Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy

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Biological and Medical Applications of Materials and Interfaces

Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy)32+-UiO-66 Nanocomposites Shengmei Zhu, Sicheng Wang, Mengmeng Xia, Baojuan Wang, Yu Huang, Dexing Zhang, Xiaojun Zhang, and Guangfeng Wang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b11025 • Publication Date (Web): 24 Jul 2019 Downloaded from pubs.acs.org on July 25, 2019

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ACS Applied Materials & Interfaces

Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy)32+-UiO-66 Nanocomposites Shengmei Zhu#a, Sicheng Wang#a, Mengmeng Xia#a, Baojuan Wangb, Yu Huangb, Dexing Zhanga, Xiaojun Zhanga, Guangfeng Wang*a a. Key Laboratory of Chem-Biosensing, Anhui province; Key Laboratory of Functional Molecular Solids, Anhui province; College of Chemistry and Materials Science, Center for Nano Science and Technology, Anhui Normal University, Wuhu 241000, PR China b. Institute of Molecular Biology and Biotechnology and Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, 241000, PR China.

ABSTRACT: Fluorescent detection of Glutathione (GSH) in living being system has attracted much attention, but current fluorescent probes were usually exposed to the exterior environment, leading to the photo-bleaching and premature leakage, and subsequently limiting the sensitivity and photostability. Herein, luminescent metal organic frameworks (MOFs) (Ru(bpy)32+ encapsulated in UiO-66) coated with manganese dioxides nanosheets (MnO2 NS@Ru(bpy)32+UiO-66) was prepared by an in-situ growth method and further explored to construct GSH switched fluorescent sensing platform. Because of the splendid fluorescence quenching ability, special probe leakage blocking role and distinguished recognition of MnO2 NS, and the improved fluorescence of Ru(bpy)32+ by UiO-66, the low background, highly sensitive and

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selective detection of GSH with a low limit of detection (LOD) as 0.28 μM was realized. At the same time, the preparation of MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites is simple, low toxic and there was no notable loss of cell survivability after being exposed to the MnO2 NS@Ru(bpy)32+-UiO-66 below the concentrations of 120 μg mL-1 for 24 h. Consequently, the results coming from this effort suggest that the new sensing platform will have a great potential to apply for detection of GSH in living cells.

KEY WORDS: glutathione (GSH), fluorescent detection, metal organic frameworks (MOFs), Ru(bpy)32+, MnO2 nanosheets (MnO2 NS)

1. INTRODUCTION Glutathione (GSH) is a kind of vital endogenous antioxygen as well as the most abundant intra-cell sulfhydryl product in biological systems. It has crucial and ubiquitous influences on numerous crucial biological activities, including defense against toxins and free radicals, keeping redox homeostasis, and regulating cell proliferation1,2. Due to the redox feature of GSH, it can be simply reacted to form the dipolymer of GSH, glutathione disulfide (GSSG), as the response of oxidative forces within the human body3. The concentration of GSH (or GSH/GSSG ratio) in human blood is related with some diseases, such as aging, Alzheimer’s disease, and cancers etc. and further reflect the health level in some extent4. Therefore, efficient detection of GSH in living biosystems is favorable to grasp GSH-related pathophysiological events5. Various methods including high-performance liquid chromatography6, electrochemistry7, colorimetry8, photoelectrochemistry9,

surface-enhanced

Raman

spectroscopy10,

enzyme-linked

immunosorbent11, as well as fluorescent assays have exert prospective assays for the detection of


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GSH12. Among them, the fluorescent detection technique would be recommendable for the successful detection of GSH13 and intracellular imaging14, owing to its non-destructive characteristics, real-time monitoring, rapid response, high selectivity and sensitivity, and the possibility of detection in a living being system15-18. Recently, 2D layered Manganese dioxides nanosheets (MnO2 NS) have attracted much attention on the exploration of fluorescent GSH sensing systems due to its distinguished redox activity to recognize GSH and splendid fluorescent quenching ability toward luminescent fluorophores19,20. However, the reported fluorescent probes were usually directly conjugated on the coverage of MnO2 NS, exposing the probes to the exterior environment, which is prone to suffer from the photo-bleaching and premature leakage, and subsequently limits the probe’s photostability and assay sensitivity

21.

