Panagiota (Naya) Giannakopoulou
Research student, School of Biosciences
I am currently a PhD research student at the Group of Biophotonics and Quantum optoelectronics working with Prof. Paola Borri, Prof. Wolfgang Langbein and Dr. Peter Watson in Cardiff University. Prior to my PhD studies I obtained my MSc in Lasers and Photonics and my Diploma in Physics (graduated at the top 6%) both from University of Patras in 2013 and 2011 respectively.
My research interests span in a wide range of fields under the label of 'light-matter interaction'. During my postgraduate studies so far I have mainly dealt with nonlinear optics, ultrafast spectroscopy, microscopy and drug delivery of gold nanoparticles (NPs). My PhD project serves the investigation of cellular uptake of various sizes gold NPs via Four-wave mixing (FWM) imaging and correlation with fluorescence microscopy.
Gold nanoparticles (NPs) are promising drug delivery vehicles owing to their facile synthesis, simple bio-conjugation, and low toxicity. However, when embedded in highly heterogeneous and fluorescing environments such as cells and tissues, these NPs have to be large (typically >50nm diameter) to be distinguished optically against backgrounds via their linear scattering at the surface plasmon resonance (SPR). As a result, cell imaging protocols often adopt the use of fluorophore tags attached onto the NP, and assume that the fluorophore is a reliable reporter. We have imaged gold NPs (10nm to 40nm diameters) background-free inside HeLa cells using an innovative nonlinear microscopy contrast based on their SPR resonant transient four-wave-mixing (FWM). Various fluorescently-labelled ligands were conjugated to the NPs and internalised through clathrin-mediated endocytosis. Their location was measured with fluorescence microscopy and was correlated to that of the NPs from FWM. Surprisingly, even covalently attached fluorescently-labelled ligands exhibited very low co-localization coefficients, highlighting the limitations of fluorescence tagging. This study opens new perspectives to the understanding of the cellular uptake of conjugated NPs and their ligands.