| AVS 62nd International Symposium & Exhibition | |
| Biomaterial Interfaces | Tuesday Sessions |
| Session BI-TuP |
| Session: | Biomaterial Interfaces Poster Session |
| Presenter: | Miki Ebisawa, Toyo University, Japan |
| Authors: | M. Ebisawa, Toyo University, Japan T. Kawakami, Toyo University, Japan H. Takei, Toyo University, Japan |
| Correspondent: | Click to Email |
OBJECTIVE
Surface-enhanced fluorescence, SEF, is a highly sensitive method for detecting fluorescent molecules using a noble metal structure. We used cap-shaped silver nanoparticles that were fabricated by vacuum deposition of silver onto a dense layer of silica nanoparticles immobilized on a glass slide. While there is much in common with surface-enhanced Raman spectroscopy, SEF requires that molecules be placed at a certain distance away from the metal surface in order to avoid quenching. To satisfy this requirement, we have evaluated the effect of introducing a dielectric layer on the substrate surface. Furthermore we have investigated a number of techniques for patterning different antibodies or DNA fragments as we are targeting immunoassay and DNA diagnosis for the application of SEF, up to several dozens of different target molecules at the same time.
METHODS
Cap-shaped silver nanoparticles prepared with the above method were soaked in a silane coupling agent (tetraethylorthosilicate, TEOS) to form a dielectric layer. With DNA measurements, we used a probe DNA (19 mer) and FITC-labeled target DNA (13 mer). After immobilization of the probe DNA, the target DNA was made to hybridize. We examined two methods for patterning. One way was to prepare polymer fibers at whose end silver nanoparticles were formed. Fibers modified with different capture molecules were bundled together to be used for measurements. As a second method, after a substrate surface was uniformly modified by a single type of capture molecule, the molecule was locally destroyed: a “subtractive” method. For destruction, ozone treatment or additional deposition of silver was used.
RESULTS
From results by a microarray scanner, we confirmed that the signal intensity of the fluorescent modified DNA from a silver nanoparticle substrate with a dielectric layer was more than doubled compared with the control substrate, demonstrating the effect of a dielectric layer. As for the ozone cleaning, the treatment of the substrate enhanced the signal intensity if applied prior to adsorption of the target molecules; if afterward, the same treatment was found to diminish the signal, as we expected. However, the effect of additional silver deposition was unexpected. We assumed that the signal would be diminished by additional deposition several nm in thickness, but on the contrary the signal was enhanced by additional deposition, the signal intensity being maximized when the thickness was 150 nm. In the future, we will examine this phenomenon in greater detail, with a hope of obtaining a fundamental insight into the mechanism of SEF.