Advances in functional fluorescent and luminescent probes for imaging intracellular small-molecule reactive species

An overview on recent advances of reversible fluorescent probes and their biological applications

Due to the simplicity and low detection limit, fluorescent probes are widely used in both analytical sensing and optical imaging. Compared to conventional fluorescent probes, reversibility endows the reversible fluorescent probe outstanding advantages and special properties, making reversible fluorescent probes with capable of quantitative, repetitive or circulatory. Reversible fluorescent probes can also monitor the concentration dynamics of target analytes in real time, such as metal ions, proteins and enzymes, as well as intracellular redox processes, which have been widely applied in various fields. This review summarized the types and excellent properties of reversible fluorescent probes designed and developed in recent years. It also summarized the applications of reversible fluorescent probe in fluorescence imaging, biological testing, monitoring redox cycles, and proposed the remaining challenges and future development directions of the reversible fluorescent probe. This review provided comprehensive overview of reversible fluorescent probe, which may provide valuable references for the design and fabrication of the reversible fluorescent probe.

Dual colorimetric and near-infrared fluorescence probe for Hg2+ detection and cell imaging

Hg²⁺ in the environment endangers human health, and a convenient monitoring method is needed for the detection of Hg²⁺. In this study, we constructed a dual colorimetric near-infrared fluorescent probe (E)-2-(3-(3-(1,3-dithian-2-yl)-4-hydroxystyryl)-5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (YF-Hg), based on the malononitrile isophorone. YF-Hg can detect Hg²⁺ rapidly and sensitively, with fluorescence emission in the near-infrared region (659 nm) with an obvious color change from violet to red in the visible light range. In addition, the low toxicity and large Stokes shift (191 nm) of YF-Hg also suggest that it is a potential tool for live-cell fluorescence imaging.

A triphenylamine-based aggregation-enhanced emission probe for viscosity and polarity analysis of lubricating oils

Lubricating oils offers abundant information about the operating state of machines. In this work, a donor-acceptor aggregation-enhanced emission fluorescent molecule, (Z)-4-(1-cyano-2-(4-(diphenylamino)phenyl)vinyl)benzonitrile (CPA-TPA), was synthesized to investigate its function to sense the viscosity and polarity of lubricant base oils. The results indicated that the molecule showed steadily-increased fluorescence emission with the base oil viscosity. In a mixture of poly-α-olefin/ester base oils, its optimal emission gradually red-shifted with the ester oil fraction, i.e., the polarity of the lubricant. A good correlation could be established between the emission intensity of the probe and the oil viscosity or between the optimal emission wavelength and the oil polarity. This demonstrates a dual-response fluorescent probe used for lubricating oil analysis and opens a new opportunity to develop a molecule-based method for the evaluation of lubricating oil quality.

Tetraphenylethene probe based fluorescent silica nanoparticles for the selective detection of nitroaromatic explosives

A simple and sensitive fluorometric method is developed utilizing aggregation-induced emission probe based silica nanoparticles for the detection of nitroaromatic explosives. A positively charged tetraphenylethene based probe (TPE-C2-2+) is doped into silica nanoparticles exploiting electrostatic interactions to produce TPE-SiO₂ nanoparticles with a uniform particle size. The TPE-SiO₂ nanoparticles exhibit strong fluorescence emission due to the aggregation-induced emission (AIE) effect of the doped TPE probe. The fluorescence emission of TPE-SiO₂ offers quantitative and sensitive response to picric acid (PA), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) which are used as model examples of nitroaromatic compounds. The fluorescence spectroscopy results show that the fluorescence emission of TPE-SiO₂ was greatly quenched in the presence of the electron-poor nitroaromatic compounds due to the inner filter effect (IFE) and possibly the contact quenching mechanism. TPE-SiO₂ nanoparticles show better sensitivity towards PA and could detect PA down to 0.01 μM with a linear detection range of 0.1-50 μM. The increased chemical stability, efficient high sensitivity and simple synthesis of the TPE-SiO₂ nanoparticles demonstrate that they can be used as an excellent fluorescent probe for a wide range of electron-poor compounds, i.e. nitroaromatic compounds. Interference studies show that common interfering species with nitroexplosives such as acids, bases, volatile organic compounds, and salt solutions have a negligible effect during the sensing process.

