Colorimetric Detection of Met Dimerization on Live Cells via Smartphone for High-Sensitivity Sensing of the HGF/Met Signaling Pathway

Amplified Production of a DNA Decoy Catalyzed by Intracellular MicroRNA

DNA decoys inhibit cellular transcription factors and are expected to be among the nucleic acid drugs used to downregulate the transcription process. However, spatially controlling the on/off efficacy of DNA decoys to avoid side effects on normal cells is challenging. To reduce undesired decoy function in normal cells, we adopted catalytic hairpin assembly (CHA) to produce a DNA duplex from a hairpin DNA pair in response to a specific microRNA (miRNA). We designed the DNA hairpin pairs to form a DNA decoy that binds to nuclear factor kappa B (NF-κB), whose overexpression is related to many diseases, including cancer. The transformation of the DNA hairpin pair to the NF-κB DNA decoy was catalyzed by miR-21, which is expressed in various types of cancers. Intracellular CHA progression and the inhibitory effect against NF-κB were observed only in miR-21 overexpressing cancer cells. The intracellular miR-21-catalyzed production of the NF-κB DNA decoy has the potential to reduce side effects on normal cells, thereby strengthening the therapeutic profile of the CHA-decoy system. The ability to customize the combination of catalytic miRNA and target transcription factors would allow our technology to serve as a "personalized drug discovery system" for a variety of challenging diseases, including cancer.

A unique fluorescence metal-organic framework for ultrasensitive fluorescent and colorimetric bimodal detection of phosphate

Monitoring the concentration of phosphate is crucial for environmental protection and human health due to its severe ecological and health risks associated with elevated concentrations. Herein, a fluorescent-colorimetric bimodal nanoprobe based on the unique fluorescent metal-organic frameworks (Zr-PDI) has been developed for high-efficiency quantification of phosphate. The metal-oxygen coordination in Zr-PDI effectively diminished its fluorescence. However, the introduction of phosphate could weaken the metal-oxygen coordination interaction, leading to fluorescence recovery and absorption spectra changes of Zr-PDI. Taking advantage of these characteristics, Zr-PDI was exploited as a fluorescent-colorimetric bimodal detection tool for phosphate, offering excellent selectivity, a wide detection range, and high accuracy. Notably, the detection limit of fluorescence detection mode was as low as 0.023 μM, enabling ultrasensitive detection of phosphate. Furthermore, the Zr-PDI-based nanoprobe has achieved sensitive and reliable quantification of phosphate in Yong River and diabetic mouse serum samples. This proposed strategy provides a powerful, convenient, and practical tool for detecting phosphate in environmental and biological samples.

A supramolecular FRET signal amplification nanoprobe for high contrast and synchronous in situ imaging of cell surface receptor homodimers/heterodimers

Epidermal growth factor receptor (EGFR) homodimers and heterodimers play significant roles in a variety of tumors, but current imaging probes remain problematic due to restricted contrast and sensitivity. Thus, we have developed aptamer-mediated activated conformational transitions to target the EGFR and HER2. Furthermore, based on signal amplification techniques, especially the FRET fluorescence enhancement properties of poly-β-CD, supramolecular FRET signal amplification nanoprobes were constructed to improve imaging contrast and sensitivity. The results confirmed that the fluorescence intensity of the supramolecular FRET group probe is 1.2 to 1.3 times that of the multi-FRET group and 11.3 to 23.2 times that of the single-FRET group. The results further confirmed that the supramolecular nanoprobe could not only be activated by tumor cells and tissues to achieve high-contrast imaging of EGFR/EGFR and EGFR/HER2 dimers, but also successfully distinguish tumor cells and tissues from normal cells and tissues. The strategy provides a generalized platform for high-contrast imaging of other dimers intending to deepen the understanding of the central roles of multiple dimers in cancer development.

Simultaneous and Sensitive Sensing of Intracellular MicroRNA and mRNA for the Detection of the PI3K/AKT Signaling Pathway in Live Cells

Simultaneous detection of the concentration variations of microRNA-221 (miRNA-221) and PTEN mRNA molecules in the PI3K/AKT signaling pathway is of significance to elucidate cancer cell migration and invasion, which is useful for cancer diagnosis and therapy. In this work, we show the biodegradable MnO2 nanosheet-assisted and target-triggered DNAzyme recycling signal amplification cascaded approach for the specific detection of the PI3K/AKT signaling pathway in live cells via simultaneous and sensitive monitoring of the variation of intracellular miRNA-221 and PTEN mRNA. Our nanoprobes enable highly sensitive and multiplexed sensing of miRNA-221 and PTEN mRNA with low detection limits of 23.6 and 0.59 pM in vitro, respectively, due to the signal amplification cascades. Importantly, the nanoprobes can be readily delivered into cancer cells and the MnO2 nanosheets can be degraded by intracellular glutathione to release the Mn2+ cofactors to trigger multiple DNAzyme recycling cycles to show highly enhanced fluorescence at different wavelengths to realize sensitive and multiplexed imaging of PTEN mRNA and miRNA-221 for detecting the PI3K/AKT signaling pathway. Moreover, the regulation of PTEN mRNA expression by miRNA-221 upon stimulation by various drugs can also be verified by our method, indicating its promising potentials for both disease diagnosis and drug screening.

Tunable metal-organic frameworks assist in catalyzing DNAzymes with amplification platforms for biomedical applications

Various binding modes of tunable metal organic frameworks (MOFs) and functional DNAzymes (Dzs) synergistically catalyze the emergence of abundant functional nanoplatforms. Given their serial variability in formation, structural designability, and functional controllability, Dzs@MOFs tend to be excellent building blocks for the precise "intelligent" manufacture of functional materials. To present a clear outline of this new field, this review systematically summarizes the progress of Dz integration into MOFs (MOFs@Dzs) through different methods, including various surface infiltration, pore encapsulation, covalent binding, and biomimetic mineralization methods. Atomic-level and time-resolved catalytic mechanisms for biosensing and imaging are made possible by the complex interplay of the distinct molecular structure of Dzs@MOF, conformational flexibility, and dynamic regulation of metal ions. Exploiting the precision of DNAzymes, MOFs@Dzs constructed a combined nanotherapy platform to guide intracellular drug synthesis, photodynamic therapy, catalytic therapy, and immunotherapy to enhance gene therapy in different ways, solving the problems of intracellular delivery inefficiency and insufficient supply of cofactors. MOFs@Dzs nanostructures have become excellent candidates for biosensing, bioimaging, amplification delivery, and targeted cancer gene therapy while emphasizing major advancements and seminal endeavors in the fields of biosensing (nucleic acid, protein, enzyme activity, small molecules, and cancer cells), biological imaging, and targeted cancer gene delivery and gene therapy. Overall, based on the results demonstrated to date, we discuss the challenges that the emerging MOFs@Dzs might encounter in practical future applications and briefly look forward to their bright prospects in other fields.