Upconverting Nanoparticle-based Enhanced Luminescence Lateral-Flow Assay for Urinary Biomarker Monitoring.

Development of efficient portable sensors for accurately detecting biomarkers is crucial for early disease diagnosis, yet remains a significant challenge. To address this need, we introduce the enhanced luminescence lateral-flow assay, which leverages highly luminescent upconverting nanoparticles (UCNPs) alongside a portable reader and a smartphone app. The sensor's efficiency and versatility were shown for kidney health monitoring as a proof of concept. We engineered Er3+- and Tm3+-doped UCNPs coated with multiple layers, including an undoped inert matrix shell, a mesoporous silica shell, and an outer layer of gold (UCNP@mSiO2@Au). These coatings synergistically enhance emission by over 40-fold and facilitate biomolecule conjugation, rendering UCNP@mSiO2@Au easy to use and suitable for a broad range of bioapplications. Employing these optimized nanoparticles in lateral-flow assays, we successfully detected two acute kidney injury-related biomarkers─kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL)─in urine samples. Using our sensor platform, KIM-1 and NGAL can be accurately detected and quantified within the range of 0.1 to 20 ng/mL, boasting impressively low limits of detection at 0.28 and 0.23 ng/mL, respectively. Validating our approach, we analyzed clinical urine samples, achieving biomarker concentrations that closely correlated with results obtained via ELISA. Importantly, our system enables biomarker quantification in less than 15 min, underscoring the performance of our novel UCNP-based approach and its potential as reliable, rapid, and user-friendly diagnostics.

Glowing wonders: exploring the diversity and ecological significance of bioluminescent organisms in Brazil.

Bioluminescence, the emission of light by living organisms, is a captivating and widespread phenomenon with diverse ecological functions. This comprehensive review explores the biodiversity, mechanisms, ecological roles, and conservation challenges of bioluminescent organisms in Brazil, a country known for its vast and diverse ecosystems. From the enchanting glow of fireflies and glow-in-the-dark mushrooms to the mesmerizing displays of marine dinoflagellates and cnidarians, Brazil showcases a remarkable array of bioluminescent species. Understanding the biochemical mechanisms and enzymes involved in bioluminescence enhances our knowledge of their evolutionary adaptations and ecological functions. However, habitat loss, climate change, and photopollution pose significant threats to these bioluminescent organisms. Conservation measures, interdisciplinary collaborations, and responsible lighting practices are crucial for their survival. Future research should focus on identifying endemic species, studying environmental factors influencing bioluminescence, and developing effective conservation strategies. Through interdisciplinary collaborations, advanced technologies, and increased funding, Brazil can unravel the mysteries of its bioluminescent biodiversity, drive scientific advancements, and ensure the long-term preservation of these captivating organisms.

Tailoring the structure and self-activated photoluminescence of carbonated amorphous calcium phosphate nanoparticles for bioimaging applications.

Self-activated luminescent calcium phosphate (CaP) nanoparticles, including hydroxyapatite (HA) and amorphous calcium phosphate (ACP), are promising for bioimaging and theragnostic applications in nanomedicine, eliminating the need for activator ions or fluorophores. In this study, we developed luminescent and stable citrate-functionalized carbonated ACP nanoparticles for bioimaging purposes. Our findings revealed that both the CO32- content and the posterior heating step at 400 °C significantly influenced the composition and the structural ordering of the chemically precipitated ACP nanoparticles, impacting the intensity, broadness, and position of the defect-related photoluminescence (PL) emission band. The heat-treated samples also exhibited excitation-dependent PL under excitation wavelengths typically used in bioimaging (λexc = 405, 488, 561, and 640 nm). Citrate functionalization improved the PL intensity of the nanoparticles by inhibiting non-radiative deactivation mechanisms in solution. Additionally, it resulted in an increased colloidal stability and reduced aggregation, high stability of the metastable amorphous phase and the PL emission for at least 96 h in water and supplemented culture medium. MTT assay of HepaRG cells, incubated for 24 and 48 h with the nanoparticles in concentrations ranging from 10 to 320 µg mL-1, evidenced their high biocompatibility. Internalization studies using the nanoparticles self-activated luminescence showed that cellular uptake of the nanoparticles is both time (4-24 h) and concentration (160-320 µg mL-1) dependent. Experiments using confocal laser scanning microscopy allowed the successful imaging of the nanoparticles inside cells via their intrinsic PL after 4 h of incubation. Our results highlight the potential use of citrate-functionalized carbonated ACP nanoparticles for use in internalization assays and bioimaging procedures.