Furthermore, only limited signal can be obtained in most of these fluorescent systems. Thus, it is really desirable to develop novel fluorescent system which can avoid the leakage of fluorescent probes and obtain enhanced fluorescent signal for GSH sensing in aqueous solution or even tumor cell imaging22. Metal–organic frameworks (MOFs) are prospective hybrid microporous and crystalline materials, which is composed of metal cations or clusters and flexible organic ligands connected with strong covalent bonds23. Given their distinguished structural diversities and function integration, MOFs have attracted much interest across a broad range of applications including gas adsorption and separation24, biomedical imaging25, drug delivery26, heterogeneous catalysis27 and sensor28, etc. As a subclass of MOFs, luminescent MOFs with integrated functions of the intrinsic porosity and luminescent performances have displayed bright promise as new luminescent probes in biosensing29-35. Generally, the signals of these luminescent MOFs bioprobes are roughly divided into two categories according to the luminescent source: one is


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from the luminescent center of MOF itself which either anchors the luminescent groups onto the reactive group of the organic ligands or incorporates luminescent lanthanide ions (eg. Eu3+, Tb3+) as metal ion center36-40. However, most are involved with stringent synthetic conditions, long reaction time, laborious purification and especially the compatibility and interference between the introduced luminescent center and the formation of the desired MOF structures. Another type is from the fluorescent guest molecules encapsulated in the cavities of the porous MOFs41, 42. The extremely regular channel structures and controllable pore sizes of MOFs enable them to serve as rigid/ﬂexible hosts for luminous guest species to produce guest-induced luminescence. This is a convenient strategy, and moreover, it can keep the MOFs intrinsic structure. Meanwhile, it can effectively prevent the undesired leakage and the aggregation-caused quenching (ACQ), improve the photostability and the fluorescence quantum yield of luminescent molecules, which is especially beneficial for the fluorescent sensing43,44. Nevertheless, the study on the guest-induced luminescent MOFs for GSH detection is still limited or existing problems such as relatively high background signal and unexpected cellular injury45,46. Herein, nanocomposites of MnO2 NS coated UiO-66 with Ru(bpy)32+ encapsulated (MnO2 NS@Ru(bpy)32+-UiO-66) were prepared and explored as a target switched fluorescent platform for GSH detection and intracellular imaging. In the preparation, MnO2 NS was first generated on Ru(bpy)32+-UiO-66 by a facile in-situ growth method. Because of the coated MnO2 NS on the surface of UiO-66, the release of the loaded Ru(bpy)32+ was effectively prohibited. Furthermore, the quenching effect of MnO2 NS towards the luminescence of Ru(bpy)32+ resulted in a low background. MnO2 NS not only served as a shell blocking the probe leakage, quenchers to eliminate the background fluorescence and improve the signal to noise ratio, but also could be as the recognition unit, decomposed by GSH switching the recovery of fluorescence. In addition,


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UiO-66 encapsulation has an enhancement on the fluorescence of Ru(bpy)32+ and thus the present fluorescent platform could be exploited for the fluorescence detection of GSH with excellent sensitivity. In addition, this is also a convenient and simple method which does not require precision instruments or high cost of chemical reagents. What's more, the preparation of MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites is low toxicity, displaying a great potential for the detection of intracellular GSH. 2. EXPERIMENTAL SECTION Synthesis and characterization of UiO-66, Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+UiO-66. We synthesized the MnO2 NS@Ru(bpy)32+-UiO-66 as the procedure illustrated in Scheme 1. First, the UiO-66 was assembled from zirconium ion and terephthalic acid (H2BDC) by a facile hydrothermal method47. Furthermore, by the incorporation of the luminescent Ru(bpy)32+ into the evacuated UiO-66, the fluorescent MOFs (Ru(bpy)32+-UiO-66) was obtained. After that, MnO2 NS were further in-situ generated on fluorescent MOFs (MnO2 NS@Ru(bpy)32+-UiO-66) through a redox process of KMnO4 in 2-morpholino-ethanesulfonic acid (MES) buffer. Figure 1A and 1B are SEM and TEM images of the bare UiO-66. As can be seen, the UiO-66 has a uniform size with an average diameter about 20 nm and at this size it showed spherical-like morphology. Meanwhile, the produced UiO-66 powders were white as the photograph showed (Inset, Figure 1B). With the luminescent guest molecules of Ru(bpy)32+ incorporated, despite there is little change in size and morphology (Figure 1C), the color of the Ru(bpy)32+-UiO-66 powders turned from white to yellow (Inset, Figure 1C). Furthermore, with the MnO2 NS coated onto the Ru(bpy)32+-UiO-66, the wrinkle and transparency film on the surface appeared, as TEM image showed (Figure 1D), and the color of the corresponding product become black (Inset, Figure 1D).


