Silica microspheres for biomolecular detection applications.

Microsphere-based biosensors have been attracting the attention of the photonics community due to their high sensitivity, selectivity and implementation. Microspheres, with their high quality-factor (Q-factor) morphology dependent resonances, are very sensitive to refractive index and size changes. The perturbation of the microsphere morphology dependent resonances can be used for the detection of biomolecules. Adsorption of different biomolecules on the surface of microspheres causes a change of effective size and refractive index leading to the shift of resonance wavelengths. A biosensor, based on this phenomenon, can detect a single molecule sensitively depending on the configuration that needs to be designed and optimised. Silica with a refractive index of 1.5, which is very close to that of bimolecular agents, is a suitable photonic material to use for biosensing applications. The transverse electric and transverse magnetic elastic scattering spectra at 90 degrees and 0 degrees are calculated at 1.55 microm with the associated shifts after adding a layer on it. 90 degrees scattering is used to monitor the scattered signal, whereas 0 degrees scattering is used to monitor the transmission signal.