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In this work, we describe the application of the self-assembled europium complex 1:Eu(III) (where 1: diethyl 8-methoxy-2-oxo-1,2,4,5-tetrahydro-cyclopenta[de]quinolin-3-yl)phosphonate) for the analysis of water content of wheat flour. The methodology herein described represents a robust and accurate way for the detection of small amounts of water in food, providing comparing results with well-established methods such as thermogravimetry and Karl-Fischer titration. Interestingly, as an advantage over other methods, our luminescence-based approach can be implemented in lab-on-a-chip microfluidic devices for real-time and on-line detection of water content of food samples. Additionally, the remarkably long luminescence lifetime of Eu(III) allows the use of state-of-the-art imaging strategies based on PLIM microscopy for the direct visualization of unique water content maps of wheat flour particles.

We have recently reported on the development and trypanocidal activity of a class of inhibitors of Trypanosome Alternative Oxidase (TAO) that are targeted to the mitochondrial matrix by coupling to lipophilic cations via C14 linkers to enable optimal interaction with the enzyme’s active site. This strategy resulted in a much-enhanced anti-parasite effect, which we ascribed to the greater accumulation of the compound at the location of the target protein, i.e. the mitochondrion, but to date this localization has not been formally established. We therefore synthesized a series of fluorescent analogues to visualize accumulation and distribution within the cell. The fluorophore chosen, julolidine, has the remarkable extra feature of being able to function as a viscosity sensor and might thus additionally act as a probe of the cellular glycerol that is expected to be produced when TAO is inhibited. Two series of fluorescent inhibitor conjugates incorporating a cationic julolidine-based viscosity sensor were synthesized and their photophysical and biological properties were studied. These probes display a red emission, with a high signal-to-noise ratio (SNR), using both single- and two-photon excitation. Upon incubation with T. brucei and mammalian cells, the fluorescent inhibitors 1a and 2a were taken up selectively in the mitochondria as shown by live-cell imaging. Efficient partition of 1a in functional isolated (rat liver) mitochondria was estimated to 66 ± 20% of the total. The compounds inhibited recombinant TAO enzyme in the submicromolar (1a, 2c, 2d) to low nanomolar range (2a) and were effective against WT and multidrug-resistant trypanosome strains (B48, AQP1-3 KO) in the submicromolar range. Good selectivity (SI > 29) over mammalian HEK cells was observed. However, no viscosity-related shift could be detected, presumably because the glycerol was produced cytosolically, and released through aquaglyceroporins, whereas the probe was located, virtually exclusively

The small molecule 8-methoxy-2-oxo-1,2,4,5- tetrahydrocyclopenta[de]quinoline-3-carboxylic acid (2b) behaves as a reactive non-fluorescent Michael acceptor, which after reaction with thiols becomes fluorescent, and an efficient Eu3+ antenna, after self-assembling with this cation in water. This behavior makes 2b a highly selective GSH biosensor, which has demonstrated high potential for studies in murine and human cells of the immune system (CD4+ T, CD8 + T, and B cells) using flow cytometry. GSH can be monitored by the fluorescence of the product of addition to 2b (445 nm) or by the luminescence of Eu3+ (592 nm). 2b was able to capture baseline differences in GSH intracellular levels among murine and human CD4 + T, CD8 + T, and B cells. We also successfully used 2b to monitor intracellular changes in GSH associated with the metabolic variations governing the induction of CD4+ naï ve T cells into regulatory T cells (TREG ).

In a recent work, we reported a methodology for imaging the different stages of amyloid aggregation in quantitative multiparametric dual-color fluorescence lifetime imaging (FLIM) and superresolution microscopy by using a pair of dyes capable of binding aggregates and undergoing subsequent intra-aggregate energy transfer (FRET) (RuizArias et al. Sensors Actuat. B, 2022, 350:130882). In this microarticle we present the optimization process for choosing the best pair of dyes through a screening of different naphthalimides and quinolimides and other known amyloid-binding dyes.

