München 2004 – scientific programme
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Q: Quantenoptik und Photonik
Q 43: Biophotonik und Laser in der Medizin
Q 43.1: Talk
Thursday, March 25, 2004, 16:30–16:45, HS 224
A single-nanoparticle biosensor based on light scattering spectroscopy — •Gunnar Raschke1, Sandra Brogl1, Stefan Kowarik1, Thomas Franzl1, Carsten Sönnichsen1, Thomas A. Klar1, Jochen Feldmann1, Alfons Nichtl2, and Konrad Kürzinger2 — 1Photonics and Optoelectronics Group, Physics Department and Center for NanoScience, Ludwig-Maximilians-Universität, Amalienstr. 54, 80799 Munich — 2Roche Diagnostics GmbH, Nonnenwald 2, 82372 Penzberg
We present a novel biosensor for the optical detection of molecular binding events based on scattering spectroscopy of single functionalized gold nanoparticles.
The scattering spectrum of a gold metal nanoparticle shows a distinct resonance in the visible due to a collective oscillation of its conduction band electrons. The spectral position of this nanoparticle plasmon resonance (NPPR) depends sensitively on the dielectric properties of the particle’s immediate surrounding. Molecular binding events inside this nanoenvironment alter the refractive index and can therefore be deduced from a shifted plasmon resonance position.
We monitor the homogenous NPPR spectrum of a single gold nanoparticle which allows us to detect spectral shifts of only a few meV. Therefore, less than 200 molecules with a molecular weight of only 50 000 D can be detected under physiological conditions. We demonstrate this concept using gold nanoparticles functionalized with biotin to detect streptavidin molecules [1].
[1] G. Raschke et al., Nano Letters, 3, 935 (2003).