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XRD and FT-IR also indicated the successful preparation of MnO2 NS@Ru(bpy)32+-UiO-66. Figure 1E illustrates XRD patterns of the UiO-66 (black curve), Ru(bpy)32+-UiO-66 (red curve) and MnO2 NS@Ru(bpy)32+-UiO-66 (blue curve). UiO-66 has two characteristic peaks between 5° and 10°, and a characteristic peak in the region of 26°, which matches well with the purephase UiO-66 MOFs as previously reported48. The other two XRD patterns (blue and red curves) displayed clear overlaps of the low angle peaks with UiO-66, implying the well preserved crystallinity and structure of UiO-66. As illustrated in Figure 1F, the FT-IR measurements of UiO-66 (black curve) showed several absorption peaks from the aromatic rings and carboxyl groups. For instance, there is a peak at 1420 cm-1 arisen from the C-C vibrational mode, and the peak at 1580 cm-1 was ascribed to the stretching vibration of the C-O bond existing in the carboxyl group49. The strong and wide band centered at 3440 cm−1 is attributed to the O-H stretching mode of crystalline water and physisorbed water condensed inside the cavities50. The strong peaks at 1563 and 1410 cm-1 are caused by the stretch modes of the carboxylate group led to the in- and out-of-phase. In the low frequency region, the band at 740 cm-1 and 670 cm-1 are generated by the Zr-O chemical bond (red curve). The peak at 1534 cm−1 is ascribed to the vibration of C=C causing by pyridines, and absorption at 2091 cm−1 could be assigned to ν (NC)51. All of these signals further confirm that the Ru(bpy)32+ luminophore has been successfully introduced into the framework of MOFs. Furthermore, the absorption peak at 516.3 cm-1 can be attributed to the Mn-O and Mn–O–Mn vibrations in [MnO6] octahedral (blue curve)52. Through the comparison, we can draw a conclusion that the MnO2 NS@Ru(bpy)32+UiO-66 nanocomposites include several characteristic peaks of both as-prepared Ru(bpy)32+-


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UiO-66 and MnO2, implying that MnO2 NS are attached to the Ru(bpy)32+-UiO-66.

Scheme 1. Schematic illustration of MnO2 NS@Ru(bpy)32+-UiO-66 synthesis and principle of the GSH detection 3. RESULTS AND DISCUSSION Optic properties of MnO2 NS@Ru(bpy)32+-UiO-66. We first investigated the absorption spectrum of the Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites, with the free Ru(bpy)32+ and UiO-66 as control in aqueous solution. It was clearly illustrated in Figure 2A that the characteristic absorption peak of Ru(bpy)32+ ranging from 350 nm to 500 nm (blue curve) due to the metal-to-ligand charge transfer (MLCT) transition of the Ru(bpy)32+ complex. As observed in the absorption curve of Ru(bpy)32+-UiO-66 (red curve), the characteristic absorption band peak of Ru(bpy)32+ becomes broader with a blue shift resulting from the absorption spectrum of UiO-66 merging53. As for the final MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites, the adsorption spectra exhibits an intense broad band (black curve), maybe because the characteristic broad absorption band ranging from 300 nm to 600 nm of MnO2 NS. The in-situ generation of MnO2 NS was suggested that the Mn atoms in the [MnO6] octahedron may conjugate with the Ru(bpy)32+-UiO-66 substrate by coordination bonding.54


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Figure 1. SEM (A) and TEM (B-D) images of the UiO-66 (A and B), Ru(bpy)32+-UiO-66 (C) and MnO2 NS@Ru(bpy)32+-UiO-66 (D); XRD patterns (E) and FTIR spectrum (F) of UiO-66 (black line), Ru(bpy)32+-UiO-66 (red line) and MnO2 NS@Ru(bpy)32+-UiO-66 (blue line).

