Binary System for MicroRNA-Targeted Imaging in Single Cells and Photothermal Cancer Therapy

Abnormal expression of microRNAs (miRNAs) is often associated with tumorigenesis, metastasis, and progression. Among them, miRNA-21 is found to be overexpressed in most of the cancer cells. Here, a binary system is designed for miRNA-21 targeted imaging and photothermal treatment in single cells. The binary system is composed by a pair of probes (probe-1 and probe-2), which are encapsulated in liposomes for cell delivery. Both of the two probes adopt gold nanoparticles (AuNPs) as the core material, and the AuNPs are functionalized with Cy5-marked molecular beacon (MB-1/MB-2 for probe-1/probe-2, respectively). The loop part of MBs are designed to be complementary with miRNA-21. Therefore, after the binary system enters into the cytoplasm, MBs can be opened upon miRNA-21 triggered hybridization, which turns “on” the fluorescence of Cy5 for the localization of miRNA-21. At the same time, a cross-linking between the probes occurs since the far ends of MB-1 and MB-2 are designed to be complementary with each other. The miRNA-induced aggregation shifts the absorption of AuNPs to near-infrared, which can be observed under dark-field microscopy (DFM) and used for the following photothermal therapy. Under near-infrared (NIR) irradiation, MCF-7 breast cancer cells are successfully killed. The proposed system can be further applied in tumor-bearing mice and shows significant therapeutic effect. This work provides a new tool for intracellular miRNA analysis and targeted treatment against cancer

Electrocatalytic Efficiency Analysis of Catechol Molecules for NADH Oxidation during Nanoparticle Collision

Electrocatalysis of molecules is a hot research topic in biological and energy-related chemistry. Here, we develop a new system to study the electrocatalytic efficiency of a single catechol molecule for NADH oxidation by single functionalized nanoparticle collision at ultramicroelectrodes (UMEs). The proposed system is composed of gold nanoparticles (AuNPs) functionalized with catechol molecules and a carbon-fiber ultramicroelectrode. In the absence of NADH, when a functionalized AuNP collides with an UME at a suitable voltage, a small current spike is generated due to the oxidation of catechol molecules modified on the surface of AuNP. In the presence of NADH, the current spike is significantly amplified by the combined effects of the oxidation and electrocatalysis for NADH of catechol molecules. By analyzing the variations of the average peak charges and durations without or with NADH, we calculate that around five thousands NADH molecules could be catalyzed per second by a single catechol molecule, suggesting the successful establishment of this novel catalytic system. Thus, the proposed strategy could be used as a promising platform for research of other molecular electrocatalytic systems

Large-Scale Manual Grinding Preparation of Ultrathin Porous Sulfur (S₈)‑Anchored ScOOH Nanosheets for Photothermal Conversion and Dye Adsorption

Porous two-dimensional (2D) nanomaterials have attracted much attention in recent years and shown unique electronic and physicochemical properties by utilizing the advantages of both porous structure and 2D architecture. However, the low-cost, large-scale, and high-quality synthesis of porous 2D nanomaterials is still very challenging. Herein, for the first time, we develop a facile manual grinding strategy for the preparation of ultrathin porous sulfur (S8)-anchored ScOOH nanosheets (S8/ScOOH-NSs) by the mechanical stripping of S8-anchored ScOOH nanorods (S8/ScOOH-NRs). The formation of S8/ScOOH-NSs should be due to the intrinsic lamellar structure of S8/ScOOH-NRs. The obtained S8/ScOOH-NSs with rich mesopores have a high-quality crystal structure. Because of hydrophobic sulfur and carbon components on the surface, S8/ScOOH-NSs show good hydrophobicity. In addition, S8/ScOOH-NSs exhibit more excellent photothermal conversion efficiency and adsorption capacity compared with S8/ScOOH-NRs, which is directly attributed to the synergistic effect of sulfur-doping, porous structure, and 2D architecture. Therefore, the facile and large-scale synthesis strategy endows S8/ScOOH-NSs with multifunctional properties that have great application prospects in water cleaning and photothermal evaporators

AuNPs-COFs Core–Shell Reversible SERS Nanosensor for Monitoring Intracellular Redox Dynamics

The redox homeostasis in living cells is greatly crucial for maintaining the redox biological function, whereas accurate and dynamic detection of intracellular redox states still remains challenging. Herein, a reversible surface-enhanced Raman scattering (SERS) nanosensor based on covalent organic frameworks (COFs) was prepared to dynamically monitor the redox processes in living cells. The nanosensor was fabricated by modifying the redox-responsive Raman reporter molecule, 2-Mercaptobenzoquione (2-MBQ), on the surface of gold nanoparticles (AuNPs), followed by the in situ coating of COFs shell. 2-MBQ molecules can repeatedly and quickly undergo reduction and oxidation when successively treated with ascorbic acid (AA) and hypochlorite (ClO–) (as models of reductive and oxidative species, respectively), which resulted in the reciprocating changes of SERS spectra at 900 cm–1. The construction of the COFs shell provided the nanosensor with great stability and anti-interference capability, thus reliably visualizing the dynamics of intracellular redox species like AA and ClO– by SERS nanosensor. Taken together, the proposed SERS strategy opens up the prospects to investigate the signal transduction pathways and pathological processes related with redox dynamics

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