Fluorescent glutathione probe based on MnO 2 -phenol formaldehyde resin nanocomposite

Nanozyme-mediated ratiometric fluorescence hydrogel for on-site detection of sulfite in food

In this work, a ratiometric fluorescence hydrogel nanosensor was developed by integrating a composite consisting of o-phenylenediamine (OPD), manganese dioxide nanoflakes (MnO2 NFs), and N-doped carbon dots (N-CDs) into an agarose hydrogel for sulfite detection. MnO2 NFs demonstrated intense oxidase-like activity, facilitating the conversion of non-fluorescent OPD into yellow-emissive 2,3-diaminophenazine (DAP). As a result, a significant emission peak belongs to DAP, alongside the fluorescence quenching of N-CDs through FRET. Upon interaction with sulfite, MnO2 NFs lost their oxidase-like function. This process decreased the fluorescence of DAP and restored the blue fluorescence of N-CDs, producing a typical ratiometric response, ranging from 3 nM ∼ 400 μM, with a detection limit (LOD) of 3.79 nM. Employing a smartphone, the fluorescence color change demonstrated by the hydrogel sensor was translated into quantitative data (LOD: 8.44 nM). This hydrogel sensor offers an affordable, portable, and user-friendly solution for sulfite detection and food safety monitoring.

MnO2-mineralized milk exosomes as a novel nanoplatform for glutathione detection

Exosomes have garnered significant attention in the realms of disease diagnosis and therapeutics, owing to their remarkable biocompatibility. While engineered exosomes have the potential to augment delivery efficiency, targeting specificity, and circulation longevity, the intricacies of sample preparation have often hindered their broader application. In this pioneering study, we introduce a novel nanoplatform by leveraging surface manganese dioxide (MnO2) mineralization of milk exosomes. This innovative technique not only amplifies the inherent properties of exosomes but also endows them with additional functionalities, transforming them into a multifaceted tool for disease detection and therapeutic intervention. To expand the application of MnO2@milk exosomes, milk exosomes were stained with lipophilic molecules (curcumin) to prepare MnO2@mEVs-curcumin (MEC). The prepared nanocomposite was employed to detect GSH in cancer cells. By integrating exosome engineering with surface mineralization, we have paved the way for the creation of advanced biomaterials.

In-situ synthesis of 2D nanozymes-coated cellulose nanofibers on paper-based chips for portable detection of biothiols

BACKGROUND

Simple, fast and low-cost paper-based analytical devices (PADs) have a good application prospect for point-of-care detection of GSH. However, effective immobilization of functional nanomaterials onto cellulose, as a critical factor in the construction of PADs, presents numerous difficulties and challenges.

RESULTS

In this study, we have developed an exceptionally straightforward and environmentally friendly synthetic approach by using ovalbumin (OVA) as a bio-mineralization template for the preparation of MnO2 nanosheets. The MnO2 nanosheets produced in the solution phase exhibited excellent intrinsic nano-enzyme activity and biodegradability. The OVA-MnO2 nanosheets can effectively oxidize Amplex red in the absence of H2O2, enabling sensitive detection of GSH with a linear range of 5 nM-10 μM and a detection limit as low as 2.8 nM. Furthermore, we utilized this method to facilitate in situ synthesis of OVA-MnO2 nanosheets directly on paper substrates. This approach eliminates the need for conventional stirring and centrifugation steps, greatly simplifying the fabrication process while reducing material usage and time expenditure. Characterization of the chemical composition and morphology confirmed the intimate growth of the 2D nano-enzymes on the cellulose fibers. Utilizing smartphone capabilities, the OVA-MnO2 nanosheet-modified PAD enabled instrument-free detection of GSH, demonstrating high sensitivity (0.74 μM) and a wide linear response range (1-1000 μM).

