Research

Current research activities

  • Biosensors based on  colloidal metallic nanoparticles

    Biomolecules, such as toxins, proteins, DNA, etc, typically found in the blood stream, are subject to a wide range of biochemical processes in the human body. The concentration of such biomolecules is often indicative of the biochemical functioning of the organism. Biomedical research is therefore pushing forwards the development of biosensors able to rapidly monitor the biological activity of these molecules.

    Noble metal nanoparticles (NPs) are intensively studied due to their particular optical properties, mainly high optical absorption and diffusion yield. These unique optical properties arise from a physical process named surface Plasmon resonance (SPR) which is a resonant coupling of incident light to the collective motion of electrons along the nanoparticles surface.

    Optical SPR biosensors are able to measure complex formation in real time. Indeed, the SPR absorption spectrum band of NPs is sensitive to the shape, size, inter-particle distance and composition of the NP as well as the dielectric properties of the surrounding medium. Due to the sensitivity of SPR to the local dielectric environment, plasmonics NPs can act as transducers that convert small changes in the local refractive index or in the inter-particle distance into spectral shifts and broadenings of the absorption spectral bands.

    In this project, we characterize biosensors based on colloidal silver and gold spherical NPs in order to detect which metals seems the best to highlight the biomolecular recognition processes. We use the well-known biocytin-avidin complex as a model system to compare optical properties, absorption and scattering, of silver NPs and gold NPs.

  • Quantum dots and non-linear optical spectroscopies to improve biosensor efficiency

    Biosensors are designed with CdSe semiconducting nanoparticles (i.e. Quantum Dots). Due to their nanometer size, they have localized energy levels lying in the visible spectral range for CdSe and highly sensitive to QDs diameter.

    Doubly-resonant sum-frequency generation (DR-SFG) spectroscopy is a non-linear optical tool, based on the use of visible and infrared lasers, which is highly surface sensitive.  This technique has been successfully applied to study biological species adsorbed on platinum. However, no work is devoted to its use for the characterization of biological entities immobilized on QDs albeit a coupling between the QDs energy levels and biomolecule optical properties is possible. Such a behavior is susceptible to allow the detection of small amount of biological molecules which is really interesting in biosensors applications.

    Collaborator: Dr. C. Humbert (University of Paris-Sud, France)

  • Nanoparticles in light photodynamic therapy

    Another interest of our laboratory concerns the use of metallic nanoparticles to improve the cancer treatment by photodynamic therapy. Porphyrin derivatives molecules (PDM) are frequently used in the treatment of skin cancer by photodynamic therapy. These molecules, when excited by light of appropriate wavelength, generate highly reactive oxygen species (ROS) having the ability to destroy infected cells.

    Metallic NPs are used as substrates for PDM molecules and the coupling between both entities is studied. This coupling is expected to give rise to an increase of ROS production yield and therefore to improve photodynamic therapy efficiency.

  • Multiscale optical characterization of confined biologic fluids

    What is the impact of the fluid motion on biochemical reactions take place in biologic cells? To solve this question, we put colloidal metallic nanoparticles in the biological fluid. By illuminating these particles, it is possible to follow the fluid motion. Moreover, we can use the surface Plasmon resonance phenomenon to probe the local biological environment of the nanoparticle. Due to the particle trajectory, particle image velocimetry (PIV) allows the determination of the fluid mapping velocity. The combination of PIV and SPR should allow the study of the interdependence between the fluid flow and the reactivity of biological material carried by this fluid.

    Collaborators: H. Caps (University of Liège, Belgium), S. Dorbolo (University of Liège, Belgium)