A Multifunctional Hydrogel for Simultaneous Visible H2 O2 Monitoring And Accelerating Diabetic Wound Healing

Diabetic wound is one of the chronic wounds that is difficult to heal, and effective treatment of it still confronts a great challenge. Monitoring the variation of diabetic wound microenvironment (such as hydrogen peroxide (H2 O2 )) can understand the wound state and guide the wound management. Herein, a multifunctional hydrogel with the abilities of monitoring the H2 O2 concentration, alleviating oxidative stress and promoting wound healing is developed, which is prepared by encapsulating manganese-containing bioactive glass (MnBG) and CePO4 :Tb in biocompatible gelatin methacryloyl (GelMA) hydrogel (CPT-MnBG-Gel). On the one hand, the H2 O2 -dependent fluorescence quenching effect of the CePO4 :Tb contributes to visible monitoring of the H2 O2 concentration of wounds via smartphone imaging, and the CPT-MnBG-Gel hydrogel can effectively monitor the H2 O2 level of 10.35-200 µmol L-1 . On the other hand, MnBG can alleviate oxidative stress and promote the proliferation, migration and differentiation of fibroblasts and endothelial cells in vitro owing to the bioactive Mn and Si ions, and in vivo evaluation also demonstrates that the CPT-MnBG-Gel hydrogels can effectively accelerate wound healing. Hence, such multifunctional hydrogel is promising for diabetic wound management and accelerating wound healing.

Boosting the sensitivity with time-gated luminescence thermometry using a nanosized molecular cluster aggregate

Luminescence thermometry with trivalent lanthanide ions is a promising avenue for contactless temperature probing. The area has been growing exponentially for the last two decades, and its viability has been successfully demonstrated in various research domains. However, moving from laboratory equipment to real-life applications remains a challenging task. One of the reasons is the possibility of a background luminescence from the probing device or probed environment. To tackle this issue, we elegantly incorporate a rarely explored thermometric approach called time-gated luminescence thermometry (TGLT). Furthermore, we demonstrate an enhanced relative sensitivity through this innovative approach and a path to move toward practical application.

Design and Mechanism of Rare-Earth Singlet Oxygen Sensing: An Experimental and Quantum Chemical Approach

The sensitive detection of singlet oxygen (¹O₂) is one key issue in various photochemical analyses, reactions, and processes; it is indispensable for designing catalysts for photodynamic therapies. Corresponding fluorescence-based organic ¹O₂ monitor luminophores may be equipped with rare-earth complexes with several intrinsic advantages. The design of the necessary ligands being a tedious, time-consuming effort, often involving empirical guesswork, we decided to support our experimental work with quantum chemical calculations. Hence, next to the experimental core, this paper suggests the additional use of time-dependent density functional theory (TDDFT) on suitable, free β-diketonate ligands to devise corresponding Eu³⁺ complexes as ¹O₂ probes eventually; the free ligand calculations obviously allow profoundly reduced computational efforts. Novel β-diketonate-substituted dimethyl anthracene complexes of Eu³⁺, Tb³⁺, and Gd³⁺ and their endoperoxidized descendants were thus synthesized, compared to known related complexes and analyzed with regard to their electronic characteristics; in addition, spectroscopy of a Eu³⁺ complex with ancillary epoxiphenanthroline for subsequent attachment to biological substrates featuring -NH₂ or -SH groups was included. The spectroscopic determination of the decisive lowest triplet (T₁) states of the Gd complexes could be matched by the Tamm-Dancoff approximation (TDA)/TDDFT calculations on the free ligands satisfactorily if suitable functionals were applied. Most significantly, the results suffice to describe the luminescence "switch-on" mechanism of this complex in the presence of ¹O₂.

Activity-Based Sensing for Chemistry-Enabled Biology: Illuminating Principles, Probes, and Prospects for Boronate Reagents for Studying Hydrogen Peroxide

Activity-based sensing (ABS) offers a general approach that exploits chemical reactivity as a method for selective detection and manipulation of biological analytes. Here, we illustrate the value of this chemical platform to enable new biological discovery through a case study in the design and application of ABS reagents for studying hydrogen peroxide (H2O2), a major type of reactive oxygen species (ROS) that regulates a diverse array of vital cellular signaling processes to sustain life. Specifically, we summarize advances in the use of activity-based boronate probes for the detection of H2O2 featuring high molecular selectivity over other ROS, with an emphasis on tailoring designs in chemical structure to promote new biological principles of redox signaling.

