|
Highly sensitive optical techniques, capable of detecting very small quantities of specific proteins in a label-free format,
offer great promise for pathogen detection because they avoid the complexity, expense, and process time associated with
the use of secondary reporter elements. Arrayed Imaging Reflectometry (AIR) is one of the simplest label-free
methodologies, combining laser reflectance imaging of a thermally oxidized silicon chip with standard microarray
printing technology to create a platform with the potential to identify and quantify 100's of target proteins in a matter of
minutes. This technique exploits a reflectance zero condition that is formed when s-polarized light strikes the surface of
a silicon wafer with a single-layer oxide coating. In the vicinity of this deep reflectance minimum, picometer-scale
variations in film thickness (surface relief) can be imaged directly in a reflected laser signal imaged with a CCD camera.
By directly arraying probe molecules onto this substrate, minute changes in the optical thickness of each spot,
corresponding to binding of the target of interest, can be measured. Array size is limited only by the resolution of the
imaging system and the array printer, enabling complex protein signatures, indicative of specific pathogens or disease
states to be measured in a biosample. The cost-effectiveness of a low-complexity substrate and reader, combined with
the short assay times associated with label-free detection make AIR a promising new technology for pathogen and toxic
exposure assessment.
|
