Simple fluorochromic detection of chromium with ascorbic acid functionalized luminescent Bio-MOF-1

The bioaccumulation of various heavy metals in the environment and agriculture is posing serious hazards to human health. Hexavalent chromium is one of the most encountered heavy metal pollutants. The routine monitoring of Cr(VI) via simple methods assumes great analytical significance in sectors like environmental safety, food quality, etc. This study reports a novel biocompatible and luminescent metal-organic framework (ascorbic acid functionalized Bio-MOF-1) based "Turn-on" nanoprobe for rapid and sensitive optical detection of Cr(VI). Bio-MOF-1 has been synthesized, functionalized with ascorbic acid (AA), and then comprehensively characterized for its key material properties. The presence of Cr(VI) results in the photoluminescence recovery of Bio-MOF-1/AA. Using the above approach, Cr(VI) is detected over a wide concentration range of 0.02 to 20 ng mL-1, with the limit of detection being 0.01 ng mL-1. The nanoprobe is capable of detecting Cr(VI) in real water as well as in some spiked food samples. Hence, the ascorbic acid functionalized Bio-MOF-1 nanoprobe is established as a potential on-field detection tool for Cr(VI).

MOFs as versatile scaffolds to explore environmental contaminants based on their luminescence bustle

Metal-Organic Frameworks (MOFs) with luminescent properties hold significant promise for environmental remediation. This review critically examines recent research on these materials design, synthesis, and applications, mainly focusing on their role in combating environmental pollutants. Through a comprehensive analysis of metal ions, ligands, and framework compositions, the review discusses the importance of tailored design and synthesis approaches in achieving desired luminescent characteristics. Key findings highlight the effectiveness of luminous MOFs as fluorescent sensors for a wide range of contaminants, including heavy metals, reactive species, antibiotics, and explosives. Considering all this, the review discusses future research needs and opportunities in the field of luminous MOFs. It emphasizes the importance of developing multifunctional materials, refining design methodologies, exploring sensing mechanisms, and ensuring environmental compatibility, scalability, and affordability. By providing insights into the current state of research and outlining future directions, this review is a valuable resource for researchers seeking to address environmental challenges using MOF-based solutions.

Ferrocene probe-assisted fluorescence quenching of PEI-carbon dots for NO detection and the logic gates based sensing of NO enabled by trimodal detection

Our research demonstrates the effectiveness of fluorescence quenching between polyethyleneimine functionalised carbon dots (PEI-CDs) and cyclodextrin encapsulated ferrocene for fluorogenic detection of nitric oxide (NO). We confirmed that ferrocene can be used as a NO probe by observing its ability to quench the fluorescence emitted from PEI-CDs, with NO concentrations ranging from 1 × 10-6 M to 5 × 10-4 M. The photoluminescence intensity (PL) of PEI-CDs decreased linearly, with a detection limit of 500 nM. Previous studies have shown that ferrocene is a selective probe for NO detection in biological systems by electrochemical and colorimetric methods. The addition of fluorogenic NO detection using ferrocene as a probe enables the development of a three-way sensor probe for NO. Furthermore, the triple mode NO detection (electrochemical, colorimetric, and fluorogenic) with ferrocene aids in processing sensing data in a controlled manner similar to Boolean logic operations. This work presents key findings on the mechanism of fluorescence quenching between ferrocene hyponitrite intermediate and PEI-CDs, the potential of using ferrocene for triple channel NO detection as a single molecular entity, and the application of logic gates for NO sensing.

Mitochondrial-Targeted Ratiometric Near-Infrared Fluorescence Probe for Monitoring Nitric Oxide in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a destructive autoimmune disease, where nitric oxide (NO) is closely implicated in the inflammatory processes of RA. Therefore, direct visualization of NO is essential to assess the pathological changes in RA. Herein, a mitochondrial-targeted near-infrared ratiometric fluorescent probe (NFL-NH2), based on the intramolecular charge transfer effect, was synthesized and applied to monitor the changes of NO content in early RA. Specially, probe NFL-NH2 showed a 44-fold fluorescent intensity ratio (I705/I780) response toward NO with a detection limit of 0.536 nM, enabling qualitative and quantitative analysis of NO. Additionally, NFL-NH2 can accurately target mitochondria and sensitively detect exogenous and endogenous NO in RAW 264.7 cells. Notably, in vivo RA monitoring assays demonstrated that NFL-NH2 can rapidly detect NO levels associated with the inflammatory damage degree in RA mice models by ratiometric fluorescence imaging. These results validate that NFL-NH2 holds significant potential for diagnosing NO-mediated RA diseases.

