A generalizable sensing platform based on molecularly imprinted polymer-aptamer double recognition and nanoenzyme assisted photoelectrochemical-colorimetric dual-mode detection.

Developing highly sensitive and selective methods that incorporate specific recognition elements is crucial for detecting small molecules because of the limited availability of small molecule antibodies and the challenges in obtaining sensitive signals. In this study, a generalizable photoelectrochemical-colorimetric dual-mode sensing platform was constructed based on the synergistic effects of a molecularly imprinted polymer (MIP)-aptamer sandwich structure and nanoenzymes. The MIP functionalized peroxidase-like Fe3O4 (Fe3O4@MIPs) and alkaline phosphatase mimic Zr-MOF labeled aptamer (Zr-mof@Apt) were used as the recognition elements. By selectively accumulating dibutyl phthalate (DBP), a small molecule target model, on Fe3O4@MIPs, the formation of Zr-MOF@Apt-DBP- Fe3O4@MIPs sandwich structure was triggered. Fe3O4@MIPs oxidized TMB to form blue-colored oxTMB. However, upon selective accumulation of DBP, the catalytic activity of Fe3O4@MIPs was inhibited, resulting in a lighter color that was detectable by the colorimetric method. Additionally, Zr-mof@Apt effectively catalyzed the hydrolysis of L-Ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAPS), generating ascorbic acid (AA) that could neutralize the photogenerated holes to decrease the photocurrent signals for PEC sensing and reduce oxTMB for colorimetric testing. The dual-mode platform showed strong linearity for different concentrations of DBP from 1.0 pM to 10 µM (PEC) and 0.1 nM to 0.5 µM (colorimetry). The detection limits were 0.263 nM (PEC) and 30.1 nM (colorimetry) (S/N = 3), respectively. The integration of dual-signal measurement mode and sandwich recognition strategy provided a sensitive and accurate platform for the detection of small molecules.

Ultrasensitive alkaline phosphatase activity assay based on controllable signal probe production coupled with the cathodic photoelectrochemical analysis.

A highly sensitive and selective split-type perovskite-based photoelectrochemical (PEC) platform was developed for measuring alkaline phosphatase (ALP) activity in milk and serum samples. ALP in the test sample hydrolyzed 2-phosphate sesquimagnesium salt hydrate (AAPS) in a 96-microwell plate to produce ascorbic acid (AA), a PEC electron donor. The resulting AA, which could preferentially annihilate the photogenerated holes, indirectly reflects ALP activity. The PEC used a cetyltrimethylammonium bromide (CTAB)-functionalized CH3NH3PbI3 (CTAB@CH3NH3PbI3) film as the cathode to monitor the controlled AA production. Due to the excellent photoelectric characteristics of the CH3NH3PbI3 perovskite and the split-type assay, excellent sensitivity and selectivity for ALP detection were obtained. Under the optimum experimental conditions, ALP activity with a limit of detection (LOD) of 2.6 × 10-4 U/L in a linear dynamic range of 10-3 âˆ¼ 102 U/L was obtained. With its sensitive, rapid, and high-throughput detection capabilities, this split-type and label-free PEC platform has great potential for use in food and biomedical analysis.

ß-Bi2O3 Nanosheets Functionalized with Bisphenol A Synthetic Receptors: A Novel Material for Sensitive Photoelectrochemical Platform Construction.

In this study, ß-Bi2O3 nanosheets functionalized with bisphenol A (BPA) synthetic receptors were developed by a simple molecular imprinting technology and applied as the photoelectric active material for the construction of a BPA photoelectrochemical (PEC) sensor. BPA was anchored on the surface of ß-Bi2O3 nanosheets via the self-polymerization of dopamine monomer in the presence of a BPA template. After the elution of BPA, the BPA molecular imprinted polymer (BPA synthetic receptors)-functionalized ß-Bi2O3 nanosheets (MIP/ß-Bi2O3) were obtained. Scanning electron microscopy (SEM) of MIP/ß-Bi2O3 revealed that the surface of ß-Bi2O3 nanosheets was covered with spherical particles, indicating the successful polymerization of the BPA imprinted layer. Under the best experimental conditions, the PEC sensor response was linearly proportional to the logarithm of BPA concentration in the range of 1.0 nM to 1.0 µM, and the detection limit was 0.179 nM. The method had high stability and good repeatability, and could be applied to the determination of BPA in standard water samples.

Competitive Displacement Triggering DBP Photoelectrochemical Aptasensor via Cetyltrimethylammonium Bromide Bridging Aptamer and Perovskite.

