Gentian Insight: PETIA

06. May 2020 | 4 min read

Gentian Insight: PETIA

Gentian’s proprietary antibody and nanoparticle-based technology supports development of highly sensitive Particle-Enhanced Turbidimetric Immunoassays (PETIA). The basis of our technological innovations are years of research on production processes and raw material specifications, including nanoparticle qualities and avian antibody production.

In this article, we will give more insight into PETIA – what it is, how it works and how it improves clinical efficiency.

PETIA – supporting diagnostic efficiency

Homogeneous Particle-Enhanced Turbidimetric Immunoassays (PETIA) are used for quantitative measurement of proteins, pathogens, and other molecules in body fluids, such as plasma, serum and urine. Since homogeneous immunoassays are used on automated clinical chemistry analysers and do not require separation steps, the time from test to result is significantly reduced. In addition, high-throughput (clinical chemistry) analysers are available 24/7 and have random access capacity, hence samples can be measured continuously as they arrive at the laboratory.

PETIA is cost-effective since it has a low reagent consumption and low labour costs due to limited hands-on times. It takes approximately 10 minutes from the initiation of the measurement until the results are ready.

How it works

The common principle of immunoassays relies on antibodies binding to their specific target within the sample and the subsequent quantification of the agglutinated immune complex. Instead of a radioactive isotope or a coloured substrate to detect the formed immune complex, PETIA is a detection technique based on the change in the opaqueness of the reaction solution. The reaction solution contains:

  • Sample
  • Assay buffer
  • Immunoparticles (nanoparticles coated with antibodies)

The optical change is caused by the agglutination of the immunoparticles. The antibodies attached to the nanoparticles bind to the target analyte and create a turbid mixture (Figure 1). The extend of agglutination is proportional to the concentration of targeted analyte in the mixture within the linear range of the assay. See figure below:



Figure 1: The sample containing the target antigen is mixed with the immunoparticles. Each of the target antigens can bind to antibodies attached to different polystyrene particles.

In the turbidimetric detection process, light is passed through the sample to determine the change in opaqueness. The change in optical characteristics is determined by monitoring the increase in absorption of monochromatic light (Figure 2):


Figure 2: Visible light is passed through a monochromator transmitting only a narrow band wavelength of light onto the sample. The light will partly be scattered and absorbed by the turbid mixture, resulting in a signal of transmitted light proportional to the agglutination within the sample.

Quantitative measurement of each sample is performed in relation to a pre-defined standard calibration curve. A six-point calibration curve is established from six standards with known concentrations. A regression line is calculated using the response and known concentration from each sample.


PETIA @ Gentian

Our success with turbidimetry is based on our innovative way to enhance the agglutination of the immunoparticles to form larger structures. These larger clusters are detectable by a common clinical analyser, even when the original target antigen (the biomarker) is present in the blood at only low concentrations. Applying these technologies to our current products and our product development pipeline, allows us to develop reagents for biomarkers that are currently measured using less sensitive and more time-consuming separation-based techniques, and support better diagnostic efficiency.

Contact us

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