In Figure 2B, it demonstrated standard one-photon fluorescence spectrums of the Ru(bpy)32+, Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites under an excitation source of 420 nm. The Ru(bpy)32+-UiO-66 indicates a fluorescent emission peak at 608 nm (red curve) displaying a 6 nm hypsochromic shift compared with that of the Ru(bpy)32+ (614 nm), due to the interaction between dye molecule and MOFs materials especially when involving hydrophobic interactions. Observably, the emission intensity of Ru(bpy)32+-UiO-66 is nearly twice than that of the free molecules when the amount of Ru(bpy)32+ are almost kept the same.


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We suggest the fluorescent enhancement of Ru(bpy)32+-UiO-66 was originated from the porous structure of UiO-66 which can host the guest luminescent molecules Ru(bpy)32+ separately, avoiding the aggregation-induced quenching efficiently. Moreover, the porous UiO-66 structure is possible to limit the molecular motion or rotation which may enhance the rigidity of Ru(bpy)32+ to some extent54. When Ru(bpy)32+-UiO-66 nanoparticles were modified by MnO2 NS, the fluorescence of Ru(bpy)32+-UiO-66 could be quenched thoroughly because the fluorescence resonance energy transfer (FRET) happened between the Ru(bpy)32+-UiO-66 and MnO2 NS (black curve). Hence, we considered that the presence of MnO2 NS could cause the fluorescence quenching of Ru(bpy)32+ composites by FRET effect. Figure 2C displayed that the luminescence lifetime of Ru(bpy)32+-UiO-66 is longer than that of Ru(bpy)32+ molecules. The extended emission lifetime of Ru(bpy)32+-UiO-66 is able to ascribe to the space limitation in porous materials, which inhibiting Ru-N bond elongation and increasing the energy of the 3d-d state in Ru(bpy)32+ as researched before55. Owing to the quenching by FRET, the lifetime of Ru(bpy)32+-UiO-66 distinctly became shorter after coated with MnO2 NS. Corresponding fluorescence lifetime data is shown in Table S1. As is well known, photostability is an extremely crucial criterion in the practical applications of fluorescent probe. As a result, we studied the photostability of the Ru(bpy)32+-UiO-66 and free Ru(bpy)32+ under irradiation of the ultraviolet lamp. As shown in Figure 2D, with the time elongation, the fluorescent intensity of the Ru(bpy)32 at 608 nm sharply decreases, while that of the Ru(bpy)32+-UiO-66 shows gradual decline under the same conditions, indicating the fluorescent signal from the Ru(bpy)32+-UiO-66 is more stable than that of the free Ru(bpy)32+ molecules. Therefore, it is suitable for Ru(bpy)32+-UiO-66 to be applied in building sensitive GSH biosensors.


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Figure 2. UV-vis absorption spectrum (A), fluorescent spectrum (Eex= 450 nm) (B), timeresolved luminescence decay curves (C), and stability of photoluminescence under UV lamp (D), of different Ru(bpy)32+ based composites

Feasibility of the proposed strategy for GSH sensing. Scheme 1 displayed the “turn-on” fluorescent detection of GSH with the MnO2 NS@Ru(bpy)32+-UiO-66 fluorescent platform. Since the fluorescent Ru(bpy)32+-UiO-66 could be quenched by the MnO2 NS, a low background signal was obtained. After the addition of GSH, MnO2 were reduced to Mn2+ by GSH (as shown in eq 1), accompanying with the regain of the luminescence of Ru(bpy)32+-UiO-66 probe. Thus, the target regulated fluorescent recovery of the MnO2 NS@Ru(bpy)32+-UiO-66 is possible for the “turn-on” detection of GSH. In addition, the low background of MnO2 NS quenching and enhanced fluorescence of Ru(bpy)32+-UiO-66 is favorable to improve the detection sensitivity. 𝑀𝑛𝑂2 + 2𝐺𝑆𝐻 + 2𝐻 + →𝑀𝑛2 + +𝐺𝑆𝑆𝐺 + 2𝐻2𝑂