Fabrication of FRET based nano sensor from biomass-derived fluorescent carbon quantum dots and naphthalimide for ratiometric detection of nitric oxide: To examine nitrite levels in meat samples

Nitric oxide (NO) is a ubiquitous, gaseous, free radical signaling molecule which plays a key role in physiological and pathological processes. Literature reports revealed that the conventional methods such as colorimetry, electron paramagnetic resonance (EPR), electrochemical etc. to detect NO are costly, time consuming and lack resolution, particularly in aqueous or biological system. Thus, in this context, herein we have developed covalently linked biomass derived carbon quantum dots (CQDs) and naphthalimide based nano sensor system for FRET based ratiometric detection of nitric oxide (NO) in pure aqueous media. The CQDs derived from orange peels were characterized using UV-visible absorption, fluorescence spectroscopy, PXRD, TEM, FT-IR and zeta potential studies. Further, the obtained CQDs were functionalized with amine functionality, and subsequently linked with naphthalimide derivative (5) using terephthaldehyde through covalent bond formation. The conjugation of naphthalimide (5) and functionalized CQDs was studied using DLS, zeta potential, FT-IR and time resolved fluorescence spectroscopy. The excitation of developed nano sensor system at λ_ex 360 nm results in fluorescence emission at λ_em 530 nm which establishes the FRET pair between the CQDs and naphthalimide unit. However, in the presence of NO, the observed FRET pair abolishes due to the cleavage of NO susceptible imine bond. The developed sensor demonstrates high selectivity towards NO with limit of detection (LOD) and limit of quantification (LOQ) of 15 nM and 50 nM respectively. Further, the developed sensor system was also utilized for indirect detection of nitrite (NO₂^-) in food samples for food safety and monitoring.

Gold nanoparticle-based two-photon fluorescent nanoprobe for monitoring intracellular nitric oxide levels

Nitric oxide (NO) plays an important role in the regulation of the immune, cardiovascular and nervous systems. Consequently, being able to monitor and quantify intracellular NO levels would provide a greater understanding of the implications of this molecule in the different biological processes, including, for example, in cancer. Here, we report a broadly applicable two-photon excitable fluorescent nanoprobe able to detect and potentially quantify NO levels in an extensive range of cellular environments. The nanoprobe consists of a thiolated photoinduced electron transfer-based two=photon fluorescent probe attached onto the surface of 2.4 ± 0.7 nm gold nanoparticles (DANPY-NO@AuNPs). The nanoprobe, which can be synthesised in a reproducible manner and exhibits great stability when stored at room temperature, is able to selectively detect NO in solution, with a dynamic range up to 150 μM, and at pH values of biological relevance. DANPY-NO@AuNPs were able to selectively detect endogenous NO in RAW264.7γ NO^- macrophages and THP-1 human leukemic cells; and endogenous and exogenous NO in endothelial cells. The nanoprobe accumulated in the acidic organelles of the tested cell lines showing negligible toxicity. Importantly, DANPY-NO@AuNPs showed potential to quantify intracellular NO concentrations in MDA-MB-231 breast cancer cells. The biological evaluation of the nanoprobe was undertaken using confocal laser scanning (images and intracellular emission spectra) and multiphoton microscopies, and flow cytometry. Based on their excellent sensitivity and stability, and outstanding versatility, DANPY-NO@AuNPs can be applied for the spatiotemporal monitoring of in vitro and in vivo NO levels.

A two-photon ratiometric fluorescent probe for real-time imaging and quantification of NO in neural stem cells during activation regulation