SIGNIFICANCE

The synthesis of MnO2 nanosheets directly on cellulose substrates substantially streamlines the modification workflow of PADs and reduces detection costs, offering new avenues for clinical diagnostics of relevant diseases.

A dual-mode ratiometric probe using europium-doped cyclen-functional carbon dots for fluorescent and point-of-care detection of tetracycline

The overuse of tetracycline (TC) has led to the accumulation of antibiotic residues in drinking water and animal products, which can consequently lead to bacteria resistance and chronic disease in humans. Urgently addressing the need for a rapid, user-friendly, and point-of-care test for TC detection. In this work, we use cyclen and citric acid to synthesise carbon dots (CDs) with a unique ring-shaped structure on their surface and combine them with europium (Eu3+) to form an Eu-CDs fluorescent probe. In the presence of TC in aqueous systems, the Eu-CDs probe emits two distinctive fluorescent signals: the stable blue emission from cyclen-modified CDs and the red emission from Eu3+,showing a proportional increase with TC concentration. The developed Eu-CDs probe demonstrates accurate and selective detection capabilities for TC class antibiotics among various interfering factors. The Eu-CDs probe exhibits excellent linearity within the concentration range of 0.04-2.4 µM and achieves an impressive detection limit of 2.7 nM. Moreover, point-of-care Eu-CDs test strips are designed, allowing convenient on-site TC analysis through the detection of a colour change from blue to red under a portable UV light. The results highlight the effectiveness of the proposed dual-mode ratiometric fluorescent Eu-CDs probe and test strips, offering a practical point-of-care testing strategy for real-world TC detection applications.

A Sensitive and Quick Fluorescent Sensor for the "Turn-On" Detection and Imaging of Glutathione Based on Sulfur Quantum Dots and MnO2 Nanosheets

Glutathione (GSH) is one of the most abundant bioethanol antioxidants in living cells. Here, a fluorescent probe based on MnO2 nanosheets and sulfur quantum dots (SQDs) was fabricated. Because of the synergistic effect of IFE and FRET, the fluorescence from SQDs was quenched by MnO2 nanosheets. In the presence of GSH, the fluorescence of SQDs could be recovered because of the reduction of MnO2 nanosheets by GSH. The method can detect GSH in the concentration range of 5 ~ 1000 μM with the detection limit as low as 1.26 μM. This quick, easy, and cost-effective sensor could be used for the quantification of GSH in serum samples and the imaging of GSH in Escherichia coli O157:H7.

Multi-deformable interpenetrating network thermosensitive hydrogel fluorescent device for real-time and visual detection of nitrite

Functionalized thermosensitive hydrogel materials exhibit excellent properties for the fabrication of sensing devices that enable real-time visual detection of food safety duo to their good plasticity and powerful loading capacity. Here, a ratiometric fluorescent device based on an interpenetrating network (IPN) thermosensitive hydrogel was designed to embed functionalized Au nanoclusters (Au NCs) and Blue Carbon dots (BCDs) composites in a multi-network structure to build a sensitive hazardous material nitrite (NO2-) chemsensor. The hydrogel was utilized poloxamer 407 (P407), lignin and cellulose to form stable IPN structure, which resulted in complementation and synergy, thereby strengthening its porous network structure. The combination of fluorescent nanoprobes with the porous network structure has the potential to enhance stable fluorescence signals and improve sensing sensitivity. Moreover, the thermosensitive liquid-solid transition characteristics of the hydrogel facilitate its preparation into diverse sensing devices following curing at room temperature. The hydrogel device, when combined with a smartphone system, converted image information into data information, thereby enabling the accurate quantification of NO2- with a detection limit of 9.38 nM in 2 s. The designed multi-functional hydrogel device is capable of real-time differentiation of NO2- dosage with the naked eye, offering a high-contrast, rapid-response sensing methodology for visual assessment of food freshness. This research contributes to the expansion of hydrogel materials applications and the detection of hazardous materials in food safety.

