Dynamically monitoring intracellular glutathione (GSH), a crucial biomarker of oxidative stress, is of significance for the diagnosis and treatment of certain diseases. Although manganese dioxide (MnO2) based GSH fluorescent sensors have exhibited high sensitivity and good selectivity owing to the specific reactivity between GSH and MnO2, near-infrared (NIR) MnO2 based nanoprobes for GSH detection are scarce. Herein, we have developed a NIR activatable fluorescence nanoprobe for the imaging and determination of intracellular GSH based on a core–shell nanoparticle, consisting of NIR emitted gold nanocluster doped silica as the fluorescent core and manganese dioxide as the GSH-responsive shell (named AuNCs@MnO2). Due to the absorption competition mechanism, the outer MnO2 shell rather than the inner AuNCs core preferentially absorbed the excitation light, thus leading to fluorescence quenching of the inner AuNCs core. Upon addition of GSH, the fluorescence of the nanoprobe restored along with the reduction of MnO2 to Mn2+ because of the absorption competition disappearance-induced emission. The activatable fluorescence linearly increased upon changing the GSH concentration in the range of 2 to 5000 μM with a detection limit of 0.67 μM. The cytotoxicity test shows that the AuNCs@MnO2 nanoprobes have a good biocompatibility. After entering the cancer cells, the intracellular GSH degraded the outermost MnO2 shell and initiated the NIR fluorescence restoration of AuNCs, which can be used to monitor the dynamic change of intracellular GSH. This strategy provides an NIR-activatable way to detect GSH levels in living cells and offers a promising platform for the diagnosis and treatment of GSH-related diseases.
Huanzong Zhang,Binhuang Cai,Fan Cai,Mingzhe Lian,Yinghui Wang
Gastric cancer is a prevalent malignant tumor of the gastrointestinal tract accompanied by a high mortality rate; therefore, early gastric cancer screening is critical for improving patient survival. In this study, we present a facile fluorescence immunoassay for highly sensitive screening of pepsinogen I (PG I) based on a one-pot biomimetic mineralization process for the synthesis of gold nanocluster-anchored manganese dioxide (AuNCs/MnO2) nanosheets. MnO2 first quenches the fluorescence of AuNCs through the Förster resonance energy transfer effect, whereas the introduction of ascorbic acid (AA) leads to the decomposition of MnO2 and rapidly recovers the fluorescence of AuNCs. Based on the above principles and phenomena, we developed a sensitive fluorescence immunoassay for the in situ generation of AA to detect PG I. Specifically, in the presence of PG I, the sandwich-type immunoreactivity-enriched alkaline phosphatase-labeled secondary antibody catalyzes the production of AA from the substrate, which enhances the fluorescence intensity. Under optimized conditions, the fluorescence intensity increased linearly with the concentration of PG I (0.05 to 200 ng mL−1) with a limit of detection (LOD) of 0.013 ng mL−1 (S/N = 3). The designed sensing platform has good stability (more than one year) and excellent anti-interference capability and demonstrates satisfactory accuracy for detection in real samples compared to commercial ELISA kits.
Xiaolun Peng,Jiaxin Zheng,Ting Bao,Wei Wen,Xiuhua Zhang,Shengfu Wang
A novel dual-amplified electrochemical biosensor based on Exonuclease III (Exo III) and Cu(II)-dependent DNAzymes (Cu 2+ -DNAzymes) was developed for ultrasensitive electrochemical evaluation of pyrophosphatase (PPase) activity with the help of one-step synthesis of BSA-directed gold nanoclusters-manganese dioxide (AuNCs-MnO 2 ) nanoflakes with peroxidase-like characteristics as a catalytic platform. For biosensor preparation, under the catalytic hydrolysis of the PPase, copper ion (Cu 2+ ) was released from the Cu 2+ -coordinated pyrophosphate ions (Cu 2+ –PPi) complex which was formed by the coordination reaction of copper ion (Cu 2+ ) and pyrophosphate ions (PPi). The released Cu 2+ , acting as an indispensable cofactor, could activate Cu 2+ -DNAzymes to turn on the amplification process and then generated the single-stranded product (S1) that hybridized to the hairpin-type capture probe (HP1). Subsequently, the addition of Exonuclease III (Exo III) enabled the reuse of S1 and produced the final cleavage fragment, which closely linked the functionalized AuNCs-MnO 2 nanoflakes to the electrode surface. The superior peroxidase-like characteristics of nanoflakes provided stable catalytic signal output and realized electrochemical monitoring of PPase activity with a detection limit of 0.0058 mU/mL. Importantly, the biosensor also had a good performance in inhibitors screening of target PPase. The use of AuNCs-MnO 2 nanoflakes instead of natural enzymes combined with DNAzymes amplification strategy offered more possibilities for the detection of various biomolecules.
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