(1)12

The feasibility of the sensing system was demonstrated by the investigation of the fluorescent response in various solutions. As shown in Figure 3A, GSH at various concentrations (from 0 to 1 mM) has little influence on the fluorescent signal of Ru(bpy)32+-UiO-66. However, MnO2 NS@Ru(bpy)32+-UiO-66 system showed sharply weak fluorescence at 608 nm (Figure 3B, black


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curve). However, the fluorescent signal was enhanced by about 10 times as 1 mM GSH was presented in this system (red curve, Figure 3B), which confirmed the fluorescent recovery was originated from the decomposition of MnO2 by GSH to Mn2+ ions, causing the inhibition of quenching effect towards Ru(bpy)32+-UiO-66. Furthermore, we investigated the fluorescent response of different concentrations of GSH (from 0 to 1 mM) to the Ru(bpy)32+-UiO-66 solution.

Figure 3. Effects of different concentrations of GSH (0, 0.025, 0.05, 0.1, 0.2, 0.5, 1.0 mM) on the fluorescent signals of Ru(bpy)32+-UiO-66 (A), Fluorescence spectra of the MnO2 NS@Ru(bpy)32+-UiO-66 in the absence and presence of GSH (100 μM) (B), Fluorescence spectra at various of concentrations of GSH (0, 5, 12.5, 25, 37.5, 50, 100, 150, 200, 250, 300 μM) (Eex= 450 nm) (C), Relationship between fluorescence intensity and the concentration of GSH (D), Inset: linear correlation between fluorescence intensity and concentration; Error bars demonstrate the standard deviations of the three experiments.

Performance of GSH detection. The assay performance of the presented sensing platform for GSH detection was verified. As displayed in Figure 3C, intriguing emission signals of MnO2 NS@Ru(bpy)32+-UiO-66 at 608 nm were regained progressively with the concentrations of GSH ranging from 0 to 300 μM. The linear plotting between fluorescence intensity (F) and the


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concentration of GSH was expressed in Figure 3D. The fitted curve was obtained as F =231 + 3.04[GSH] (μM) with a correlation coefficient of 0.996, and the detection limit was low to 0.28 μM, which was defined by the three times deviations of the blank signal (3σ). Furthermore, we compared this approach with other reported methods (Table S2). The result showed that this sensor strategy had comparable or superior sensitivity to the previous strategies. Selectivity and stability of MnO2 NS@Ru(bpy)32+-UiO-66 towards GSH assay. As an excellent fluorescent platform with promising application in actual biological samples, sufficient selectivity towards the assay target is required. Therefore, the selectivity of this platform was evaluated by investigating the fluorescence response towards various potentially competing interferences. As presented in Figure 4A, strikingly larger fluorescence intensity was observed for 100 μM GSH than those of other substances with same or relative higher concentrations. It should point out that high concentrations of cysteine (Cys) and ascorbic acid (AA) was able to induce certain fluorescence response either. However, GSH concentration (mM levels) is much higher than that of cysteine (Cys) and ascorbic acid (AA) (μM levels) in biological systems. Thus, the MnO2 NS@Ru(bpy)32+-UiO-66 was able to apply as a selective fluorescent nanoplatform on GSH detection. In addition, the 8 successive fluorescent detection of 20 μM GSH by the present system showed no significant variation, and the relative standard deviation (RSD) was 3.2%, demonstrating good stability of our present fluorescent detection system.


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Figure 4. Selectivity of the developed GSH assay (A), survivability of the HeLa cells after being treated with the Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+-UiO-66 for 24 h (B).

Cell cytotoxicity study. Toxicity is a significant factor to be considered in the biological application for the intracellular nanoprobe. Taking HeLa cells as an example, the cytotoxicity of the Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+-UiO-66 were analyzed using MTT assay. It was illustrated in Figure 4B, there was no notable loss of cell survivability for HeLa cells after being exposed to the MnO2 NS@Ru(bpy)32+-UiO-66 below the concentrations of 120 μg mL-1 for 24 h (red bars). Similarly, for Ru(bpy)32+-UiO-66, the cell death rate is only about 15% even the Ru(bpy)32+-UiO-66 concentration is as high as 120 μg mL-1 (black bars). These conclusions demonstrate that both of the MnO2 NS@Ru(bpy)32+-UiO-66 and Ru(bpy)32+-UiO-66 have low cytotoxicity and good biocompatibility, and thus the MnO2 NS@ Ru(bpy)32+-UiO-66 has a remarkable application prospect in living detection of GSH.