Dinuclear Lanthanide Compound as a Promising Luminescent Probe for Al3+ Ions

Luminescent probes have wide applications in biological system analysis and environmental science. Here, one novel luminescent dinuclear europium compound with a crown ether analogous ligand was synthesized through a solvent-thermal reaction. Through transformation, upon the addition of Al³⁺ ions to the N,N'-dimethyl formamide solution of the europium compound, the luminescent intensity of the characteristic emission of Eu³⁺ decreased, and a new emission peak appeared at 346 nm and increased rapidly. The luminescent investigation indicated that it could act as a highly sensitive and selective luminescent probe for Al³⁺ ions. Moreover, mass spectrometry and single-crystal X-ray diffraction confirmed the formation of a new more stable trinuclear aluminium compound during the sensing process.

Lanthanide complexes (GdIII and EuIII) based on a DOTA-TEMPO platform for redox monitoring via relaxivity

Three lanthanide complexes (Ln=Gd, Eu) based on a DO3 A ([Ln(L₁)]) or DO2 A ([Ln(L_2–3)]⁺) platform appended by a redox active TEMPO‐based arm were prepared. Complex [Ln(L₂)]⁺ shows an alkyne arm, offering the possibility of postfunctionalization by click reaction to yield [Ln(L₃)]⁺. The complexes demonstrate a redox response whereby the hydroxylamine, nitroxide and oxoammonium forms of the arm can be obtained in turn. Luminescence measurements on the europium complexes support an octadentate (L₁, L₃) or heptadentate (L₂) chelation by the ligand, with one water molecule in the inner coordination sphere. The relaxivity was determined from 20 kHz to 30 MHz by fast‐field cycling NMR. The three Gd^III complexes under their hydroxylamine form [Gd(L₁)] and [Gd(L_2–3)]⁺ show r₁ values of 7.0, 5.1 and 5.0 mM⁻¹ s⁻¹ (30 KHz), which increase to 8.8, 5.5 and 6.1 mM⁻¹ s⁻¹ in the nitroxide form. The radical complexes are not toxic against M21 cell lines, at least up to 40 μM. By using EPR spectroscopy we establish that they do not penetrate the cells with the exception of [Eu(L₂)]⁺.

Naked-Eye Detection of Hydrogen Peroxide on Photoluminescent Paper Discs

We have developed a turn-on photoluminescence protocol to detect hydrogen peroxide (H₂O₂) utilizing a supramolecular hydrogel as a sensing platform. Hydrogen peroxide is widely used in formulations, starting from healthcare products to explosives. It is also known to induce deleterious health effects at its irregular physiological concentration and considered as a biomarker in various disease conditions. We designed molecule 2, which releases the Tb³⁺ sensitizer biphenyl-4-carboxylic acid (1) upon unmasking by hydrogen peroxide. This chemistry led us to develop a sensitive photoluminescence assay for H₂O₂ through the 1-induced photoluminescence of terbium (Tb³⁺) in a hydrogel matrix. Paper discs (0.45 cm) were coated with the soft hydrogel to make the sensing process simple and cost-effective. The green luminescence from the paper discs, observed under a UV lamp, allowed naked-eye detection of H₂O₂ in the micromolar level without any sophisticated instrumentation. Image processing software or a plate reader can be used for the accurate quantification of the analyte in micromolar and nanomolar ranges. Several commercial hand sanitizers containing hydrogen peroxide were tested by this method. The results indicated that this low-cost system could be practically adopted, especially in resource-limited areas, to quantify/detect H₂O₂ for quality control purposes or other applications.

