Endoxifen is the most powerful metabolite of tamoxifen (TX), the main endocrine therapy administered worldwide for the treatment of estrogen-receptor (ER) positive metastatic breast cancer. Tamoxifen itself is a prodrug with weak affinity for ER, but it is converted into endoxifen, with up to 100-fold higher affinity for ER than TX. In this study, we introduce the first fluorescent endoxifen derivative (FLTX3), formed by covalent attachment of the small fluorophore NBD to the basic side chain of endoxifen. We have characterized the optical properties of FLTX3, demonstrating its ability as a laser dye. FLTX3 is an efficient target-directed fluorescent probe for the cellular labelling of ER in MCF7 breast cancer cell line as well as in uterine tissues. FLTX3 is also endowed with an intrinsic photodynamic effect when irradiated at the optimal excitation wavelength of FLTX3. Further, we show that FLTX3 has an optical gain behaviour that leads to random laser (RL) when the light emitted by the drug is scattered in the cell cultures. Indeed, analyses of coherent spectra by power function Fourier transform revealed a RL dominant cavity in the range of average cell sizes. As one of the main causes for tamoxifen treatment failure is resistance, we explored the potential discriminative value of FLTX3-induced RL between tamoxifen-resistant and tamoxifen-sensitive MCF7 cells. Using multivariate approaches, we unravelled significant differences in the RL signal between tamoxifen-sensitive and tamoxifen-resistant cells. These findings indicate that FLTX3-generated RL might provide a target-directed diagnostic tool for tamoxifen resistance in metastatic ER+ breast cancer.

A novel application of microresonators for refractometric sensing in aqueous media is presented. To carry out this approach, microspheres of different materials and sizes were fabricated and doped with Nd3+ ions. Under 532 nm excitation, the microspheres presented typical NIR Nd3+ emission bands with superimposed sharp peaks, related to the Whispering Gallery Modes (WGMs), due to the geometry of the microspheres. When the microspheres were submerged in water with increasing concentrations of glycerol, spectral shifts for the WGMs were observed as a function of the glycerol concentration. These spectral shifts were studied and calibrated for three different microspheres and validated with the theoretical shifts, obtained by solving the Helmholtz equations for the electromagnetic field, considering the geometry of the system, and also by calculating the extinction cross-section. WGM shifts strongly depend on the diameter of the microspheres and their refractive index (RI) difference compared with the external medium, and are greater for decreasing values of the diameter and lower values of RI difference. Experimental sensitivities ranging from 2.18 to 113.36 nm/RIU (refractive index unit) were obtained for different microspheres. Furthermore, reproducibility measurements were carried out, leading to a repeatability of 2.3 pm and a limit of detection of 5 × 10−4 RIU. The proposed sensors, taking advantage of confocal microscopy for excitation and detection, offer a robust, reliable, and contactless alternative for environmental water analysis.

Rotaxanation is an efficient method to control the tetrazine-mediated inverse electron demand Diels–Alder (IEDDA) reaction. Tetrazine rotaxanes were synthesized in high yield by crown ether active template applied to the nucleophilic aromatic substitution of tetrazines. Kinetics of the bioorthogonal reaction with tetrazine rotaxanes were much slower than those with the corresponding threads. Interestingly, disassembly of the mechanical bond upon the application of the right stimulus activates IEDDA. Control of IEDDA in live cells was proved by means of a β-galactosidase sensitive tetrazine rotaxane: Enzymatic digestion allowed the Diels–Alder reaction, which resulted in a fluorescent compound.

Random lasing (RL) is an optical phenomenon that arises from the combination of light amplification with optical feedback through multiple scattering events. In this paper, we present our investigations of RL generation from human blood samples. We tested mixtures of rhodamine B dye solutions with different blood components, including platelets, lymphocytes, erythrocytes, and whole blood. Intense coherent RL was obtained in all cases at relatively low pump thresholds, except for erythrocytes. We also studied the potential of RL signal analysis for biosensing applications using blood samples from healthy individuals and patients suffering from Chronic Lymphocytic Leukemia (CLL). CLL is a blood disease characterized by a high count of lymphocytes with significant morphological changes. A statistical analysis of the RL spectra based on principal component and linear discriminant analyses was conducted for classification purposes. RL-based sample discrimination was conducted for whole blood, platelet, and lymphocyte samples, being especially successful (86.7%) for the latter. Our results highlight the potential of RL analysis as a sensing tool in blood.