An efficient fluorescent nano-sensor of N-doped carbon dots for the determination of 2,4,6-trinitrophenol and other applications

N-Doped carbon dots (CDs) had been simply produced by a one-pot synthesis process using amygdalic acid and threonine. The resulting product was water-soluble and exhibited strong luminescence emission with a fluorescence quantum yield of 19.25%. The emission of CDs was obviously and selectively decreased upon adding 2,4,6-trinitrophenol (TNP). It was proved that the fluorescence resonance energy transfer was the main mechanism for quenching. An efficient fluorescence probe with satisfied sensitivity for TNP determination was found. The range of the linear response for TNP detection was 0.5-40.0 μmol L^-1, and the limit of detection was 20 nmol L^-1. The content of trace TNP in water samples was successfully detected with this method. The CDs were also applied in HepG2 cell imaging and the fabrication of fluorescent films by dispersing the solid freeze-drying CD (SCD) powder into PMMA, which exhibited some application value in biology and photovoltaics.

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems.

Furo[3,2-c]coumarin-derived Fe3+ Selective Fluorescence Sensor: Synthesis, Fluorescence Study and Application to Water Analysis

Furocoumarin (furo[3,2-c]coumarin) derivatives have been synthesized from single step, high yielding (82-92%) chemistry involving a 4-hydroxycoumarin 4 + 1 cycloaddition reaction. They are characterized by FTIR, 1H-NMR, and, for the first time, a comprehensive UV-Vis and fluorescence spectroscopy study has been carried out to determine if these compounds can serve as useful sensors. Based on the fluorescence data, the most promising furocoumarin derivative (2-(cyclohexylamino)-3-phenyl-4H-furo[3,2-c]chromen-4-one, FH), exhibits strong fluorescence (ФF = 0.48) with long fluorescence lifetime (5.6 ns) and large Stokes' shift, suggesting FH could be used as a novel fluorescent chemosensor. FH exhibits a highly selective, sensitive and instant turn-off fluorescence response to Fe3+ over other metal ions which was attributed to a charge transfer mechanism. Selectivity was demonstrated against 13 other competing metal ions (Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Al3+, Ni2+, Cu2+, Zn2+, Co2+, Pb2+ and Ru3+) and aqueous compatibility was demonstrated in 10% MeOH-H2O solution. The FH sensor coordinates Fe3+ in a 1:2 stoichiometry with a binding constant, Ka = 5.25 × 103 M-1. This novel sensor has a limit of detection of 1.93 µM, below that of the US environmental protection agency guidelines (5.37 µM), with a linear dynamic range of ~28 (~2-30 µM) and an R2 value of 0.9975. As an exemplar application we demonstrate the potential of this sensor for the rapid measurement of Fe3+ in mineral and tap water samples demonstrating the real-world application of FH as a "turn off" fluorescence sensor.

Gold nanoclusters for biomedical applications: toward in vivo studies

In parallel with the rapidly growing and widespread use of nanomedicine in the clinic, we are also witnessing the development of so-called theranostic agents that combine diagnostic and therapeutic properties.

Recent advances in ultra-small fluorescent Au nanoclusters toward oncological research

Au nanoclusters possess a series of excellent properties owing to their size being comparable to the Fermi wavelength of electrons. For example, they show excellent biocompatibility, optical stability, large Stokes shift, intense size-dependent emission and monodispersion, and thus could effectively compensate for the shortcomings of traditional organic fluorescent dyes and fluorescent quantum. In this review, we detail the latest developments of Au nanoclusters employed in the field of biomedicine, especially in oncology research, by summarizing the application of imaging, sensing and drug delivery based on their excellent luminescent properties and unique structural features. We also discuss the significant work relating to Au NCs that now is being devoted in other therapeutic strategies, such as radiotherapy, photothermal therapy and photodynamic therapy, for example. It is anticipated that this review will provide new insights and theoretical guidance to allow the advantages of Au nanoclusters to be realized in oncotherapy.

A dual-excitation fluorescent probe EuIII-dtpa-bis(HBT) for hydrazine detection in aqueous solutions and living cells

The Eu^III-dtpa-bis(HBT) dual-excitation fluorescence probe has good selectivity and strong anti-interference ability for the detection of N₂H₄.

