Label-free highly sensitive detection of (small) molecules by wavelength interrogation of integrated optical chips

A bio-chemical sensor system based on wavelength interrogation of integrated optical sensor chips is presented. The combination of a non-mechanical scanning approach with sensor chips of high quality and stability allows fast and accurate multi-channel measurements. The emphasis of the present paper lies in presenting detailed design considerations, and in reporting the application of the system to several high sensitivity sensing tasks. An excellent performance of the sensor is demonstrated for bulk refractometry and affinity measurements. The bulk refractometric measurements show a detection limit of <10-6. For detecting small molecules, a standard deviation in terms of mass coverage of 100 fg/mm2 is obtained, corresponding to a detection limit of 0.3 pg/mm2. Furthermore, a very clear signal is observed for biotin (244 Da), indicating a detection limit for the present wavelength interrogated optical sensor (WIOS) system distinctly below 200 Da. For a direct inummoassay at low concentrations, a detection limit in the order of 10-11 M is estimated based on the experimental results. The results show that the sensor is perfectly suited for application areas such as medical, food and environmental. 2003 Elsevier Science B.V. All rights reserved.