Abstract
We present a new size-selective detection method for integrated optical interferometric biosensors that can strongly enhance their performance. We demonstrate that by launching multiple wavelengths into a Young interferometer waveguide sensor it is feasible to derive refractive index changes from different regions above the waveguide surface, enabling one to distinguish between bound particles (e.g. proteins, viruses, bacteria) based on their differences in size and simultaneously eliminating interference from bulk refractive index changes. Therefore it is anticipated that this new method will be ideally suited for the detection of viruses in complex media. Numerical calculations are used to optimize sensor design and the detection method. Furthermore the specific case of virus detection is analyzed theoretically showing a minimum detectable virus mass coverage of 4 × 10(2) fg/mm(2) < (typically corresponding to 5 × 10(1) particles/ml).
Highlights
Integrated optical (IO) biosensors have been demonstrated as a powerful detection and analysis tool for biosensing
In this paper we have described a new approach, based on the use of multiple wavelengths in combination with an integrated optical Young interferometer sensor, which allows detecting analytes based on size
The use of multiple wavelengths allows discriminating between refractive index (RI) changes from different locations
Summary
Integrated optical (IO) biosensors have been demonstrated as a powerful detection and analysis tool for biosensing. Integrated optical interferometric biosensors sense refractive index (RI) changes, induced by analyte binding, occurring in the evanescent field These sensors, including the Mach Zehnder interferometer and the Young interferometer (YI), show extremely high (10−710−8 refractive index units (RIU)) RI sensitivity. The detection of virus particles in complex matrices such as serum is hampered by both bulk RI changes and non-specific binding, from which we need to discriminate simultaneously. We show that this is possible using the approach developed here because of the differences in size between virus particles (50-200 nm), proteins (1-10 nm) responsible for non-specific binding and bulk RI changes.
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