Luminescent Supramolecular Metallogels: Drug Loading and Eu(III) as Structural Probe.

Supramolecular metallogels combine the rheological properties of gels with the color, magnetism, and other properties of metal ions. Lanthanide ions such as Eu(III) can be valuable components of metallogels due to their fascinating luminescence. In this work, we combine Eu(III) and iminodiacetic acid (IDA) into luminescent hydrogels. We investigate the tailoring of the rheological properties of these gels by changes in their metal:ligand ratio. Further, we use the highly sensitive Eu(III) luminescence to obtain information about the chemical structure of the materials. In special, we take advantage of computational calculations to employ an indirect method for structural elucidation, in which the simulated luminescent properties of candidate structures are matched to the experimental data. With this strategy, we can propose molecular structures for different EuIDA gels. We also explore the usage of these gels for the loading of bioactive molecules such as OXA, observing that its aldose reductase activity remains present in the gel. We envision that the findings from this work could inspire the development of luminescent hydrogels with tunable rheology for applications such as 3D printing and imaging-guided drug delivery platforms. Finally, Eu(III) emission-based structural elucidation could be a powerful tool in the characterization of advanced materials.

Pesticides luminescent sensing by a Tb3+-doped Zn metal-organic framework with selectivity towards parathion.

Organophosphorus pesticides (OPPs) such as parathion have extensive uses in agriculture and household applications. Chronic exposure to these pesticides can cause severe health and environmental issues. Therefore, a current ecological concern is associated with accumulating these noxious OPPs in food and water sources. In this work, a new Tb3+-doped Zn-LMOF (Zn-LMOF= (3D) {[Zn3(1,4 benzenedicarboxylate)3(EtOH)2]·(EtOH)0.6}∞) was synthesized by a solvent-free reaction between the Zn-LMOF and the salt TbCl3·6H2O using a high-speed ball milling. The Tb@Zn-LMOF was thoroughly characterized by multiple spectroscopic tools, including Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy, and studied in-depth as a luminescent sensor for a series of pesticides (parathion, malathion, methalaxil, carbofuran, iprodione, captan and glyphosate) in aqueous methanol. The Tb@Zn-LMOF is a long-lived green-emitting compound with luminescence originated by an efficient antenna effect from the excited energy levels of Zn-LMOF toward the 5D state of Tb3+ ions, as it is displayed by its strong emission bands at 488, 545, 585, and 620 nm and a lifetime of 1.01 ms upon excitation at 290 nm. Additions of pesticides to a neutral methanolic dispersion of Tb@Zn-LMOF modified its green emission intensity with a pronounced selectivity toward parathion within the micromolar concentration range. The detection limit for parathion was calculated to be 3.04 ± 0.2 µM for Tb@Zn-LMOF. Based on 31P NMR and mass spectrometry studies, it is attributed to the release of lanthanide ions from Tb@Zn-LMOF with the simultaneous formation of a Tb3+-parathion complex.

Biophosphorescence in fluorescent millipedes (Diplopoda: Xystodesmidae) and its relationships with bioluminescence.

