NPOI Detects Biomolecular Interactions and Measures Rates

3D biosensor chips are prepared by Silicon Kinetics by electrochemical etching of a nano-porous region on a silicon wafer. Average pore size is 80 nanometers. Porous structure surfaces are passivated with silane chemistry, then coated with hydrophillic surface chemistries. The chips are then embedded either in multiwell plate probes or in flow cells. All these steps are done by Silicon Kinetics prior to shipment of biosensors called SKi Sensors™.

The researcher immobilizes the first biomolecule of interest (the "target") on SKi Sensor 3D surface with the desired surface chemistry. When the solution with the second biomolecule of interest (the "analyte") is introduced, any net binding of the analyte to the target changes the effective index of refraction in the porous region as biomolocules displace buffer solutions with lower in indices of refraction.

Optical interferometry precisely measures the changes in refractive index in the porous region in real time, as follows: optical interference patterns are created when light reflected from the top of the porous region interferes with light reflected from the bottom of the porous region. The optical path difference signal (OPD signal) is derived from the interferogram and rises proportionately with the amount of biomolecule bound.