Luminescent Metal Complexes as Emerging Tools for Lipid Imaging

Abstract

Fluorescence microscopy is a key tool in the biological sciences, which finds use as a routine laboratory technique (e.g., epifluorescence microscope) or more advanced confocal, two-photon, and super-resolution applications. Through continued developments in microscopy, and other analytical methods, the importance of lipids as constituents of subcellular organelles, signalling or regulating molecules continues to emerge. The increasing recognition of the importance of lipids to fundamental cell biology (in health and disease) has prompted the development of protocols and techniques to image the distribution of lipids in cells and tissues. A diverse suite of spectroscopic and microscopy tools are continuously being developed and explored to add to the “toolbox” to study lipid biology. A relatively recent breakthrough in this field has been the development and subsequent application of metal-based luminescent complexes for imaging lipids in biological systems. These metal-based compounds appear to offer advantages with respect to their tunability of the photophysical properties, in addition to capabilities centred around selectively targeting specific lipid structures or classes of lipids. The presence of the metal centre also opens the path to alternative imaging modalities that might not be applicable to traditional organic fluorophores. This review examines the current progress and developments in metal-based luminescent complexes to study lipids, in addition to exploring potential new avenues and challenges for the field to take.

Near-infrared metal agents assisting precision medicine: from strategic design to bioimaging and therapeutic applications

“…281,282 In addition, based on the advantages of NIR luminescence, many NIR metal agents have been devised to facilitate cell imaging in order to expose many biological processes. 283 Peng et al reported a novel Ru–I complex containing cyanine fluorophores. 147 Ru-1 is positively charged, easily soluble in water, can be quickly absorbed by cancer cells, and emits green light.…”

Noncontact photoacoustic lipid imaging by remote sensing on first overtone of the C-H bond

“… – 8 However, these examinations of lipids hinge on biopsy invasion or external labeling, which demands complex sample preparation procedures and might incur toxicity or changes in metabolic conditions 7 – 10 Hence, a label-free and noninvasive imaging modality is desired for biomedical lipid studies, which eliminates biosafety concerns and allows easy implementation.…”

In Vivo Imaging of Lipid Droplets and Oxygen Status in Hepatic Tissues of Nonalcoholic Fatty Liver Model Mice Using a Lipophilic Ir(III) Complex

“…Various LD-specific fluorescent probes have been developed, including commercially available ones. − These probes provide a useful means to assess the progression of NAFLD by observing changes in the number and size of LDs in hepatic tissues in vivo and ex vivo . − However, it is usually difficult to quantitatively evaluate oxygen levels in hepatic tissues in NAFLD using these fluorescent LD probes. To image LDs in the hepatic tissues of NAFLD and quantitatively assess their oxygen levels simultaneously, it is essential to develop oxygen probes with high cellular uptake efficiency and specific localization to LDs.…”