Advanced Concepts

New Detection Technologies
Besides traditional detection technologies (fluorescence, luminescence or latex nanoparticles) E&A developed detection technologies that allow study of biomolecular interactions in real time. These technologies rely on the use of chemicals that experience chromic transitions in solution when ligand-receptor interactions occur. They are applicable in automated systems for High Throughput Screening (HTS) or diagnostic applications, such as plate readers or automated clinical analyzers.

One such technology is based on the surface plasmon resonance (SPR) effect of colloidal noble metal nanoparticles, such as gold or silver. The principle is explained in the following figure.
The figure schematically shows the progressive red shift in the visible absorption spectrum (upper right) of a colloidal gold solution in which the nanoparticles are coated with antibody molecules that interact with the ligand in a spectrophotometer cuvette (left side). The lower right part of the figure shows the plot of the interaction kinetics.

When a receptor attached to such nanoparticles interacts with its specific ligand, the change in refractive index at the particle surface produces a red shift in the visible absorption spectrum of the solution. This shift is time and dose dependent. The results can therefore be analyzed both in terms of the kinetics and dose response relationships.

 

ARTICLES - detailing the various aspects of the process, can be found on the following Acrobat files:

Another technology developed for similar applications uses the capacity of conductive polymers attached to ligands in solution to change color when the recognition event occurs. This chromic transition results from a change in their geometry or charge as shown in the following figure. This results in modifications of their visible absorption spectrum that can be monitored in plate readers or automated analyzers. The results from the interaction can also be analyzed in terms of kinetics and dose-response.


The figure shows the change in color from yellow to blue that occurs in polythiophene molecule linked to a ligand when it interacts with the specific binding protein. The chromic transition results either from a departure from coplanarity (left), or a change in charges within the polymer (right).

More details about conductive polymers applications can be found in the following article: Chem1999newdiag

E&A welcomes inquiries about development of diagnostic and HTS application services.

More details are contained on "Advanced Concepts, Continued" regarding:

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