Sol-Gel Glasses as New Waveguides for Optical Immunosensors
- PDF / 371,206 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 23 Downloads / 193 Views
1033 Mat. Res. Soc. Symp. Proc. Vol. 345. 01994 Materials Research Society
As the Incidence angle is scanned:
At fixed angle:
-
-4
4) 4)
Tune Incidence angle Fig.): Shows the optical system used in the SPR-basedinstrument. It also illustrates how the observed reflectance of light changes when biomoleculesfrom solution are bound onto the guide.
SOL-GEL FILM PREPARATION Three types of functionalized silicon precursors were used in this study: Methylaminopropyltriethoxysilane (MAPDES), aminopropyltriethoxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES). The preparation of the inorganic-organic hybrid films containing functional groups (SH, NH2) has been performed as follows. The coating solutions were obtained from copolymerization of the functionalized alkoxysilane with methyltriethoxysilane (MTEOS) for the MAPDES and APTES precursors and with tetraethoxysilane (TEOS) for the MPTES precursor. The hydrolysis was performed under acidic conditions with ethanol as the common solvent. The initial molar ratios of MTEOS (or TEOS):functionalized alkoxysilane:water-ethanol were 1:1:3:3. Thin films, 2-4 gm thick, were deposited by spin coating onto gold coated glass substrates. At the appropriate stage of the polymerization reaction, the viscous sol was poured onto the gold layer. The angular velocity of the spinner was 4000 rpm. The samples were left to dry for a few days at room temperature until the film surface became tack-free. SURFACE MODIFICATION AND COUPLING CHEMISTRY Chemically active functional groups, like amines or thiols, allow covalent binding of active biomolecules such as antibodies to the insoluble matrices after activation by bifunctional coupling agents. Aminated supports are treated with 1% glutaraldehyde solution in 0.1M phosphate buffer at pH6.8 and thiolated supports are treated with 1M pyridyldithio-propionic acid Nhydroxysuccinimide ester (SPDP) solution in 0.1M phosphate/0.1M sodium chloride buffer at pH 7.5. Incubation is carried out for 24 hours at room temperature. The slides are then incubated with different concentrations of immunoglobulin solutions (1, 0.2, 0.04, 0.008, 0 mg/ml of mouse IgG directed against Staphylococcal enterotoxin B) in the appropriate buffer.
1034
RESULTS AND DISCUSSION Optical properties of waveguides in the air. The study of optical properties of a waveguide consist on considering many different parameters. Knowing the angular position of each guided mode and using a theoretical model, the thickness and the refractive index of the layer can be calculated. But the most important criterion to consider is the quality of the peaks. Large peaks, not very deep and appearing to split into two mean that the layer, diffusing and absorbing the incident light, is too inhomogeneous to be considered as a good waveguide. On the contrary, if peaks are deep and thin the sol-gel film could be recognized as being optimal. All sol-gel mixtures listed have been tested with the optical sytem described above. Figure 2 shows the reflectivity curves as the incidence angle is s
Data Loading...
