Measuring the kinetic properties of biomolecules has become increasingly important in drug discovery and biomanufacturing. In areas such as immunization monitoring, clonal selection, and expression analysis, biosensors offer a clear advantage. In the past, it has been necessary to obtain purified or highly diluted molecules for such studies since crude samples have posed challenges for nonspecific binding, referencing, and system microfluidics.
The ability to analyze crude samples directly saves time, labor, and money. In this article, we show how the Attana 200 system (Figure 1) can be used directly with crude samples for off-rate screening of antibodies in hybridoma supernatants containing serum as well as for scaffold proteins in crude E. coli lysates.
Attana’s biosensors are based on the quartz crystal microbalance (QCM) technology. By applying an alternating potential to a piezoelectric quartz crystal, the crystal can be controlled to oscillate at its resonance frequency. A change in mass on the crystal surface results in a proportional change in resonance frequency.
This means that when a ligand is initially immobilized on the crystal surface, the added mass can be measured in real-time without the need for labeling. The analyte is then injected, and binding of the analyte to the surface-bound ligand increases the mass further, whereupon a new shift in the resonance frequency is registered. Flowing buffer through the sensor chamber enables detection of the release of bound analyte.
Using different surface coatings provides the option of capturing or immobilizing molecules and, accordingly, QCM can be used to study molecular interactions in real time. The QCM technology enables not only the study of biomolecules of varying species such as proteins, nucleic acids, and carbohydrates, but also of vastly different sizes, ranging from peptides to cells.