Rectifying artificial nanochannels with multiple interconvertible permeability states.

Transmembrane channels play a vital role in regulating the permeation process, and have inspired recent development of biomimetic channels. Herein, we report a class of artificial biomimetic nanochannels based on DNAzyme-functionalized glass nanopipettes to realize delicate control of channel permeability, whereby the surface wettability and charge can be tuned by metal ions and DNAzyme-substrates, allowing reversible conversion between different permeability states. We demonstrate that the nanochannels can be reversibly switched between four different permeability states showing distinct permeability to various functional molecules. By embedding the artificial nanochannels into the plasma membrane of single living cells, we achieve selective transport of dye molecules across the cell membrane. Finally, we report on the advanced functions including gene silencing of miR-21 in single cancer cells and selective transport of Ca2+ into single PC-12 cells. In this work, we provide a versatile tool for the design of rectifying artificial nanochannels with on-demand functions.

Nanoconfined Electrokinetic Chromatography (NEC): Gradient Separation and Sensing of Short DNA Fragments at the Single-Molecule Level.

Glass nanopipets have been demonstrated to be a powerful tool for the sensing and discrimination of biomolecules, such as DNA strands with different lengths or configurations. Despite progress made in nanopipet-based sensors, it remains challenging to develop effective strategies that separate and sense in one operation. In this study, we demonstrate an agarose gel-filled nanopipet that enables hyphenated length-dependent separation and electrochemical sensing of short DNA fragments based on the electrokinetic flow of DNA molecules in the nanoconfined channel at the tip of the nanopipet. This nanoconfined electrokinetic chromatography (NEC) method is used to distinguish the mixture of DNA strands without labels, and the ionic current signals measured in real time show that the mixed DNA strands pass through the tip hole in order according to the molecular weight. With NEC, gradient separation and electrochemical measurement of biomolecules can be achieved simultaneously at the single-molecule level, which is further applied for programmable gene delivery into single living cells. Overall, NEC provides a multipurpose platform integrating separation, sensing, single-cell delivery, and manipulation, which may bring new insights into advanced bioapplication.

Smart Nanoplatform for Visualizing Hydrogen Sulfide and Amplifying Oxidative Stress to Tumor Apoptosis.

Oxidative stress is involved in various signaling pathways and serves a key role in inducing cell apoptosis. Therefore, it is significant to monitor oxidative stress upon drug release for the assessment of therapeutic effects in cancer cells. Herein, a glutathione (GSH)-responsive surface-enhanced Raman scattering (SERS) nanoplatform is proposed for ultra-sensitively monitoring the substance related with oxidative stress (hydrogen sulfide, H2S), depleting reactive sulfur species and releasing anticancer drugs to amplify oxidative stress for tumor apoptosis. The Au@Raman reporter@Ag (Au@M@Ag) nanoparticles, where a 4-mercaptobenzonitrile molecule as a Raman reporter was embedded between layers of gold and silver to obtain sensitive SERS response, were coated with a covalent organic framework (COF) shell to form a core-shell structure (Au@M@Ag@COFs) as the SERS nanoplatform. The COF shell loading doxorubicin (DOX) of Au@M@Ag@COFs exhibited the GSH-responsive degradation capacity to release DOX, and its Ag layer as the sensing agent was oxidized to Ag2S by H2S to result in its prominent changes in SERS signals with a low detection limit of 0.33 nM. Moreover, the releasing DOX can inhibit the generation of H2S to promote the production of reactive oxygen species, and the depletion of reactive sulfur species (GSH and H2S) in cancer cells can further enhance the oxidative stress to induce tumor apoptosis. Overall, the SERS strategy could provide a powerful tool to monitor the dynamic changes of oxidative stress during therapeutic processes in a tumor microenvironment.

Engineered Extracellular Vesicle-Encapsuled Nanoreactors for Effective Targeting and Cascade Killing of Cancer Cells.

Nanomaterials have presented great potential for cancer therapy. However, their therapeutic efficacy is not always satisfied because of inefficient biocompatibility and targeting efficacy. Here, we report engineered extracellular vesicle (EV)-encapsuled nanoreactors for the targeting and killing of cancer cells. EVs are extracted from engineered cancer cells with surface N-glycans cut and intracellular microRNA-21 (miR-21) silenced to generate cancer-targeting membranes for the following coating of gold-polydopamine (PDA) core-shell nanoparticles. The encapsuled nanoparticles are decorated with doxorubicin (Dox), glucose oxidase (GOx), and miR-21-indicative DNA tags. Once endocytosed, the acidic pH, together with the photothermal effect of the PDA shell, can promote the release of Dox and GOx-catalyzed H2O2 generation/glucose consumption, while the DNA tags allow enhanced fluorescence imaging of miR-21 to indicate the targeting effect. The coadministration of EV-assisted delivery and cascade treatment represents a promising strategy for combination therapy.

