An activatable fluorescent-photoacoustic dual-modal probe for highly sensitive imaging of nitroxyl in vivo.

Nitroxyl (HNO) plays a vital role in various biological functions and pharmacological activities, so the development of an excellent near-infrared fluorescent (NIRF) and photoacoustic (PA) dual-modality probe is crucial for understanding HNO-related physiological and pathological progression. Herein, we proposed and synthesized a novel NIRF/PA dual probe (QL-HNO) by substituting an indole with quinolinium in hemicyanine for the sensitive detection of exogenous and endogenous HNO in vivo. The designed probe showed the highest sensitivity in NIRF mode and a desirable PA signal-to-noise ratio for HNO detection in vitro and was further applied for NIRF/PA dual-modal imaging of HNO with high contrast in living cells and tumor-bearing animals. Based on the excellent performance of QL-HNO, we believe that this study provides a promising molecular tool for further understanding of HNO-related physiological and pathological progression.

Recombinant Fusion Streptavidin as a Scaffold for DNA Nanotetrads for Nucleic Acid Delivery and Telomerase Activity Imaging in Living Cells.

Efficient platforms for intracellular delivery of nucleic acids are essential for biomedical imaging and gene regulation. We develop a recombinant fusion streptavidin as a novel protein scaffold for DNA nanotetrads for highly efficient nucleic acid delivery and telomerase activity imaging in living cells via cross-linking hybridization chain reaction (cHCR). The recombinant streptavidin protein is designed to fuse with multiple SV40 NLS (nuclear localization signal) and NES (nuclear export signal) domains and prepared through Escherichia coli expression. The recombinant NLS-SA protein allows facile assembly with four biotinylated DNA probes via high-affinity noncovalent interactions, forming a well-defined DNA tetrad nanostructure. The DNA nanotetrads are demonstrated to confer efficient cytosolic delivery of nucleic acid via a caveolar mediated endocytosis pathway, allowing efficient escape from lysosomal degradation. Moreover, the nanotetrads enable efficient cHCR assembly in response to telomerase in vitro and in cellulo, affording ultrasensitive detection and spatially resolved imaging for telomerase with a detection limit as low as 90 HeLa cells/mL. The fluorescence brightness obtained in live cell imaging is found to be dynamically correlated to telomerase activity and the inhibitor concentrations. Therefore, the proposed strategy may provide a highly efficient platform for nucleic acid delivery and imaging of biomarkers in living cells.

Tumor-Targeted Graphitic Carbon Nitride Nanoassembly for Activatable Two-Photon Fluorescence Imaging.

Unique physicochemical characteristics of graphitic carbon nitride (g-CN) nanosheets suit them to be a useful tool for two-photon fluorescence bioimaging. Current g-CN nanosheets based imaging probes typically use the "always-on" design strategies, which may suffer from increased fluorescence background and limited contrast. To advance corresponding applications, g-CN nanosheets based activatable two-photon fluorescence probes remain to be explored. For the first time, we developed an activatable two-photon fluorescence probe, constructed from a nanoassembly of g-CN nanosheets and hyaluronic acid (HA)-gold nanoparticles (HA-AuNPs), for detection and imaging of hyaluronidase (HAase) in cancer cells. The deliberately introduced HA in our design not only functions as the buffering layer for stabilizing AuNPs and inducing corresponding self-assembly on g-CN nanosheets but also as a pilot for targeting HA receptors overexpressed on cancer cell surfaces. Our results show that the developed nanoassembly enables specific detection and activatable imaging of HAase in cancer cells and deep tissues, with superb signal-to-background ratio and high sensitivity. This nanoassembly can afford a promising platform for highly specific and sensitive imaging of HAase and for related cancer diagnosis.

Potential biomarkers for monitoring the toxicity of long-term exposure to atrazine in rat by metabonomic analysis.

1. Herbicide atrazine (ATR) poses harmful effects on human health. The purpose of this study is to study potential biomarkers used for monitoring the toxic effects after chronic exposure to ATR by studying urine metabolites. 2. Rats were assigned into clinical chemistry and metabonomics arms, and each arm was divided into low-dose, high-dose and control groups. ATR was administered to rats along with their feed. At the end of 16, 20 and 24 weeks, clinical parameters and histopathologic changes was assessed to monitor the toxic effects. Twenty-four hour urine samples was analyzed by UPLC-MS, to find the significant alterations in metabolic profiling. 3. The body weight of rats in ATR group was lower than that of control starting from 12th week; abnormal levels of serum biochemistry and histopathologic alterations of organs were found initially from 16th and 20th week, respectively. Five exogenous and five endogenous metabolites were found which showed significant differences between ATR groups and control group at above-mentioned time points. 4. These metabolites may be used as potential indicators to monitor ATR toxicity, and also may provide some clues for understanding the mechanism of toxicity of ATR. The exact relationship between endogenous metabolites and ATR toxicity needs further investigation.