Developing a novel tool capable of real-time monitoring and accurate quantification of NO is critical to understanding its role in physiological and pathological processes. Herein, a two-photon ratiometric fluorescent probe (NOP) was developed for real-time imaging and quantification of NO based on fluorescence resonance energy transfer-photoinduced electron transfer (FRET-PET). In this developed probe, coumarin (CM) and naphthalimide with o-phenylenediamine (NPM) were rationally designed as a fluorescent donor and acceptor, respectively, to enable a ratiometric fluorescence response to NO. The developed NO probe demonstrated good detection linearity with the concentration of NO in the range of 0.100–200 μM, with a detection limit of 19.5 ± 1.00 nM. Considering the advantages of high selectivity, good accuracy and rapid dynamic response (<15 s), the developed NO probe was successfully applied for real-time imaging and accurate quantification of NO in neural stem cells (NSCs) and different regions of mouse brain tissue with a penetration depth of 350 μm. Using this powerful tool, it was found that NO regulated the activation and differentiation of quiescent NSCs (qNSCs). In addition, NO-induced differentiation of qNSCs into neurons was found to be dose-dependent: 50.0 μM NO caused about 50.0% of qNSCs to differentiate into neurons. Moreover, different regions of the mouse brain were observed to be closely related to the concentration of NO, and the concentration of NO in the DG region was found to be lower than that in the S1BF, CA1, LD and CPu of the Alzheimer's disease (AD) mouse brain. The symptoms of AD mice were significantly improved through the treatment with NO-activated NSCs in the DG region.

Developing a novel tool capable of real-time monitoring and accurate quantification of NO is critical to understanding its role in physiological and pathological processes.

ICT-based fluorescent ratiometric probe for monitoring mitochondrial peroxynitrite in living cells

Mitochondria-targeted near-infrared fluorescent probe for the detection of peroxynitrite and the bioimaging of peroxynitrite in cells.

Photoluminescence Response in Carbon Nanomaterials to Enzymatic Degradation

Myeloperoxidase (MPO), a key enzyme released by neutrophils during inflammation, has been shown to catalyze the biodegradation of carbon nanomaterials. In this work, we perform photoluminescence studies on the MPO-catalyzed oxidation of graphene oxide (GO) and surfactant-coated pristine (6,5) single-walled carbon nanotubes (SWCNTs). The enzymatic degradation mechanism involves the introduction of defects, which promotes further degradation. Interestingly, the photoluminescence responses of GO and SWCNTs to enzymatic degradation are counterposed. Although the near-infrared (NIR) fluorescence intensity of SWCNTs at 998 nm is either unchanged or decreases depending on the surfactant identity, the blue fluorescence intensity of GO at 440 nm increases with the progression of oxidation by MPO/H₂O₂/Cl^- due to the formation of graphene quantum dots (GQDs). Turn-on GO fluorescence is also observed with neutrophil-like HL-60 cells, indicative of potential applications of GO for imaging MPO activity in live cells. Based on these results, we further construct two ratiometric sensors using SWCNT/GO nanoscrolls by incorporating surfactant-wrapped pristine SWCNTs as the internal either turn-off (with sodium cholate (SC)) or reference (with carboxymethylcellulose (CMC)) sensor. The ratiometric approach enables the sensors to be more stable to external noise by providing response invariant to the absolute intensity emitted from the sensors. Our sensors show linear response to MPO oxidative machinery and hold the promise to be used as self-calibrating carbon nanomaterial-based MPO activity indicators.

Quantum dots as nanosensors for detection of toxics: a literature review

Great advances have been made in sensor-based methods for chemical analysis owing to their high sensitivity, selectivity, less testing time, and minimal usage of chemical reagents. Quantum Dots (QDs) having excellent optical properties have been thoroughly explored for variety of scientific applications wherein light plays an important role. In recent years, there have been an increasing number of publications on the applications of QDs as photoluminescent nanosensors for the detection of chemicals and biomolecules. However, there has been hardly any publication describing the use of QDs in the detection of various toxic chemicals at one place. Hence, a literature survey has been made on the applications of QDs as chemosensors for the detection of gaseous, anionic, phenolic, metallic, drug-overdose, and pesticide poison so as to open a new perspective towards the role of sensors in analytical toxicology. In this review, the QD-based analysis of biospecimens for poison detection in clinical and forensic toxicology laboratories is highlighted.

A new strategy to improve the water solubility of an organic fluorescent probe using silicon nanodots and fabricate two-photon SiND-ANPA-N3 for visualizing hydrogen sulfide in living cells and onion tissues

A water-soluble fluorescent probe based on SiNDs for H₂S detection can be used in both fully aqueous media and living cells.