Here, a label-free perovskite-based photoelectrochemical (PEC) aptasensor was rationally designed for the displacement assay of dibutyl phthalate (DBP), a well-known endocrine disruptor, with the aid of cetyltrimethylammonium bromide (CTAB). In this method, CTAB significantly enhanced the PEC response and humidity resistance of the CH3NH3PbI3 perovskite by forming a protecting layer and passivating the X- and A-sites vacancies of CH3NH3PbI3. In addition, CTAB facilitated the immobilization of an aptamer through van der Waals and hydrophobicity forces, as well as the electrostatic interactions between the phosphate group of the aptamer and the cationic group of CTAB. When exposed to DBP in the affinity solution, the DBP aptamer was released from the electrode because the affinity between DBP and its aptamer competes with the interaction of the aptamer and CTAB. The displacement of the aptamer from the perovskite surface relieves the block effect and thus enhances the photoelectric signal of perovskite. By virtue of the good photoelectrochemical characters of CH3NH3PbI3 and the specific recognition ability of aptamer, the linear range of the PEC sensor was 1.0 × 10-13 to 1.0 × 10-8 M and the detection and quantification limits were down to 2.5 × 10-14 and 8.2 × 10-14 M (S/N = 3), respectively. This work offers a novel strategy for designing aptasensors for the detection of various targets and exhibits the marvelous potential of organic-inorganic perovskite in the field of PEC analysis.

High-sensitivity photo-electrochemical heterostructure of the cuprous oxide-metal organic framework for a dioctyl phthalate molecularly imprinted sensor.

This work designed a novel dioctyl phthalate (DOP) photoelectrochemical (PEC) sensor based on a molecularly imprinted polymer (MIP) modified Cu3(BTC)2@Cu2O heterostructure. In this work, a metal organic framework (MOF), Cu3(BTC)2, was coated on Cu2O through a simple immersion method to form a Cu3(BTC)2@Cu2O heterostructure. The heterostructure exhibited strong light adsorption ability, good stability and enhanced photocurrent under visible light irradiation. Using the Cu3(BTC)2@Cu2O heterostructure as the photoelectric converter, a PEC sensor was constructed by imprinting DOP on the heterostructure. Under the optimal experimental conditions, the PEC sensor showed a wide linear range from 25.0 pM-0.1 µM and a low detection limit of 9.15 pM. This method with good sensitivity, stability, selectivity and reproducibility in actual sample analyses showed promising applications of the MOF-based heterostructure in photoelectrochemical analysis fields.

Myricetin induces apoptosis in HepG2 cells through Akt/p70S6K/bad signaling and mitochondrial apoptotic pathway.

The present investigation was undertaken to gain insight into the molecular mechanism by which myricetin induces apoptosis in human hepatocarcinoma HepG2 cells. Myricetin caused the disruption of mitochondrial membrane potential in a dose-dependent manner. Moreover, myricetin triggered translocation of the pro-apoptotic protein Bax to the mitochondria, downregulation of anti-apoptotic Bcl-2 expression and upregulated the expression of pro-apoptotic protein Bad in the mitochondria. The present study also showed that myricetin promoted the release of cytochrome C from mitochondria into the cytosol followed by an increase in the proteolytic activation of caspase-3 and the concomitant degradation of PARP protein. Additionally, western blot analysis showed that the Akt/p70s6k1 pathway was inhibited in myricetin-treated HepG2 cells, accordingly the phosphorylation of Bad at Ser136 was downregulated. Collectively, these findings indicate that myricetin induced apoptosis in HepG2 cell through mitochondria apoptotic pathway and Akt/p70s6k1/Bad signaling. Present results provide new information on the possible mechanisms for the anti-cancer activity of myricetin.

Myricetin induces G2/M phase arrest in HepG2 cells by inhibiting the activity of the cyclin B/Cdc2 complex.

Myricetin, a naturally occurring flavonol, has been shown to inhibit the proliferation of human hepatoma HepG2 cells and to induce G2/M phase arrest. However, the underlying mechanisms of Myricetin activity have yet to be revealed. The aim of the present study was to clarify the molecular mechanisms of cell cycle arrest induced by myricetin in HepG2 cells. The MTT assay confirmed that exposure of HepG2 cells to myricetin triggered G2/M phase arrest. Western blot analysis showed that myricetin increased the protein levels of the p53/p21 cascade, and markedly decreased Cdc2 and cyclin B1 protein levels in HepG2 cells. Additionally, myricetin treatment resulted in the up-regulation of Thr14/Tyr15 phosphorylated (inactive) Cdc2 and p27, and the down-regulation of CDK7 kinase protein, as well as CDK7-mediated Thr161 phosphorylated (active) Cdc2. These data indicate that a decrease in cyclin B/Cdc2 complex activity mediated G2/M phase arrest induced by myricetin in HepG2 cells. This novel finding provides insight into the potential applications of myricetin in the treatment of hepatocellular carcinoma.