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UK Engineering and Physical Sciences Research Council (EPSRC) (EP/J01771/X); European Union project FAMOS (FP7 ICT no. 317744); PreDiCT-TB consortium (IMI 115337); European Union's Horizon 2020 Marie Sklodowska-Curie Actions (MSCA) (707084). ; Vibrational spectroscopy is a widespread, powerful method of recording the spectra of constituent molecules within a sample in a label-free manner. As an example, Raman spectroscopy has major applications in materials science, biomedical analysis and clinical studies. The need to access deep tissues and organs in vivo has triggered major advances in fibre Raman probes that are compatible with endoscopic settings. However, imaging in confined geometries still remains out of reach for the current state of art fibre Raman systems without compromising the compactness and flexibility. Here we demonstrate Raman spectroscopic imaging via complex correction in single multimode fibre without using any additional optics and filters in the probe design. Our approach retains the information content typical to traditional fibre bundle imaging, yet within an ultra-thin footprint of diameter 125 µm which is the thinnest Raman imaging probe realised to date. We are able to acquire Raman images, including for bacteria samples, with fields of view exceeding 200 µm in diameter. ; Publisher PDF ; Peer reviewed

Funding: Funding: European Union FAMOS project (FP7-ICT-317744); Engineering and Physical Sciences Research Council (EP/P030017/1); RS MacDonald Charitable Trust. ; Homocysteine (HCy) is a sulphur-containing amino acid that correlates with several maladaptive health conditions, including an enhanced risk of cardiovascular and neurodegenerative diseases. Detection of HCy and its potentially pathogenic metabolites are studied here for the first time, to the first of our knowledge, using Raman spectroscopy. This study shows that different HCy metabolites have distinct Raman spectra and that the limits of detection reach the sub-mM level for these compounds. This investigation paves the way for photonics–based approaches for detection of HCy–related fluids as predictive biomarkers of disease in blood, which would assist in early intervention for improved clinical outcomes. ; Publisher PDF ; Peer reviewed

UK Engineering and Physical Sciences Research Council (EPSRC) (EP/P030017/1); European Union's Horizon 2020 Marie Skłodowska-Curie Actions (MSCA) (707084) ; Optical clearing is emerging as a popular approach particularly for studies in neuroscience. However the use of corrosive clearing solutions typically requires sophisticated objectives or extreme care with optical components chosen for single- or multi-photon imaging. In contrast to the use of complex, custom-made microscope objectives, we show that the use of a corrected multimode fibre (MMF) offers a route that is resistant to corrosion, can be used in clearing media, is not constrained by the refractive index of the immersion medium and offers flexible working distances. Using a corrected MMF, we demonstrate fluorescence imaging of beads and stained neuroblastoma cells through optically cleared mouse brain tissue, as well as imaging in an extreme oxidative environment to show the versatility of our approach. Additionally, we perform Raman imaging of polystyrene beads in clearing media to demonstrate that this approach may be used for vibrational spectroscopy of optically cleared samples. ; Publisher PDF ; Peer reviewed

This work was supported by the UK Engineering and Physical Sciences Research Council under grant EP/J01771X/1, A European Union FAMOS project (FP7 ICT, 317744), and the 'BRAINS' 600th anniversary appeal, and Dr. E. Killick. We would also like to thank The RS Macdonald Charitable Trust for funding support. KD acknowledges support of a Royal Society Leverhulme Trust Senior Fellowship. This work was also supported by the PreDiCT-TB consortium [IMI Joint undertaking grant agreement number 115337, resources of which are composed of financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013) and EFPIA companies' in kind contribution (www.imi.europa.eu)] ; The ability to identify and characterise individual cells of the immune system under label-free conditions would be a significant advantage in biomedical and clinical studies where untouched and unmodified cells are required. We present a multi-modal system capable of simultaneously acquiring both single point Raman spectra and digital holographic images of single cells. We use this combined approach to identify and discriminate between immune cell populations CD4+ T cells, B cells and monocytes. We investigate several approaches to interpret the phase images including signal intensity histograms and texture analysis. Both modalities are independently able to discriminate between cell subsets and dual-modality may therefore be used a means for validation. We demonstrate here sensitivities achieved in the range of 86.8% to 100%, and specificities in the range of 85.4% to 100%. Additionally each modality provides information not available from the other providing both a molecular and a morphological signature of each cell. ; Publisher PDF ; Peer reviewed

