Fluorescence Enhancement Method for Aptamer-Templated Silver Nanoclusters and Its Application in the Construction of a ß-Amyloid Oligomer Sensor.

DNA-templated silver nanoclusters (DNA-AgNCs) have attracted significant attention due to their unique fluorescence properties. However, so far, the relatively low quantum yields of the DNA-AgNCs and the complex design of DNA-AgNC-based sensors have limited their application in biosensing or bioimaging. Herein, we report a novel fluorescence enhancement method. The ß-Amyloid Oligomer (AßO) aptamer (AptAßO) with A10/T10 at its 3' end can be directly used as the template to fabricate the AgNCs. When the AgNCs were hybridized with the complementary strand that has 12 bases suspended at its 3' terminal, being the same or complementary to the A/T at the 3' end of the AptAßO, and two-base mismatches in the complementary region of the aptamer excluded A10/T10, a dramatic fluorescence enhancement (maximum: ∼500-fold; maximum quantum yield: 31.5%) can be realized. The fluorescence enhancement should result from the aggregation-induced emission of the AgNCs, which can be attributed to forming the reticular structure of the hybridized product. To some extent, the method developed in this work is extendable. The fluorescence enhancement was also realized from the thrombin aptamer-templated AgNCs through designing the aptamer and the corresponding complementary strand according to the method. Based on the fluorescence enhancement of the AptAßO-templated AgNCs, an "on-off" fluorescence sensor was constructed for the sensitive and selective detection of AßO. This work provides a rational strategy to realize fluorescence enhancement for the aptamer-templated AgNCs and design an aptamer-based fluorescence sensor.

Simultaneous Monitoring of the Adenosine Triphosphate Levels in the Cytoplasm and Nucleus of a Single Cell with a Single Nanowire-Based Fluorescent Biosensor.

Simultaneous monitoring of the ATP levels at various sites of a single cell is crucial for revealing the ATP-related processes and diseases. In this work, we rationally fabricated single nanowire-based fluorescence biosensors, by which the ATP levels of the cytoplasm and nucleus in a single cell can be simultaneously monitored with a high spatial resolution. Utilizing the as-fabricated single nanowire biosensor, we demonstrated that the ATP levels of the cytoplasm were around 20-30% lower than that of the nucleus in both L929 and HeLa cells. Observing the ATP fluctuation of the cytoplasm and nucleus of the L929 and HeLa cells stimulated by Ca2+, oligomycin, or under cisplatin-induced apoptosis, we found that the ATP levels at two cellular sites exhibited discriminative changes, revealing the different mechanisms of the ATP at these two cellular sites in response to the stimulations.

Sensitive and Stable Thermometer Based on the Long Fluorescence Lifetime of Au Nanoclusters for Mitochondria.

Detecting the temperature of intracellular mitochondria with high sensitivity and stability is crucial to understanding the cellular metabolism and revealing the processes of mitochondria-related physiology. In this paper, employing the long fluorescence lifetime of modified Au nanoclusters (mAuNCs) by 4-(carboxybutyl) triphenylphosphonium bromide, we developed a fluorescence lifetime thermometer with high sensitivity and stability for the temperature of the intracellular mitochondria. A high relative temperature sensitivity of 2.8% and excellent photostability were achieved from the present thermometer. After incubation with L929 cells, the mAuNCs could be endocytosed into the cells and targeted the mitochondria, and the temperature changes at the L929 cells' mitochondria, which were stimulated by carbonyl cyanide 3-chlorophenylhydrazone and Ca2+, were successfully detected via the fluorescence lifetime images of the mAuNCs. Furthermore, utilizing the mAuNCs, we clarified the effect of Mg2+ on the temperature of the intracellular mitochondria. The strategy of employing a material with a long fluorescence lifetime and remarkable stability to fabricate the fluorescence lifetime thermometer for mitochondria can be used to design various thermometers for other organelles.

Comparative Study of Different Methods in Vibration-Based Terrain Classification for Wheeled Robots with Shock Absorbers.