This work aims to amplify the fluorescence of (Z)-4-hetarylidene-5(4H)-oxazolones 1 by suppression of the hula-twist non-radiative deactivation pathway by C^N-orthopalladation of the 4-hetarylidene ring. Different (Z)-4-hetarylidene-2-phenyl-5(4H)-oxazolones, 1a–1c, prepared by the Erlenmeyer–Plöchl method, have been studied. The orthopalladation of (Z)-2-phenyl-4-(5-thiazolylmethylene)-5(4H)-oxazolone (1a) takes place by C-H bond activation of the H4 of the heterocycle and C^N-chelation, giving the dinuclear trifluoroacetate derivative 2a. By further metathesis of bridging ligands in 2a, complexes containing the orthometalated oxazolone and a variety of ligands 3a–5a, were prepared. The study of the photophysical properties of 1a–5a shows that the bonding of the Pd metal to the 4-hetaryliden-5(4H)-oxazolone does not promote, in these cases, an increase in fluorescence. Interestingly, the orthopalladation of (Z)-2-phenyl-4-(4-thiazolylmethylene)-5(4H)-oxazolone (1b) gives orthopalladated 2b, where the incorporation of the Pd to the oxazolone takes place by C-H bond activation of the ortho-H2 of the 2-phenyl group, ring opening of the oxazolone heterocycle and simultaneous N,N-bonding of the N atoms of the thiazole ring and the generated benzamide fragment. This N^N^C-tridentate dianionic bonding mode is obtained for the first time in oxazolones. Despite a similar lock of the hula-twist deactivation, 2b does not show fluorescence.

Currently, breast cancer is the most common type of cancer worldwide, being the so-called estrogen receptor (ER) positive the subtype with highest prevalence. For decades, the most successful strategy to prevent recurrence of ER + breast cancers is tamoxifen coadjuvant therapy. However, the involvement of the different estrogen receptors (ER alpha, ER beta and GPER) and the interaction in their signaling pathways, the evidence for sideeffects in chronic tamoxifen treatments, as well as the appearance of tamoxifen-resistant breast cancers, have encouraged the need for novel receptor-targeted fluorescent probes. In line with this, multifunctional antiestrogen conjugates, exhibiting fluorescent properties while retaining the ability to antagonize estrogen actions, have been synthesized and proven to be particularly useful in the study of the molecular biology of ER + breast cancers. These novel fluorescent tamoxifen derivatives (FTDs) exhibit pharmacological features of pure antiestrogens, with similar or even greater affinity for ER alpha than tamoxifen, inhibit ER-dependent gene transcription and cell proliferation, and are devoid of uterotrophic effects. In the present study we have aim at providing a detailed view of their biophotonic potential, including their spectroscopic properties, their usefulness for fluorescent labelling of cellular compartments and intracellular targets, their application in the identification of nonER antiestrogen binding sites thought fluorescence competition assays, and finally, in their ability to function as efficient ER-targeted photosensitizers.

Large amount of wastewater is produced by washing machines and dishwashers, which are used in a daily basis. This domestic wastewater generated in households or office buildings (also called greywater) is drained directly to the drainpipes without differentiation from that with fecal contamination from toilets. Detergents are arguably the pollutants most frequently found in greywater from home appliances. Their concentrations vary in the successive stages in a wash cycle, which could be taken into account in a rational design of home appliances wastewater management. Analytical chemistry procedures are commonly used to determine the pollutant content in wastewater. They require collecting samples and their transport to properly equipped laboratories, which hampers real time wastewater management. In this paper, optofluidic devices based on planar Fabry-Perot microresonators operating in transmission mode in the visible and near infrared spectral ranges have been studied to determine the concentration of five brands of soap dissolved in water. It is found that the spectral positions of the optical resonances redshift when the soap concentration increases in the corresponding solutions. Experimental calibration curves of the optofluidic device were used to determine the soap concentration of wastewater from the successive stages of a washing machine wash cycle either loaded with garments or unloaded. Interestingly, the analysis of the optical sensor indicated that the greywater from the last water discharge of the wash cycle could be reused for gardening or agriculture. The integration of this kind of microfluidic devices into the home appliances design could lead to reduce our hydric environmental impact.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by an expansion of CAG triplet repeats in the gene that encodes the protein Huntingtin (HTT). Proteolytic fragments of the mutant HTT (mHTT) are accumulated in neurons leading to neurodegeneration. HD has no cure, and most research efforts are focused on finding disease-modifying therapies and biomarkers of disease progression and treatment efficacy. Random lasing (RL) has been successfully used in biomedicine to differentiate normal from pathological tissues showing robust morphological and structural differences. Here, we evaluate the potential of RL in discriminating brain samples of a transgenic mouse model of HD from those of its wild-type littermates. Furthermore, we also investigate the sensibility of RL to the effects of a mHTT lowering treatment in transgenic mice therapy. The results reveal that multivariate statistical analysis of RL signals discriminates between healthy and transgenic mice and also between treated and untreated transgenic mice. These findings open up perspectives for RL as a sensing tool in HD and, possibly, in other neurodegenerative diseases whose pathogenic hallmark is the accumulation of anomalous proteins.

