Electrochemical biosensor for detecting antibodies

Although it frequently necessitates a challenging laboratory procedure, the quantitative detection of specific antibodies in complex samples like blood can provide information on a variety of diseases.

An Italian research team has just published a novel technique for the quick, affordable, quantitative, and precise point-of-care detection of antibodies in the journal Angewandte Chemie. It makes use of an electrochemical cell-free biosensor that can quickly and easily find antibodies to illnesses like the flu in blood serum.

Influenza is a serious, contagious epidemic disease that can be fatal and has the potential to have serious social and economic repercussions. Therefore, it is crucial to clinically assess immune responses to flu infections and vaccines.

Instead of the current expensive and complex laboratory analysis, a straightforward, affordable, point-of-care diagnostic method would be preferable.

Sara Bracaglia, Simona Ranallo, and Francesco Ricci (University of Rome) have developed a new method that gratifies this need. It is based on cell-free transcription, “programmable” gene circuits, and electrochemical detection.

RNA polymerases read genes in living cells and translate them into an RNA sequence that serves as a guide for making proteins (translation). Cell-free systems can also use this “machinery.”

The team combined this kind of equipment with specially created synthetic gene circuits that only become “switched on” when the antibody being tested for is present in the sample to create their new detector. As an illustration, they created a test to identify anti-influenza antibodies, which are focused on a molecule found on the surface of influenza viruses.

The team created a synthetic gene with an insufficient promoter to accomplish this. A DNA segment called the promoter regulates how the gene is read. RNA polymerase cannot begin the transcription of RNA if the promoter is insufficient.

A pair of artificial DNA strands that are bound to a protein fragment (also known as a peptide) that is specifically recognized by anti-influenza antibodies are also present in the test solution. The two DNA strands are put in a position during antibody-peptide binding that completes the promoter and turns on the synthetic gene.

Now that the RNA polymerase has docked on the artificial gene, transcription of RNA strands can begin. These RNA strands can then specifically bind to a DNA probe attached to a tiny disposable electrode and produce a change in the current signal that can be measured.

No RNA will be produced, and the disposable electrode will not detect any changes in the current signal as long as there are no antibodies. The machinery creates RNA that binds to the electrode and produces a current signal if the sample has influenza antibodies.

The system is very precise and sensitive, inexpensive, dependable, and only needs very small sample volumes. As a result, it is easily miniaturized to create a portable and user-friendly diagnostic tool. It can also be modified to detect a variety of other antibodies.