The joined research project aims to investigate multi-functional nanoparticles for optical chemical and biochemical sensing. The beneficial functionalities combined in one nano particle include: magnetism, luminescence up-conversion, sensing and light harvesting. These sensor particles are excited with near-infrared (NIR) light. The anti-Stokes phosphorescence generated is used to excite an indicator or label dye enabling the detection of chemical parameters and the performance of bioassays. The NIR excitation and the up-conversion effect do not induce background luminescence of the biological sample. These nanosensor particles can be easily separated from the sample and collected at distinct positions by magnetic fields. This “in-situ” sensor spot leads to a sensitivity enhancement due to the high concentration of luminescent label at this point. The sensors are read-out by luminescence lifetime measurements, which is advantageous, because they are virtually independent of the overall signal intensity. The necessary instrumentation is simple due to the long lifetime of the up-conversion nanocrystals (upcon NCs). Multifunctional nano-particles will be prepared by entrapping magnetic nanocrystals and upcon NCs in the polymeric host matrix. Depending on the application, plain and core-shell particles will be investigated. The surface shell of the multifunctional particles contains carboxyl groups to obtain stable suspensions in aqueous samples and to conjugate receptors, ligands, enzymes or fluorescent indicator dyes to introduce the sensing function. In addition, the highly innovative click-chemistry approach will be applied to conjugate these functional molecules to the surface. Alternatively, the polymeric core or shell will be doped with fluorescent indicator dyes to introduce sensitivity to chemical parameters. The nano sensor will be applied to monitor the key parameters oxygen and pH of bio-films and cell cultures and to perform model affinity binding assays using antibodies and DNA oligomers. The specialized and complementary expertises of the two groups will be fully exploited within this project.