Plasmon Coupling Enhanced Raman Scattering Nanobeacon for Single-Step, Ultrasensitive Detection of Cholera Toxin.

We report the development of a novel plasmon coupling enhanced Raman scattering (PCERS) method, PCERS nanobeacon, for ultrasensitive, single-step, homogeneous detection of cholera toxin (CT). This method relies on our design of the plasmonic nanoparticles, which have a bilayer phospholipid coating with embedded Raman indicators and CT-binding ligands of monosialoganglioside (GM1). This design allows a facile synthesis of the plasmonic nanoparticle via two-step self-assembly without any specific modification or chemical immobilization. The realization of tethering GM1 on the surface imparts the plasmonic nanoparticles with high affinity, excellent specificity, and multivalence for interaction with CT. The unique lipid-based bilayer coated structure also affords excellent biocompatibility and stability for the plasmonic nanoparticles. The plasmonic nanoparticles are able to show substantial enhancement of the surface-enhanced Raman scattering (SERS) signals in a single-step interaction with CT, because of their assembly into aggregates in response to the CT-sandwiched interactions. The results reveal that the developed nanobeacon provides a simple but ultrasensitive sensor for rapid detection of CT with a large signal-to-background ratio and excellent reproducibility in a wide dynamic range, implying its potential for point-of-care applications in preventive and diagnostic monitoring of cholera.

Catalytic Hairpin Assembly-Based Self-Ratiometric Gel Electrophoresis Detection Platform for Reliable Nucleic Acid Analysis.

The development of gel electrophoresis-based biodetection assays for point-of-care analysis are highly demanding. In this work, we proposed a ratiometric gel electrophoresis-based biosensing platform by employing catalytic hairpin assembly (CHA) process functions as both the signal output and the signal amplification module. Two types of nucleic acids, DNA and miRNA, are chosen for demonstration. The proposed strategy indeed provides a new paradigm for the design of a portable detection platform and may hold great potential for sensitive diagnoses.

Enzymatic control of plasmonic coupling and surface enhanced Raman scattering transduction for sensitive detection of DNA demethylation.

We have developed a novel concept for enzymatic control of plasmonic coupling as a surface enhanced Raman scattering (SERS) nanosensor for DNA demethylation. This nanosensor is constructed by decorating gold nanoparticles (AuNPs) with Raman reporters and hemimethylated DNA probes. Demethylation of DNA probes initiates a degradation reaction of the probes by methylation-sensitive endonuclease Bsh 1236I and single-strand selective exonuclease I. This destabilizes AuNPs and mediates the aggregation of AuNPs, generating a strong plasmonic coupling SERS signal in response to DNA demethylation. This nanosensor has the advantages in its high signal-to-noise ratio, superb specificity, and rapid, convenient, and reproducible detection with homogeneous, single-step operation. Thus, it provides a useful platform for detecting DNA demethylation and related molecular diagnostics and drug screening. This work is the first time that enzymatic degradation of DNA substrate probes has been utilized to induce aggregation of AuNPs such that reproducible, sensitive SERS signals can be achieved from biological recognition events. This enzymatic control mechanism for plasmonic coupling may create a new paradigm for the development of SERS nanosensors.

pH-Responsive DNA nanoassembly for detection and combined therapy of tumor.

We have developed a novel cancer theragnostic nanoassembly with high biocompatibility, stability and low toxicity which are activated rapidly by tumor microenvironment to realize selective fluorescence imaging, chemotherapy as well as chemoenzymatic therapy. The nanoprobes are synthesized by hybridization of fluorophore labeled hairpin DNAs containing a 5-aza-dC at hemimethylated CpG sites and pH-sensitive DNA sequence covalently conjugated with PEGylated GO. The aptamer, which is also covalently conjugated on PEGylated GO, enables to target the tumor site and the weak acid environment of tumor triggers the release of drug loaded by nanoprobes including functionalized DNA and DOXs, effectively activating fluorescence signals and selectively killing the tumor cells. The results revealed that the nanoprobe enables sensitive detection of pH changes within subcellular environment, selectively imaging and great synergy of multicombination therapeutic including chemotherapy and chemoenzymatic therapy, implying that developed pH activatable probe has considerable potential for diagnosis and efficient therapy of cancer.

