Infra-Red
The next step is to add an infrared spectroscopic facility to the micro-thermal analysis instrument.
The microscope’s thermal probe allows us to detect the photothermal response of a specimen exposed to the beam of a Fourier transform infrared spectrometer and heated thereby.
The signal from this probe measures the resulting temperature fluctuations, thus provides an interferogram which replaces the interferogram normally obtained by means of direct detection of the IR transmitted by a sample.
While a considerable amount of work still needs to be done before FTIR spectroscopy is integrated with scanning probe microscopy, once this has been achieved the spatial resolution will be limited simply by the size of the probe rather than the IR wavelength.
This new form of FTIR microscopy is known as photothermal IR micro-spectroscopy (PTMS). It will be combined in one instrument with the existing modes of micro-thermal analysis. A new cancer-diagnostic tool based on PTMS is being developed thanks to a £386,876 award from the Engineering and Physical Sciences Research Council.
Methods to identify pre-malignant cells based on the their abnormalities in comparison with normal cells are being investigated by this collaboration which includes Dr Frank Martin and Dr Nigel Fullwood of the department of Biological Sciences alongside external co-investigators from Daresbury Synchrotron Radiation Laboratory and the companies TA Instruments and Specac.
There is a current problem during routine diagnosis where abnormal cells may hide amongst larger populations of normal cells during the analysis of a biopsy sample.
Our technology should be sensitive enough to identify cancerous or pre-malignant cells even when such cells make up only a very small proportion of the overall cell numbers; a very important limitation in conventional cancer diagnosis.
The new approach is being compared with such conventional approaches (cytology following staining, TEM or immunohistochemistry) to establish a “biochemical fingerprint” database of characteristic changes associated with abnormal cells. This approach will identify such rogue cells and lead to more effective treatment.
Our latest half-million pound project is carrying out crucial research on adult (non-embryonic) stem cells. The team, funded by BBSRC and EPSRC, consists of (Biology) Dr Nigel Fullwood and Dr Frank Martin, (Physics) Dr Azzedine Hammiche, Dr Hubert Pollock and Prof Tony Krier, (Newcastle University) Dr Matt German, and (industrial partner) Anasys Instruments. It aims to develop a technique which will enable researchers to accurately identify adult stem cells in the human body – opening up the possibility of new treatments for life threatening diseases.
Adult stem cells are found in many different parts of the human body – for example in bone marrow, the cornea and the brain. They have unique biological properties which enable them to self-renew by producing a carbon copy of themselves. They can also differentiate – or turn into more specialised cells.
These qualities mean that, in theory, adult stem cells could be used to repair and replace damaged and diseased cells in the body, and could hold the key to effective treatment for serious conditions such as Parkinsons disease, diabetes and heart disease. They could even be used to grow entire organs such as hearts, livers and kidneys. But currently adult stem cells are something of an enigma – there is no established single method of identifying and categorising them. Our results so far indicate that PTMS shows great promise as a key to overcoming this problem.
This PTMS technique may be applied to the spectroscopic characterisation of many different kinds of real-world samples, and little if any sample preparation is required. Examples include powder samples, strands of hair or coated wire, solutions in the form of microdroplets or as wiped by tissue, prostate cells treated with suspected carcinogens, and DNA from cells exposed to pesticides.
Theoretical calculations confirm that the highest obtainable
spatial discrimination depends upon the frequency at which the infrared light is modulated
Recent Publications
- The important technique known as Photothermal IR micro-spectroscopy (PTMS) has recently been described in a review chapter entitled “Microspectroscopy as a tool to discriminate nano-molecular cellular alterations in biomedical research”, F L Martin and H M Pollock, accepted for publication in: Oxford Handbook of Nanoscience and Technology 2 (A V Narlikar and Y Y Fu, eds.), 2009. Recent PTMS publications include:
- FTIR micro-spectroscopy identifies symmetric PO2- modifications as a marker of the putative stem cell region of human intestinal crypts, Michael J. Walsh, Tariq G. Fellous, Azzedine Hammiche, Wey-Ran Lin, Nigel J. Fullwood, Olaug Grude, Fariba Bahrami, James M. Nicholson, Marine Cotte, Jean Susini, Hubert M. Pollock, Mairi Brittan, Pierre L. Martin-Hirsch, Malcolm R. Alison and Francis L. Martin, Stem Cells 26, 108-118 (2008)
- Discrimination of human stem cells by photothermal microspectroscopy, O Grude, T Nakamura, A Hammiche, A J Bentley, F L Martin, H M Pollock, S Kinoshita and N J Fullwood, Vibrational Spectroscopy (2008), doi:10.1016/j.vibspec.2008.04.008
- A Hammiche, M J Walsh, H M Pollock, P L. Martin-Hirsch, and F L. Martin, Non-contact micro-cantilevers detect photothermally-induced vibrations that can segregate different categories of exfoliative cervical cytology, J Biochem Biophys Methods 70, 675-7 (2007),
doi: http://dx.doi.org/10.1016/j.jbbm.2007.01.011
- Near-field photothermal microspectroscopy for adult stem-cell identification and characterization, O. Grude, A Hammiche, H M Pollock, A J Bentley, M J Walsh, F L Martin and N J Fullwood, J Microscopy 228, 366-372 (2007)