Understanding the interaction of carbon quantum dots with CuO and Cu2O by fluorescence quenching

In spite copper oxide being one of the essential micronutrient, copper oxide in its nano size is found to be toxic in nature; this instigates for the detection of copper oxides in trace levels. In the present study, we demonstrate simple cost effective detection method for CuO/Cu₂O using carbon quantum dots (CQD) by fluorescence quenching technique. CuO/Cu₂O nanoparticles are synthesised by mere variation of fuel ratio by solution combustion technique. The resulting oxides are characterized by various analytical and spectroscopic techniques. Powder X- ray diffraction (PXRD) results reveals that samples prepared with oxidizer to fuel (O/F) ratios 1:1, 1:1.5 and 1:2 showed pure nano CuO, major CuO phase (minor Cu₂O) and major Cu₂O phase (minor CuO) respectively. Further, the samples prepared using 1:1 O/F ratio and calcinated at 700 °C showed highly crystalline CuO phase. In order to study the interaction of CuO/ Cu₂O with CQDs the fluorescence quenching method has been employed. The bimolecular quenching rate constants for the samples prepared with different O/F ratios have been measured. The interaction between CQDs and copper oxides, indicates fluorescence quenching greatly depends on the oxidation state of the copper oxide and can be a promising method for detecting CuO/Cu₂O through CQDs.

Synthesis of Carbon Quantum Dot Nanoparticles Derived from Byproducts in Bio-Refinery Process for Cell Imaging and In Vivo Bioimaging

The carbon quantum dot (CQD), a fluorescent carbon nanoparticle, has attracted considerable interest due to its photoluminescent property and promising applications in cell imaging and bioimaging. In this work, biocompatible, photostable, and sustainably sourced CQDs were synthesized from byproducts derived from a biorefinery process using one-pot hydrothermal treatment. The main components of byproducts were the degradation products (autohydrolyzate) of biomass pretreated by autohydrolysis. The as-synthesized CQDs had a size distribution from 2.0⁻6.0 nm and had high percentage of sp² and sp³ carbon groups. The CQDs showed blue-green fluorescence with a quantum yield of ~13%, and the fluorescence behaviors were found to be stable with strong resistance to photobleaching and temperature change. In addition, it is found that the as-synthesized CQDs could be used for imaging of cells and tumors, which show potential applications in bioimaging and related fields such as phototherapy and imaging.

BODIPY-based hydrazine as a fluorescent probe for sensitive and selective detection of nitric oxide: a new strategy

A novel fluorescent probe 8-HB was developed with a BODIPY as a fluorophore and 8-substituted hydrazine as a reactive site for sensitive and selective detection of nitric oxide (NO), generating major fluorescent dehydrazinated BODIPY and minor non-fluorescent azide BODIPY.

Carbon dots: The next generation platform for biomedical applications

Among the wide range of carbon family nanomaterials, carbon dots (CDs) one of the promising candidate which has attracted tremendous attention due to its unique advantages such as facile synthesis procedure, easy surface functionalization, outstanding water solubility, low toxicity and excellent photo-physical properties. Due to these unique advantages, CDs are extensively used in catalysis, electronics, sensing, power as well as in biological sectors. In this review we will discuss recent progress in synthesis, structure and fluorescence properties of CDs with special highlight on its biomedical applications, more precisely we will highlight on CDs, for drug/gene delivery, bioimaging and photothermal and photodynamic therapy applications. Furthermore, we discuss the current challenges and future perspective of CDs in the field of biomedical sector.

Ratiometric optical nanoprobes enable accurate molecular detection and imaging

Exploring and understanding biological and pathological changes are of great significance for early diagnosis and therapy of diseases. Optical sensing and imaging approaches have experienced major progress in this field. Particularly, an emergence of various functional optical nanoprobes has provided enhanced sensitivity, specificity, targeting ability, as well as multiplexing and multimodal capabilities due to improvements in their intrinsic physicochemical and optical properties. However, one of the biggest challenges of conventional optical nanoprobes is their absolute intensity-dependent signal readout, which causes inaccurate sensing and imaging results due to the presence of various analyte-independent factors that can cause fluctuations in their absolute signal intensity. Ratiometric measurements provide built-in self-calibration for signal correction, enabling more sensitive and reliable detection. Optimizing nanoprobe designs with ratiometric strategies can surmount many of the limitations encountered by traditional optical nanoprobes. This review first elaborates upon existing optical nanoprobes that exploit ratiometric measurements for improved sensing and imaging, including fluorescence, surface enhanced Raman scattering (SERS), and photoacoustic nanoprobes. Next, a thorough discussion is provided on design strategies for these nanoprobes, and their potential biomedical applications for targeting specific biomolecule populations (e.g. cancer biomarkers and small molecules with physiological relevance), for imaging the tumor microenvironment (e.g. pH, reactive oxygen species, hypoxia, enzyme and metal ions), as well as for intraoperative image guidance of tumor-resection procedures.