Three types of luminescence have been reported in living organisms: bioluminescence (BL), ultraweak chemiluminescence and biofluorescence (FL). In millipedes, both BL and FL have been reported in Motyxia sequoiae and related Xystodesmidae species. Noteworthy, when walking at night with a UV lantern at the Biological Station of Highlands, I found three blue-fluorescent millipedes (Deltotaria brimleii, Deltotoria sp and Euryus orestes) that also displayed phosphorescence after turning off the UV source. The phosphorescence of the cuticle was in the green region (λmax = 525 nm). The phosphorescence remained associated with cuticle and pellets, but frozen fluorescent supernatants, also displayed phosphorescence. The fluorescent compounds extracted from the cuticles in water and methanol and separated by TLC, displayed fluorescence spectra similar to that of 6-pteridine carboxylic acid. In contrast to Motyxia sequoiae cuticle extracts, no bioluminescence was found in Deltatoria and Euryus extracts  in the presence of MgATP, but weak green chemiluminescence was detected with H2O2 and superoxide. The spectral overlapping of phosphorescence of these millipedes with the bioluminescence of Motyxia (~ 507 nm) and the intimate association of both types of luminescence with the cuticles, raises the possibility that bioluminescence in Motyxia may arise from chemiluminescence reactions preferentially generating triplet excited states instead of singlet states.

Bioactive Luminescent Silver Clusters Confined in Zeolites Enable Quick and Wash-Free Biosensing.

The simultaneous capture and detection of biomolecules is crucial for revolutionizing bioanalytical platforms in terms of portability, response time and cost-efficiency. Herein, we demonstrate how the sensitivity to external stimuli and changes in the local electronic environment of silver clusters lead to an advantageous biosensing platform based on the fluorometric response of bioactive luminescent silver clusters (BioLuSiC) confined in faujasite X zeolites functionalized with antibodies. The photoluminescence response of BioLuSiC was enhanced upon immunocomplex formation, empowering a wash-free and quick biodetection system offering optimal results from 5 min. Proteins and pathogens (immunoglobulin G and Escherichia coli) were targeted to demonstrate the biosensing performance of BioLuSiC, and a human serum titration assay was also established. BioLuSiC will pave the way for innovative bioanalytical platforms, including real-time monitoring systems, point-of-care devices and bioimaging techniques.

Bi-coloured enhanced luminescence imaging by targeted switch on/off laser MEF coupling for synthetic biosensing of nanostructured human serum albumin.

In this communication luminescent bioconjugated human serum albumin nanostructures (HSA NPs) with tiny ultraluminescent gold core-shell silica nanoparticles (Au@SiO2-Fl) were designed with enhanced bi-coloured luminescence properties. The HSA NPs were obtained from Human Serum Albumin free (HSA free) through the desolvation method, and Au@SiO2-Fl, through modified Turkevich and Störber methods. In this manner, porous HSA Nanostructures of 150.0-200 nm and Au@SiO2-Fl 45.0 nm final diameters were obtained. Both methodologies and structures were conjugated to obtain modified Nanocomposites based on tiny gold cores of 15 nm surrounded with well spatial Nanostructured architectures of HSA (d15 Au@SiO2-Fl-HSA) that generated variable nanopatterns depending on the modified methodology of synthesis applied within colloidal dispersions. Therefore, three methodologies of non-covalent conjugation were developed. In optimal conditions, through Transmission Electronic Microscopy (TEM), well resolved multilayered nano-architectures with a size 190.0-200 nm in average with variable contrast depending of the focused nanomaterial within the nanocomposite were shown. Optimized nanoarchitecture was based on a template tiny gold core-shell surrounded by nanostructured HSA NPs (d15 Au@SiO2-Fl-HSA). In this manner, the NanoImaging generated by laser fluorescence microscopy permitted to record improved optical properties and functionalities, such as: (i) enhanced ultraluminescent d15 Au@SiO2-Fl-HSA composites in comparison to individual components based on Metal Enhanced Fluorescence (MEF); (ii) diminished photobleaching; (iii) higher dispersibility; (iv) higher resolution of single bright nano-emitters of 210.0 nm sizes; and (v) enhanced bi-coloured Bio-MEF coupling with potential non-classical light delivery towards other non-optical active biostructures for varied applications. The characterization of these nanocomposites allowed the comparison, evaluation and discussion focused on new properties generated and functionalities based on the incorporation of different types of tuneable materials. In this context, the biocompatibility, Cargo confined spaces, protein-based materials, optical transparent could be highlighted, as well as optical active materials. Thus, the potential applications of nanotechnology to both nanomedicine and nano-pharmaceutics were discussed.

