Micro-photonic cylindrical waveguide based protein biosensor

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.