A dual-analyte probe: hypoxia activated nitric oxide detection with phototriggered drug release ability

A new strategy for the detection of hypoxia and NO succeeded by photocontrolled delivery of an anticancer agent has been demonstrated.

Fast response two-photon fluorogenic probe based on Schiff base derivatives for monitoring nitric oxide levels in living cells and zebrafish

A novel two-photon fluorogenic probe based on Schiff base derivative for rapidly monitoring nitric oxide level in living cells and zebrafish has been developed.

Carbon Nanodots as Dual-Mode Nanosensors for Selective Detection of Hydrogen Peroxide

Hydrogen peroxide (H2O2) is an important product of oxidase-based enzymatic reactions, such as glucose/glucose oxidase (GOD) reaction. Therefore, the probing of generated H2O2 for achieving the detection of various carbohydrates and their oxidases is very significative. Herein, we report one kind of dual-emission carbon nanodots (CDs) that can serve as novel dual-mode nanosensors with both fluorometric and colorimetric output for the selective detection of H2O2. The dual-model nanosensors are established only by the undecorated dual-emission CDs, where significant fluorometric and colorimetric changes are observed with the addition of different concentrations of H2O2 in the CD solution, which benefit to the achievement of the naked-eye detection for H2O2. The mechanism of the nanosensors can be attributed to the fact that the external chemical stimuli like hydroxyl radicals from H2O2 bring about the change of surface properties and the aggregation of CDs, which dominate the emission and absorption of CDs. The constructed dual-mode nanosensors exhibit good biocompatibility and high selectivity toward H2O2 with a linear detection range spanning from 0.05 to 0.5 M and allow the detection of H2O2 as low as 14 mM.

Imaging of compartmentalised intracellular nitric oxide, induced during bacterial phagocytosis, using a metalloprotein-gold nanoparticle conjugate

Nitric oxide (NO) plays an essential role within the immune system since it is involved in the break-down of infectious agents such as viruses and bacteria. The ability to measure the presence of NO in the intracellular environment would provide a greater understanding of the pathophysiological mechanism of this important molecule. Here we report the detection of NO from the intracellular phagolysosome using a fluorescently tagged metalloprotein-gold nanoparticle conjugate. The metalloprotein cytochrome c, fluorescently tagged with an Alexa Fluor dye, was self-assembled onto gold nanoparticles to produce a NO specific nanobiosensor. Upon binding of NO, the cytochrome c protein changes conformation which induces an increase of fluorescence intensity of the tagged protein proportional to the NO concentration. The nanobiosensor was sensitive to NO in a reversible and selective manner, and exhibited a linear response at NO concentrations between 1 and 300 μM. In RAW264.7γ NO- macrophage cells, the nanobiosensor was used to detect the presence of NO that had been endogenously generated upon stimulation of the cells with interferon-γ and lipopolysaccharide, or spontaneously released following treatment of the cells with a NO donor. Significantly, the nanobiosensor was shown to be taken up by the macrophages within phagolysosomes, i.e., the precise location where the NO, together with other species, destroys bacterial infection. The nanobiosensor measured, for the first time, increasing concentrations of NO produced during combined stimulation and phagocytosis of Escherichia coli bacteria from within localised intracellular phagolysosomes, a key part of the immune system.

iRGD-decorated red shift emissive carbon nanodots for tumor targeting fluorescence imaging

Carbon nanodots (CDs) have been exhibiting increasing applications owing to their luminescence properties and biocompatibility as imaging probes in diagnosis. However, poor tumor targeting and penetration of CDs is still the biggest challenge limiting their tumor imaging efficacy. To improve the tumor targeting and penetration efficiency of CDs, we developed an active tumor targeting imaging system by simply fabricating a tumor-homing penetration peptide iRGD (CRGDKGPDC) to red shift emissive CDs (iRGD-CDs) with a physical method. Particularly, iRGD-CDs showed a small size and red shift fluorescence signals as CDs, which made iRGD-CDs suitable for in vivo fluorescence imaging. iRGD-CDs showed higher cellular uptake in vitro, while presented higher penetration and accumulation in tumor tissue in vivo, leading to better tumor imaging efficacy. In conclusion, decoration with iRGD could significantly increase the permeability of CDs in tumor vessels and tumor tissue, generating more CDs leaking out from tumor vasculature, consequently improving the sensitivity of tumor imaging.

