Noble metal nanoparticles are well known for their unique optical properties. Density oscillations of the nanoparticle conduction electrons are induced at a specific frequency by an external incident light beam. This phenomenon is known under the term localized surface plasmon resonance (LSPR). The spectral position of the resonance band is determined by shape, size, and material of the nanoparticle and influenced by changes of the local refractive index of the surrounding medium. The latter gives the opportunity to use noble metal nanoparticles as label-free bioanalytical sensors. Biomolecules can be bound directly on the nanoparticle surface, which leads to a change of the local refractive index, and a shift of the peak maximum is detected by absorbance spectroscopy. This method is used for bioanalytical diagnostics. Here, a DNA sensing protocol for real-time measurements in situ using this system will be presented. A dense layer of noble metal nanoparticles is immobilized on a glass substrate and implemented in a microfluidic chamber, where the spectroscopic measurements are conducted.
Keywords: Bioanalytical diagnostic; DNA; Detection; Localized surface plasmon resonance; Nanoparticles.