Lemon-derived carbon dots as antioxidant and light emitter in fluorescent films applied to nanothermometry.

The design of luminescent nanomaterials for the development of nanothermometers with high sensitivity and free of potentially toxic metals has developed in several fields, such as optoelectronics, sensors, and bioimaging. In addition, luminescent nanothermometers have advantages related to non-invasive measurement, with their wide detection range and high spatial resolution at the nano/microscale. Our study is the first, to our knowledge, to demonstrate a detailed study of a fluorescent film (Film-L) thermal sensor based on carbon dots derived from lemon bagasse extract (CD-L). The CD-L properties were explored as an antioxidant agent; their cytotoxicity was evaluated by using a human non-tumoral skin fibroblast (HFF-1) cell line from an MTT assay. The CD-L were characterized by HRTEM, DLS, FTIR, UV-VIS, and fluorescence spectroscopy. These confirmed their particle size distribution below 10 nm, graphitic structure in the core and surface organic groups, and strong blue emission. The CD-L showed cytocompatibility behavior and scavenging potential reactive species of biological importance: O2•- and HOCl, with IC50 of 276.8 ± 4.0 and 21.6 ± 0.7, respectively. The Film-L emission intensities (I425 nm) are temperature-dependent in the 298 to 333 K range. The Film-L luminescent thermometer shows a maximum relative thermal sensitivity of 2.69 % K-1 at 333 K.

Actualización de informe de prueba de quimioluminiscencia para diagnóstico de COVID-19: (17 de agosto del 2023) / COVID-19 Diagnostic Chemiluminescence Test Report Update: (August 17, 2023)

