Development of a DNA sensor based on Localized Surface Plasmon Resonance (LSPR) using gold nanoparticles


There is an increasing need for fast and sensitive detection of specific DNA sequences for use in applications such as viral and bacterial pathogen detection and disease diagnosis. Currently polymerase chain reaction (PCR) is the most common method to detect small quantities of DNA. However PCR is time consuming and labour intensive and operators need to be well trained to get reproducible results.

Previously in this group, proof of concept was shown for a sensor which is
capable of detecting DNA down to femtomolar concentrations. The detection principle is based on Localized Surface Plasmon Resonance (LSPR). LSPR occurs when an incoming electromagnetic wave (light) displaces conducting electrons on the surface of a metallic/conductive nanoparticle. At a certain frequency of the incoming light, the rate of displacement matches the oscillation of the electrons and resonance occurs (Fig. 1). At the resonance wavelength the particles exhibit a number of effects, such as near-field enhancement of electromagnetic fields, enhanced absorption and scattering.

Depending on particle characteristics (i.e. shape, size, material, dielectric environment) the LSPR occurs at different wavelengths. An example of the influence of particle size on the plasmon resonance can be seen in Fig. 1. For sensing purposes the most interesting part of the LSPR effect is that changes in the immediate environment of the particle result in a shift in the plasmon resonance. These shifts can be detected and related to absorption or desorption of molecules on the interface between the gold particle and its dielectric environment.

Figure 1. Left: Collective displacement of electrons by an incoming electromagnetic field results in Localized Surface Plasmon Resonance (LSPR) of a metallic nanoparticle. Right: Vials containing spherical gold nanoparticles of varying sizes dispersed in an aqueous solution showing scattering and absorption of different wavelengths, resulting in colours ranging from dark red to blue.

In this research project, gold nanoparticles (AuNPs) are physisorbed to an optically transparent substrate and subsequently functionalized with specific single stranded oligonucleotides. A target strand (i.e. a piece of pathogenic DNA to be detected) is then introduced which binds to their complementary counterpart on the surface of the AuNPs. This results in a slight shift of the plasmon resonance. To increase this shift, a secondary set of AuNPs is introduced, which is also complementary to a part of the target DNA strand (Fig. 2). This AuNP-DNA-AuNP complex results in a relatively large shift of the plasmon resonance wavelength. In principle single binding events can be detected as a shift of the wavelength of scattered light of singular nanoparticles using optical methods such as dark field microscopy (Fig 2).

The goal of this project is to integrate this sensor scheme in a microfluidic chip capable of on-chip lysis and detection of the bacterial DNA contained in sputum samples of patients who are infected with tuberculosis. This microfluidic chip will be developed in cooperation with a PhD student from the BIOS group.

Figure 2. Left: 1: Physisorption of gold nanoparticles on an optically transparent surface. 2: Functionalization of gold particle surface with tag oligonucleotides. 3: Hybridization of complementary target sequence to tag sequence. 4: Hybridization of a second tag-AuNP to the primary particle. Right: typical dark field image of physisorbed 80 nm AuNPs. After a binding event, the characteristic green colour of the nanoparticles redshifts.

Selected publications:


Verdoold, R., Gill, R., Ungureanu, F., Molenaar, R., & Kooyman, R. P. H. (2011). Femtomolar DNA detection by parallel colorimetric darkfield microscopy of functionalized gold nanoparticles. Biosensors & bioelectronics, 27(1), 77-81. Elsevier B.V. doi:10.1016/j.bios.2011.06.019

PHD student: Kristian Göeken

Project supervisor: Dr. Ron Gill