An AIE-based fluorescent test strip for the portable detection of gaseous phosgene

An AIE-based fluorescent test strip (OPD-TPE-Py-2CN) for rapid and sensitive detection of gaseous phosgene was designed. The fluorescence changes from blue to green upon exposure to phosgene. And the detection limit (1.87 ppm) is lower than the "harmless" level of human response to acute phosgene exposure.

Nitric Oxide Sensing through Azo-Dye Formation on Carbon Dots

Carbon dots (C-dots) prepared through heating of aminoguanidine and citric acid enable bimodal (colorimetric and fluorescence) detection of nitric oxide (NO) in aqueous solutions. The C-dots retained the functional units of aminoguanidine, which upon reaction with NO produced surface residues responsible for the color and fluorescence transformations. Notably, the aminoguanidine/citric acid C-dots were noncytotoxic, making possible real-time and high sensitivity detection of NO in cellular environments. Using multiprong spectroscopic and chromatography analyses we deciphered the molecular mechanism accounting for the NO-induced structural and photophysical transformations of the C-dots, demonstrating for the first time N₂ release and azo dye formation upon the C-dots' surface.

Preparation of Yellow-Green-Emissive Carbon Dots and Their Application in Constructing a Fluorescent Turn-On Nanoprobe for Imaging of Selenol in Living Cells

Selenocysteine (Sec) carries out the majority of the functions of the various Se-containing species in vivo. Thus, it is of great importance to develop sensitive and selective assays to detect Sec. Herein, a carbon-dot-based fluorescent turn-on probe for highly selective detection of selenol in living cells is presented. The highly photoluminescent carbon dots that emit yellow-green fluorescence (Y-G-CDs; λ_max = 520 nm in water) were prepared by using m-aminophenol as carbon precursor through a facile solvothermal method. The surface of Y-G-CDs was then covalently functionalized with 2,4-dinitrobenzenesulfonyl chloride (DNS-Cl) to afford the 2,4-dinitrobenzene-functionalized CDs (CD-DNS) as a nanoprobe for selenol. CD-DNS is almost nonfluorescent. However, upon treating with Sec, the DNS moiety of CD-DNS can be readily cleaved by selenolate through a nucleophilic substitution process, resulting in the formation of highly fluorescent Y-G-CDs and hence leads to a dramatic increase in fluorescence intensity. The proposed nanoprobe exhibits high sensitivity and selectivity toward Sec over biothiols and other biological species. A preliminary study shows that CD-DNS can function as a useful tool for fluorescence imaging of exogenous and endogenous selenol in living cells.

A self-immolative and DT-diaphorase-activatable prodrug for drug-release tracking and therapy

A DT-diaphorase-activatable theranostic prodrug has been developed for visualizing the release of active drug and enhancing the therapeutic effect.

Direct ratiometric detection of nitric oxide with Cu(ii)-based fluorescent probes

We report the first Cu(ii)-based ratiometric sensors for direct, rapid, and selective fluorescent detection of nitric oxide.

A ratiometric mitochondria-targeting two-photon fluorescent probe for imaging of nitric oxide in vivo

A two-photon ratiometric fluorescent probe (Mito-N) has been developed for monitoring mitochondrial nitric oxide (NO) in vivo.

Development and sensing applications of fluorescent motifs within the mitochondrial environment

The potential use of fluorescent molecular probes to measure ions and biomolecules has contributed incessantly to the understanding of chemical and biological systems. The approach has many advantages such as high sensitivity, simplicity and non-destructive cellular imaging that offer visible information about the targeted species. In this article, our objective is to discuss fluorescent probes that have sensing applications within the mitochondrial environment. Mitochondria are cellular organelles which are well known for their unique physiological functions and have been found to be associated with various diseases and disorders. It is therefore, important to develop new tools and tactics that can provide useful information concerning the mitochondrial environment which in turn is essential to understand its biophysical functioning and related diseases.

A turn on fluorescent sensor based on lanthanide coordination polymer nanoparticles for the detection of mercury(ii) in biological fluids

Im-quenched fluorescence of Eu/IPA CPNPs can be recovered upon the addition of Hg²⁺ through the formation of a Hg/Im complex.

