A sensitive and rapid detection of glutathione based on a fluorescence-enhanced "turn-on" strategy

Multifunctional nitrogen-sulfur codoped carbon quantum dots: Determining reduced glutathione, broad-spectrum antibacterial activity, and cell imaging

In this study, nitrogen-sulfur codoped carbon quantum dots (N-S/CQDs) with various functions and properties were synthesized through a one-step method utilizing citric acid and cysteine as reaction substrates. The fluorescence of N-S/CQDs can be specifically quenched by permanganate ion (MnO4 -), and the quenched fluorescence can be recovered by the presence of reduced glutathione (GSH). A fluorescence sensing system based on N-S/CQDs@MnO4 - was developed and successfully applied for the determination of GSH in pharmaceutical preparations. Additionally, N-S/CQDs demonstrated broad-spectrum antibacterial activity, with minimum inhibitory concentrations of 32 μg/ml against Staphylococcus aureus (gram-positive bacterium) and 64 μg/ml against Escherichia coli (gram-negative bacterium). N-S/CQDs also proved effective for cell imaging, exhibiting excellent biocompatibility. These findings underscore the multifunctional characteristics and promising application potential of N-S/CQDs. Furthermore, this study provides a solid foundation for the development of multifunctional carbon quantum dots and the expansion of their applications in various fields.

Glutathione-responsive Aggregation-induced Emission Photosensitizers for Enhanced Photodynamic Therapy of Lung Cancer

Lung cancer, a highly prevalent and lethal form of cancer, is often associated with oxidative stress. Photodynamic therapy (PDT) has emerged as a promising alternative therapeutic tool in cancer treatments, but its efficacy is closely correlated to the photosensitizers generating reactive oxygen species (ROS) and the antioxidant capacity of tumor cells. In particular, glutathione (GSH) can reduce the ROS and thus compromise PDT efficacy. In this study, a GSH-responsive near-infrared photosensitizer (TBPPN) based on aggregation-induced emission for real-time monitoring of GSH levels and enhanced PDT for lung cancer treatment is developed. The strategic design of TBPPN, consisting of a donor-acceptor structure and incorporation of dinitrobenzene, enables dual functionality by not only the fluorescence being activated by GSH but also depleting GSH to enhance the cytotoxic effect of PDT. TBPPN demonstrates synergistic PDT efficacy in vitro against A549 lung cancer cells by specifically targeting different cellular compartments and depleting intracellular GSH. In vivo studies further confirm that TBPPN can effectively inhibit tumor growth in a mouse model with lung cancer, highlighting its potential as an integrated agent for the diagnosis and treatment of lung cancer. This approach enhances the effectiveness of PDT for lung cancer and deserves further exploration of its potential for clinical application.

Super-assembled periodic mesoporous organosilica membranes with hierarchical channels for efficient glutathione sensing

Bioinspired nanochannel-based sensors have elicited significant interest because of their excellent sensing performance, and robust mechanical and tunable chemical properties. However, the existing designs face limitations due to material constraints, which hamper broader application possibilities. Herein, a heteromembrane system composed of a periodic mesoporous organosilica (PMO) layer with three-dimensional (3D) network nanochannels is constructed for glutathione (GSH) detection. The unique hierarchical pore architecture provides a large surface area, abundant reaction sites and plentiful interconnected pathways for rapid ionic transport, contributing to efficient and sensitive detection. Moreover, the thioether groups in nanochannels can be selectively cleaved by GSH to generate hydrophilic thiol groups. Benefiting from the increased hydrophilic surface, the proposed sensor achieves efficient GSH detection with a detection limit of 1.2 μM by monitoring the transmembrane ionic current and shows good recovery ranges in fetal bovine serum sample detection. This work paves an avenue for designing and fabricating nanofluidic sensing systems for practical and biosensing applications.