ANTECEDENTES: Según la REVISIÓN RÁPIDA N°02-2020 realizado en Agosto del 2020, por solicitud del Equipo Funcional de Infectología, se realiza una revisión rápida con el fin de realizar una búsqueda y análisis de Ia mejor evidencia científica disponible en relación a la utilización de la prueba serológica por quimioluminiscencia para detección de SARS-COV-2. La Unidad Funcional de Evaluación de Tecnologías Sanitarias de INEN se creó el 15 de enero del 2020 mediante R.J. 020-2020-J/INEN y dentro de sus funciones están el "Evaluar aquellas tecnologías sanitarias requeridas por órganos usuarios, que sean nuevas para la entidad y/o no cuenten con cobertura financiera para la/s IAFAS". Definiendo tecnologías sanitarias a "cualquier intervención que pueda ser utilizada en la promoción de la salud, prevención, diagnóstico o tratamiento de una enfermedad, rehabilitación o cuidados prolongados. Se incluyen los medicamentos, los dispositivos, los procedimientos médicos y quirúrgicos, así como los sistemas organizativos dentro de los cuales se proporciona dicha atención sanitaria". Dentro de las funciones de UFETS-INEN es re-evaluar tecnologías que fueron evaluadas previamente con alguna recomendación en contra o una aprobación que requiera evaluación. METODOLOGÍA PARA ACTUALIZACIÓN: En el presente documento se hace una actualización a la metodología usada en el primer informe, actualización de resultados de la búsqueda científica y de estudios. No se cambiará la pregunta PICO. ACERCA DE LA TECNOLOGÍA: La pandemia por el nuevo coronavirus durante el 2019 (COVID-19) originado en Wuhan, China, generó hasta la fecha más de 6 millones de muertes2 en todo el mundo. La mayoría de las personas infectadas con este virus desarrolló una forma leve y el 12%-32% requirió un ingreso a la Unidad de Cuidados Intensivos. La quimioluminiscencia o CLIA es una reacción química que consiste en la emisión de luz por parte de algunas sustancias cuando reaccionan entre sí, con ello se puede realizar inmunoensayos, que son técnicas analíticas que utilizan anticuerpos. Los inmunoensayos CLIA se basan en el mismo principio que los inmunoensayos (ELISA), pero con la diferencia de que el anticuerpo de detección lleva acoplada una enzima que cataliza una reacción quimioluminiscente, produciendo una señal luminosa proporcional a la cantidad de analito presente en la muestra. Para la fecha de la emisión de la evaluación de tecnología sanitaria de quimioluminiscencia para el diagnóstico de SARS-CoV-2 (Agosto 2020), se contaba con el documento normativo con la Resolución Ministerial N* 139-2020-MINSA que aprobó el Documento Técnico: Prevención y Atención de personas afectadas por COVID-19 en el Perú. En este documento se establece la realización de pruebas diagnósticas moleculares y debido a limitaciones de disponibilidad, infraestructura, equipos biomédicos y personal de salud disponible a nivel nacional necesarios para su realización se optó por incorporar pruebas rápidas serológicas como una estrategia de detección de casos en pacientes y profesionales de la salud". En el apartado de tamizaje de dicho documento se establece "En el escenario de transmisión comunitaria, con la finalidad de fortalecer las medidas de contención, es necesario implementar estrategias de tamizaje con la Prueba Rápida IgM/IgG para COVID-19 en personas asintomáticas, pero que se encuentran en mayor riesgo de infección". Se especifica también un instructivo de cómo realizar la toma de muestra y como reportar la información generada. METODOLOGÍA: Primero se realizó una revisión de los documentos que fueron enviados a la unidad y se actualizó la estrategia de búsqueda del Instituto Nacional de Enfermedades Neoplásicas (INEN). ANÁLISIS: La principal evidencia de la revisión rápida anteriormente publicada provino de un estudio de revisión sistemática y meta-análisis de Lisboa et al7 , que evaluaron la exactitud diagnóstica de las pruebas serológicas para COVID-19. Como parte del diseño del estudio se realizó una búsqueda sistemática en Medline, BbioRxiv y medRxiv de enero a abril del presente año siguiendo una estrategia de búsqueda que permitió identificar los principales estudios relacionados a COVID-19 y pruebas serológicas para COVID-19. Se compararon las medidas de sensibilidad o especificidad con un referente estándar por PCR. Los riesgos de sesgos fueron identificados utilizando la herramienta QUADAS-2. Con la búsqueda sistemática se lograron identificar 5016 estudios de los cuales se eligió 40 estudios según criterios de inclusión y exclusión. La sensibilidad tomando en cuenta ambos anticuerpos en las pruebas de ELISA que miden IgG o IgM fue del 84,3% (intervalo de confianza del 95% del 75,6% al 90,9%), de las pruebas LFA fue del 66,0% (49,3% al 79,3%) y de las pruebas serológicas CLIA del 97,8% (46,2% al 100%). La Especificidad tomando en cuenta ambos anticuerpos en las pruebas de ELISA que miden IgG o IgM fue del 97.6% (intervalo de confianza del 95% del 93,2% al 99,4%), de las pruebas LFA fue del 96,6% (94,3% al 98,2%) y de las pruebas serológicas CLIA del 97,8% (62,9% al 99,9%). En todos los análisis, la sensibilidad agrupada de ambos anticuerpos fue menor para los LFA. Se evaluaron 49 riesgos de sesgos encontrándose el 98% de los riesgos en los estudios seguidos de riesgos en la interpretación en el 73%. Para cada uno de los métodos con respecto a sensibilidad y especifica no fueron asociados a las medidas de inmunoglobulinas. Se evidencio sesgos de heterogeneidad en todos los análisis. La sensibilidad fue mayor cuando las pruebas fueron realizadas por lo menos 03 semanas después del inicio de síntomas. Cabe mencionar que este estudio es previo a la era de vacunación de SARS-CoV-2, por lo que todos los estudios no tomaron en cuenta los aspectos relevantes durante la vacunación. CONCLUSIONES: En base a las funciones de UFETS-INEN se actualizó el documento de revisión rápida del uso de pruebas de quimioluminiscencia para el diagnóstico de COVID19. La experiencia del uso de las pruebas CLIA para el diagnóstico de COVID-19 fue necesario e importante durante la era pre-vacunas, sin embargo, después ya no han sido utilizados. En el proceso actual post-pandemia, la vacunación de SARS-CoV-2 ha logrado disminuir los casos severos de COVID-19. Además, durante periodos de prevalencias bajas, el rendimiento de la prueba CLIA puede verse disminuido. Nuestra conclusión es que el uso de la prueba de quimioluminiscencia para antígenos de SARS-CoV-2 durante la era post-vacunación servirá con el fin de revelar los individuos que requieren un refuerzo adicional temprano y/o tardío, para investigación o estudios de seroprevalencias, mas no debe usarse para el diagnóstico de pacientes con COVID-19. Se recomienda enviar a la oficina de seguros este informe para su evaluación.

