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Biochemical changes in specific organelles underpin cellular function, and studying these changes is crucial to understand health and disease. Fluorescent probes have become important biosensing and imaging tools as they can be targeted to specific organelles and can detect changes in their chemical environment. However, the sensing capacity of fluorescent probes is highly specific and is often limited to a single analyte of interest. A novel approach to imaging organelles is to combine fluorescent sensors with vibrational spectroscopic imaging techniques; the latter provides a comprehensive map of the relative biochemical distributions throughout the cell to gain a more complete picture of the biochemistry of organelles. We have developed NpCN1, a bimodal fluorescence-Raman probe targeted to the lipid droplets, incorporating a nitrile as a Raman tag. NpCN1 was successfully used to image lipid droplets in 3T3-L1 cells in both fluorescence and Raman modalities, reporting on the chemical composition and distribution of the lipid droplets in the cells.

New naphthalimide tetrazine probes permit fluorescent imaging of biomolecules in vitro and in living cells. They can be modified to provide previously unknown information about health and disease in biological systems.

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The COVID‐19 pandemic has had a devastating impact on global health, highlighting the need to understand how the SARS‐CoV‐2 virus damages the lungs in order to develop effective treatments. Recent research has shown that patients with COVID‐19 experience severe oxidative damage to various biomolecules. We propose that the overproduction of reactive oxygen species (ROS) in SARS‐CoV‐2 infection involves an interaction between copper ions and the virus's spike protein. We tested two peptide fragments, Ac‐ELDKYFKNH‐NH2 (L1) and Ac‐WSHPQFEK‐NH2 (L2), derived from the spike protein of the Wuhan strain and the β variant, respectively, and found that they bind Cu(II) ions and form a three‐nitrogen complexes at lung pH. Our research demonstrates that these complexes trigger the overproduction of ROS, which can break both DNA strands and transform DNA into its linear form. Using A549 cells, we demonstrated that ROS overproduction occurs in the mitochondria, not in the cytoplasm. Our findings highlight the importance of the interaction between copper ions and the virus's spike protein in the development of lung damage and may aid in the development of therapeutic procedures.

Copper participates in a range of critical functions in the nervous system in the human brain. Disturbances in brain copper content is strongly associated with neurological disease. For example, changes in the level and distribution of copper are reported in neuroblastoma, Alzheimer's disease and Lewy body disorders. There is a need for more sensitive techniques to measure intracellular copper levels to have a better understanding of the role of copper homeostasis in neuronal disorders. Here we report a reaction-based near-infrared (NIR) ratiometric fluorescent probe CyCu1 for imaging Cu2+ in biological samples. High stability and selectivity of CyCu1 enabled the probe to be deployed as a sensor in a range of systems, including SH-SY5Y and neuroblastoma cells. Furthermore, it can be used in plant cells, reporting copper added to Arabidopsis roots. We also used CyCu1 to explore Cu2+ levels and distribution in postmortem brain tissues from patients with the Lewy body disorder, Dementia with Lewy bodies (DLB). We found significant decreases in Cu2+ content in the nuclei, cytoplasm, neurons and extraneuronal space in the degenerating substantia nigra (SN) in DLB compared with healthy age-matched control tissues. These findings enhance our understanding of Cu2+ dysregulation in Lewy body disorders. Our probe also shows promise as a photoacoustic imaging agent, with potential for applications in bimodal imaging.

Synthetic anion transporters that mediate electroneutral (H+/Cl-) transport have demonstrated anti-cancer activity due to their ability to disrupt subcellular homeostasis. Elucidation of the cell death mechanism revealed the transporters’ ability to neutralise lysosomal pH gradients and inhibit autophagy. However, their effect on other subcellular compartments is unknown. Herein, we disclose the first subcellular targeted anionophores that accumulate in various membrane bound organelles to bias their natural propensity to depolarise lysosomes. The series of naphthalimide-based transporters were studied by confocal microscopy, and were found to accumulate in different subcellular organelles. The analogues that contained endoplasmic reticulum (ER)- and lysosomal targeting motifs showed enhanced the H+/Cl- transport ability compared to their non-targeted analogues. Moreover, ER and lysosomal localisation was found to enhance the cytotoxic effect of the transporters on cancerous cells. Our work provides an alternative approach in the design of therapeutically focused synthetic anion transporters and an insight into possible subcellular compartment-specific effects on homeostasis.

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