In this paper we experimentally demonstrate the fabrication and operation of a
rapidly prototyped optical cylindrical micro-waveguide based biosensor. This device
works on the principle of variation to the light intensity and path of coupled
input light due to the binding of protein bio-molecules onto the micro-waveguide
surface as a method of physical transduction. The variation to the coupled light
intensity and path is dependent on the nature of the bio-molecule and the
density of the bio-molecules. This technique has been used to identify protein
biomarkers for inflammation and thrombosis, namely myeloperoxidase (MPO) and
C-reactive protein (CRP). The detection limit that has been demonstrated is
pg ml−1. The detection speed is of the order of seconds from the time of injection of the
bio-molecule. The optical signature that is obtained to identify a protein bio-molecule is
entirely dependent on the nature of adsorption of the bio-molecule on to the
cylindrical cavity surfaces. This in turn is dependent on the protein conformation and
the surface charge of the bio-molecules. Hence a specific protein bio-molecule
generates a unique optical identifier based on the nature of binding/adsorption to
the cavity surface. This physical phenomenon is exploited to identify individual
proteins. This technique is a demonstration of detection of nano-scale protein
bio-molecules using the optical biosensor technique with unprecedented sensitivity.
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