Atherosclerosis is a leading cause of global mortality. Current clinically available imaging techniques suffer from limited spatial resolution and lack the ability to identify biomolecular features of atherosclerotic plaques. To address this, our team has developed a bimodal imaging system which consists of optical coherence tomography (OCT) and fluorescence. In addition, a nanoparticle named porphysomes is used as a fluorescence contrast agent to target macrophages in the plaques of diseased mice. Results suggest that our intravascular imaging system is capable of detecting the fluorescence from nanoparticles which provides complementary biological information to the structural information obtained from simultaneously-acquired OCT images.
Preclinical studies and clinical diagnostics increasingly rely on optical techniques to visualize internal organs. Miniaturised catheters or endoscopes are necessary for imaging small and/or delicate arteries. However, current lens fabrication methods limit the performance of these ultrathin devices, resulting in a poor combination of resolution, depth of focus and multimodal imaging capability. This talk will introduce our latest research to address these combined challenges. In particular, we have utilized 3D micro-printing technology to fabricate freeform optics directly onto an optical fiber to achieve freeform designs for aberration-corrected optical coherence tomography (OCT) and to enable highly-sensitive multimodal fluorescence+OCT imaging in vivo.
3D micro-printing enables the formation of complex shapes at a print resolution of tens of nanometers using two-photon lithography. Our team have explored the use of 3D micro-printing to fabricate complex optical geometries directly on the end of a fiber. In this work, we have developed a lens-in-lens design that enables in-vivo high-sensitivity fluorescence and OCT imaging through a single-fiber-based probe, with a diameter <550 microns including a protective catheter sheath. In a parallel work, we have also fabricated a side-facing OCT fiber probe (<300 microns diameter) creating an elongated Bessel beam and simultaneously correct for aberrations.
This work reports nanodiamond-silk membranes as an optical platform for biosensing and cell growth applications. The hybrid structure was fabricated through electrospinning and mimics a 2D scaffold with high porosity. The negatively charged nitrogen vacancy (NV-) centres in diamond exhibits optically detected magnetic resonance (ODMR), which enables sensing of temperature variations. The NV- centre, as reported in literature, provides a shift of 74 kHz in the ODMR frequency per degree rise in temperature. For our hybrid membranes, we have however observed that the embedded NV- centre provide a greater shift of 95±5 kHz/K in the ODMR frequency. This higher shift in the frequency will result in improved temperature sensitivity enabling the tracking of thermal variations in the biologically relevant window of 25-50 ºC. The thermal conductivity of silk and diamond-silk hybrid will be explored to investigate this enhanced temperature sensing ability of diamond. The hybrid diamond-silk membranes are found to be hydrophilic with a contact angle of (65±2)º. The biocompatibility of the membranes is tested both in vitro in skin keratinocyte (HaCaT) cells and in vivo in a live mouse wound model. The membranes did not induce any toxicity to the cell growth and survival. Moreover, we observed resistance towards the growth and attachment of bacteria.
Cytokines play critical roles in homeostatic control of health and they are integral for the creation and maintenance of a myriad of disease states. Their ultra-low concentration, often in the picomolar range, and extremely dynamic transient secretion process place stringent demands on cytokine quantification. We developed a nanoparticle-based strategy to detect trace cytokine secretion from individual, single live cells, for which we coined the term “OnCELISA”. Using a capture surface on the cell membrane and fluorescent magnetic nanoparticles as assay reporters, our universal OnCELISA assay achieved the sensitivity 0.1 pg mL-1, an over 10-fold enhancement, compared to state-of-the-art. The sensitive OnCELISA cell labelling made it possible to select and sort different cell types to determine highly cytokine - secreting cell subpopulations . The capture surfaces on cell membranes did not show noticeable effect on cell viability and their subsequent proliferation. The capability to specifically select such highly cytokine-secreting cells and purify their populations is pivotal for their use in multicellular pathologies such as atherosclerosis. Accordingly, we used this new approach to label cytokine secretion from vascular tissues of apolipoprotein E-/- mice; an in vivo model of atherosclerosis. In response to lipopolysaccharide, we observed increased capture of cytokine using this model. With the capacity of monitoring multiple cytokine secretions (IL-6 and IL-1β)), our OnCELISA method is able to probe how the individual cells and tissues secrete cytokines as they respond in real time to the surrounding signals.
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