A novel rhodamine-based fluorescent probe for selective detection of ClO– and its application in living cell imaging

A novel fluorescent rhodamine-based probe L for selective responding to ClO– has been synthesized and characterized. The spectroscopy showed that probe L can detect ClO– in aqueous solution without interaction with other interfering ions, and the detection is also evident by the colour change from colourless to reddish purple under white light. The remarkable fluorescence enhancement showed the high selectivity and sensitivity of probe L for the detection of ClO–. Furthermore, probe L was applied to intracellular fluorescent imaging of HeLa cells treated with ClO– and MTT assay showed nontoxicity in living cells.

Polydopamine Dots-Based Fluorescent Nanoswitch Assay for Reversible Recognition of Glutamic Acid and Al3+ in Human Serum and Living Cell

We developed a facile and feasible fluorescent nanoswitch assay for reversible recognition of glutamate (Glu) and Al³⁺ in human serum and living cell. The proposed nanoswitch assay is based on our recently developed method for controlled synthesis of fluorescent polydopamine dots (PDADs) at room temperature with dopamine as the sole precursor. The fluorescence of nanoswitch assay could be quickly and efficiently quenched by Glu (turn-Off), and the addition of Al³⁺ could recover the fluorescence of the PDADs-Glu system (turn-On). Meanwhile, the reversible recognition of Glu and Al³⁺ in this nanoswitch system was stable after three cycles. Additionally, the system displayed excellent performance for Glu and Al³⁺ determination with a low detection limit of 0.12 and 0.2 μM, respectively. Moreover, PDADs are successfully applied to determine Glu and monitor Al³⁺ in human serum. Noteworthy, the nanoswitch assay is transported into HepG2 cells and realized "Off" detection of Glu and "On" sensing Al³⁺ in the living cells. Therefore, this PDADs-based nanoswitch assay provides a strategy to develop reversible recognition biosensors for intracellular and external molecular analysis.

Fluorescent Disulfide-functional Coordination Polymers for Sensitive Detection of Hydrogen Peroxide

A new type of fluorescent coordination polymer (NCP_Cd) based on disulfide carboxylate ligand was prepared by using one-pot synthesis for sensitive detection of reactive oxygen species (ROS). With the reaction between NCP_Cd and ROS, the morphology of the NCP_Cd was transformed from nanorods to hexagon particles, then broken into nano-fragments. Meanwhile, the fluorescence of NCP_Cd (at 421 nm) was quenched accordingly. For designing the highly sensitive probe for ROS, Rhodamine 6G (R6G) was doped in NCP_Cd. In the presence of ROS, the fluorescence of NCP_Cd moiety at 421 nm was quenched, but the R6G moiety was released from the broken nanorods and the fluorescence at 555 nm from R6G moiety was recovered. The R6G doped NCP_Cd (NCP_Cd-R) can be used as a highly sensitive and selective probe for hydrogen peroxide (H₂O₂) with detection limit of 12.4 nM. Moreover, the NCP_Cd-R was further extended to the glucose sensing combined with glucose oxidase (GOx) to oxidate glucose and generate H₂O₂, demonstrating the potential for practical applications.

One-step synthesis of red/green dual-emissive carbon dots for ratiometric sensitive ONOO- probing and cell imaging

The synthesis of dual-emissive carbon dots (CDs) with a longer emission wavelength by using a facile strategy is of great importance for the fabrication of ratiometric fluorescent nanoprobes. Herein, red/green dual-emissive carbon dots (RGDE CDs) were synthesized in one step using 2,5-diaminotoluene sulfate (DATS) as a carbon source. The as-prepared RGDE CDs not only exhibited dual emission fluorescence peaks (525 nm, 603 nm) at the single excitation wavelength of 370 nm, but also possessed good water solubility and excellent fluorescence stability. Moreover, the as-prepared RGDE CDs could be directly utilized as a ratiometric fluorescent probe for the determination of trace ONOO- due to the electron transfer process from ONOO- to the excited RGDE CDs. Under optimal conditions, the linear range was 0.03-60 μM with the limit of detection of 11.6 nM. Importantly, this RGDE CD probe could be applied for the detection of intracellular ONOO- with excellent biocompatibility and cellular imaging capability, indicating great promise in biomedical applications.

