Development of scanning probe surface plasmon resonance microscopy

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The development of novel analytical methodologies is required to face the current challenges in bioanalysis. The quantification of the chemical messengers released from a single cell or a small group of cells in relation with cellular morphology will help understand the biological mechanism of diseases. However, miniaturisation of sensors is required to achieve protein quantification in the extracellular space of a single cell. Surface Plasmon Resonance (SPR) biosensors exhibit the potential to locally monitor proteins with spatial resolution better than the size of a cell. Hence, our research will focus on developing a micro-plasmonic sensor exhibiting a strong SPR response to proteins. The integration of the SPR micro-biosensor on the tip of an Atomic Force Microscopy (AFM) cantilever will enable the simultaneous measurement of proteins in the extracellular space above cells and cellular morphology. We will apply "scanning probe SPR microscopy" to a model system. A chemokine is a messenger protein. They have been recently identified as a major contributor to the signalling mechanism regulating cancer growth and metastasis. However, it remains unknown how chemokines migrate and infect other cells. Thus, we aim at utilising scanning probe SPR microscopy for the quantification of the chemokine gradient from cancerous to healthy cells. To reach our objectives, we will focus on the optimisation of the response of SPR micro-biosensors to chemokines by optimising various experimental parameters: the cantilever material and geometry, the composition and the thickness of the metal thin film (Au or Ag) supporting the SPR micro-biosensor, and the data analysis method. Conventional SPR sensors will also be optimised to maximise the response generated by low concentration of chemokines in cell culture media samples. The sensors will be specifically applied to monitor the chemokine CXCL12. This chemokine of importance is involved in the biological mechanism of breast cancer metastasis.