Molecular Probes for Autofluorescence-Free Optical Imaging

Optical imaging is an indispensable tool in clinical diagnostics and fundamental biomedical research. Autofluorescence-free optical imaging, which eliminates real-time optical excitation to minimize background noise, enables clear visualization of biological architecture and physiopathological events deep within living subjects. Molecular probes especially developed for autofluorescence-free optical imaging have been proven to remarkably improve the imaging sensitivity, penetration depth, target specificity, and multiplexing capability. In this Review, we focus on the advancements of autofluorescence-free molecular probes through the lens of particular molecular or photophysical mechanisms that produce long-lasting luminescence after the cessation of light excitation. The versatile design strategies of these molecular probes are discussed along with a broad range of biological applications. Finally, challenges and perspectives are discussed to further advance the next-generation autofluorescence-free molecular probes for in vivo imaging and in vitro biosensors.

Hydrogen Peroxide-Triggered Conversion of Boronic Acid-Appended Insulin into Insulin and Its Application as a Glucose-Responsive Insulin Formulation

p-Boronophenylmethoxycarbonyl (BPmoc) is a protecting group for amines that is removable by treatment with hydrogen peroxide (H₂O₂). We prepared BPmoc-modified insulin (BPmoc-Ins) and subcutaneously injected the formulation into diabetic rats. The results demonstrated that BPmoc effectively sealed the blood glucose (Glc)-lowering effects of Ins. Conversely, coinjection of BPmoc-Ins and Glc oxidase (GOx) resulted in reduced blood Glc levels, indicating that Ins was generated from BPmoc-Ins through the following reactions: oxidation of endogenous Glc by GOx; production of H₂O₂ accompanied by Glc oxidation; removal of BPmoc residues by H₂O₂. These results show the potential of BPmoc-Ins for a Glc-responsive Ins release system.

Luminescent lanthanide complexes for reactive oxygen species biosensing and possible application in Alzheimer's diseases

Histopathological hallmarks of Alzheimer's disease (AD) are intracellular neurofibrillary tangles and extracellular formation of senile plaques composed of the aggregated amyloid-beta peptide along with metal ions (copper, iron or zinc). In addition, oxidative stress is considered as an important factor in the etiology of AD and a multitude of metalloproteins and transporters is affected, leading to metal ion misregulation. Redox-active metal ions (e.g., copper) can catalyze the production of reactive oxygen species (ROS) in the presence of molecular oxygen and a reductant such as ascorbate. The ROS thus produced, in particular the hydroxyl radical which is the most reactive one, may contribute to oxidative stress conditions. Thus, detecting ROS in vivo or in biological models of AD is of interest for better understanding AD etiology. The use of biocompatible and highly specific and sensitive probes is needed for such a purpose, since ROS are transient species whose steady-state concentrations are very low. Luminescent lanthanide complexes are sensitive probes that can meet these criteria. The present review focuses on the recent advances in the use of luminescent lanthanide complexes for ROS biosensing. It shows why the use of luminescent lanthanide complexes is of particular interest for selectively detecting ROS ( O 2 · - , HO^• , ¹ O₂ , H₂ O₂ , etc.) in biological samples in the µM-nM range. It particularly focuses on the most recent strategies and discusses what could be expected with the use of luminescent lanthanide complexes for better understanding some of the molecular mechanisms underlying the development of Alzheimer's disease.

Real-Time Evaluation of Hydrogen Peroxide Injuries in Pulmonary Fibrosis Mice Models with a Mitochondria-Targeted Near-Infrared Fluorescent Probe