A Chitosan-Based Fluorescent Probe Combined with Smartphone Technology for the Detection of Hypochlorite in Pure Water

Using chitosan as a raw material, 1,8-naphthimide as the fluorescent chromophore, and sulfur-containing compounds as the recognition groups, a novel naphthimide-functionalized chitosan probe, CS-BNS, for the detection of ClO- was successfully synthesized. The modification of chitosan was verified by SEM, XRD, FTIR, mapping, 13C-NMR, TG and the structure of the probe molecule was characterized. The identification performance of the probes was studied using UV and fluorescence spectrophotometers. The results show that CS-BNS exhibits a specific response to ClO- based on the oxidative reaction of ClO- to the recognition motifs, as well as a good resistance to interference. And the probe has high sensitivity and fast response time, and can complete the detection of ClO- in a pure water system within 60 s. The probe can also quantify ClO- (y = 30.698x + 532.37, R2 = 0.9833) with a detection limit as low as 0.27 μM. In addition, the combination of the probe with smartphone technology enables the visualization and real-time monitoring of ClO-. Moreover, an identification system for ClO- was established by combining the probe with smartphone technology, which realized the visualization and real-time monitoring of ClO-.

Covalent organic framework-MnO2 nanoparticle composites for shape-selective sensing of bithiols

Covalent organic frameworks (COFs) for detecting biological macromolecules in water or biological environments are generally challenging. In this work, a composite material IEP-MnO₂ is obtained by combining manganese dioxide (MnO₂) nanocrystals and a fluorescent COF (IEP), which is synthesized by using 2,4,6-tris(4-aminophenyl)-s-triazine and 2,5-dimethoxyterephthalaldehyde. By the addition of biothiols, such as glutathione, cysteine or homocysteine with different sizes, the fluorescence emission spectra of IEP-MnO₂ changed ("turn-on" or "turn-off") via different mechanisms. The fluorescence emission of IEP-MnO₂ increased in the presence of GSH by the elimination of the FRET (Förster resonance energy transfer) effect between MnO₂ and IEP. Surprisingly, due to the formation of a hydrogen bond between Cys/Hcy and IEP, the fluorescence quenching for IEP-MnO₂ + Cys/Hcy may be explained via the photoelectron transfer (PET) process, which endows IEP-MnO₂ with specificity in distinguishing the detection of GSH and Cys/Hcy compared to other MnO₂ complex materials. Therefore, IEP-MnO₂ was used to detect GSH and Cys in human whole blood and serum, respectively. The limit of detection for GSH in whole blood and Cys in human serum was calculated to be 25.58 μM and 4.43 μM, which indicates that IEP-MnO₂ can be used to investigate some diseases related to GSH and Cys concentration. Moreover, the research expands the application of covalent organic frameworks in the fluorescence sensing field.

Tetrabutylammonium-chloride-glycerol of deep eutectic solvent functionalized MnO2: a novel mimic enzyme for the quantitative and qualitative colorimetric detection of L-cysteine

