WhiSense
WhiSense — A patented innovative device to monitor label-free protein interactions.
Smallest Biosensors Each microparticle is a microsensor: Real-time bioanalysis in microfluidic chips, cell cultures and organ-on-a-chip is now possible
High Sensitivity WhiSense: The first commercial label-free bioanalysis platform exploiting microparticles and Whispering Gallery Modes (WGM).
With a sensitivity of below 1ng/ml, WhiSense is as powerful as similar label-free methods such as SPR and QCM
High Speed - Low Costs One microfluidic chip – hundreds of sensors. Multiplexed assays are redefined by microparticles
Label-Free Bioanalysis with Microsensors Online, multiplexed bioanalysis in micron-scale cavities is now possible! Meet WhisperSense: The first commercial label-free bioanalysis platform exploiting microparticles and Whispering Gallery Modes (WGM).
Spherical microparticles can generate an optical phenomenon called Whispering Gallery Modes (WGM) once light is trapped within them. WGM has a unique wavelength fingerprint, which is extremely sensitive to environmental changes around the particle and to any adsorption at the particle surface.
We bio-functionalize the microparticle surface so that they are powerful microsensors for specific biologics.
What are Low-Q Whispering Gallery Modes
・Waves travelling in a circular resonator (rings, spheres)
・already used in Middle Ages to eavesdrop on kings without being detected
・famous example of acoustic reflections is St Paul's Cathedral in London
・WGM was later adopted for optical waves, acoustic wavelength (120 Hz) 3 metres, light 500 nm
・Quality factor 104 depends on resonator quality (surface, diameter, RI, sphericity), go up to 109
Principle Low-Q-Whispering Gallery Modes
・10 µm particle with high refractive index, smooth surface, spherical, labelled with fluorescence dye
・Excitation by normal laser irradiation
・Dye molecules emit fluorescent light, which circulates by total internal reflection up to 10 000 times
・Resonance results from wavelength, particle diameter and reflection angle (inside-outside)
・Resonant waves circulate around 10,000 times before they are scattered out and measured by us; non-resonant waves are cancelled out
・In contrast to SPR one attached molecule influences the photon not only 1 x but 10 000 times, requiring much smaller surface area and analyte amount for same sensitivity
What can be measured
・Emission spectrum shows narrow peaks (FWHM 150 pm) that shift when the resonance condition changes in dependence on diameter and refractive index in evanescent field (100 nm)
・Time-dependent measurement (D100 ms) of shift allow evaluation of:
- Swelling/Shrinking of particle diameter (nanometer accuracy)
- Refractive index of the solution
- Adsorption/desorption of molecules (label-free bioanalysis)
- Deformations of the particle (splitting of the modes, pressure measurement)
Comparison to label free methods on the market
・Surface Plasmon Resonance (SPR), Biacore, planar Chip 16 mm² ➔ 16 ng protein saturation
・Quartz Crystal Microbalance (QCM), planar Chip 64 mm² ➔ 64 ng necessary
・BioLayerInterference (BLI), planar surface 4 mm² ➔ 4 ng necessary
・Low-Q WGM spherical measuring field 0,00031 mm² ➔ 0, 0003 ng protein for saturation
System
Applications
Advantages for Bioanalytics and further label free measurements
・Fast measurement
・Low-cost consumables
・Small and robust instrumentation
・Identical bio-prefunctionalization of billions sensors
・Long term storage of prefunctionalized sensor beads in buffer
・Almost no temperature dependence
・Measurements in tiny cavities (even inside living cells)
・Freely selectable microfluidic setup
・High statistic safety by fast screening
・Multiplexing possible