A FRET fluorescent nanosensor based on carbon dots for ratiometric detection of Fe3+ in aqueous solution

A highly selective and sensitive FRET ratiometric fluorescent nanosensor has been developed for detecting Fe³⁺ in aqueous solution and on test papers. It works based on a Fe³⁺-triggered FRET process between CDs and ring-opened rhodamine 6G.

Fluorescent probes for the selective detection of chemical species inside mitochondria

This feature article systematically summarizes the development of fluorescent probes for the selective detection of chemical species inside mitochondria.

In situ photochemical synthesis of fluorescent carbon dots for optical sensing of hydrogen peroxide and antioxidants

A new synthesis approach for obtaining fluorescent carbon dots (CDs) based on UV irradiation of carbohydrates was developed. The photochemical synthesis pathway allows the formation of water soluble CDs of analytical usefulness within one min. CDs obtained by photochemical treatment from the sucrose/NaOH/poly(ethylene glycol) system are monodisperse with an average size of 8 nm as determined by transmission electron microscopy. A dramatic increase in the CDs fluorescence (turn on) is observed when H2O2 is added. The decrease in CDs size occurring by the action of highly oxidant OH radicals gives rise to confinement of emissive energy traps and, in turn, to fluorescence enhancement. Antioxidants such as ascorbic acid and glutathione inhibit the photochemical reaction giving rise to a decrease in fluorescence of the CDs/H2O2 system (turn on-off). The detection limit was 5 µM H2O2 and the repeatability expressed as the relative standard deviation was 3.8% (N=7). The photochemical synthesis of CDs allows building a green, low-cost, safe and fast assay for the detection of H2O2 and antioxidants. An application of the novel fluorescent nanoprobe to H2O2 detection in contact lens cleaning solutions is performed.

New reagents for detecting free radicals and oxidative stress

Free radicals and oxidative stress play important roles in the deterioration of materials, and free radicals are important intermediates in many biological processes. The ability to detect these reactive species is a key step on the road to their understanding and ultimate control. This short review highlights recent progress in the development of reagents for the detection of free radicals and reactive oxygen species with broad application to materials science as well as biology.

A FRET chemsensor based on graphene quantum dots for detecting and intracellular imaging of Hg²⁺

The detection of Hg(2+) has attracted considerable attention because of the serious health and environmental problems caused by it. Herein, a novel ratiometric fluorescent chemsensor (GQDs-SR) based on the fluorescence resonance energy transfer (FRET) process for detecting of Hg(2+) was designed and synthesized with rhodamine derivative covalently linked onto graphene quantum dots. In this sensor, the graphene quantum dots (GQDs) served as energy donor and the rhodamine derivative turned into an energy acceptor when encountered Hg(2+). The chemsensor exhibited high selectivity, low cytotoxicity, biocompatibility and good water solubility. The results of intracellular imaging experiment demonstrated that GQDs-SR was cell permeable and could be used for monitoring Hg(2+) in living cells, and it was also successfully applied to the detection of Hg(2+) in practical water samples.

One-pot electrochemical synthesis of functionalized fluorescent carbon dots and their selective sensing for mercury ion

We propose a simple, economical, and one-pot method to synthesize water-soluble functionalized fluorescent carbon dots (C-Dots) through electrochemical carbonization of sodium citrate and urea. The as-prepared C-Dots have good photostability and exhibit a high quantum yield of 11.9%. The sizes of the C-Dots are mainly distributed in the range of 1.0-3.5 nm with an average size of 2.4 nm. It has been further used as a novel label-free sensing probe for selective detection of Hg(2+) ions with detection limit as low as 3.3 nM. The detection linear range is 0.01-10 μM. The as-prepared C-Dots are also successfully applied for the determination of Hg(2+) in real water samples.

A colorimetric and ratiometric fluorescent probe for ClO−targeting in mitochondria and its application in vivo

A colorimetric and ratiometric fluorescent probe PMN–TPP for imaging mitochondrial ClO⁻was prepared. The probe performed well in detecting ClO⁻in the mitochondria of living RAW264.7 macrophage cells and a living nude mouse.

A ratiometric fluorescent nanoprobe based on terbium functionalized carbon dots for highly sensitive detection of an anthrax biomarker

By preparing biocompatible carbon dots (CDs) that act as the scaffold and fluorescence reference, a ratiometric fluorescent nanoprobe based on Tb³⁺ ions functionalized CDs was designed and fabricated to detect an anthrax biomarker with high selectivity and sensitivity.