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Super-resolution microscopy (SRM) has revolutionized the study of cell biology, enabling researchers to visualize cellular structures with nanometric resolution, single-molecule sensitivity, and with multiple colors using conventional fluorophores. SRM is well-suited for volumetric live-cell imaging and helps in extracting quantitative information on spatial distributions. It can be used to estimate the absolute numbers of proteins or other macromolecules or nanostructured material within subcellular compartments, characterize their structures, and their nano/bio interactions. Although a number of recent general reviews on SRM have elaborated its role in chemical and clinical biology, as well as nanomedicine, herein, we provide an overview of the use of luminescent nanocarriers (LNC) in SRM imaging and single-molecule tracking. The role of LNCs in controlling the brightness and stability of emissive states is discussed with a special focus on organelle-specific delivery and how this approach can be utilized to produce novel optical-switched systems. We also discuss the challenges related to the molecular targeting of such material in biological systems. In doing so, we will provide practical guidance for super-resolution imaging in nanomedicine research, its technical challenges, and the opportunities for future advancement.

Organelles such as mitochondria, lysosome, and nucleus, are essential for controlling basic cellular operations and metabolism. Because mitochondria play a critical role in energy production and programmed cell death, they act as prime therapeutic targets for various diseases and dysfunctional states. In this study, a multifunctional nanoplatform based on lanthanide upconverting nanorods is developed for concurrent mitochondria-targeted fluorescence imaging and preclinical MRI. This study provides critical insights into the spectral profiles of mitochondria and paves the way to developing novel, multimodal nanoprobes for mitochondria-targeted theranostics.

This review discusses the advantages of using luminescent d6-transition-metal complexes as cell probes for optical microscopy. In particular it focusses on the Thomas group's use of specific complexes as “building blocks” toward the construction of biomolecular binding substrates, with DNA being a particular target. Using this approach, a range of new imaging probes for conventional optical microscopy, nanoscopy and transmission electron microscopy have been identified. Through selection of specific metal centres and by substitution of coordinated ligands we illustrate how new chemotherapeutics, photo-therapeutics, and theranostics have been identified and developed from the original architectures.

The synthesis of new dinuclear complexes containing linked RuII(dppz) and ReI(dppz) moieties is reported. The photophysical and biological properties of the new complex, which incorporates a N,N′-bis(4-pyridylmethyl)-1,6-hexanediamine tether ligand, are compared to a previously reported RuII/ReI complex linked by a simple dipyridyl alkane ligand. Although both complexes bind to DNA with similar affinities, steady-state and time-resolved photophysical studies reveal that the nature of the linker affects the excited state dynamics of the complexes and their DNA photocleavage properties. Quantum-based DFT calculations on these systems offer insights into these effects. While both complexes are live cells permeant, their intracellular localizations are significantly affected by the nature of the linker. Notably, one of the complexes displayed concentration-dependent localization and possesses photophysical properties that are compatible with SIM and STED nanoscopy. This allowed the dynamics of its intracellular localization to be tracked at super resolutions.

A new physiologically benign and cell membrane permeable BODIPY based molecular probe, MB-Sn, specifically senses intracellular hydrogen polysulfides (H2Sn, n > 1) localized in the endoplasmic reticulum. This reagent is suitable for mapping the intracellular distribution of H2Sn by wide-field as well as super-resolution Structured Illumination Microscopy (SIM).\ud \ud

Two new biscyclometalated complexes [Ir(ptzR)2(dppz)]+ (dppz = dipyridophenazene; ptzRH = 4-phenyl-1-benzyl-1,2,3-triazole (1+) and 4-phenyl-1-propyl-1,2,3-triazole (2+)) have been prepared. The hexafluorophosphate salts of these complexes have been fully characterized and, in one case, the X-ray structure of a nitrate salt was obtained. The DNA binding properties of the chloride salts of the complexes were investigated, as well as their cellular uptake by A2780 and MCF7 cell lines. Both complexes display an increase in the intensity of phosphorescence upon titration with duplex DNA, indicating the intercalation of the dppz ligand and, given that they are monocations, the complexes exhibit appreciable DNA binding affinity. Optical microscopy studies reveal that both complexes are taken up by live cancer cell lines displaying cytosol based luminescence. Colocalization studies with commercial probes show high Pearson coefficients with mitotracker dyes confirming that the new complexes specifically localize on mitochondria.