The Molecular Basis of Organic Chemiluminescence.

Bioluminescence (BL) and chemiluminescence (CL) are interesting and intriguing phenomena that involve the emission of visible light as a consequence of chemical reactions. The mechanistic basis of BL and CL has been investigated in detail since the 1960s, when the synthesis of several models of cyclic peroxides enabled mechanistic studies on the CL transformations, which led to the formulation of general chemiexcitation mechanisms operating in BL and CL. This review describes these general chemiexcitation mechanisms-the unimolecular decomposition of cyclic peroxides and peroxide decomposition catalyzed by electron/charge transfer from an external (intermolecular) or an internal (intramolecular) electron donor-and discusses recent insights from experimental and theoretical investigation. Additionally, some recent representative examples of chemiluminescence assays are given.

Impacts of dielectric screening on the luminescence of monolayer WSe2.

Single layers of transition metal dichalcogenides (TMDCs), such as WSe2have gathered increasing attention due to their intense electron-hole interactions, being considered promising candidates for developing novel optical applications. Within the few-layer regime, these systems become highly sensitive to the surrounding environment, enabling the possibility of using a proper substrate to tune desired aspects of these atomically-thin semiconductors. In this scenario, the dielectric environment provided by the substrates exerts significant influence on electronic and optical properties of these layered materials, affecting the electronic band-gap and the exciton binding energy. However, the corresponding effect on the luminescence of TMDCs is still under discussion. To elucidate these impacts, we used a broad set of materials as substrates for single-layers of WSe2, enabling the observation of these effects over a wide range of electrical permittivities. Our results demonstrate that an increasing permittivity induces a systematic red-shift of the optical band-gap of WSe2, intrinsically related to a considerable reduction of the luminescence intensity. Moreover, we annealed the samples to ensure a tight coupling between WSe2and its substrates, reducing the effect of undesired adsorbates trapped in the interface. Ultimately, our findings reveal how critical the annealing temperature can be, indicating that above a certain threshold, the heating treatment can induce adverse impacts on the luminescence. Furthermore, our conclusions highlight the influence the dielectric properties of the substrate have on the luminescence of WSe2, showing that a low electrical permittivity favours preserving the native properties of the adjacent monolayer.

Lignocellulosic-Based Nanoparticles with Photoluminescent Properties for Bioimaging.

Natural and renewable resources from plants or animals are an important source of biomaterials due to their biocompatibility and high availability. Lignin is a biopolymer present in the biomass of plants, where it is intertwined and cross-linked with other polymers and macromolecules in the cell walls, generating a lignocellulosic material with potential applications. We have prepared lignocellulosic-based nanoparticles with an average size of 156 nm that exhibit a high photoluminescence signal when excited at 500 nm with emission in the near-infrared (NIR) region at 800 nm. The advantage of these lignocellulosic-based nanoparticles is their natural luminescent properties and their origin from rose biomass waste, which eliminates the need for encapsulation or functionalization of imaging agents. Moreover, the in vitro cell growth inhibition (IC50) of lignocellulosic-based nanoparticles is about 3 mg/mL, and no in vivo toxicity was registered up to 57 mg/kg, which suggests that they are suitable for bioimaging applications. In addition, these nanoparticles can circulate in the blood and are excreted in urine. The combined high luminescence signal in NIR, small size, low in vitro toxicity, low in vivo toxicity, and blood circulation support the potential of lignin-based nanoparticles as a novel bioimaging agent.