The presence of neuritic plaques and amyloid fibrils arising from the misfolding of certain proteins is the principal molecular indicator of neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Methodologies for studying the early stages of amyloid aggregation are rapidly arising to provide a better understanding of the mechanism of fibrillization and cytotoxicity and to identify potential targets for diagnosis and therapy. The method presented here involves the simultaneous use of two different fluorophores, a quinolimide derivative and Nile Blue A. These are capable of interacting with and reporting on the formation of preamyloid aggregates and fibrils of apoferritin through fluorescence resonance energy transfer (FRET), which occurs between them, thus maximizing the contrast in detection and quantitative information of such amyloid species by using multidimensional fluorescence lifetime imaging microscopy (FLIM).

[ES] La presente invención se refiere a haloacetamidas derivadas de quinolin-2(1H)-onas de fórmula (I), que sensibilizan la luminiscencia de lantánidos, y su aplicación como reactivos de marcaje de la luminiscencia de lantánidos en diversas biomoléculas, entre otras, en péptidos y proteínas., [EN] The present invention relates to haloacetamides derived from quinolin-2 (1H) -ones of formula (I), which sensitize lanthanide luminescence, and their application as labeling reagents for lanthanide luminescence in various biomolecules, among others, in peptides and proteins.

La presente invención se refiere al diseño y síntesis de nuevos fluoróforos con aplicación en el desarrollo de biosensores de fluorescencia, y particularmente, a derivados de 8- metoxi-2-oxo-1,2-dihidrociclopenta[de]quinolina y su aplicación como reactivos de marcaje de la luminiscencia de lantánidos. [ES], The present invention relates to the design and synthesis of new fluorophores that can be used to develop fluorescence biosensors, and particularly, to 8-methoxy-2-oxo-1,2-dihydrocyclopenta[de]quinoline derivatives and the use thereof as reagents for labelling lanthanide luminescence. [EN]

CDK5 kinase is activated through interactions with different partners including the p35/p25 regulators. Active CDK5 plays a key role in several neuronal functions and its hyperactivity contributes to a variety of neurodegenerative processes and several human cancers, in particular glioblastomas and neuroblastomas. In order to probe partners that interact with CDK5, we designed and synthesized fluorescent quinolimide-labelled peptides derived from the C-helix of CDK5, which were implemented to probe CDK5 partners in vitro and by in cellulo imaging in U87 glioblastoma and N2a neuroblastoma cells. Ectopic expression of a NIR fluorescent protein miRFP670 fusion with p25 (p25-miRFP670) in N2a cells induced FRET between a quinolimide-labelled peptide biosensor and p25-miRFP670, and fluorescence intensity was proportional to the expression level of p25, thereby demonstrating the potential of the quinolimide-labelled peptide biosensor to report on p25 relative abundance.

The photophysical properties of naphthalimide-based fluorophores can be easily tuned by chemical manipulation of the substituents on that privileged scaffold. Replacement of a OMe group at position 6 in 2-(hydroxyl)ethyl-naphthalimide derivatives by diverse amines, including 2-(hydroxyl)ethylamine, trans-(4-acetamido)cyclohexylamine and azetidine increases the solvatochromic (ICT) character, while this replacement in 2-(dimethylamino)ethyl-naphthalimide analogues (PET fluorophores) decrease their solvent polarity sensitivity or even reversed them to solvatochromic fluorophores. These fluorophores resulted macrophage nucleus imaging probes, which bind DNA as intercalants and showed low cytotoxicity in human cancer cells

Two new families of lanthanide antennas are described. 8-Methoxy- 4,5-dihydrocyclopenta[de]quinolin-2(1H)-one phosphonates or carboxylates behave as selective antennas exhibiting Eu3+ luminescence in organic solvents, while quinolin-2(1H)-one analogues selectively sensitize the Tb3+ emission. These emissions are quenched by H2O addition. Based on this behaviour, the new lanthanide antennas can be used as highly sensitive water sensors.

The 1,8-naphthalimide scaffold is found among the most fruitful structures in the design of fluorophores with application in the development of fluorescence biosensors, due to its favorable photophysical properties, such as strong absorption and emission, large Stokes shifts, and photostability[1]. Considering that introduction of a nitrogen atom into the 1,8-naphtalimide skeleton could red-shift the fluorescence emission and increase water solubility, we have recently studied the design, synthesis and photophysical properties of 8-methoxy-4,5-quinolimides[2]. The photophysical properties of both scaffolds depend on the attached substituents and can be tuned by chemical manipulation. We have synthesized and will communicate new naphthalimide (A) and quinolimide (B) derivatives with a dimethylaminoethyl chain at the imide nitrogen atom, which behave as macrophage fluorescence sensors. Depending on the nature of the R substituent, these fluorophores can be used to imagine either the macrophage cytoplasm or the nucleus. The nucleus sensors bind DNA as intercalants.

