Project title: Microwave technologies for label-free imaging of drugs in cells and tissues

PhD supervisor: Professor Tony Cass and Dr Tim Albrecht

Most current methods for probing the chemical and physical mechanisms of biological phenomena at a cellular scale, such as drug uptake, rely upon the use of different means of labelling (e.g. fluorophores or nanoparticles encapsulating the drug) that act as contrast agents. This usually leads to several issues that need to be taken into account: for example, introduction of fluorescent labelling may alter the biological properties of the drug, and consequently its interaction with the biological media in which it is inserted and studied; moreover, photobleaching of fluorophores may hinder the possibility of a quantitative analysis of cellular uptake over time. Alternative systems for labelling have been thoroughly implemented, such as the use of deuterated drugs which seem to act analogously to their non-deuterated conventional counterparts [1] but a great emphasis is put on the use of a viable label-free method for biomedical imaging and drug detection.

This specific PhD project is inscribed into the FP7 Initial Training Network (ITN) “Nanomicrowave” research project, which has the overarching objective of training a whole generation of researchers across Europe in the field of nanoscale microwave technologies and related emerging applications, most notably in the field of life sciences. In particular, its specific target is to explore the potential of Scanning Microwave Microscopy (SMM), a technique whose use is relatively new in biomedical applications and imaging, although proofs of concept of its functioning have been displayed in scientific literature [2].

Investigation will firstly focus on defining, by means of SMM, the microwave electrical fingerprints of bacteria that allows them to be identified in a label-free way: in particular, Rhodococcus bacteria will be studied, as a strong expertise on it is available within Cass’s group, and compared to analogous studies performed at the Institute of BioEngineering of Catalonia (IBEC), one of the “Nanomicrowave” network partners, on other systems, such as E. Coli. The results of this first milestone of the PhD research project will be compared to studies performed with Atomic Force Microscopy (AFM) and Surface-enhanced Raman Spectroscopy (SERS), which both have been demonstrated to be valid label-free techniques for biomedical imaging [3-6].

All these experiments will be, in a first moment, performed on fixed bacteria cells and progressively extended to living samples in liquid environment, in which some challenges such as immobilisation of the samples [7, 8] have to be faced. Then, investigation will shift the attention to human cells so that drugs will be, finally, introduced in these systems, in order to confirm the validity of SMM as a label-free imaging tool for drugs, and perform a study of their distribution in cells and tissues.

1. Garrett, N.L., et al., Label-free imaging of polymeric nanomedicines using coherent anti-stokes Raman scattering microscopy. Journal of Raman Spectroscopy, 2012. 43(5): p. 681-688.

2. Park, J., et al., Observation of biological samples using a scanning microwave microscope. Ultramicroscopy, 2005. 102(2): p. 101-6.

3. Dufrene, Y.F., Towards nanomicrobiology using atomic force microscopy. Nature reviews. Microbiology, 2008. 6(9): p. 674-80.

4. Han, X.X., Y. Ozaki, and B. Zhao, Label-free detection in biological applications of surface-enhanced Raman scattering. TrAC Trends in Analytical Chemistry, 2012. 38: p. 67-78.

5. Yamashita, H., et al., Single-molecule imaging on living bacterial cell surface by high-speed AFM. Journal of molecular biology, 2012. 422(2): p. 300-9.

6. Vendrell, M., et al., Surface-enhanced Raman scattering in cancer detection and imaging. Trends in biotechnology, 2013. 31(4): p. 249-57.

7. Doktycz, M.J., et al., AFM imaging of bacteria in liquid media immobilized on gelatin coated mica surfaces. Ultramicroscopy, 2003. 97(1-4): p. 209-216.

8. Louise Meyer, R., et al., Immobilisation of living bacteria for AFM imaging under physiological conditions. Ultramicroscopy, 2010. 110(11): p. 1349-57.