Quantum Dot Based Fluorescent Traffic Light Nanoprobe for Specific Imaging of Avidin-Type Biotin Receptor and Differentiation of Cancer Cells.

Sensitive and specific visualization of cell surface biotin receptors (BRs) a class of clinically important biomarkers, remains a challenge. In this work, a dual-emission ratiometric fluorescent nanoprobe is developed for specific imaging of cell surface avidin, a subtype of BRs. The nanoprobe comprises a dual-emission quantum dot nanohybrid, wherein a silica-encapsulated red-emitting QD (rQD@SiO2) is used as the "core" and green-emitting QDs (gQDs) are used as "satellites", which are further decorated with a new "love-hate"-type BR ligand, a phenanthroline-biotin conjugate with an amino linker. The nanoprobe shows intense rQD emission but quenched gQD emission by the BR ligand. Upon imaging, the rQD emission stays constant and the gQD emission is restored as cell surface avidin accrues. Accordingly, the overlaid fluorescence color collected from red and green emission changes from red to yellow and then to green. We refer to such a color change as a traffic light pattern and the nanoprobe as a fluorescent traffic light nanoprobe. We demonstrate the application of our fluorescent traffic light nanoprobe to characterize cancer cells. By the traffic light pattern, cervical carcinoma and normal cells, as well as different-type cancer cells including BR-negative colon cancer cells, BR-positive hepatoma carcinoma cells, breast cancer cells, and their subtypes, have been visually differentiated. We further demonstrate a use of our nanoprobe to distinguish the G2 phase from other stages in a cell cycle. These applications provide new insights into visualizing cell surface biomarkers with remarkable imaging resolution and accuracy.

Strand Displacement Amplification Reaction on Quantum Dot-Encoded Silica Bead for Visual Detection of Multiplex MicroRNAs.

The combination of microbead array, isothermal amplification, and molecular signaling enables the continuous development of next-generation molecular diagnostic techniques. Herein we reported the implementation of nicking endonuclease-assisted strand displacement amplification reaction on quantum dots-encoded microbead (Qbead), and demonstrated its feasibility for multiplexed miRNA assay in real sample. The Qbead featured with well-defined core-shell superstructure with dual-colored quantum dots loaded in silica core and shell, respectively, exhibiting remarkably high optical encoding stability. Specially designed stem-loop-structured probes were immobilized onto the Qbead for specific target recognition and amplification. In the presence of low abundance of miRNA target, the target triggered exponential amplification, producing a large quantity of stem-G-quadruplexes, which could be selectively signaled by a fluorescent G-quadruplex intercalator. In one-step operation, the Qbead-based isothermal amplification and signaling generated emissive "core-shell-satellite" superstructure, changing the Qbead emission-color. The target abundance-dependent emission-color changes of the Qbead allowed direct, visual detection of specific miRNA target. This visualization method achieved limit of detection at the subfemtomolar level with a linear dynamic range of 4.5 logs, and point-mutation discrimination capability for precise miRNA analyses. The array of three encoded Qbeads could simultaneously quantify three miRNA biomarkers in ∼500 human hepatoma carcinoma cells. With the advancements in ease of operation, multiplexing, and visualization capabilities, the isothermal amplification-on-Qbead assay could potentially enable the development of point-of-care diagnostics.

Quantum Dots-Ligand Complex as Ratiometric Fluorescent Nanoprobe for Visual and Specific Detection of G-Quadruplex.

By complexing a nonionic G-quadruplex ligand with hybrid dual-emission quantum dots (QDs), a ratiometric fluorescent nanoprobe is developed for G-quadruplex detection in a sensitive and specific manner. The QDs nanohybrid comprised of a green-emission QD (gQD) and multiple red-emission QDs (rQDs) inside and outside of a silica shell, respectively, is utilized as the signal displaying unit. Only the presence of G-quadruplex can displace the ligand from QDs, breaking up the QDs-ligand complexation, and inducing the restoration of the rQDs fluorescence. Since the fluorescence of embedded gQD stays constant, variations of the dual-emission intensity ratios display continuous color changes from green to bright orange, which can be clearly observed by the naked eye. Furthermore, by utilizing competitive binding of a cationic ligand versus the nonionic ligand toward G-quadruplex, the nanoprobe is demonstrated to be applicable for assessing the affinity of a G-quadruplex-targeted anticancer drug candidate, exhibiting ratiometric fluorescence signals (reverse of that for G-quadruplex detection). By making use of the specificity of the ligand binding with G-quadruplex against a double helix, this nanoprobe is also demonstrated to be capable of sensitive detection of one-base mutation, exhibiting sequence-specific ratiometric fluorescence signals. By functionalizing with a nuclear localization peptide, the nanoprobe can be used for visualization of G-quadruplex in the nucleus of human cells.