The lack of polarity sensing fluorophores with OFF-ON features when increasing the environment polarity has limited the monitoring of biological processes that involve an increase in local hydrophilicity. In this work, replacement of a hydroxyl group by a dimethylamino group transformed solvatochromic ICT naphthalimide- and quinolimide-based fluorophores into reversed solvatochromic ones, with higher emission in polar than in apolar environments. Excited-state dynamics studies, TD-DFT calculations, X-ray and NMR support the existence of a folded conformation for the 2-(dimethylamino)ethyl chain upon the imide ring in apolar solvents, where the dimethylamino group would quench the fluorescence by a PET effect, while in polar solvents the chain has an extended conformation, where the PET is hindered. These PET fluorophores have given rise to H2O and pH sensors in organic solvents as well as to bright macrophage cytoplasm imaging probes.

We investigated a chemical strategy to boost the trypanocidal activity of 2,4-dihydroxybenzoic acid (2,4-DHBA)- and salicylhydroxamic acid (SHAM)-based trypanocides with triphenylphosphonium and quinolinium lipophilic cations (LC). Three series of LC conjugates were synthesized that were active in the submicromolar (5a-d and 10d-f) to low nanomolar (6a-f) range against wild-type and multidrug resistant strains of African trypanosomes (Trypanosoma brucei brucei and T. congolense). This represented an improvement in trypanocidal potency of at least 200-fold, and up to >10 000-fold, compared with that of non-LC-coupled parent compounds 2,4-DHBA and SHAM. Selectivity over human cells was >500 and reached >23 000 for 6e. Mechanistic studies showed that 6e did not inhibit the cell cycle but affected parasite respiration in a dose-dependent manner. Inhibition of trypanosome alternative oxidase and the mitochondrial membrane potential was also studied for selected compounds. We conclude that effective mitochondrial targeting greatly potentiated the activity of these series of compounds.

During their life-cycle, trypanosomes adapt their energy metabolism to the availability of nutrients in their environment. Hence, procyclic forms of T. brucei have a fully functional respiratory chain and synthesize ATP by oxidative phosphorylation in the mitochondrion. In contrast, respiration of bloodstream forms (BSF) of T. brucei (i.e. the human-infective form) relies exclusively on glycolysis for energy production. The trypanosome alternative oxidase (TAO) is the sole terminal oxidase enzyme to re-oxidize NADH accumulated during glycolysis. It is a cyanide-resistant and cytochrome-independent ubiquinol oxidase which is sensitive to the specific inhibitors salicylhydroxamic acid (SHAM) and ascofuranone. This enzyme which is essential to the viability of BSF trypanosomes and has no counterpart in the mammalian host is a potential target for chemotherapy. To boost the activity of TAO inhibitors against T. brucei, we investigated a chemical strategy consisting in the conjugation of the inhibitor with lipophilic cations (LC) that can cross lipid bilayers by non-carrier mediated transport, and thus accumulate specifically into the mitochondrion, driven by the plasma and mitochondrial transmembrane potentials (negative inside). This design afforded several LC¿TAO inhibitor conjugates active in the submicromolar to low nanomolar range against wild type and resistant strains of African trypanosomes (T. b. brucei, T. congolense). Selectivity over human cells was >500. Studies of the effects on purified TAO, parasite respiration, mitochondrial membrane potential (¿m), and cell cycle suggest that TAO is a likely target of the compounds in vivo.

Novel 4,5-quinolimide-based fluorophores are more solvatochromic and red-shifted than known naphthalimide analogues. Conjugation of one of these fluorophores to a peptide derived from CDK5 kinase demonstrated its sensitivity for monitoring the interaction with its regulatory partner p25. Introduction of the quinolimide-labelled peptide into living glioblastoma cells probed the interaction with endogenous p25.