L-Cysteine is a common amino acid that plays an important role in human livelihood and production. Therefore, a novel method for the simultaneous quantitative and qualitative determination of L-cysteine by a colorimetric detection system is proposed. As a viable oxidase mimic, [N₄₄₄₄]Cl-G/MnO₂, which consisted of MnO₂ nanosheets functionalized by a tetrabutylammonium chloride-glycerol ([N₄₄₄₄]Cl-G) based deep eutectic solvent (DES) was fabricated. Owing to the oxidation of MnO₂ nanosheets, [N₄₄₄₄]Cl-G/MnO₂ could oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (oxTMB) with the characteristic UV-vis spectrum absorbance at 652 nm. The oxidation of TMB by DES/MnO₂ was inhibited when L-cysteine was introduced, and the absorbance decreased proportionally with the increase in L-cysteine concentration. Due to this inhibition effect, a colorimetric detection system ([N₄₄₄₄]Cl-G/MnO₂-TMB) was developed for the quantitative determination of L-cysteine. Under optimal conditions, the assay showed good linearity over the concentration range of 0.125-2.00 μg mL^-1 with a low detection limit of 5.96 ng mL^-1. A study of the inhibition mechanism demonstrated that the sulfhydryl group of L-cysteine could decompose [N₄₄₄₄]Cl-G/MnO₂ into Mn²⁺, thus limiting the conversion of TMB to oxTMB. In addition, the [N₄₄₄₄]Cl-G/MnO₂-TMB system was used in test strips for the visual qualitative detection of L-cysteine. The selectivity and test strip results demonstrated the high selectivity, simple operation, and rapid response of the [N₄₄₄₄]Cl-G/MnO₂-TMB system for the qualitative detection of L-cysteine. Given the satisfying performance of the detection strategy, colorimetric sensing based on the [N₄₄₄₄]Cl-G/MnO₂-TMB system is considered to have prospective application value in the quantitative and qualitative detection of L-cysteine.

Progress on two-dimensional binary oxide materials

Two-dimensional van der Waals (2D vdW) materials have attracted much attention because of their unique electronic and optical properties. Since the successful isolation of graphene in 2004, many interesting 2D materials have emerged, including elemental olefins (silicene, germanene, etc.), transition metal chalcogenides, transition metal carbides (nitrides), hexagonal boron, etc. On the other hand, 2D binary oxide materials are an important group in the 2D family owing to their high structural diversity, low cost, high stability, and strong adjustability. This review systematically summarizes the research progress on 2D binary oxide materials. We discuss their composition and structure in terms of vdW and non-vdW categories in detail, followed by a discussion of their synthesis methods. In particular, we focus on strategies to tailor the properties of 2D oxides and their emerging applications in different fields. Finally, the challenges and future developments of 2D binary oxides are provided.

A novel artificial peroxisome candidate based on nanozyme with excellent catalytic performance for biosensing

Artificial peroxisome is of critical importance to supersede natural peroxisome in fabricating protocell system and disease treatment. Nevertheless, developing feasible artificial peroxisome with various stable functions remains a monumental challenge. Nanozyme with multiple enzyme-like activities can mimic natural enzymes in peroxisome, which make it a prospective candidate for artificial peroxisome design. Herein, we prepared a nanozyme with multiple peroxisomal-like activities - Pd nanoparticles functionalized nitrogen-doped porous carbon-reduced graphene oxide (PdNPs/N-PC-rGO). Due to its sandwich-like structure, the incorporation of N heteroatoms and the synergistic effect between PdNPs and N-PC-rGO bi-support, the PdNPs/N-PC-rGO exhibited triple peroxisomal-like activities including oxidase (OXD), peroxidase (POD) and catalase (CAT), leading it a promising alternative for artificial peroxisome exploration. Furthermore, the PdNPs/N-PC-rGO showed high electrocatalytic activity, which could be employed for the detection of electrochemical active substances reduced glutathione (GSH). The PdNPs/N-PC-rGO modified electrode displayed a wide concentration range from 70 nM to 1500 μM, with a very low detection limit of 9.8 nM (S/N = 3). Therefore, PdNPs/N-PC-rGO was a promising nanozyme for various biotechnological applications such as artificial organelles, biosensing, cytoprotection, disease diagnosis and treatment.