3-Nitrotyrosine (NT) is generated by the action of peroxynitrite and other reactive nitrogen species (RNS), and as a consequence it is accumulated in inflammation-associated conditions. This is particularly relevant in kidney disease, where NT concentration in blood is considerably high. Therefore, NT is a crucial biomarker of renal damage, although it has been underestimated in clinical diagnosis due to the lack of an appropriate sensing method. Herein we report the first fluorescent supramolecular sensor for such a relevant compound: Fluorescence by rotational restriction of tetraphenylethenes (TPE) in a covalent cage is selectively quenched in human blood serum by 3-nitrotyrosine (NT) that binds to the cage with high affinity, allowing a limit of detection within the reported physiological concentrations of NT in chronic kidney disease.

Huntington’s disease (HD) is an autosomal dominant, incurable neurodegenerative disease caused by mutation in the huntingtin gene (HTT). HTT mutation leads to protein misfolding and aggregation, which affect cells’ functions and structural features. Because these changes might modify the scattering strength of affected cells, we propose that random lasing (RL) is an appropriate technique for detecting cells that express mutated HTT. To explore this hypothesis, we used a cell model of HD based on the expression of two different forms—pathogenic and non-pathogenic—of HTT. The RL signals from both cell profiles were compared. A multivariate statistical analysis of the RL signals based on the principal component analysis (PCA) and linear discriminant analysis (LDA) techniques revealed substantial differences between cells that expressed the pathogenic and the non-pathogenic forms of HTT.

Carbon dots (CDs) and G4-G6 (polyamidoamine)PAMAM-NH2 dendrimers were self-assembled to produce CDs@PAMAM nanohybrids for transfection and bioimaging purposes. CDs were synthesized by the hydrothermal method, using ascorbic acid as a starting precursor and characterized by transmission electron microscopy, UV-Vis, and fluorescence (in solution and solid-state) techniques. CDs were electrostatically combined with PAMAM dendrimers at room temperature, and the UV-Vis, fluorescence, and NMR spectroscopies were used to confirm the self-assembly. When compared to pristine CDs, nanohybrids were more photostable, resisting high acidic and basic pH. Moreover, they were considerably internalized by cells, as assessed by flow cytometry and fluorescence microscopy, and, when excited, displayed multi-color emission easily quantified and visualized. These nanoscale hybrids, coined hybridplexes, can condense pDNA and transfecting cells successfully, particularly the G5 CDs@PAMAM nanohybrids. In summary, CDs prepared in mild and smooth lab conditions, showing good optical properties, were used to prepare elegantly CDs@PAMAM nanohybrids with promising biomedical applications.

Huntington’s disease (HD) is a neurodegenerative genetic condition, whose progress we are currently unable to assess with easy, non-invasive techniques. We show that Random Laser (RL) is sensitive to the effects of HD in cell cultures.

Tamoxifen is the most widely used selective modulator of estrogen receptors (SERM) and the first strategy as coadjuvant therapy for the treatment of estrogen-receptor (ER) positive breast cancer worldwide. In spite of such success, tamoxifen is not devoid of undesirable effects, the most life-threatening reported so far affecting uterine tissues. Indeed, tamoxifen treatment is discouraged in women under risk of uterine cancers. Recent molecular design efforts have endeavoured the development of tamoxifen derivatives with antiestrogen properties but lacking agonistic uterine tropism. One of this is FLTX2, formed by the covalent binding of tamoxifen as ER binding core, 7-nitrobenzofurazan (NBD) as the florescent dye, and Rose Bengal (RB) as source for reactive oxygen species. Our analyses demonstrate (1) FLTX2 is endowed with similar antiestrogen potency as tamoxifen and its predecessor FLTX1, (2) shows a strong absorption in the blue spectral range, associated to the NBD moiety, which efficiently transfers the excitation energy to RB through intramolecular FRET mechanism, (3) generates superoxide anions in a concentration- and irradiation time-dependent process, and (4) Induces concentration- and time-dependent MCF7 apoptotic cell death. These properties make FLTX2 a very promising candidate to lead a novel generation of SERMs with the endogenous capacity to promote breast tumour cell death in situ by photosensitization.

Poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is a semiconducting optically active polymer widely used in optoelectronics research. MEH-PPV can be commercially acquired in a large range of molecular weights. However, the influence of this property on the optical performance of the polymer is often disregarded. In this paper, the thermal dependence of the refractive index of MEH-PPV thin films prepared from high and medium molecular weight polymers is investigated. Thus, monolithic Fabry-Perot (FP) microcavities are fabricated, in which the active polymer film is part of their defect layer. It is found that when these devices are used as optical temperature sensors, the position of the emission band of the microcavities excited with a blue diode laser shifts to lower wavelengths when temperature increases with sensitivities in the 0.2-0.3 nm/degrees C range. This effect is ascribed to the variation in the refractive index of the polymer active layer within the resonator with temperature. According to theoretical simulations of optical transmittance by classical transfer matrix method and the evaluation of the optical eigenmodes by finite element methods of the manufactured FP resonator cavities, it is found that the MEH-PPV films present negative thermo-optic coefficients of about-0.018 K-1 and-0.0022 K-1 for high and medium molecular weight polymers, respectively, in the temperature range between 20 and 60 degrees C. These values are about the highest reported so far, to the best of our knowledge, and points to high performance thermal sensor applications.

Glass microspheres embedded with Nd 3+ ‐doped nanoperovskites based on yttrium orthoaluminate are synthesized and used as optical vacuum sensor. Under 532 nm excitation, the microspheres show two emission bands centered at 820 and 890 nm, corresponding to the 2 H 9/2 , 4 F 5/2 → 4 I 9/2 and 4 F 3/2 → 4 I 9/2 transitions. When the microspheres are heated by laser excitation in air (ambient conditions), the positions of the Stark level transitions shift toward red or blue spectral regions. Additionally, the full width at half maximum of these peaks increases. Furthermore, due to the specific geometry of the microspheres, it is possible to trap the emitted light inside the microsphere resonator, in the form of whispering‐gallery‐modes (WGM). When the microspheres are heated, these resonant modes present higher shifts toward lower energies than those for the Stark levels. As pressure decreases, the thermal exchange (convection process) between the microsphere and the surrounding air molecules decreases, which leads to an increase on the temperature of the microsphere. Based on this effect, the response of the WGM spectral positions as a function of pressure level is used to calibrate the luminescent microspheres as optical vacuum sensors. Relative sensitivity and limit of detection are obtained and compared with other optical vacuum sensors.

Optofluidic devices are of high scientific and industrial interest in chemistry, biology, material science, pharmacy, and medicine [...]

Like other bionanomaterials, dendrimers are usually labelled with fluorescent compounds in order to be optically detected within cells. However, this process can interfere with their biological properties, so it is crucial to find other solutions for their traceability. Here, the blue intrinsic fluorescence of amine-terminated poly(amidoamine) (PAMAM) dendrimers was enhanced using oxidative treatment with ammonium persulfate (APS). The effects of dendrimer generation (G3, G4, and G5) and pH on the spectroscopic behavior of both pristine and APS-treated PAMAM dendrimers were studied in aqueous solution. Overall, the results pointed out that there are at least two types of emitting electron-rich hetero-atomic sub-luminophores (HASLs) confined within the dendrimer scaffold that have very close maximum emission wavelengths and whose emission properties strongly depend on pH. The APS treatment significantly enhanced the fluorescence intensity by leading to the protonation of the interior of the dendrimer. However, fluorescence intensity was not only dependent on the number of HASLs in the dendrimer scaffold (i.e., on dendrimer generation), but also on the rigidification suffered by the dendrimer due to the acidic environment (at low pH values, APS-treated G4 was indeed the most emissive species). Moreover, photoluminescence studies with lyophilized samples were also conducted, which confirmed the coexistence of more than one type of HASLs emitting in the dendrimer structure. The APS treatment affected these HASLs to a different extent. Time-resolved fluorescence experiments always showed higher average lifetimes of HASLs for APS-treated dendrimers than for pristine ones, in accordance with the fluorescence intensity results. On the other hand, the fraction and lifetimes of HASLs in APS-treated dendrimers were similar in solution and the lyophilized form. This behaviour was different for the pristine dendrimers that presented increased luminescence upon aggregation. Finally, the highly emissive oxidized dendrimers were shown not only to be much less cytotoxic and hemotoxic than pristine dendrimers but also to be detectable inside cells upon excitation with UV light.

Tamoxifen is one of the most frequently used drugs for the treatment of estrogen receptor positive breast cancer, which is the most prevalent form of hormone dependent breast cancer. A few years ago, we developed a fluorescent derivative of tamoxifen formed by the covalent binding of tamoxifen to a common dye biomarker. The new compound, known as FLTX1, showed the pharmacological activity of the tamoxifen moiety and efficient fluorescence properties, which could be used synergistically to improve the effect of the drug. In this paper, we demonstrate that irradiation at the absorption band of FLTX1 can result in fluorescence resonance energy transfer to photosensitizers such as Rose Bengal and Merocyanine 540, activating the production of reactive oxygen species (ROS). Indeed, the generation of ROS was demonstrated using a colorimetric assay. Since FLTX1 mostly binds estrogen-receptor overexpressing cancer cells, the results obtained are very promising and suggest a new therapeutic strategy combining chemo- and photodynamic therapies.