Radiosurgery dosimetry using CaSO4:Eu OSLD film-a feasibility study.

Recent studies demonstrated that optically stimulated luminescence (OSL) systems allow the evaluation of doses for 2D mapping in a relatively fast and simple way and results show submillimeter resolution. This work presents, for the first time, an optically stimulated luminescence dosemeter (OSLD) in the form of film made with CaSO4:Eu particles embedded in a silicone elastomer matrix. The OSLD film was produced using a low-cost and relatively simple methodology. This film is reusable and the signal can be satisfactorily bleached using blue LEDs. The main dosimetric properties were evaluated using TL/OSL Risø reader with blue stimulation and Hoya U-340 filter. Investigation shows repeatability within 3% when measuring with the same film sample. Regarding the OSLD film homogeneity, nearly 12% sensitivity change was observed within the 5 × 5 cm2 produced film. Additionally, the dose response curve shows linearity from 5 to 25 Gy. Fading of the OSL signal is relatively high, about 50% in the first week and then is stable. Nevertheless, a 3 × 3 cm2 OSLD film was successfully used to map dose distribution in radiosurgery (6 MV photon beam). This work demonstrates the feasibility of 2D dosimetry using reusable OSLD films based on CaSO4:Eu.

Laccase-luminol chemiluminescence system: an investigation of substrate inhibition.

Chemiluminescence (CL) reactions are widely used for the detection and quantification of many types of analytes. Laccase has previously been proposed in CL reactions; however, its light emission behaviour has not been characterized. This study was conducted to characterize the laccase-luminol system, determine its kinetic parameters, and analyze the effects of protein and OH- concentration on the CL signal. Laccase from Coriolopsis gallica was combined with different concentrations of luminol (125 nM to 4 mM), and the enzyme kinetics were evaluated using diverse kinetic models. The laccase-luminol system was able to produce CL without an intermediate molecule, but it exhibited substrate-inhibition behaviour. A two-site random model was used and suggested that when the first luminol molecule was bound to the active site, laccase affinity for the second luminol molecule was increased. This inhibition effect could be avoided using a low luminol concentration. At 5 µM luminol concentration, 1 mg/ml (0.13 U) laccase is needed to achieve nearly 90% of the maximum CL signal, suggesting that the available luminol could not bind to all active sites. Furthermore, the concentration of NaOH negatively affected the CL signal. The laccase-luminol system represents an alternative to existing CL systems, with potential uses in molecular detection and quantification.

Fluorescence intensity ratio for BaHfO3:Eu3+ temperature sensor.

We use 395 nm ultraviolet radiation to excite the matrix of barium hafnate doped with europium ions to develop an optical temperature sensor. Luminescent analysis as a function of temperature was performed in the physiological range. The Emission spectra showed significant variations in luminescent intensity at all transitions, obtaining a relative sensitivity of 1574.3/T2, when the temperature of the material increases from 289.7 to 323.8 K. The 5D0 -> 7F2 transition presented the better temperature resolution (1.1 × 102 K).

Bifunctional Temperature and Oxygen Dual Probe Based on Anthracene and Europium Complex Luminescence.

In this work, we synthesized a polydimethylsiloxane membrane containing two emitter groups chemically attached to the membrane structure. For this, we attached the anthracene group and the [Eu(bzac)3] complex as blue and red emitters, respectively, in the matrix via hydrosilylation reactions. The synthesized membrane can be used as a bifunctional temperature and oxygen ratiometric optical probe by analyzing the effects that temperature changes and oxygen levels produce on the ratio of anthracene and europium(III) emission components. As a temperature probe, the system is operational in the 203-323 K range, with an observed maximum relative sensitivity of 2.06% K-1 at 290 K and temperature uncertainties below 0.1 K over all the operational range. As an oxygen probe, we evaluated the ratiometric response at 25, 30, 35, and 40 °C. These results show an interesting approach to obtaining bifunctional ratiometric optical probes and also suggest the presence of an anthracene → europium(III) energy transfer, even though there is no chemical bonding between species.