Pulmonary fibrosis is a fatal chronic lung disease, leading to poor prognosis and high mortality. Accumulating evidence suggests that oxidative stress characterized by excessive production of hydrogen peroxide (H₂O₂) is an important molecular mechanism causing pulmonary fibrosis. We conceive a new type of mitochondria-targeted near-infrared fluorescent probe Mito-Bor to investigate changes in the level of endogenous H₂O₂ in living cells and mice models with pulmonary fibrosis. In the design strategy of the Mito-Bor probe, we selected azo-BODIPY as the fluorophore owing to its near-infrared fluorescence, strong photochemical stability, and low biological toxicity. Under physiological conditions, the response moiety 4-bromomethylphenylboronic acid pinacol ester could easily detect H₂O₂, and turn the fluorescence switch on. The modification of the lipophilic triphenylphosphine cation on the fluorophore would allow the probe to easily pass through the phospholipid bilayer of cells, and the internal positive charge could contribute to the selectivity of the mitochondria accumulation. The Mito-Bor probe provides high selectivity, low limit of detection, high biocompatibility, and excellent photostability. It can be used to detect changes in the level of H₂O₂ in living cells and in vivo. Therefore, the probe is applied to investigate the fluctuation of the H₂O₂ level during the process of inducing pulmonary fibrosis in cells, with changes in its fluorescence intensity correlating with the concentration of H₂O₂ and indicating the level of oxidative stress in fibroblasts. Conversely, pulmonary fibrosis can be modulated by adjusting the level of H₂O₂ in cells. A further study in mice models of bleomycin-induced pulmonary fibrosis confirms that NADPH oxidase 4 (NOX4) acts as a "button" to regulate H₂O₂ levels. The direct inhibition of NOX4 can significantly reduce the level of H₂O₂, which can delay the progression of lung fibrosis. These results provide an innovative way for the clinical treatment of pulmonary fibrosis.

Chemosensing of neurotransmitters with selectivity and naked eye detection of l-DOPA based on fluorescent Zn(ii)-terpyridine bearing boronic acid complexes

A new range of fluorescent Zn(ii)-terpyridine complexes are described and studied in-depth as chemosensors for catecholamine-based neurotransmitters in pure water.

Boronate-Based Probes for Biological Oxidants: A Novel Class of Molecular Tools for Redox Biology

Boronate-based molecular probes are emerging as one of the most effective tools for detection and quantitation of peroxynitrite and hydroperoxides. This review discusses the chemical reactivity of boronate compounds in the context of their use for detection of biological oxidants, and presents examples of the practical use of those probes in selected chemical, enzymatic, and biological systems. The particular reactivity of boronates toward nucleophilic oxidants makes them a distinct class of probes for redox biology studies. We focus on the recent progress in the design and application of boronate-based probes in redox studies and perspectives for further developments.

Emerging Multifunctional Single-Atom Catalysts/Nanozymes

Single-atom catalysts (SACs), in which the metal active sites are isolated on the support and stabilized by coordinated atoms such as oxygen, nitrogen, sulfur, etc., represent the maximum usage efficiency of the metal atoms. Benefiting from the recent progress in synthetic strategies, characterization methods, and computational models, many SACs that deliver an impressive catalytic performance for a variety of reactions have been developed. The catalytic selectivity and activity are critical issues that need to be optimized and augmented in the areas of nanotechnology and biomedicine. This review summarizes some recent experimental and theoretical progress aimed at clarifying the structure of SACs and how they influence the catalytic performance. The examples described here elaborate on the utility of SACs and highlight the strengths of these catalysts in the applications of biomedicine, environmental protection, and energy conversion. Finally, some current challenges and future perspectives for SACs are also discussed.

Activity-Based Sensing: A Synthetic Methods Approach for Selective Molecular Imaging and Beyond

Emerging from the origins of supramolecular chemistry and the development of selective chemical receptors that rely on lock-and-key binding, activity-based sensing (ABS)-which utilizes molecular reactivity rather than molecular recognition for analyte detection-has rapidly grown into a distinct field to investigate the production and regulation of chemical species that mediate biological signaling and stress pathways, particularly metal ions and small molecules. Chemical reactions exploit the diverse chemical reactivity of biological species to enable the development of selective and sensitive synthetic methods to decipher their contributions within complex living environments. The broad utility of this reaction-driven approach facilitates application to imaging platforms ranging from fluorescence, luminescence, photoacoustic, magnetic resonance, and positron emission tomography modalities. ABS methods are also being expanded to other fields, such as drug and materials discovery.