Rational design of a HA-AuNPs@AIED nanoassembly for activatable fluorescence detection of HAase and imaging in tumor cells.

Aggregation induced emission (AIE) dots have gained broad attention in fluorescence bioimaging and biosensors in virtue of their distinctive optical properties of splendid biocompatibility, high brightness and good photostability. However, the application of AIE dots in sensing and imaging of enzymes in cells remains at an early stage and needs to be further explored. In this report, we proposed a novel AIE-dot-based nanoprobe for hyaluronidase (HAase) detection using a simple electrostatic self-assembly of AIE dots with gold nanoparticles functionalized using hyaluronic acid (HA-AuNPs), named HA-AuNPs@AIEDs. The fluorescence of AIE dots can be obviously quenched by HA-AuNPs via fluorescence resonance energy transfer (FRET). HAase could degrade HA into small pieces and thus induce disassembly of AuNPs and AIEDs, accompanied by fluorescence recovery of AIEDs. The as-prepared nanoprobe exhibited high sensitivity, excellent selectivity, wide response range and desirable anti-interference for quantitative sensing of HAase in vitro. The detection limit was down to 0.0072 U mL-1. Moreover, the nanoprobe displayed good biocompatibility and excellent photostability, and thus offered a practicable "turn-on" strategy for specific, high-contrast fluorescence imaging of HAase in live tumor cells. The AIE-based nanoprobe may provide a novel universal platform for recognition and imaging of HAase in tumors, and may be beneficial for related biological research.

[Effects of spraying salicylic acid and potassium dihydrogen phosphate on physiological cha-racteristics and grain yield of single-season rice under high temperature condition]. / é«˜æ¸©ä¸‹å–·æ–½æ°´æ¨é ¸å’Œç£·é ¸äºŒæ°¢é’¾å¯¹ä¸­ç¨»ç”Ÿç†ç‰¹å¾å’Œäº§é‡çš„å½±å“.

To explore new practical means of alleviating the negative effect of heat stress on rice plants during the heading-flowering stage, a field experiment was conducted in Ji'an, Yugan, and Nanchang counties of Jiangxi Province from 2017 to 2018 with three indica hybrid rice varieties. Under ambient high temperature condition during the heading-flowering period, we sprayed five concentrations of salicylic acid (SA) (SA1-SA5: 100, 500, 1000, 1500, 2000 µmol·L-1) and five concentrations of KH2PO4 (K1-K5: 7.35, 14.70, 22.05, 29.40, 36.75 mmol·L-1) on the leave of rice, with deionized water as the control (CK), to mesure the physiological characteristics and grain yield. The results showed that compared to CK,plants treated with SA and KH2PO4 had higher chlorophyll content, soluble sugar content, soluble protein content, proline content, supero-xide dismutase activity, and peroxidase activity, but a lower malonaldehyde content, among which SA2 and K3 treatments performed the best. The treatments of SA2, SA3, K3, and K4 increased the number of grains per panicle, seed-setting rate, and grain yield, with the effects of SA2 and K3 treatments being significant. Compared to CK, the SA2 treatments enhanced the number of grains per panicle, seed-setting rate, and grain yield by 7.0%, 4.0%, and 11.9%, respectively; the K3 treatments enhanced the number of grains per panicle, seed-setting rate, and grain yield by 3.9%, 4.7%, and 6.6%, respectively. The optimal measure was spraying 500 µmol·L-1 SA or 22.05 mmol·L-1 KH2PO4, which could significantly increase grain yield of single-season rice under high temperature condition during the heading-flowering period.

Sub-chronic Toxicity of Defoamer Used in Seawater Desalination.

