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Optical Gratings Coated with Thin Si3N4 Layer for Efficient Immunosensing by Optical Waveguide Lightmode Spectroscopy.

Diéguez L, Caballero D, Calderer J, Moreno M, Martínez E, Samitier J - Biosensors (Basel) (2012)

Bottom Line: A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering.The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy.The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics, University of Barcelona, C/Martí i Franquès 1, Barcelona, ES 08028, Spain. lorena.dieguez@unisa.edu.au.

ABSTRACT
New silicon nitride coated optical gratings were tested by means of Optical Waveguide Lightmode Spectroscopy (OWLS). A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering. The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy. As a proof of concept, the sensors were successfully tested with OWLS by monitoring the concentration dependence on the detection of an antibody-protein pair. The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

No MeSH data available.


Related in: MedlinePlus

Scheme of the silicon nitride surface functionalization of the direct immobilization of anti-HSA antibodies.
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biosensors-02-00114-f002: Scheme of the silicon nitride surface functionalization of the direct immobilization of anti-HSA antibodies.

Mentions: To test the capability of the new structure to work as an immunosensor, standard antibody-antigen detection experiments were performed. The pair anti-HSA/HSA was selected for this purpose, as a model. In order to functionalize the silicon nitride coated OWLS chips for the antibody immobilization, the procedure described by Caballero et al. was followed [29] (Figure 2). Briefly, after cleaning with organic solvents and Milli-Q water, the silicon nitride coated chip was immersed in Piranha solution (1:3 v/v H2O2:H2SO4; Caution:Piranha is an extremely strong oxidant and should be handled very carefully) at 90 °C for 30 min. Afterwards, sequential immersion in aqueous solutions of NaOH (0.5 M) for 20 min., HCl (0.1 M) for 10 min. and a final immersion in NaOH (0.5 M) solution for 10 min. were performed to activate the surface. The samples were then rinsed thoroughly with HCl and Milli-Q water and dried in an oven at 100 °C for 20 min. Then, the chip was functionalized with triethoxysilane aldehyde (TEA) by the vapor-phase method for 1 hour and cured into the oven for 1 h at 100 °C. Afterwards, the samples were rinsed with absolute ethanol and dried under nitrogen. Once functionalized with the organosilane, the antibodies were immobilized on the chip surface by immersing it into a 10−7 M anti-HSA monoclonal antibody PBS solution (0.01 M phosphate buffer, 2.7 × 10−3 M potassium chloride and 0.137 M sodium chloride, pH 8.4), containing 4 mM sodium cyanoborohydride and allowed to react for 1 h at 37 °C. Afterwards, it was thoroughly rinsed with PBS to remove antibody excess. Subsequently, the aldehyde free surface groups were blocked by a solution of ethanolamine (100 mM ethanolamine in 10 mM PBS, pH 8.4) in the presence of 4 mM cyanoborohydride for 1–2 h at room temperature. Finally, the surface was thoroughly rinsed with PBS, pH 8.4. These antibodies will later recognize the HSA protein from the flowing solution.


Optical Gratings Coated with Thin Si3N4 Layer for Efficient Immunosensing by Optical Waveguide Lightmode Spectroscopy.

Diéguez L, Caballero D, Calderer J, Moreno M, Martínez E, Samitier J - Biosensors (Basel) (2012)

Scheme of the silicon nitride surface functionalization of the direct immobilization of anti-HSA antibodies.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263575&req=5

biosensors-02-00114-f002: Scheme of the silicon nitride surface functionalization of the direct immobilization of anti-HSA antibodies.
Mentions: To test the capability of the new structure to work as an immunosensor, standard antibody-antigen detection experiments were performed. The pair anti-HSA/HSA was selected for this purpose, as a model. In order to functionalize the silicon nitride coated OWLS chips for the antibody immobilization, the procedure described by Caballero et al. was followed [29] (Figure 2). Briefly, after cleaning with organic solvents and Milli-Q water, the silicon nitride coated chip was immersed in Piranha solution (1:3 v/v H2O2:H2SO4; Caution:Piranha is an extremely strong oxidant and should be handled very carefully) at 90 °C for 30 min. Afterwards, sequential immersion in aqueous solutions of NaOH (0.5 M) for 20 min., HCl (0.1 M) for 10 min. and a final immersion in NaOH (0.5 M) solution for 10 min. were performed to activate the surface. The samples were then rinsed thoroughly with HCl and Milli-Q water and dried in an oven at 100 °C for 20 min. Then, the chip was functionalized with triethoxysilane aldehyde (TEA) by the vapor-phase method for 1 hour and cured into the oven for 1 h at 100 °C. Afterwards, the samples were rinsed with absolute ethanol and dried under nitrogen. Once functionalized with the organosilane, the antibodies were immobilized on the chip surface by immersing it into a 10−7 M anti-HSA monoclonal antibody PBS solution (0.01 M phosphate buffer, 2.7 × 10−3 M potassium chloride and 0.137 M sodium chloride, pH 8.4), containing 4 mM sodium cyanoborohydride and allowed to react for 1 h at 37 °C. Afterwards, it was thoroughly rinsed with PBS to remove antibody excess. Subsequently, the aldehyde free surface groups were blocked by a solution of ethanolamine (100 mM ethanolamine in 10 mM PBS, pH 8.4) in the presence of 4 mM cyanoborohydride for 1–2 h at room temperature. Finally, the surface was thoroughly rinsed with PBS, pH 8.4. These antibodies will later recognize the HSA protein from the flowing solution.

Bottom Line: A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering.The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy.The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronics, University of Barcelona, C/Martí i Franquès 1, Barcelona, ES 08028, Spain. lorena.dieguez@unisa.edu.au.

ABSTRACT
New silicon nitride coated optical gratings were tested by means of Optical Waveguide Lightmode Spectroscopy (OWLS). A thin layer of 10 nm of transparent silicon nitride was deposited on commercial optical gratings by means of sputtering. The quality of the layer was tested by x-ray photoelectron spectroscopy and atomic force microscopy. As a proof of concept, the sensors were successfully tested with OWLS by monitoring the concentration dependence on the detection of an antibody-protein pair. The potential of the Si3N4 as functional layer in a real-time biosensor opens new ways for the integration of optical waveguides with microelectronics.

No MeSH data available.


Related in: MedlinePlus