Responsive Metal Complex Probes for Time-Gated Luminescence Biosensing and Imaging

The development of reliable bioanalytical probes for selective and sensitive detection of particular analytes in biological systems is essential for better understanding the roles of the analytes in their native contexts. In the last two decades, luminescent metal complexes have greatly contributed to the development of such probes for biosensing and imaging due to their unique spectral and temporal properties, controllable cell membrane permeability, and cytotoxicity. Conjugating an analyte-activatable moiety to the metal complex luminophores allows the production of responsive metal complex probes for this analyte detection. Owing to their long-lifetime emissions, the responsive metal complex probes are accessible to the technique of time-gated luminescence (TGL) detection and imaging. With a delay time after pulsed excitation, the TGL technique allows for collection of only long-lived luminescence from responsive metal complex probes, while filtering out short-lived background autofluorescence, providing a background-free approach for the detection and imaging of the analyte at subcellular and/or molecular levels. Responsive metal complex probes, therefore, have emerged as complementary sensing and imaging tools of organic dye-based fluorescent probes for the in situ detection of analytes in complicated biological environments.In this Account, we describe the advances in the development of metal complex probes and their applications for TGL bioassays with particular focus on our efforts made in this field. We first introduce the photophysical/-chemical properties of luminescent metal complexes, including lanthanide (europium and terbium) and transition metal (ruthenium and iridium) complexes. The luminescence lifetimes (τ) of lanthanide and transition metal complexes are at micro/millisecond (μs/ms) and hundreds/thousands nanosecond (ns) levels, respectively. The emission lifetimes are significantly longer than the autofluorescence lifetime (τ < 10 ns) of biological samples. Such long-lived luminescence of these metal complexes enables our research on demonstrating responsive probes for background-free TGL detection of some reactive biomolecules, such as reactive oxygen/nitrogen species (ROS/RNS) and biothiols.We conclude this Account by outlining the future directions to further develop new generation responsive TGL probes for promoting their practical applications. The responsive TGL probes are expected to be translated for biomedical and/or (pre)clinical investigations of biomolecules in situ. Reversibility, lower toxicity, ability of excitation at longer wavelength, and potential to be translated are key criteria for the development of next-generation probes. We also anticipate that further development of responsive TGL probes will contribute to the bioassay in more challenging biological systems, such as plants that have significant higher background autofluorescence than animals.

Structural and spectroscopic investigations of nine-coordinate redox active lanthanide complexes with a pincer O,N,O ligand

The lanthanide complexes EuL3, GdL3, YbL3 and LuL3 of the N,N'-bis(2-hydroxy-di-3,5-tert-butylphenyl)amine were prepared. The X-Ray crystal structures of GdL3 and LuL3 demonstrated a nine-coordinate sphere with three ligand molecules under their anionic diamagnetic form (Cat-N-BQ)-. The complexes showed three oxidation events (Eox11/2 = 0.15-0.16 V, E1/22 = 0.51-55 V, and E1/23 = 0.75-0.78 V vs. Fc+/Fc) via cyclic voltammetry, corresponding to the successive oxidation of the aminophenolate moeities to iminosemiquinone species. The complexes GdL3 and YbL3 were characterized by EPR spectroscopy, allowing for the determination of the zero field splitting (ZFS) parameters in the first case. The monocations (LnL3)+ and monoanions (LnL3)- were electrochemically generated (Ln = Eu, Gd, Yb, Lu), as well as the dications YbL32+ and LuL32+. The spins are antiferromagnetically exchange coupled in the diradical species LuL32+ (|D| = 260 MHz, E = 0). All the complexes (incl. neutral) possess a strong absorption band in the NIR region (730-840 nm, ε > 19 mM-1 cm-1) corresponding to ligand-based transitions.

HOCl Responsive Lanthanide Complexes Using Hydroquinone Caging Units

Redox biology is still looking for tools to monitor redox potential in cellular biology and, despite a large and sustained effort, reliable molecular probes have yet to emerge. In contrast, molecular probes for reactive oxygen and nitrogen have been widely explored. In this manuscript, three kinetically inert lanthanide complexes that selectively react with hypochlorous acid are prepared and characterized. The design is based on 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) and 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (DO2A) ligands appended with one or two redox active hydroquinone derived arms, thereby forming octadentate ligands ideally suited to complex trivalent lanthanide ions. The three complexes are found to react selectively with hypochlorous acid to form highly symmetric lanthanide(III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacedic acid (DOTA) complexes. The conversion of the probe to [Ln.DOTA]- is followed by luminescence, absorption, and NMR spectroscopy in a model system comprised of a Triton-X modified HEPES buffer. It was concluded that the design principle works, and that simple caging units like hydroquinones can work well in conjugation with lanthanide(III) complexes.