Figure 5. (A) Confocal fluorescence images of HeLa cells nuclei tinted with DAPI; (B) HeLa cells incubated with MnO2 NS@Ru(bpy)32+-UiO-66; (C) Merging image of DAPI and MnO2 NS@Ru(bpy)32+-UiO-66; (D) Corresponding bright-field images.


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Fluorescence confocal imaging for GSH sensing. As described above, since GSH plays a key role in biological systems and the proposed “turn on” fluorescent platform towards GSH have displayed distinct features such as fluorescence enhancement, photostabiliy, high selectivity and great biocompability, it is very attractive to explore the intracellular GSH imaging in living cells on the present MnO2 NS@Ru(bpy)32+-UiO-66 platform. Thus, we incubated HeLa cells with the MnO2 NS@Ru(bpy)32+-UiO-66 and subsequently analyzed the results by CLSM. As illustrated in Figure 5A, there was an intense blue fluorescence emission simply recorded for HeLa cell nucleus that was stained by DAPI for easier observation. After incubated with the MnO2 NS@Ru(bpy)32+-UiO-66 (80 μg mL-1) in culture media for 4 h, the fluorescence images of HeLa cells were obtained on CLSM. Figure 5B displayed red fluorescence response in live cells under excitation at 488 nm. This observation was due to the presence of endogenous GSH reacting with MnO2 NS@Ru(bpy)32+-UiO-66, which was consistent with the results of fluorescence analysis. The merged image in Figure 5C presented low overlapping between DAPI and Ru(bpy)32+-UiO66 fluorescence clearly demonstrated that the internalized Ru(bpy)32+-UiO-66 was specifically located in the cytoplasm. In Figure 5D, the bright-field images indicate that all cells can wellkeep their normal morphology. This result proves that this MnO2 NS@Ru(bpy)32+-UiO-66 can be fast transferred into the cytoplasm, which could be used for evaluating the concentration of GSH in HeLa cells. To verify that MnO2 NS@Ru(bpy)32+-UiO-66 can response to the alterations of the intracellular GSH concentration. Before imaging experiments, the HeLa cells had been treated with the GSH scavenger NEM and the GSH enhancer ALA. After that, the cells were treated with the MnO2 NS@Ru(bpy)32+-UiO-66 in culture media. As indicated in Figure 6, there was no obvious red fluorescence signal recorded for NEM-treated HeLa cells, owing to the declension of GSH concentration. On the contrary, ALA-treated HeLa cells indicated a more


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intense fluorescence signal than that of untreated HeLa cells. These results imply that the MnO2 NS@Ru(bpy)32+-UiO-66 probe can be applied to monitor the expression level of GSH in live cells.

Figure 6. Confocal fluorescent microscopy images of HeLa cells treated with different chemicals and MnO2 NS@Ru(bpy)32+-UiO-66. The top row is the fluorescence microscopy images; the bottom row is the bright-field images. 4. CONCLUSION In summary, we have prepared a MnO2 NS@Ru(bpy)32+-UiO-66 as a fluorescence sensing platform to detect GSH. The MnO2 NS@Ru(bpy)32+-UiO-66 fluorescent platform displayed low background due to the quenching effect of MnO2 NS and improved signals due to the enhancement of UiO-66 towards Ru(bpy)32+, which is favorable to provide a powerful detection capability for GSH with a wide concentration range as well as a detection limit of 0.28 μM. This strategy based on MnO2 NS@Ru(bpy)32+-UiO-66 with the brilliant performances such as sensitive, rapid, convenient and low toxic process, not only could work in aqueous solution for GSH detection but also demonstrated reliable responses to GSH in cancer cells.


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ASSOCIATED CONTENT Supporting Information Experimental section, the characterization of UiO-66, Ru(bpy)32+-UiO-66 and MnO2 NS@Ru(bpy)32+-UiO-66, optimizing experimental conditions, supporting figures and tables. AUTHOR INFORMATION #Co-first Author: Shengmei Zhu#, Sicheng Wang#, Mengmeng Xia# Corresponding Author *E-mail: [email protected] Fax: +86-553-3869303 Tel: +86-553-3869302 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (Grants 21675001). REFERENCES 1.

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Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy

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