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIT) (No. 2019R1A2C2011293) and the UK Engineering and Physical Sciences Research Council (Grant EP/P030017/1). ; We report a new method to optically manipulate a single dielectric particle along closed-loop polygonal trajectories by crossing a suite of all-fiber Bessel-like beams within a single water droplet. Exploiting optical radiation pressure, this method demonstrates the circulation of a single polystyrene bead in both a triangular and a rectangle geometry enabling the trapped particle to undergo multiple circulations successfully. The crossing of the Bessel-like beams creates polygonal corners where the trapped particles successfully make abrupt turns with acute angles, which is a novel capability in microfluidics. This offers an optofluidic paradigm for particle transport overcoming turbulences in conventional microfluidic chips. ; Publisher PDF ; Peer reviewed

We thank the UK Engineering and Physical Sciences Research Council for funding (grants EP/P030017/1 and EP/R004854/1), the European Union's Horizon 2020 Framework Programme (H2020) (675512, BE-OPTICAL), the Danish Council for Independent Research (DFF FTP grant 7017-00021), and the Otto Mønsted Foundation (grant 19-70-0109). ; Attenuation of optical fields owing to scattering and absorption limits the penetration depth for imaging. Whilst aberration correction may be used, this is difficult to implement over a large field-of-view in heterogeneous tissue. Attenuation-compensation allows tailoring of the maximum lobe of a propagation-invariant light field and promises an increase in depth penetration for imaging. Here we show this promising approach may be implemented in multi-photon (two-photon) light-sheet fluorescence microscopy and, furthermore, can be achieved in a facile manner utilizing a graded neutral density filter, circumventing the need for complex beam shaping apparatus. A "gold standard" system utilizing a spatial light modulator for beam shaping is used to benchmark our implementation. The approach will open up enhanced depth penetration in light-sheet imaging to a wide range of end users. ; Publisher PDF ; Peer reviewed

This work was supported by the PreDiCT-TB consortium [IMI Joint undertaking grant agreement number 115337, resources of which are composed of financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013) and EFPIA companies' in kind contribution (www.imi.europa.eu)]. M.C. and K.D. thank the UK Engineering and Physical Sciences Research Council (Grant code EP/J01771X/1) and a European Union FAMOS project (FP7 ICT, 317744) for funding. K.D. acknowledges support from a Royal Society Leverhulme Trust Senior Fellowship and the loan of a laser from M Squared Lasers. This work was supported by the Department of Health, UK. The views expressed in this publication are those of the authors and not necessarily those of the Department of Health. ; Tuberculosis relapse is a barrier to shorter treatment. It is thought that lipid rich cells, phenotypically resistant to antibiotics, may play a major role. Most studies investigating relapse use sputum samples although tissue bacteria may play an important role. We developed a nondestructive, label-free technique combining wavelength modulated Raman (WMR) spectroscopy and fluorescence detection (Nile Red staining) to interrogate Mycobacterium tuberculosis cell state. This approach could differentiate single "dormant" (lipid rich, LR) and "non-dormant" (lipid poor, LP) cells with high sensitivity and specificity. We applied this to experimentally infected guinea pig lung sections and were able to distinguish both cell types showing that the LR phenotype dominates in infected tissue. Both in-vitro and ex-vivo spectra correlated well, showing for the first time that Mycobacterium tuberculosis, likely to be phenotypically resistant to antibiotics, are present in large numbers in tissue. This is an important step in understanding the pathology of relapse supporting the idea that they may be caused by M. tuberculosis cells with lipid inclusions. ; Publisher PDF ; Peer reviewed

