to flu vaccines and infections
is thus correspondingly important. A simple, inexpensive, point-of-care
diagnostic method would be preferable to current expensive and complex
laboratory analysis.
A new method developed by Sara Bracaglia, Simona Ranallo, and
Francesco Ricci (University of Rome) fulfills this wish. It is based on
“programmable” gene circuits, cell-free transcription, and
electrochemical detection.
In living cells, genes are read by RNA polymerases and transcribed
into an RNA sequence, which then serves as a blueprint for building
proteins (translation). This “machinery” can also be used by cell-free
systems. To build their new detector, the team combined this type of
machinery with specifically designed synthetic gene circuits that only
get “switched on” when the antibody being tested for is present in the
sample. As an example, they designed a test that detects anti-influenza
antibodies, which are directed against a surface molecule on influenza
viruses.
To do this, the team developed a synthetic gene with an incomplete
promoter. The promoter is a DNA segment that controls the reading of the
gene. If the promoter is incomplete RNA polymerase cannot start the
transcription of RNA. The test solution also contains a pair of
synthetic DNA strands that are bound to a protein portion (also called
peptide) that is specifically recognized by anti-influenza antibodies.
Upon binding between the antibodies and the peptide, the two DNA strands
are arranged in a way that completes the promoter and switches the
synthetic gene on. The RNA polymerase can now dock on the synthetic gene
and start transcribing RNA strands. These RNA strands in turn can bind
specifically to a DNA probe fixed to a small disposable electrode and
give a measurable current signal change. As long as no antibodies are
present, no RNA will be transcribed and no change in current signal will
be measured by the disposable electrode. If the sample contains
influenza antibodies, the machinery synthesizes RNA, which binds to the
electrode leading to a current signal.
The system requires only very small sample volumes, is very specific
and sensitive, reliable, and inexpensive. Thus, it can be readily
miniaturized to make a portable and easy-to-use diagnostic tool. It is
also adaptable for the detection of a wide variety of other antibodies.
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About the Author
Dr. Francesco RicciFrancesco Ricci
is Professor of Analytical Chemistry at the Department of Chemical
Sciences and Technologies of the University of Rome Tor Vergata. His
main interests are in the field of DNA nanotechnology, biosensors, and
supramolecular chemistry. He is the recipient of numerous awards.
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