Catalytic Chemiluminescence Polymer Dots for Ultrasensitive In Vivo Imaging of Intrinsic Reactive Oxygen Species in Mice

Chemiluminescence (CL) is a promising bioimaging method due to no interferences of light source and autofluorescence. However, compared to fluorescent emission, most CL reactions show short emission time and wavelength and weak emission intensity, which limit their applications in in vivo imaging. Here, we report mimic-enzyme catalytic CL polymer dots (hemin-Pdots) consisting of hemin and fluorescent conjugated polymer based on chemiluminescence resonance energy transfer. Hemin-Pdots show about 700× enhanced CL and over 10 h light emission in the presence of CL substrates and H₂O₂. These properties are mainly due to high-catalytic activity of hemin-Pdots and slow-diffusion-controlled heterogeneous reaction. Hemin-Pdots also possess excellent biocompatibility, good stability, emission wavelength redshift, and ultrasensitive response to reactive oxygen species (ROS), and they were successfully used for real-time imaging ROS levels in the peritoneal cavity and normal and tumor tissues of mice. Hemin-Pdots as new CL probes have wide applications in bioassays, bioimaging, and photodynamic therapy.

Fluorescent analysis of bioactive molecules in single cells based on microfluidic chips

Single-cell analysis of bioactive molecules is an essential strategy for a better understanding of cell biology, exploring cell heterogeneity, and improvement of the ability to detect early diseases. In single-cell analysis, highly efficient single-cell manipulation techniques and high-sensitive detection schemes are in urgent need. The rapid development of fluorescent analysis techniques combined with microfluidic chips have offered a widely applicable solution. Thus, in this review, we mainly focus on the application of fluorescence methods in components analysis on microchips at a single-cell level. By targeting different types of biological molecules in cells such as nucleic acids, proteins, and active small molecules, we specially introduce and comment on their corresponding fluorescent probes, fluorescence labelling and sensing strategies, and different fluorescence detection instruments used in single-cell analysis on a microfluidic chip. We hope that through this review, readers will have a better understanding of single-cell fluorescence analysis, especially for single-cell component fluorescence analysis based on microfluidic chips.

Tracking of Short Distance Transport Pathways in Biological Tissues by Ultra-Small Nanoparticles

In this work, ultra-small europium-doped HfO₂ nanoparticles were infiltrated into native wood and used as trackers for studying penetrability and diffusion pathways in the hierarchical wood structure. The high electron density, laser induced luminescence, and crystallinity of these particles allowed for a complementary detection of the particles in the cellular tissue. Confocal Raman microscopy and high-resolution synchrotron scanning wide-angle X-ray scattering (WAXS) measurements were used to detect the infiltrated particles in the native wood cell walls. This approach allows for simultaneously obtaining chemical information of the probed biological tissue and the spatial distribution of the integrated particles. The in-depth information about particle distribution in the complex wood structure can be used for revealing transport pathways in plant tissues, but also for gaining better understanding of modification treatments of plant scaffolds aiming at novel functionalized materials.

Te-containing carbon dots for fluorescence imaging of superoxide anion in mice during acute strenuous exercise or emotional changes

Acute strenuous exercise and emotional changes are closely related to important aspects of human health. The superoxide anion (O₂˙^-), as one of the primary reactive oxygen species (ROS), is intimately associated with major diseases. However, there is no relevant in vivo research for directly indicating the link between O₂˙^- level and acute physical exercise or emotional changes. Hence, we constructed three fluorescent probes for the detection of O₂˙^-, including a Te-containing molecular probe and Se- and Te-containing CDs, and evaluated their properties such as selectivity, sensitivity, instantaneity and dynamic response to O₂˙^-. Through performance comparisons, we found that the Te-containing CDs exhibited reversibility, instantaneity and the highest sensitivity (LOD ∼ 8.0 pM), under guarantees of specific recognition of O₂˙^-, which ensure they are suitable for tracing native level changes in O₂˙^- within living systems. The probe was applied for monitoring the levels of O₂˙^- in mice under the state of intense exercise, irritability and mild depression, which led to the levels of O₂˙^- significantly increasing compared to the normal condition. Furthermore, we used the Te-containing CDs for real-time and dynamic imaging of O₂˙^- fluxes in the brain of mild depression mice and witnessed a positive correlation between O₂˙^- levels and depression. This work provides a new strategy for studying the relationship between acute exercise or emotional changes and diseases at the level of ROS.

