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Imaging

Imaging in the nanodomain theme focuses attention to unravelling the complexity of living cells and tissues at the sub-micron level. Our aim is to lever the strengths in optical and sensor research at the University for the benefit of the biomedical community. There is widespread expertise and interest in imaging and microscopy development across the University, especially in non-conventional techniques which seek to overcome current limitations and push current boundaries, activities which the IfLS is keen to harness and support.

Professor Sumeet Mahajan
Professor Sumeet Mahajan

The most prolific tool currently for monitoring cellular processes is the palette of fluorescent proteins which are easily photo-bleached and often cannot be detected at low levels of expression. Although techniques based on fluorescence have led to huge strides in our understanding of biomedical phenomena, the approach is fundamentally invasive (disruptive) to the cell, not conducive to monitoring multiple interactions between different molecules or monitoring over prolonged periods due to photo-bleaching. Hence, along with creating state-of-the-art imaging abilities and pushing the boundaries of resolution (to nanoscopy) a range of complimentary label-free techniques are available and are being further developed. Such suite of techniques is required to advance our current understanding and also for quantitative, in vivo and translational applications.

Label-free microscopy

Spontaneous Raman spectroscopy is a well-established technique capable of identification of materials, using intrinsic molecular vibrations thus without any labelling and photo-bleaching, at the multi-molecular level but signals are extremely weak under normal circumstances. By utilizing nanoscale metallic materials (typically nanoparticles or nanotextured surfaces) Raman signals of molecules near such surfaces are enhanced by more than a million times, and even enable single molecule detection. This is called surface-enhanced Raman scattering (SERS) and this allows imaging of molecular level changes inside cells or on and near cell membranes [1].

Lipid droplets (red) and collagen (blue) imaged label-free with CARS and SHG microscopy in lung tissue. Scale bar is 5 microns.
Prof. T Postle and Prof S Mahajan

Further, by using non-linear optical effects induced by fast-pulsed sources, huge enhancements (x10,000) of Raman signals can be obtained. The cohort of these techniques called coherent Raman scattering (CRS) are multi-photon optical techniques with z-sectioning ability. With use of near-infrared sources high depth penetration is achieved. They are thus ideally suited for non-invasive, 3D chemically specific imaging in living cells and in vivo. Many applications tracking small molecules such as drugs and lipids, protein and DNA in cells, tissues and organisms have been demonstrated and are being further explored [2].

Multimodal microscopy systems with combinations of CRS, second harmonic generation (SHG) imaging - for label-free imaging of ordered structures such as collagen and microtubules, two-photon fluorescence (TPF) and simultaneous electrophysiology (patch clamp, voltage and current clamp) as well as scanning, boundary layer potentiometric and amperometric, electrochemical measurements are being developed.

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Imaging in the nanodomain theme focuses attention to unravelling the complexity of living cells and tissues at the sub-micron level. Our aim is to lever the strengths in optical and sensor research at the University for the benefit of the biomedical community. There is widespread expertise and interest in imaging and microscopy development across the University, especially in non-conventional techniques which seek to overcome current limitations and push current boundaries, activities which the IfLS is keen to harness and support.

Visit Dr Sumeet Mahajan's research pages.

For more information on the Imaging in the Nanodomain theme please email S.Mahajan@soton.ac.uk

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