A cellulosic multi-bands fluorescence probe for rapid detection of pH and glutathione

The detection of pH and glutathione (GSH) is positively significant for the cell microenvironment imaging. Here, to assess the pH value and the concentration of GSH efficiently and visually, a cellulose-based multi-bands ratiometric fluorescence probe was designed by assembling MnO2-modified cellulose gold nanoclusters, fluorescein isothiocyanate-grafted cellulose nanocrystals (CNCs) and protoporphyrin IX-modified CNCs. The probe exhibits GSH-responsive, pH-sensitive and GSH/pH-independent fluorescent properties at 440 nm, 520 nm, and 633 nm, respectively. Furthermore, the probe identifies GSH within 4 s by degrading MnO2 into Mn2+ in response to GSH. Ingeniously, the green fluorescence of the probe at 520 nm was decreased with pH, and the red fluorescence at 633 nm remained stable. Therefore, the probe displayed distinguishing fluorescence colors from pink to blue and from green to blue for the synchronous detection of pH and GSH concentration within 4 s. The design strategy provides insights to construct multi-bands fluorescence probes for the rapid detection of multiple target analytes.

Multicolor detection of glutathione by manganese dioxide nanosheets and gold nanotetrapods based on an anti-etching mechanism

Glutathione (GSH) is a crucial non-protein thiol and an indispensable endogenous antioxidant. The aberrant expression of GSH in plasma and cytosol is closely related to numerous diseases, including cancer. Therefore, establishing a sensitive method for analyzing GSH has important application value for biomedical research and clinical medical detection. Herein, A method for the rapid and simple detection of GSH was proposed, which is based on an anti-etching mechanism by utilizing gold nanotetrapods (Au NTPs) and manganese dioxide nanosheets (MnO2 NSs). In the absence of GSH, Au NTPs solution can cause a distinct color change from gray-green to red through the etching effect of MnO2 NSs. However, in the presence of GSH, the redox reaction between GSH and MnO2 NSs inhibits the etching of Au NTPs by MnO2 NSs, and Au NTPs solution maintains persistent gray-green color. The colorimetric probe exhibited excellent selectivity for GSH. The limits of detection for GSH were 43.5 nM (UV-vis spectrum) and 0.25 μM (naked eyes). The sensing technique exhibited excellent linearity between wavelength shift and GSH concentration within the range of 0.25 μM-1.5 μM. The outcomes of GSH detection in actual biological samples demonstrate that this probe has the potential to be applied to GSH detection in intricate biological samples.

A novel fluorescent strategy for Golgi protein 73 determination based on aptamer/nitrogen-doped graphene quantum dots/molybdenum disulfide @ reduced graphene oxide nanosheets

The effective detection of biomarkers associated with hepatocellular carcinoma (HCC) is of great importance. Golgi protein 73 (GP73), a serum biomarker of HCC, has better diagnostic value than Alpha-fetoprotein (AFP) has been reported. In this paper, highly accurate fluorescence sensing platform for detecting GP73 was constructed based on fluorescence resonance energy transfer (FRET), in which nitrogen-doped graphene quantum dots (NGQDs) labelling with GP73 aptamer (GP73_Apt) was used as fluorescence probe, and molybdenum disulfide @ reduced graphene oxide (MoS₂@RGO) nanosheets was used as fluorescent receptors. MoS₂@RGO nanosheets can quench the fluorescence of NGQDs-GP73_Apt owing to FRET mechanisms. In the presence of GP73, the NGQDs-GP73_Apt specifically bound with GP73 to from the deployable structures, making NGQDs-GP73_Apt far away from MoS₂@RGO nanosheets, blocking the FRET process, resulting in fluorescence recovery of NGQDs-GP73_Apt. Under optimal conditions, the recovery intensity of fluorescence in the detection system is linearly related to the concentration of GP73 in the range of 5 ng/mL - 100 ng/mL and the limit of detection is 4.54 ng/mL (S/N = 3). Moreover, detection of GP73 was performed in human serum samples with good recovery (97.21-100.83%). This platform provides a feasible method for the early diagnosis of HCC, and can be easily extended to the detection of other biomarkers.

