Sensing Technology
Outline
SpectroSens is Stratophase’s proprietary sensing technology. SpectroSens is ideally suited to a range of detection and analysis applications; detecting biological entities and analysing bimolecular interactions, chemical detection, process control, environmental monitoring, and ultra-precise refractive index measurement.
SpectroSens works by detecting very small changes in the portion of a liquid which is on the sensor chip surface. In a biological context this means antibody, protein or DNA interactions can be detected and analysed using immunoassays – ie an antibody is immobilised on the SpectroSens chip and then binding of the antigen to this antibody can be monitored. This process can be used to detect biological entities or study their reaction kinetics. A similar approach can be taken in a chemical context, whereby a chemically active layer is bound to the surface and when the target chemical is present that change in the chemically active layer is detected by the SpectroSens chip. The SpectroSens chip is also very sensitive to refractive index changes so often the change in the liquid can be monitored directly by monitoring the changes in refractive index when the composition of the liquid changes – this approach is often well suited to process control applications.
SpectroSens chips are small (typically 10x20mm) silicon optical chips produced using our proprietary Direct Writing technique. These chips are monolithic, have no moving parts and are self referenced to remove temperature effects, therefore they are very robust. The signal read out is accomplished using a simple optical fibre to take the signal to a readout unit. Each chip can contain many sensor areas and the liquid under test is selectably brought to these individual sensor areas using a fluidic system. This allows each chip to take multiple measurements using a single readout unit.
Principle
SpectroSens works by monitoring the change in colour of light caused by the presence of the liquid. The sensing areas are formed above regions on the chip where the light travels just below the surface of the chip, parallel to the surface through a specially written device known as a ‘grating’. This grating causes some of the light to be reflected inside the chip. As a proportion of the light travels over the surface in the sensing region, changes to the sensing surface cause detectable changes in the colour of the reflected light. This enables detection of binding of the target agent to the surface without expensive ‘tagging’ of the sample as is required in some other techniques
Detection of changes in the colour of the light reflected from the grating is accomplished by connecting interchangeable Spectrosens detection chips through a standard optical fibre to an integrated light source and detector. These detection electronics are designed to monitor changes in the colour of the reflected light seemlessly and can be configured to provide a low-cost direct readout of detection probability.
SpectroSens systems combine replaceable sensing chips,
integrated liquid flow cells and the detection electronics to enable
read out of the binding event. These flow cells can be connected to
standard fluid handling, enabling SpectroSens
detection systems to be simply integrated into existing detection
platforms.
Selectivity
The first form of selectivity in a SpectroSens systems comes from the design of the surface assay. Many thousands of assays have been developed over the last few years and they have become the standard way to identify compounds in biomedical and pharmaceutical industry. SpectroSens systems are compatible with most of these assays which can be deposited on the glass surface of a SpectroSens chip providing a reliable and established mechanism for selecting the target agent from the sample.
Where SpectroSens differs is in the way in which the binding of the target agent to the surface assay is detected. In most assay based techniques the sample must be tagged with a fluorescent, magnetic or radiological marker so that any bound elements can be revealed. In the SpectroSens technology the change in the physical properties of the surface on binding are detected directly so no markers are required. This also makes the detection process very fast with real time monitoring of the binding interaction possible.
Compared to other 'tagless' detection techniques such as Surface Plasmon Resonance (SPR), the SpectroSens technology offers much greater selectivity against false detection events. Information on the thickness of the layer binding to the surface is obtained by using sensors working with several colours of light simultaneously. This gives information on the nature of the binding event, helping to distinguish the target agent from non-specific events.
For more detailed technical information on SpectroSens please contact Stratophase
or consult our SpectroSens
product area.