Black titanium dioxide@manganese dioxide for glutathione-responsive MR imaging and enhanced photothermal therapy

Multifunctional nanoprobes with tumor microenvironment response are playing important roles in highly efficient theranostics of cancers. Herein, a kind of theranostic nanoprobe was synthesized by coating manganese dioxide (MnO₂) on the surface of black commercial P25 titanium dioxide (b-P25). The resultant nanoprobe (b-P25@MnO₂) possessed glutathione (GSH)-responsive magnetic resonance (MR) imaging and enhanced photothermal therapy (PTT). In tumor microenvironments, the excessive GSH was consumed by reacting with MnO₂ to generate Mn²⁺ for GSH-responsive MR imaging, in which the longitudinal relaxation rate of b-P25@MnO₂ was up to 30.44 mM^-1 s^-1, showing excellent cellular and intratumoral MR imaging. Moreover, the prepared b-P25@MnO₂ exhibited stable and strong photothermal conversion capability with a high photothermal conversion efficiency of 30.67%, by which the 4T1 tumors disappeared completely, indicating safe and highly efficient PTT performance. The current work developed GSH-responsive b-P25@MnO₂ nanoprobes, demonstrated for MR imaging and enhanced PTT in cancers.

A dual-response ratiometric fluorescent sensor by europium-doped CdTe quantum dots for visual and colorimetric detection of tetracycline

Residues in animal food and drinking water caused by the abuse of antibiotics lead to cell resistance and many chronic diseases in the human body. Therefore, it has become an inevitable trend to develop a fast, easy-to-use, on-site/real-time visualization method for the detection of antibiotics. Herein, we report a dual-response ratiometric fluorescence sensor which is fabricated by chelating europium ions (Eu³⁺) onto cadmium telluride quantum dots (CdTe QDs) for real-time and visible detection of tetracycline (TC). With the TC addition, the fluorescence of probe can be seen by the naked eye, from green to yellow and finally to red, exhibiting a dosage-sensitive and broad-chromatic detection strategy for TC. The fluorescence intensity ratio of I₆₁₆/I₅₁₂ of Eu/CdTe QDs sensor displays a good linear relation to TC concentrations in the range of 0-80 μM with a limit of detection (LOD) of 2.2 nM. In addition, the sensor can visually detect 200 nM TC in actual samples, which is lower than the maximum residue limit (MRL) of the safety standard. The methodology reported here opens a window toward the real applications of fluorescent and shows the wide applicability in pursuing the concepts simple, rapid, visual, and real-time for food safety and environmental protection.

Manganese Oxide Nanomaterials: Synthesis, Properties, and Theranostic Applications

Despite the comprehensive applications in bioimaging, biosensing, drug/gene delivery, and tumor therapy of manganese oxide nanomaterials (MONs including MnO₂ , MnO, Mn₂ O₃ , Mn₃ O₄ , and MnO_x ) and their derivatives, a review article focusing on MON-based nanoplatforms has not been reported yet. Herein, the representative progresses of MONs on synthesis, heterogene, properties, surface modification, toxicity, imaging, biodetection, and therapy are mainly introduced. First, five kinds of primary synthetic methods of MONs are presented, including thermal decomposition method, exfoliation strategy, permanganates reduction method, adsorption-oxidation method, and hydro/solvothermal. Second, the preparations of hollow MONs and MON-based composite materials are summarized specially. Then, the chemical properties, surface modification, and toxicity of MONs are discussed. Next, the diagnostic applications including imaging and sensing are outlined. Finally, some representative rational designs of MONs in photodynamic therapy, photothermal therapy, chemodynamic therapy, sonodynamic therapy, radiotherapy, magnetic hyperthermia, chemotherapy, gene therapy, starvation therapy, ferroptosis, immunotherapy, and various combination therapy are highlighted.

Construction of CPs@MnO2-AgNPs as a multifunctional nanosensor for glutathione sensing and cancer theranostics