Tracking isotopically labeled oxidants using boronate-based redox probes

Reactive oxygen and nitrogen species have been implicated in many biological processes and diseases, including immune responses, cardiovascular dysfunction, neurodegeneration, and cancer. These chemical species are short-lived in biological settings, and detecting them in these conditions and diseases requires the use of molecular probes that form stable, easily detectable, products. The chemical mechanisms and limitations of many of the currently used probes are not well-understood, hampering their effective applications. Boronates have emerged as a class of probes for the detection of nucleophilic two-electron oxidants. Here, we report the results of an oxygen-18-labeling MS study to identify the origin of oxygen atoms in the oxidation products of phenylboronate targeted to mitochondria. We demonstrate that boronate oxidation by hydrogen peroxide, peroxymonocarbonate, hypochlorite, or peroxynitrite involves the incorporation of oxygen atoms from these oxidants. We therefore conclude that boronates can be used as probes to track isotopically labeled oxidants. This suggests that the detection of specific products formed from these redox probes could enable precise identification of oxidants formed in biological systems. We discuss the implications of these results for understanding the mechanism of conversion of the boronate-based redox probes to oxidant-specific products.

Luminescent pro-nitroxide lanthanide complexes for the detection of reactive oxygen species

A DOTA-based ligand appended with a pro-nitroxide moiety has been chelated to trivalent Eu and Yb, giving luminescent complexes. Under Fenton conditions both are converted into iminonitroxide and subsequently nitronyl nitroxide complexes.

Theoretical study of lanthanide-based in vivo luminescent probes for detecting hydrogen peroxide

The 4f-4f emissions from lanthanide trication (Ln³⁺ ) complexes are widely used in bioimaging probes. The emission intensity from Ln³⁺ depends on the surroundings, and thus, the design of appropriate photo-antenna ligands is indispensable. In this study, we focus on two probes for detecting hydrogen peroxide, for which emission intensities from Tb³⁺ are enhanced chemo-selectively by the H₂ O₂ -mediated oxidation of ligands. To understand the mechanism, the Gibbs free energy profiles of the ground and excited states related to emission and quenching are computed by combining our approximation-called the energy shift method-and density functional theory. The different emission intensities are mainly attributed to different activation barriers for excitation energy transfer from the ligand-centered triplet (T1) to the Tb³⁺ -centered excited state. Additionally, quenching from T1 to the ground state via intersystem crossing was inhibited by intramolecular hydrogen bonds only in the highly emissive Tb³⁺ complexes. © 2018 Wiley Periodicals, Inc.

Selectively light-up hydrogen peroxide in hypoxic cancer cells with a novel fluorescent probe

A novel fluorescent turn-on probe (HCyHP) was developed in a simple two-step synthesis for monitoring of exogenous and endogenous H2O2 levels in biological samples and hypoxic cancer diagnosis.

Boronic acids as building blocks for the construction of therapeutically useful bioconjugates

This review summarizes boronic acid's contribution to the development of bioconjugates with a particular focus on the molecular mechanisms underlying its role in the construction and function of the bioconjugate, namely as a bioconjugation warhead, as a payload and as part of a bioconjugate linker.

Recent development of boronic acid-based fluorescent sensors

As Lewis acids, boronic acids can bind with 1,2- or 1,3-diols in aqueous solution reversibly and covalently to form five or six cyclic esters, thus resulting in significant fluorescence changes. Based on this phenomenon, boronic acid compounds have been well developed as sensors to recognize carbohydrates or other substances. Several reviews in this area have been reported before, however, novel boronic acid-based fluorescent sensors have emerged in large numbers in recent years. This paper reviews new boron-based sensors from the last five years that can detect carbohydrates such as glucose, ribose and sialyl Lewis A/X, and other substances including catecholamines, reactive oxygen species, and ionic compounds. And emerging electrochemically related fluorescent sensors and functionalized boronic acid as new materials including nanoparticles, smart polymer gels, and quantum dots were also involved. By summarizing and discussing these newly developed sensors, we expect new inspiration in the design of boronic acid-based fluorescent sensors.