BODIPY derivative, SF-1, exclusively shows a fluorescence ON response to HOCl and images endogenously generated HOCl in RAW 264.7 macrophages. Widefield and super resolution structured illumination microscopy images confirm localization in the Golgi complex and lysosomes, and hence specifically detects HOCl generated in these organelles. SF-1 is compatible with 3D-SIM imaging of individual cells.

Bioenhancers can be defined as chemical entities, which when mixed with drugs promote and augment their bioavailability without showing any synergistic effect with the drug. The factors like toxicity, cost, poor bioavailability and long term administration of drugs give rise to the need of bioenhancers which help overcome most of these problems. Piper species produce a pungent alkaloid named Piperine or 1-peperoyl piperidine. Piperine increases permeability at the site of absorption by modulating lipid environment and membrane dynamics. Piperine has a molecular structure that is suitable for enzyme inhibition. It augments the bioavailability of several drugs like carbamazepine, curcumin, ciprofloxacin, ampicillin, metronidazole, oxytetracycline and many others by inhibiting various metabolizing enzymes. Thus piperine, being an efficacious inhibitor of drug metabolism is a powerful enhancer of absorption. The following review explores the mechanism, metabolism inhibition, influence of structural changes on activity, and drugs bioenhanced by piperine. It provides an insight on the application of piperine as an effective bioenhancer and the superiority of a bioenhanced drug formulation over the one without a bioenhancer. This concept which is found to be beneficial, has its roots in Ayurveda-the traditional Indian system of medicine and has been applied to various drugs. It presents a fine instance of the advantage of amalgamating a traditional system with contemporary medicine.

Selective detection of nitroxyl (HNO), which has recently been identified as a reactive nitrogen species, is a challenging task. We report a BODIPY-based luminescence ON reagent for detection of HNO in aqueous solution and in live RAW 264.7 cells, based on the soft nucleophilicity of the phosphine oxide functionality towards HNO. The probe shows high selectivity to HNO over other reactive oxygen/nitrogen and sulphur species. Luminescence properties of the BODIPY based chemodosimetric reagent make it an ideal candidate for use as a reagent for super resolution structured illumination microscopy. The viability of the reagent for biological in-vivo imaging application was also confirmed using Artemia as a model.

Detailed studies on the live cell uptake properties of a dinuclear membrane permeable permeable RuII cell probe show that, at low concentrations, the complex localizes and images mitochondria. At concentrations above ~20 μM the complex images nuclear DNA. Since the complex is extremely photostable, has a large Stokes shift, and displays intrinsic subcellular targeting, its compatibility with super-resolution techniques was investigated. It was found to be very well suited to image mitochondria and nuclear chromatin in two col-our, 2C-SIM; and STED and 3D-STED both in fixed and live cell. In particular, due to its vastly improved photostability compared to conventional SR probes, it can provide images of nuclear DNA at unprecedented resolution.

Using a new mononuclear “building block,” for the first time, a dinuclear RuII(dppn) complex and a heteroleptic system containing both RuII(dppz) and RuII(dppn) moieties are reported. The complexes, including the mixed dppz/dppn system, are 1O2 sensitizers. However, unlike the homoleptic dppn systems, the mixed dppz/dppn complex also displays a luminescence “switch on” DNA light-switch effect. In both cisplatin sensitive and resistant human ovarian carcinoma lines the dinuclear complexes show enhanced uptake compared to their mononuclear analogue. Thanks to a favorable combination of singlet oxygen generation and cellular uptake properties all three of the new complexes are phototoxic and display potent activity against chemotherapeutically resistant cells.