A multifunctional nanosensor of CPs@MnO₂-AgNPs was constructed for sensitive and selective sensing of GSH and cancer theranostics in this work. The CPs@MnO₂ nanocomposite was synthesized by capping MnO₂ onto carbon nanoparticles through an in situ redox reaction under ultrasonication. AgNPs with fluorescence were obtained through a silver-mirror-like reaction using BSA as both a template and reductant and further anchored onto the surface of CPs@MnO₂ through electrostatic interaction to construct the CPs@MnO₂-AgNP nanocomposite. The fluorescence of AgNPs was effectively quenched by MnO₂ through an inner filter effect and a static quenching effect and further recovered by GSH owing to the unique redox reaction between GSH and MnO₂. Therefore, a novel fluorescent turn-on nanosensor was established for GSH sensing in vitro and in vivo. For GSH sensing, a satisfactory linear range of 0.8-80 μM with a detection limit of 0.55 μM was obtained under optimal conditions. Moreover, by integrating the GSH-responsive fluorescence imaging capacity, the photothermal activity of carbon nanoparticles and the anticancer effect of AgNPs, the CPs@MnO₂-AgNP nanocomposite was successfully applied for cancer theranostics. The fluorescence recognition of cancer was achieved by overexpressing GSH in cancer, meanwhile the photothermal therapy from CPs and chemotherapy from AgNPs jointly produced an enhanced therapeutic effect. This redox-responsive nanocomposite of CPs@MnO₂-AgNPs improves the MnO₂ nanomaterial-based applications in GSH sensing and cancer theranostics.

A dual (colorimetric and fluorometric) detection scheme for glutathione and silver (I) based on the oxidase mimicking activity of MnO2 nanosheets

A fluorimetric and colorimetric method is described for the determination of glutathione (GSH) and silver (I). It is based on the use of MnO₂ nanosheets that were prepared by solution mixing and exfoliation. They display oxidase-mimicking activity and can catalyze the oxidation of o-phenylenediamine (OPD) to form yellow 2,3-diaminophenazine (DAP) with an absorption maximum at 410 nm. DAP also has a yellow fluorescence (with a peak at 560 nm). The MnO₂ nanosheets can be rapidly reduced to Mn²⁺ by GSH. This reduces the efficiency of the oxidase mimic MnO₂ and causes a decrease in fluorescence and absorbance intensity. However, on addition of Ag⁺, a complex is formed with GSH. It prevents the destruction of MnO₂ nanosheets so that the enzyme mimicking activity is retained. A dual-method for the determination of GSH and Ag(I) was developed. It has excellent sensitivity for GSH with lower detection limits of 62 nM (fluorimetric) and 0.94 μM (colorimetric). The respective data for Ag(I) are 70 nM and 1.15 μM. The assay was successfully applied to the determination of GSH and Ag(I) in spiked serum samples. Graphical abstract Schematic presentation of a method for colorimetric and fluorometric determination of glutathione (GSH) and silver(I). MnO₂ nanosheets are reduced to Mn(II) by GSH. This reduces the enzyme-mimicking activity of MnO₂ nanosheets and causes a decrease in fluorescence and absorbance. On addition of Ag(I), the enzyme-like activity is increasingly retained. A decrease in fluorescence and absorbance is not observed any longer.

Recent advances in functionalized MnO2 nanosheets for biosensing and biomedicine applications

As one kind of redox active layered transition-metal dioxide nanomaterials, single-layer manganese dioxide (MnO₂) nanosheets have gained significant research attention in the fields of biosensing and biomedicine because of their large surface area, intense and broad optical absorption, strong oxidation ability, catalytic activity, and robust mechanical properties. This review provides a brief overview of the recent advances in the development of MnO₂ nanosheet-based biosensors, bioimaging as well as drug delivery for cancer therapy. The methodologies for the preparation of MnO₂ nanosheets are summarized, followed by an introduction of the nanostructure and properties of MnO₂ nanosheets. Special attention is paid to their applications in biosensing, bioimaging and cancer therapy. Future perspectives and the challenges of high-performance MnO₂ nanosheets are also discussed.