Autonomous robots that operate in the field can enhance their security and efficiency by accurate terrain classification, which can be realized by means of robot-terrain interaction-generated vibration signals. In this paper, we explore the vibration-based terrain classification (VTC), in particular for a wheeled robot with shock absorbers. Because the vibration sensors are usually mounted on the main body of the robot, the vibration signals are dampened significantly, which results in the vibration signals collected on different terrains being more difficult to discriminate. Hence, the existing VTC methods applied to a robot with shock absorbers may degrade. The contributions are two-fold: (1) Several experiments are conducted to exhibit the performance of the existing feature-engineering and feature-learning classification methods; and (2) According to the long short-term memory (LSTM) network, we propose a one-dimensional convolutional LSTM (1DCL)-based VTC method to learn both spatial and temporal characteristics of the dampened vibration signals. The experiment results demonstrate that: (1) The feature-engineering methods, which are efficient in VTC of the robot without shock absorbers, are not so accurate in our project; meanwhile, the feature-learning methods are better choices; and (2) The 1DCL-based VTC method outperforms the conventional methods with an accuracy of 80.18%, which exceeds the second method (LSTM) by 8.23%.

Single nanowire-based fluorescence lifetime thermometer for simultaneous measurement of intra- and extra-cellular temperatures.

A silicon nanowire-based fluorescence lifetime thermometer (NWFLT) was fabricated for the simultaneous measurement of intra- and extra-cellular temperatures. Using the NWFLT, an obvious heterogeneity of the temperature was found along the longitude direction of the NWFLT, especially between the inside and outside of the cell.

A general configurational strategy to quencher-free aptasensors.

The aptasensor, developed from the aptamer, has aroused wide concern in recent years owing to its high sensitivity and specificity. However, the quenching unit involved in the most of the aptasensors is indispensable to the fabrication of an aptasensor, which would undoubtedly increase the complexity of the device. In this study, a facile strategy was developed for construction of the quencher-free aptasensors, in which the quenching units can be omitted, and only an aptamer strand and a fluorophore are necessary. Distinguishable from the configuration of the traditional ones, the aptasensors developed in this work rationally employed the intrinsic quenching abilities of the analytes to directly regulate the fluorescence of the fluorophore. Furthermore, the aptamer strand as a discriminatory unit efficiently captured the corresponding analytes to around the fluorophores. As a result, the fluorescence of the aptasensor can be significantly sensitive to the analytes. The generality of the current design is evidenced by the successful fabrication of seven quencher-free aptasensors for Cu2+, Ag+, Hg2+, ATP and dopamine through 6-FAM labeling aptamers of Cu2+, Ag+, Hg2+, ATP, dopamine, 5-TAMRA and ROX labeling aptamers of Cu2+. Present strategy endows an aptasensor with a simple structure, high selectivity and fine sensitivity. The configuration of the quencher-free aptasensors fabricated in this work can be readily utilized for more aptasensors.

The loading of coordination complex modified polyoxometalate nanobelts on activated carbon fiber: a feasible strategy to obtain visible light active and highly efficient polyoxometalate based photocatalysts.

To enhance the photocatalytic properties of coordination complex modified polyoxometalates (CC/POMs) in the visible light region, its nanobelts (CC/POMNBs) were loaded on activated carbon fiber (ACF) through a simple colloidal blending process. The resulting coordination complex modified polyoxometalate nanobelts loaded activated carbon fiber composite materials (CC/POMNBs/ACF) exhibited dramatic photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation. Optical and electrochemical methods illustrated the enhanced photocatalytic activity of CC/POMNBs/ACF, which originates from the high separation efficiency of the photogenerated electrons and holes on the interface of the CC/POMNBs and ACF, which results from the synergistic effects between them. In the composite material, the role of ACF could be described as a photosensitizer and a good electron transporter. Furthermore, the influence of the mass ratio between the CC/POMNBs and ACF on the photocatalytic performance of the resulting composite material was discussed, and an ideal value to obtain highly efficient photocatalysts was obtained. The results suggested that the loading of CC/POMNBs on the surface of ACF would be a feasible strategy to enhance their photocatalytic activity.