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Worth their weight in gold: Immunosensors
Worth their weight in gold: Immunosensors

An antigen and an antibody are a pair of interacting molecules that match each other like a lock and key. When various foreign substances (antigens) are ingested, corresponding antibodies are produced which bind antigens for their subsequent removal from the body. There is a hypothesis that released-active drugs can influence the binding of the corresponding antigen and antibody pair. Assessing the activity of such drugs requires a method to determine the affinity of the binding. One way to solve this problem is the so-called piezoelectric immunosensor method. This method is highly sensitive (up to 10-12 g), allowing direct study of the interaction between different molecules.

Worth their weight in gold: Immunosensors Schematic image of the antibody molecule.

An immunosensor is like a super-sensitive microbalance in its modus operandi. A glass plate (chip) with a layer of gold (as a material with inert properties) applied to the surface is used as a 'pan' in such a set of scales. The chip is placed in a case with holes that allow a pump to be used to pass solutions of the samples through the device. A special layer of substances, a matrix of threadlike organic molecules, is then applied onto the gold of the chip. 

Worth their weight in gold: Immunosensors Matrix-coated chip with antibodies planted on the surface.

Antibodies to the test molecule are 'planted' onto the matrix, and then a solution containing the antigen is passed through the device. In this case, the measured signal of the immunosensor is the change in the frequency of oscillations of another device connected to the chip: a piezoelectric resonator, which acts as the gauge of the scales. The oscillation frequency of the resonator varies with the change in the mass of the chip's coating. The mass of the chip increases due to the binding of the antigen with the antibody: now there is not only an antibody molecule at the end of each 'thread', but also the antigen molecule attached to it.

Worth their weight in gold: Immunosensors Schematic diagram of the chip's sensitive surface structure.

As part of testing ultrahigh dilutions of antibodies to interferon-gamma*, their effect on the binding of interferon-gamma (antigen) with their antibodies was studied.  In so doing, it was imperative to ensure that it was the binding of the antibody to the antigen that caused the signal change, and not other factors, such as the dilution of the solution or non-specific binding. Therefore ultrahigh dilutions (UHD) effect score was made taking into account the noise level, achieved by comparing the signal level of the sample with the signal level of a control that did not contain released-active antibodies. Over 10 days, 150 independent measurements were taken. It was shown that the pre-incubation of antibodies to interferon-gamma with UHD of antibodies to interferon-gamma resulted in a statistically significant change in the sensor signal compared to the control. This result allows us to conclude there is a change in the affinity of antibodies to interferon-gamma with the antigen after the antibodies are treated with a UHD based drug. Thus, the hypothesis of the possible influence of UHD based drugs on the interaction of specific antibodies with their antigens is confirmed. Relevant data are published in the journal Sensors, one of the leading international peer-reviewed journals on biosensors.

* - in the cited article term "ultrahigh dilutions of antibodies to interferon-gamma" is equivalent to the term "Released-active antibodies to interferon-gamma". For more details press here