Dual-Modal Apoptosis Assay Enabling Dynamic Visualization of ATP and Reactive Oxygen Species in Living Cells.

ATP and reactive oxygen species (ROS) are considered significant indicators of cell apoptosis. However, visualizing the interplay between apoptosis-related ATP and ROS is challenging. Herein, we developed a metal-organic framework (MOF)-based nanoprobe for an apoptosis assay using duplex imaging of cellular ATP and ROS. The nanoprobe was fabricated through controlled encapsulation of gold nanorods with a thin zirconium-based MOF layer, followed by modification of the ROS-responsive molecules 2-mercaptohydroquinone and 6-carboxyfluorescein-labeled ATP aptamer. The nanoprobe enables ATP and ROS visualization via fluorescence and surface-enhanced Raman spectroscopy, respectively, avoiding the mutual interference that often occurs in single-mode methods. Moreover, the dual-modal assay effectively showed dynamic imaging of ATP and ROS in cancer cells treated with various drugs, revealing their apoptosis-related pathways and interactions that differ from those under normal conditions. This study provides a method for studying the relationship between energy metabolism and redox homeostasis in cell apoptosis processes.

Dynamic Visualization of Endoplasmic Reticulum Stress in Living Cells via a Two-Stage Cascade Recognition Process.

The endoplasmic reticulum (ER) is crucial for the regulation of multiple cellular processes, such as cellular responses to stress and protein synthesis, folding, and posttranslational modification. Nevertheless, monitoring ER physiological activity remains challenging due to the lack of powerful detection methods. Herein, we built a two-stage cascade recognition process to achieve dynamic visualization of ER stress in living cells based on a fluorescent carbon dot (CD) probe, which is synthesized by a facile one-pot hydrothermal method without additional modification. The fluorescent CD probe enables two-stage cascade ER recognition by first accumulating in the ER as the positively charged and lipophilic surface of the CD probe allows its fast crossing of multiple membrane barriers. Next, the CD probe can specifically anchor on the ER membrane via recognition between boronic acids and o-dihydroxy groups of mannose in the ER lumen. The two-stage cascade recognition process significantly increases the ER affinity of the CD probe, thus allowing the following evaluation of ER stress by tracking autophagy-induced mannose transfer from the ER to the cytoplasm. Thus, the boronic acid-functionalized cationic CD probe represents an attractive tool for targeted ER imaging and dynamic tracking of ER stress in living cells.

Potential environmental risks of nanopesticides: Application of Cu(OH)2 nanopesticides to soil mitigates the degradation of neonicotinoid thiacloprid.

Cu(OH)2 nanopesticides and organic insecticides are continuously applied to soil at a temporal interval, while knowledge about the impact of Cu(OH)2 nanopesticides on organic insecticides degradation is currently scarce, resulting in poorly comprehensive evaluation of the potential environmental risks of Cu(OH)2 nanopesticides. Herein, a commercial Cu(OH)2 nanopesticide formulation (NPF), the active ingredient of NPF (AI-NPF), the prepared Cu(OH)2 nanotubes (NT) with comparable morphology and size to AI-NPF, and CuSO4 were respectively applied to soil at normal doses (0.5, 5 and 50 mg/kg), followed by an application of neonicotinoid thiacloprid after an interval of 21 d, showing that NPF at doses of 5 and 50 mg/kg significantly (p < 0.05) mitigated thiacloprid degradation compared to control and CuSO4. Furthermore, AI-NPF was the primary component that contributed to the mitigation effect of NPF, which was also validated by the NT. Large differences in the degradation efficiency of thiacloprid in sterilized and unsterilized soils with Cu(OH)2 nanopesticides suggested that biodegradation was the primary process responsible for thiacloprid degradation, especially as chemical degradation was negligible. Besides a decrease of thiacloprid bioavailability due to adsorption by Cu(OH)2 nanopesticides, we demonstrated that Cu(OH)2 nanopesticides changed soil microbial communities, reduced nitrile hydratase activity and down-regulated thiacloprid-degradative nth gene abundance, which thus mitigated thiacloprid biodegradation. Clearly, this study shed light on the potential environmental risks of Cu(OH)2 nanopesticide.