Recent Advances in Light Penetration Depth for Postharvest Quality Evaluation of Fruits and Vegetables.

Light penetration depth, as a characteristic parameter reflecting light attenuation and transmission in biological tissues, has been applied in nondestructive detection of fruits and vegetables. Recently, with emergence of new optical detection technologies, researchers have begun to explore methods evaluating optical properties of double-layer or even multilayer fruit and vegetable tissues due to the differences between peel and pulp in the chemical composition and physical properties, which has gradually promoted studies on light penetration depth. A series of demonstrated research on light penetration depth could ensure the accuracy of the optical information obtained from each layer of tissue, which is beneficial to enhance detection accuracy for quality assessment of fruits and vegetables. Therefore, the aim of this review is to give detailed outlines about the theory and principle of light penetration depth based on several emerging optical detection technologies and to focus primarily on its applications in the field of quality evaluation of fruits and vegetables, its future applicability in fruits and vegetables and the challenges it may face in the future.

Identification of Hub Genes and Their Correlation With Immune Infiltration Cells in Hepatocellular Carcinoma Based on GEO and TCGA Databases.

Hepatocellular carcinoma (HCC) is a primary liver cancer with extremely high mortality in worldwide. HCC is hard to diagnose and has a poor prognosis due to the less understanding of the molecular pathological mechanisms and the regulation mechanism on immune cell infiltration during hepatocarcinogenesis. Herein, by performing multiple bioinformatics analysis methods, including the RobustRankAggreg (RRA) rank analysis, weighted gene co-expression network analysis (WGCNA), and a devolution algorithm (CIBERSORT), we first identified 14 hub genes (NDC80, DLGAP5, BUB1B, KIF20A, KIF2C, KIF11, NCAPG, NUSAP1, PBK, ASPM, FOXM1, TPX2, UBE2C, and PRC1) in HCC, whose expression levels were significantly up-regulated and negatively correlated with overall survival time. Moreover, we found that the expression of these hub genes was significantly positively correlated with immune infiltration cells, including regulatory T cells (Treg), T follicular helper (TFH) cells, macrophages M0, but negatively correlated with immune infiltration cells including monocytes. Among these hub genes, KIF2C and UBE2C showed the most significant correlation and were associated with immune cell infiltration in HCC, which was speculated as the potential prognostic biomarker for guiding immunotherapy.

Co3(2-OOCC6H4PO3)2(H2O)3·H2O: a layered metal phosphonate showing reversible dehydration-rehydration behavior and ferrimagnetism.

Two isostructural metal phosphonates M3(2-cpp)2(H2O)3·H2O [M(II) = Co (1), Zn (2), 2-cppH3 = 2-carboxyphenylphosphonic acid] are synthesized and structurally characterized. Both exhibit layer structures in which -Co-O- "columns" are connected by the {PO3C} linkages. The "column" consists of triangular shaped {M3O3} trimers, inter-linked through either corner- or edge-sharing of the {MO6} octahedra. The phenyl groups are grafted on the two sides of the inorganic layer. Thermal analyses suggest that the layer structures of 1 and 2 are stable after removal of the lattice and coordination water. The dehydrated sample can be rehydrated reversibly in the case of compound 1. Magnetic studies reveal that antiferromagnetic interactions dominate in both 1 and 1-de, resulting in ferrimagnetic layers in both cases. The large inter-layer distance in 1 favors a ferromagnetic interaction between the layers. Hence ferrimagnetism is observed in both cases at low temperature. For 1-de, slow magnetization relaxation is also observed below ca. 2.8 K.