As Lewis acids, boronic acids can bind with 1,2- or 1,3-diols in aqueous solution reversibly and covalently to form five or six cyclic esters, thus resulting in significant fluorescence changes.

Tracking mitochondrial 1O2-ROS production through a differential mitochondria-nucleoli fluorescent probe

A dual-emissive fluorescent probe enabled unique tracking of ¹O₂-ROS species through a differential mitochondrial–nucleoli localization dynamic.

A redox active switch for lanthanide luminescence in phenolate complexes

The reversible oxidation of coordinated phenolates into phenoxyl radicals results in a dramatic quenching (>95%) of the luminescence of the f metal ion.

Alcohol, Aldehyde, and Ketone Liberation and Intracellular Cargo Release through Peroxide-Mediated α-Boryl Ether Fragmentation

α-Boryl ethers, carbonates, and acetals, readily prepared from the corresponding alcohols that are accessed through ketone diboration, react rapidly with hydrogen peroxide to release alcohols, aldehydes, and ketones through the collapse of hemiacetal intermediates. Experiments with α-boryl acetals containing a latent fluorophore clearly demonstrate that cargo can be released inside cells in the presence of exogenous or endogenous hydrogen peroxide. These experiments show that this protocol can be used for drug activation in an oxidative environment without generating toxic byproducts.

Physical, Chemical, and Biological Structures based on ROS-Sensitive Moieties that are Able to Respond to Oxidative Microenvironments

Reactive oxygen species (ROS) (H2 O2 , OCl(-) , (•) OH, O2 (-) ) are a family of reactive molecules that are generated intracellularly and are engaged in many biological processes. In physiological concentrations, ROS act as signaling molecules to a number of metabolic pathways; however, in excess they can be harmful to living organisms. Overproduction of ROS has been related to many pathophysiological conditions and a number of studies have been reported in elucidating their mechanism in these conditions. With the aim of harnessing this role, a number of imaging tools and therapeutic compounds have been developed. Here these imaging and therapeutic tools are reviewed and particularly those structures with ROS-sensitivity based on their biomedical applications and their functional groups. There is also a brief discussion about the method of preparation as well as the mechanism of action.

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.

A CoII complex for 19F MRI-based detection of reactive oxygen species

A fluorinated, cobalt(ii)-based ¹⁹F MRI imaging agent switches from a paramagnetic high spin Co^II state to a diamagnetic low spin Co^III state following oxidation by H₂O₂ and other reactive oxygen species, resulting in a turn-on response via both ¹⁹F NMR and MRI.

An extremely rapid-response fluorescent probe for hydrogen peroxide and its application in living cells

An extremely rapid-response fluorescent probe for H₂O₂was constructed for monitoring the H₂O₂levels in biological processes.

Luminescent lanthanide nanomaterials: an emerging tool for theranostic applications

Lanthanide materials have been gaining popularity for use in various theranostic applications, primarily due to their unique optical properties such as narrow emission bands, multiple emission wavelengths, emission tunability, long fluorescence lifetime and large Stokes shift. Apart from these, some lanthanide materials also exhibit magnetic and light-up conversion properties. Such nanomaterials have been used for a wide range of applications ranging from detection of biomarkers, in vitro and in vivo imaging to therapeutic applications. Recently, combined modalities of lanthanide nanomaterials for simultaneous detection/imaging and delivery of therapeutic agents (termed ‘theranostics’) have been explored. The various advantages and disadvantages of using lanthanide nanomaterials as theranostic agents and potential areas for future development have been discussed in this review.

A lanthanide based sensor for the time-gated detection of hydrogen sulfide

A kinetically stable Eu(III) complex for the detection of sulfide in water is reported. The probe shows excellent selectivity and fast reaction time. Its long-lived luminescence makes this the first probe for the time-gated detection of sulfide in complex biological samples.