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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

OWLS graphic showing the mass of HSA protein adsorbed on the Si3N4 functionalized chip.
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biosensors-02-00114-f006: OWLS graphic showing the mass of HSA protein adsorbed on the Si3N4 functionalized chip.

Mentions: Human serum albumin detection experiments were performed in order to establish the biosensing viability of the whole developed system. The albumin concentration in the blood serum of an average adult human is 42.0 ± 3.5 mg/mL, (~0.6 mM) with an interval of 35–50 mg/mL [32,33]. Hyperalbuminemia and hypoalbuminemia are pathogenesis related with high or low HSA concentrations in body fluids, respectively. The immunosensing experiments have been specifically design to show high sensitivity and dynamic range performance in the range of interest. HSA was recognized by the anti-HSA antibody attached to the silicon nitride coated OWLS waveguide chip. The system proved to be stable; responses did not decrease significantly during the measurement. A typical curve of the measurements performed with the system is shown in Figure 6. Measurements started by stabilizing the system by flowing PBS for two hours approximately in order to obtain a steady baseline. Then, solutions with increasing HSA protein concentrations within the range of 10−13 M–10−3 M were injected in the cell. After each injection, the system was kept in stop-flow mode in order to stabilize the signal, and then it was thoroughly rinsed with PBS in order to remove all the protein non-specifically adhered to the chip surface. The system response was sigmoidal with the protein concentration, as predicted by the Nerst equation and the Langmuir adsorption theory [34]. The system proved to be very stable, achieving repeatable results with an error of less than 10%. Considering the amount of antibody captured probes used on the immobilization procedure (equivalent to 104 pmol/cm2) and taking into account that an antibody perfect monolayer would have a density of is 1.7 pmol/cm2 (antibodies are around 10 nm in diameter [35]) the antibody amount used in the immobilization process is well in excess. If the recognition ratio between the protein and the antibody is 0.37:1 [36], the maximum saturation value of protein to be recognised for an ideal antibody monolayer would be 336 ng/cm2. Thus, the experimental data measured for the adsorbed protein in the detection range assayed, shown in Figure 6, is far from saturation, therefore confirming that the biosensing system is well designed to work in the desired range.


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)

OWLS graphic showing the mass of HSA protein adsorbed on the Si3N4 functionalized chip.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-02-00114-f006: OWLS graphic showing the mass of HSA protein adsorbed on the Si3N4 functionalized chip.
Mentions: Human serum albumin detection experiments were performed in order to establish the biosensing viability of the whole developed system. The albumin concentration in the blood serum of an average adult human is 42.0 ± 3.5 mg/mL, (~0.6 mM) with an interval of 35–50 mg/mL [32,33]. Hyperalbuminemia and hypoalbuminemia are pathogenesis related with high or low HSA concentrations in body fluids, respectively. The immunosensing experiments have been specifically design to show high sensitivity and dynamic range performance in the range of interest. HSA was recognized by the anti-HSA antibody attached to the silicon nitride coated OWLS waveguide chip. The system proved to be stable; responses did not decrease significantly during the measurement. A typical curve of the measurements performed with the system is shown in Figure 6. Measurements started by stabilizing the system by flowing PBS for two hours approximately in order to obtain a steady baseline. Then, solutions with increasing HSA protein concentrations within the range of 10−13 M–10−3 M were injected in the cell. After each injection, the system was kept in stop-flow mode in order to stabilize the signal, and then it was thoroughly rinsed with PBS in order to remove all the protein non-specifically adhered to the chip surface. The system response was sigmoidal with the protein concentration, as predicted by the Nerst equation and the Langmuir adsorption theory [34]. The system proved to be very stable, achieving repeatable results with an error of less than 10%. Considering the amount of antibody captured probes used on the immobilization procedure (equivalent to 104 pmol/cm2) and taking into account that an antibody perfect monolayer would have a density of is 1.7 pmol/cm2 (antibodies are around 10 nm in diameter [35]) the antibody amount used in the immobilization process is well in excess. If the recognition ratio between the protein and the antibody is 0.37:1 [36], the maximum saturation value of protein to be recognised for an ideal antibody monolayer would be 336 ng/cm2. Thus, the experimental data measured for the adsorbed protein in the detection range assayed, shown in Figure 6, is far from saturation, therefore confirming that the biosensing system is well designed to work in the desired range.

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