This work was supported by the National Research Foundation of Korea (NRF) grant by the Korea government (MSIT) (No. 2019R1A2C2011293) and University of Sydney – Yonsei University Partnership Collaboration Awards. M. P. acknowledges European Union's Horizon 2020 Marie Sklodowska-Curie Actions (MSCA) individual fellowship under Contract No. 846218. KD thanks the UK Engineering and Physical Sciences Research Council for funding (grant EP/P030017/1). ; From mechanical syringes to electric field-assisted injection devices, precise control of liquid droplet generation has been sought after, and the present state-of-the-art technologies have provided droplets ranging from nanoliter to subpicoliter volume sizes. In this study, we present a new laser-driven method to generate liquid droplets with a zeptoliter volume, breaking the fundamental limits of previous studies. We guided an infrared laser beam through a hollow optical fiber (HOF) with a ring core whose end facet was coated with single-walled carbon nanotubes. The laser light was absorbed by this nanotube film and efficiently generated a highly localized microring heat source. This evaporated the liquid inside the HOF, which rapidly recondensed into zeptoliter droplets in the surrounding air at room temperature. We spectroscopically confirmed the chemical structures of the liquid precursor maintained in the droplets by atomizing dye-dissolved glycerol. Moreover, we explain the fundamental physical principles as well as functionalities of the optical atomizer and perform a detailed characterization of the droplets. Our approach has strong prospects for nanoscale delivery of biochemical substances in minuscule zeptoliter volumes. ; Postprint ; Publisher PDF ; Peer reviewed

Funding: UK Engineering and Physical Sciences Research Council for funding through grant EP/P030017/1 and fellowship EP/L025035/1. This work was also supported by the PreDiCT-TB consortium [IMI Joint undertaking grant agreement number 115337, resources of which are composed of financial contribution from the European Union's Seventh Framework Programme (FP7/2007–2013) and EFPIA companies' in kind contribution (www.imi.europa.eu)] and the PanACEA consortium [funded by the European & Developing Countries Clinical Trials Partnership (EDCTP); grant agreement: TRIA-2015-1102] ; Tuberculosis (TB) remains a leading cause of death worldwide. Lipid rich, phenotypically antibiotic tolerant, bacteria are more resistant to antibiotics and may be responsible for relapse and the need for long-term TB treatment. We present a microfluidic system that acoustically traps live mycobacteria, M. smegmatis, a model organism for M. tuberculosis. We then perform optical analysis in the form of wavelength modulated Raman spectroscopy (WMRS) on the trapped M. smegmatis for up to eight hours, and also in the presence of isoniazid (INH). The Raman fingerprints of M. smegmatis exposed to INH change substantially in comparison to the unstressed condition. Our work provides a real-time assessment of the impact of INH on the increase of lipids in these mycobacteria, which could render the cells more tolerant to antibiotics. This microfluidic platform may be used to study any microorganism and to dynamically monitor its response to different conditions and stimuli. ; Publisher PDF ; Peer reviewed

The authors thank the UK Engineering and Physical Sciences Research Council (grant EP/J01771/X) and the European Union project FAMOS (FP7 ICT, contract no. 317744) for funding. P.P. acknowledges funding by the Estonian Research Council (grants PUTJD8 and PUT369). ; We demonstrate the first light sheet microscope using propagation invariant, accelerating Airy beams that operates both in single- and two-photon modes. The use of the Airy beam permits us to develop an ultra compact, high resolution light sheet system without beam scanning. In two-photon mode, an increase in the field of view over the use of a standard Gaussian beam by a factor of six is demonstrated. This implementation for light sheet microscopy opens up new possibilities across a wide range of biomedical applications, especially for the study of neuronal processes. ; Publisher PDF ; Peer reviewed