Two-Dimensional Ultrathin CeVO4 Nanozyme: Fabricated through Non-Oxidic Material

In recent years, the synthesis of materials in lower dimensions, like two-dimensional (2D) or ultrathin crystals, with distinctive characteristics has attracted substantial scientific attention. The mixed transition metal oxides (MTMOs) nanomaterials are the promising group of materials, which have been extensively utilized for various potential applications. Most of the MTMOs were explored as three-dimensional (3D) nanospheres, nanoparticles, one-dimensional (1D) nanorods, and nanotubes. However, these materials are not well explored in 2D morphology because of the difficulties in removing tightly woven thin oxide layers or exfoliations of 2D oxide layers, which hinder the exfoliation of beneficial features of MTMO. Here, through the exfoliation via Li⁺ ion intercalation and subsequent oxidation of CeVS₃ under hydrothermal condition, we have demonstrated a novel synthetic route for the fabrication of 2D ultrathin CeVO₄ NS. The as-synthesized CeVO₄ NS exhibit adequate stability and activity in a harsh reaction environment, which gives excellent peroxidase-mimicking activity with a K _M value of 0.04 mM, noticeably better than natural peroxidase and previously reported CeVO₄ nanoparticles. We have also used this enzyme mimic activity for the efficient detection of biomolecules like glutathione with a LOD of 53 nM.

A smartphone-integrated dual-mode nanosensor based on Fe3O4@Au for rapid and highly selective detection of glutathione

A simple, rapid and straightforward method for detecting reduced glutathione (GSH) was developed supported on smartphone analysis software package and a peroxide simulated catalyst nanoparticles (Fe₃O₄@Au) system. The nanocomposite was prepared by self-assembling technique, and the characterization was carried out using transmission electron microscopy, Fourier transforms infrared, and X-ray diffractometer. Fe₃O₄@Au materials have catalyzed the oxidation of a typical colorimetric substrate in the presence of H₂O₂, with the color changes from colorless to green oxidized. A smartphone with a free self-developed app referred to as "Color Capture" was accustomed live the RGB (red-greenblue) values of color intensity within the Fe₃O₄@Au system and computationally convert them GSH concentrations. The smartphone detection system showed high property and sensitivity of GSH detection. It gave a constant correlation (R² = 0.9973) between the colour intensity of I and the GSH concentration, with a linear vary of 0-0.25 mmol/L, and a detection limit of 0.013 μmol/L. The results obtained were most consistent with the results obtained in ultraviolet spectrophotometry. The colorimetric system is based on smartphone analysis software developed to detect GSH in actual samples with potential application values.

Sensitive detection of glutathione through inhibiting quenching of copper nanoclusters fluorescence

A method for a sensitive fluorescence detection of glutathione was established. Glutathione-stabilized copper nanoclusters (CuNCs) were synthesized via a facile process. These CuNCs showed blue fluorescence with a peak around 450 nm. In the presence of p-benzoquinone (PBQ), the electron transfer from the copper nanoclusters to PBQ quenched the fluorescence of the CuNCs. Glutathione (GSH), as a reducing agent, formed a complex with PBQ. This formation inhibited the quenching from PBQ, and a restored fluorescence was obtained. This interaction provided a fluorescence enhancement for the measurement of GSH. Under the optimal condition, linear responses were obtained toward GSH in the ranges of 0.06-6.0 μM, with a limit of detection at 20 nM. This developed assay was easy in operation with high sensitivity and selectivity. The applicability was approved with successful glutathione measurements in real samples.

Self-assembled nanoplatforms with ZIF-8 as a framework for FRET-based glutathione sensing in biological samples

A nanoprobe was constructed by embedding QDs and a rhodamine B derivative (RBD) into ZIF-8. Then, the ultraviolet absorption of RBD that reacted with glutathione can overlap with the emission spectrum of the QDs, causing FRET-based glutathione sensing.