OBJECTIVE: To explore the possible long-term health effects of the defoamer used in seawater desalination by sub-chronic toxicity testing. METHODS: Blood analysis, internal organ assessment, and histopathological examination were carried out in rats exposed to low, medium, and high (0.5, 1.0, and 2.0 g/kg BW, respectively) doses of defoamer for 90 days through oral administration. RESULTS: The high dose group showed decreased blood alanine aminotransferase and aspartate aminotransferase (P < 0.05). All doses resulted in a significant increase in albumin and decrease in globulin (P < 0.05). The direct bilirubin and indirect bilirubin were decreased in the medium and high dose groups (P < 0.05). All dose groups showed significant induction of alkaline phosphatase (P < 0.05). Pathological examination revealed a case of liver mononuclear cell infiltration in the medium dose group and three cases of liver congestion, steatosis of hepatic cells around the central vein, and punctate necrosis with multiple focal mononuclear cell infiltration in male rats administered the high dose. The No Observed Adverse Effect Level was 0.5 g/kg BW in rats, with albumin and total bilirubin as health effect indices. CONCLUSION: Long-term defoamer exposure may cause liver injury but has no significant impact on renal function in rats. The effect on blood cells in female rats was more prominent than that in male rats.

Conjugated polymer nanoparticles-based fluorescent biosensor for ultrasensitive detection of hydroquinone.

This work describes a simple and sensitive fluorescent method for detection of hydroquinone utilizing conjugated polymer nanoparticles (CPNs). The CPNs serve both as a catalyst to accelerate the conversion of hydroquinone to benzoquinone and a fluorescent probe. In the presence of hydroquinone, the fluorescence of CPNs can be effectively quenched by benzoquinone. The detection limit of hydroquinone was down to 5 nM and excellent selectivity toward possible interferences was obtained. This method was successfully applied for hydroquinone detection in lake water and satisfactory results were achieved.

Amplified Split Aptamer Sensor Delivered Using Block Copolymer Nanoparticles for Small Molecule Imaging in Living Cells.

We develop a novel amplified split aptamer sensor for highly sensitive detection and imaging of small molecules in living cells by using cationic block copolymer nanoparticles (BCNs) with entrapped fluorescent conjugated polymer as a delivery agent. The design of a split aptamer as the initiator of hybridization chain reaction (HCR) affords the possibility of enhancing the signal-to-background ratio and thus allows high-contrast imaging for small molecules with relatively weak interactions with their aptamers. The novel design of using fluorescent cationic BCNs as the nanocarrier enables efficient and self-tracking transfection of DNA probes. Results reveal that BCNs exhibit high fluorescence brightness allowing direct tracking of the delivery location. The developed amplified split aptamer sensor is shown to have high sensitivity and selectivity for in vitro quantitative detection of adenosine triphosphate (ATP) with a detection limit of 30 nM. Live cell studies show that the sensor provides a "signal on" approach for specific, high-contrast imaging of ATP. The DNA sensor based HCR system may provide a new generally applicable platform for detection and imaging of low-abundance biomarkers.

Enzymatic activatable self-assembled peptide nanowire for targeted therapy and fluorescence imaging of tumors.

We developed novel activatable probe using self-assembled peptide nanowires with low affinity and toxicity to tumor cells in the absence of matrix metalloproteinase that showed activated high affinity and toxicity and provided a highly selective and efficient platform for targeted therapy and tumor imaging.

Ultrasensitive detection of microRNAs using catalytic hairpin assembly coupled with enzymatic repairing amplification.

A novel isothermal nucleic acid amplification technology is developed by coupling catalytic hairpin assembly with enzymatic repairing amplification as a highly sensitive and selective platform for miRNA detection.

[Apoptosis of olfactory receptor neurons induced by bulbectomy].

OBJECTIVE: To study whether apoptosis plays a role in controlling the number of olfactory receptor neurons, so as to reveal the specialty and mystery of neurogenesis. METHODS: Using terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL) and transmission electron microscopy to detect apoptosis in olfactory mucosa of normal adult rats and damaged olfactory mucosa of 16, 32, 48 hours and 3, 7, 30 days after bulbectomy. RESULTS: In normal olfactory epithelium, a subpopulation of immature neurons, as well as mature neurons, showed internucleosomal DNA-fragmentation. The number of TUNEL-labeled neurons increased dramatically 32 hours after removal of olfactory bulb. Then it declined quickly and remained at low level. Ultrastructural data of olfactory mucosa showed that the feature of apoptotic neurons was chromatin condensation and cell shrinkage. Besides, some dying cells were characterized by the formation of numerous autophagic vacuoles, and few had some of the features of necrosis but without obvious mitochondrial swelling. CONCLUSIONS: Apoptosis might play a role in turnover of the olfactory epithelium and regeneration in adult rats. There might be other two types of neural death through different mechanism.