Red and near-infrared emitting phosphors based on Eu3+- or Nd3+-doped lanthanum niobates prepared by the sol-gel route.

We have evaluated the structural and luminescence properties of Eu3+- or Nd3+-doped lanthanum niobate systems synthesized via a sol-gel route and containing different dopant contents. XRD analysis revealed that the orthorhombic La3NbO7 and monoclinic LaNbO4 crystalline phases were present in all the samples, regardless of the dopant concentration. The excitation spectra of the samples displayed a broad band due to Nb5+→O2- charge transfer; this band was quite sensitive to the increasing Eu3+ content. The photoluminescence emission spectra of the samples with a lower Eu3+ content showed that Eu3+ occupied both crystalline phases. However, when the Eu3+ content increased, these ions preferentially occupied the C2 symmetry sites in the LaNbO4 host lattice. There was no emission quenching for the Eu3+-doped samples with a Eu3+ content as high as 20 mol%. The emission spectra of the Nd3+-doped samples displayed an intense emission band in the NIR-II biological window under NIR-I excitation, at 808 nm. In the case of the samples with a lower Nd3+ content, Nd3+ occupied distinct symmetry sites in La3NbO7. In contrast, in the samples with a higher Nd3+ content, these ions preferentially occupied LaNbO4 sites. The Nd3+ concentration that quenched emission in the Nd3+-doped samples was about 2.6 mol%, due to Nd3+-Nd3+ cross-relaxation processes. On the basis of these findings, the Eu3+-doped samples explored herein have promising applications in the lighting field, whereas the Nd3+-doped samples have potential use as solid-state lasers and biomarkers.

Bioluminescent Dinoflagellates as a Bioassay for Toxicity Assessment.

Dinoflagellates bioluminescence mechanism depends upon a luciferin-luciferase reaction that promotes blue light emission (480 nm) in specialized luminogenic organelles called scintillons. The scintillons contain luciferin, luciferase and, in some cases, a luciferin-binding protein (LBP), which prevents luciferin from non-enzymatic oxidation in vivo. Even though dinoflagellate bioluminescence has been studied since the 1950s, there is still a lack of mechanistic understanding on whether the light emission process involves a peroxidic intermediate or not. Still, bioassays employing luminous dinoflagellates, usually from Gonyaulax or Pyrocystis genus, can be used to assess the toxicity of metals or organic compounds. In these dinoflagellates, the response to toxicity is observed as a change in luminescence, which is linked to cellular respiration. As a result, these changes can be used to calculate a percentage of light inhibition that correlates directly with toxicity. This current approach, which lies in between fast bacterial assays and more complex toxicity tests involving vertebrates and invertebrates, can provide a valuable tool for detecting certain pollutants, e.g., metals, in marine sediment and seawater. Thus, the present review focuses on how the dinoflagellates bioluminescence can be applied to evaluate the risks caused by contaminants in the marine environment.

Using the optically stimulated luminescence technique for one- and two-dimensional dose mapping: a brief review.

In respect of radiation dosimetry, several applications require dose distribution verification rather than absolute dosimetry. Most protocols use radiological and radiochromic films and ionization chambers or diode arrays for dose mapping. The films are disposable which causes the precision of the results dependent on film production variability. The measurements with arrays of ionization chambers or diodes mainly lack spatial resolution. This review aims to provide an overview of the use of optically stimulated luminescence detectors (OSLDs) for one-dimensional (1D) and two-dimensional (2D) dose mapping in different applications. It reviews the ideas, OSL materials, and applications related to the assessment of dose distribution using OSLDs in the form of film or ceramic plate (BeO). Additionally, it reviews research published in the international scientific literature from 1998 to 2021. As an outcome, a table containing the main characteristics of each relevant paper is shown. The results section was divided by the type of OSL material, and we briefly described the principal findings and the significant developments of each mentioned study such as film production and OSL reader assembly. The purpose of this study was to present an overview of the main findings of several research groups on the use of OSLD in the form of film or plate for 1D and 2D dose mapping. Finally, the potential future development of dose mapping using OSLD films was outlined.