RESUMEN

A label-free optical waveguide immunosensor was designed, fabricated and tested. Different from other popular resonance-based biosensors, such as surface-plasmon-resonance (SPR) or ring/disk resonance biosensors, the local evanescent array coupled (LEAC) biosensor relies on a local evanescent field shift mechanism and can be readily manufactured using trailing-edge integrated-circuit technology with chip-scale microfluidics technology to provide very low cost. The anticipated final form of the sensor technology will require no external equipment enabling disposable use for point-of-care disease detection in non-traditional health-care settings. The local detection ability enables the LEAC biosensor the capability to detect and identify multiple analytes on the same waveguide. On-chip detection is accomplished by integrating buried polysilicon detector arrays under a silicon nitride waveguide. Observations of antibody-antigen interactions using the LEAC biosensor are reported.

RESUMEN

An integrated, inexpensive, label-free photonic waveguide biosensor system with multi-analyte capability has been implemented on a silicon photonics integrated circuit from a commercial CMOS line and tested with nanofilms. The local evanescent array coupled (LEAC) biosensor is based on a new physical phenomenon that is fundamentally different from the mechanisms of other evanescent field sensors. Increased local refractive index at the waveguide's upper surface due to the formation of a biological nanofilm causes local modulation of the evanescent field coupled into an array of photodetectors buried under the waveguide. The planar optical waveguide biosensor system exhibits sensitivity of 20%/nm photocurrent modulation in response to adsorbed bovine serum albumin (BSA) layers less than 3 nm thick. In addition to response to BSA, an experiment with patterned photoresist as well as beam propagation method simulations support the evanescent field shift principle. The sensing mechanism enables the integration of all optical and electronic components for a multi-analyte biosensor system on a chip.

Asunto(s)

Técnicas Biosensibles/instrumentación , Técnicas Analíticas Microfluídicas/instrumentación , Silicio/química , Animales , Técnicas Biosensibles/métodos , Bovinos , Diseño de Equipo , Técnicas Analíticas Microfluídicas/métodos , Modelos Teóricos , Óptica y Fotónica , Procesos Fotoquímicos , Albúmina Sérica Bovina/química

RESUMEN

The response of a compact photonic immunoassay biosensor based on a planar waveguide to variation in antigen (C-reactive protein) concentration as well as waveguide ridge height has been investigated. Near-field scanning optical microscope measurements indicate 1.7%nm and 3.3%nm top surface optical intensity modulation due to changes in effective adlayer thickness on waveguides with 16.5 and 10 nm ridge heights, respectively. Beam propagation method simulations are in good agreement with the experimental sensitivities as well as the observation of leaky mode interference both within and after the adlayer region.