NaYbF4@CaF2 core-satellite upconversion nanoparticles: one-pot synthesis and sensitive detection of glutathione

A new class of core-satellite upconversion nanoparticles (UCNPs) formed through a kinetically controlled oriented attachment is presented. The core-satellite UCNPs comprising an optically active α-NaYbF4 core and several CaF2 satellites are synthesized by a one-pot sequential injection technique. Compared to conventional core-shell UCNPs, these core-satellite UCNPs show larger surface-to-volume ratios and are suitable for further surface modifications. As a proof-of-concept, a biosensing system is constructed by coating MnO2 nanosheets on the α-NaYbF4:Tm@CaF2 core-satellite UCNPs for high-sensitivity biothiol detection. These core-satellite UCNPs show great potential in the development of UCNP-based nanohybrids for biosensing, multimodal imaging and drug delivery.

Highly sensitive fluorescent detection of glutathione and histidine based on the Cu(ii)-thiamine system

A novel fluorescence method for the simultaneous detection of glutathione and histidine based on their inhibitory effects on the oxidation of thiamine by Cu(ii) is proposed.

Turn-on fluorescent sensor for the detection of glucose using manganese dioxide-phenol formaldehyde resin nanocomposite

Monitoring blood glucose has attracted considerable attention because diabetes mellitus is a global public health problem. Herein, we reported a turn-on fluorescence detection strategy based on manganese dioxide (MnO₂)-phenol formaldehyde resin (PFR) nanocomposite for rapid, sensitive, and selective detection of glucose levels in human blood. In this biosensing system, MnO₂ nanoshell on the PFR nanoparticle surfaces serve as a quencher. PFR fluorescence can make a recovery in the presence of H₂O₂, reducing MnO₂ to Mn²⁺. The sensor shows a linear range from 50nM to 90μM with a low detection limit of 20nM for H₂O₂ detection. Thus, the glucose can be detected on the basis of the enzymatic conversion of glucose by glucose oxidase to produce H₂O₂. This method exhibits a wide linear range from 5μM to 1mM with a low detection limit of 1.5μM. Because of the excellent photostability offered by PFR, the developed strategy has been successfully applied for the diagnosis of diabetes mellitus in human blood samples. Compared with commercial glucometer, our method showed satisfactory results, indicating the significant reliability. The developed turn-on fluorescent sensor might hold great promise in nanomedicine and bioanalysis.

MnO2in situ formed into the pores of C-dots/ZIF-8 hybrid nanocomposites as an effective quencher for fluorescence sensing ascorbic acid

Rapid construction of C-dots/ZIF-8 composites and in situ growth of MnO₂ into their pores as a quencher for ascorbic acid fluorescence sensing.

Ultrasensitive fluorescent ratio imaging probe for the detection of glutathione ultratrace change in mitochondria of cancer cells

Glutathione (GSH) ultratrace change in mitochondria of cancer cells can mildly and effectively induce cancer cells apoptosis in early stage. Thus, if GSH ultratrace change in mitochondria of cancer cells could be recognized and imaged, it will be beneficial for fundamental research of cancer therapy. There have reported a lot of fluorescent probes for GSH, but the fluorescent probe with ultrasensitivity and high selectivity for the ratio imaging of GSH ultratrace changes in mitochondria of cancer cells is scarce. Herein, based on different reaction mechanism of sulfonamide under different pH, a sulfonamide-based reactive ratiometric fluorescent probe (IQDC-M) was reported for the recognizing and imaging of GSH ultratrace change in mitochondria of cancer cells. The detection limit of IQDC-M for GSH ultratrace change is low to 2.02nM, which is far less than 1.0‰ of endogenic GSH in living cells. And during the recognition process, IQDC-M can emit different fluorescent signals at 520nm and 592nm, which results in it recognizing GSH ultratrace change on ratio mode. More importantly, IQDC-M recognizing GSH ultratrace change specifically occurs in mitochondria of cancer cells because of appropriate water/oil amphipathy (log P) of IQDC-M. So, these make IQDC-M possible to image and monitor GSH ultratrace change in mitochondria during cancer cells apoptosis for the first time.