RESUMEN
We present experimental and theoretical results of label-free molecular sensing using the transverse magnetic mode of a 0.22 mum thick silicon slab waveguide with a surface grating implemented in a guided mode resonance configuration. Due to the strong overlap of the evanescent field of the waveguide mode with a molecular layer attached to the surface, these sensors exhibit high sensitivity, while their fabrication and packaging requirements are modest. Experimentally, we demonstrate a resonance wavelength shift of approximately 1 nm when a monolayer of the protein streptavidin is attached to the surface, in good agreement with calculations based on rigorous coupled wave analysis. In our current optical setup this shift corresponds to an estimated limit of detection of 0.2% of a monolayer of streptavidin.
Asunto(s)
Técnicas Biosensibles/instrumentación , Técnicas de Sonda Molecular/instrumentación , Refractometría/instrumentación , Silicio/química , Resonancia por Plasmón de Superficie/instrumentación , Transductores , Diseño Asistido por Computadora , Diseño de Equipo , Análisis de Falla de Equipo , Luz , Reproducibilidad de los Resultados , Dispersión de Radiación , Sensibilidad y Especificidad , Silicio/efectos de la radiaciónRESUMEN
We demonstrate folded waveguide ring resonators for biomolecular sensing. We show that extending the ring cavity length increases the resonator quality factor, and thereby enhances the sensor resolution and minimum level of detection, while at the same time relaxing the tolerance on the coupling conditions to provide stable and large resonance contrast. The folded spiral path geometry allows a 1.2 mm long ring waveguide to be enclosed in a 150 microm diameter sensor area. The spiral cavity resonator is used to monitor the streptavidin protein binding with a detection limit of approximately 3 pg/mm(2), or a total mass of approximately 5 fg. The real time measurements are used to analyze the kinetics of biotin-streptavidin binding.
Asunto(s)
Técnicas Biosensibles/instrumentación , Óptica y Fotónica/instrumentación , Fotometría/instrumentación , Mapeo de Interacción de Proteínas/instrumentación , Proteínas/química , Sitios de Unión , Miniaturización , Unión ProteicaRESUMEN
We demonstrate a new silicon photonic wire waveguide evanescent field (PWEF) sensor that exploits the strong evanescent field of the transverse magnetic mode of this high-index-contrast, submicrometer-dimension waveguide. High sensitivity is achieved by using a 2 mm long double-spiral waveguide structure that fits within a compact circular area of 150 microm diameter, facilitating compatibility with commercial spotting apparatus and the fabrication of densely spaced sensor arrays. By incorporating the PWEF sensor element into a balanced waveguide Mach-Zehnder interferometer circuit, a minimum detectable mass of approximately 10 fg of streptavidin protein is demonstrated with near temperature-independent response.
Asunto(s)
Técnicas Biosensibles , Óptica y Fotónica , Silicio/química , Electroquímica , Diseño de Equipo , Interferometría , Ensayo de Materiales , Fosfatos/química , Fotones , Sensibilidad y Especificidad , Espectrofotometría Infrarroja/métodos , Estreptavidina/química , Propiedades de Superficie , Temperatura , Factores de TiempoRESUMEN
A series of Dmt-Tic analogues with substitution on the Tic aromatic ring has been synthesized and evaluated for opioid receptor affinity and activation. Incorporation of large hydrophobic groups at position 7 of Tic did not greatly alter the delta opioid receptor binding affinities of the dipeptides whereas substitution at position 6 substantially diminished their affinity. These modified Dmt-Tic peptides showed binding affinities as low as 2.5 nM with up to 500-fold selectivity for the delta versus mu opioid receptor and proved to be delta receptor antagonists.