Ratiometric Catalyzed-Assembly of NanoCluster Beacons: A Nonenzymatic Approach for Amplified DNA Detection

In this work, a novel fluorescent transformation phenomenon of oligonucleotide-encapsulated silver nanoclusters (AgNCs) was demonstrated, in which green-emissive AgNCs effectively transformed to red-emissive AgNCs when placed in close proximity to a special DNA fragment (denoted as convertor here). Taking advantage of a catalyzed-hairpin-assembly (CHA) amplification strategy, we rationally and compatibly engineered a simple and sensitive AgNC-based fluorescent signal amplification strategy through the ratiometric catalyzed-assembly (RCA) of green-emissive NanoCluster Beacon (NCB) with a convertor modified DNA hairpin to induce the template transformation circularly. The proposed ratiometric fluorescent biosensing platform based on RCA-amplified NCB (RCA-NCB) emits intense green fluorescence in the absence of target DNA and will undergo consecutively fluorescent signal transformation from green emission to red emission upon exposure to its target DNA. The ratiometric adaptation of the NCB to CHA circuit advances their general usability as biosensing platform with great improvements in detection sensitivity. By measuring the fluorescence intensity ratio of the red emission and green emission, the proposed RCA-NCB platform exhibits sensitive and accurate analytical performance toward Werner Syndrome-relevant gene, the proof-of-concept target in this work. A low detection limit down to the pM level was achieved, which is lower than most of the reported AgNC-based fluorescent DNA biosensors, making the proposed RCA-NCB biosensing strategy appealing in amplifying the ratiometric fluorescent signal for sensitive DNA detection. Moreover, our proposed RCA-NCB platform shows good recovery toward the target DNA in real human serum samples, illustrating their potential promise for clinical and imaging applications in the future.

Ratiometric NanoCluster Beacon: A Label-Free and Sensitive Fluorescent DNA Detection Platform

Although researches until now have emphasized the influence of an oligonucleotide sequence on the fluorescence of oligonucleotide-stabilized silver nanoclusters (AgNCs), this influence has been explored as a novel ratiometric fluorescent signal transduction in this work. This study builds on our original discovery of a template-transformation phenomenon, which demonstrated that the connection of a special DNA fragment (5'-CACCGCTTT-3') with a green-emitting AgNC nucleation sequence (GNuS, 5'-TGCCTTTTGGGGACGGATA-3') creates a red-emitting AgNC nucleation sequence (RNuS, 5'-CACCGCTTTTGCCTTTTGGGGACGGATA-3'). Attempts to expand this idea and construct elegant ratiometric NanoCluster Beacons (NCBs) for DNA sequence detection are not straightforward, and, thus, we carried out a series of investigations with the goal of understanding the mechanism of this template-transformation phenomenon. Experimental results showed that the six-nucleotide fragment (5'-CACCGC-3') at the 5'-end of RNuS acts as a template convertor and takes full responsibility for the template transformation from GNuS to RNuS. Moreover, we found that the appropriate proximity of the convertor to GNuS also plays a significant role in the template transformation. We then show that the insights gained here for the template-transformation mechanism allow us to construct ratiometric NCBs by simply appending the convertor and the GNuS onto a rationally designed stem-loop probe. This new type of NCB emits intense red fluorescence without the addition of a target DNA and emerges as a new, bright green emission only when hybridized to its target DNA. By measuring the distinct variation in the fluorescence intensity ratios of green and red emission, this ratiometric NCB was demonstrated to sensitively detect Hepatitis-A virus gene sequences, a proof-of-concept target in this work, with good selectivity.

A mitochondria-targeting time-gated luminescence probe for hypochlorous acid based on a europium complex

A europium complex-based mitochondria-targeting probe has been developed for the time-gated luminescence imaging of hypochlorous acid in living samples.

A viscosity sensitive fluorescent dye for real-time monitoring of mitochondria transport in neurons

We present here a viscosity sensitive fluorescent dye, namely thiophene dihemicyanine (TDHC), that enables the specific staining of mitochondria. In comparison to the common mitochondria tracker (Mitotracker Deep Red, MTDR), this dye demonstrated its unique ability for robust staining of mitochondria with high photostability and ultrahigh signal-to-noise ratio (SNR). Moreover, TDHC also showed high sensitivity towards mitochondria membrane potential (ΔΨm) and intramitochondria viscosity change. Consequently, this dye was utilized in real-time monitoring of mitochondria transport in primary cortical neurons. Finally, the Two-Photon Microscopy (TPM) imaging ability of TDHC was also demonstrated.

Coupling the folding of a β-hairpin with chelation-enhanced luminescence of Tb(III) and Eu(III) ions for specific sensing of a viral RNA

Rational modification of a natural RNA-binding peptide with a lanthanide EDTA chelator, and a phenanthroline ligand yields a highly selective luminescent sensor. The sensing mechanism relies on the RNA-triggered folding of the peptide into a β-hairpin, which promotes the coordination of the phenanthroline sensitizer, and the efficient sensitization of complexed lanthanide ions.

A novel SERS nanoprobe for the ratiometric imaging of hydrogen peroxide in living cells

Via the assembly of 4-mercaptophenylboronic ester on the gold nanorod's surface, a novel ratiometric SERS nanosensor for H₂O₂ imaging in living cells or cancer tissues has been developed in the present study.

Rapid tumor bioimaging and photothermal treatment based on GSH-capped red fluorescent gold nanoclusters

Au NCs used for fluorescent bioimaging and photothermal treatment through combining with porphyrin derivatives (TSPP).

Aptamer/Polydopamine Nanospheres Nanocomplex for in Situ Molecular Sensing in Living Cells

A nanocomplex was developed for molecular sensing in living cells, based on the fluorophore-labeled aptamer and the polydopamine nanospheres (PDANS). Due to the interaction between ssDNA and PDANS, the aptamer was adsorbed onto the surface of PDANS forming the aptamer/PDANS nanocomplex, and the fluorescence was quenched by PDANS through Förster resonance energy transfer (FRET). In vitro assay, the introduction of adenosine triphosphate (ATP) led to the dissociation of the aptamer from the PDANS and the recovery of the fluorescence. The retained fluorescence of the nanocomplex was found to be linear with the concentration of ATP in the range of 0.01-2 mM, and the nanocomplex was highly selective toward ATP. For the strong protecting capability to nucleic acids from enzymatic cleavage and the excellent biocompatibility of PDANS, the nanocomplex was transported into cells and successfully realized "signal on" sensing of ATP in living cells; moreover, the nanocomplex could be employed for ATP semiquantification. This design provides a strategy to develop biosensors based on the polydopamine nanomaterials for intracellular molecules analysis. For the advantages of polydopamine, it would be an excellent candidate for many biological applications, such as gene and drug delivery, intracellular imaging, and in vivo monitoring.

A Rotational BODIPY Nucleotide: An Environment-Sensitive Fluorescence-Lifetime Probe for DNA Interactions and Applications in Live-Cell Microscopy

Fluorescent probes for detecting the physical properties of cellular structures have become valuable tools in life sciences. The fluorescence lifetime of molecular rotors can be used to report on variations in local molecular packing or viscosity. We used a nucleoside linked to a meso-substituted BODIPY fluorescent molecular rotor (dC(bdp)) to sense changes in DNA microenvironment both in vitro and in living cells. DNA incorporating dC(bdp) can respond to interactions with DNA-binding proteins and lipids by changes in the fluorescence lifetimes in the range 0.5-2.2 ns. We can directly visualize changes in the local environment of exogenous DNA during transfection of living cells. Relatively long fluorescence lifetimes and extensive contrast for detecting changes in the microenvironment together with good photostability and versatility for DNA synthesis make this probe suitable for analysis of DNA-associated processes, cellular structures, and also DNA-based nanomaterials.

Biomolecule conjugated nanoparticle synthons for detection of food contaminants

This article investigates recent research on a series of photoluminescent nanoparticles (NPs) and supramolecular chemistry at their surface. This in turn prompts the concept of quantum dots supramolecular synthons (QDSS) and foresees the inevitable path towards biomimetics and bioinspired technology. We highlight the methodology how to create QDSS by functional assembly of photoluminescent semiconductors and the surface binding of supramolecular ligands.

The synthesis of new fluorescent bichromophoric compounds as ratiometric pH probes for intracellular measurements

Three different bichromophoric compounds (1–3) containing an aminomethyl anthracene moiety linked to a second chromophore have been prepared and their fluorescent properties studied.