Ratiometric Electrochemical Sensor for Effective and Reliable Detection of Ascorbic Acid in Living Brains

The <i>in vivo</i> detection of ascorbic acid (AA), one of the physiologically important cerebral neurochemicals, is critical to probe and understand brain functions. Electrochemical sensors are convenient for AA detection. However, conventional electrochemical sensors usually suffer from several challenges, such as sluggish electron transfer kinetics for AA oxidation and poor reproducibility. To address these challenges, here we report ratiometric electrochemical sensors for effective and reliable detection of AA in living brains. The sensors were constructed by immobilizing preassembled thionine/Ketjen black (KB) nanocomposites onto glassy carbon (GC) electrodes or carbon fiber microelectrodes (CFMEs). The KB in the rationally functionalized nanocomposites efficiently facilitated AA oxidation at a relatively negative potential (∼−0.14 V) without particular physical or chemical pretreatment, forming the basis of selective measurement of AA. With a well-defined and reversible pair of redox wave at −0.22 V, the assembled thionine acted as an internal reference to substantially alleviate the lab-to-lab, person-to-person, and electrode-to-electrode variations. The <i>in vitro</i> experiments demonstrated that the sensors exhibited extremely high reproducibility and stability toward selective measurement of AA. More, with operational simplicity and robustness in analytical performance, the designed sensors were successfully applied to <i>in vivo</i> effectively, selectively, and reliably monitor the dynamic change of cerebral AA associated with pathological processes (i.e., salicylate-induced tinnitus as the model) in living rats’ brains. This study not only offers a new strategy for construction of ratiometric electrochemical sensors but also opens a new way for selective and reliable detection of neurochemicals for probing brain functions

Map of the China Health and Nutrition Survey (CHNS) coverage 2004–2009.

<p>Map of the China Health and Nutrition Survey (CHNS) coverage 2004–2009.</p

Facile Synthesis of Biocompatible Fluorescent Nanoparticles for Cellular Imaging and Targeted Detection of Cancer Cells

In this work, we report the facile synthesis of functional core–shell structured nanoparticles with fluorescence enhancement, which show specific targeting of cancer cells. Biopolymer poly-l-lysine was used to coat the silver core with various shell thicknesses. Then, the nanoparticles were functionalized with folic acid as a targeting agent for folic acid receptor. The metal-enhanced fluorescence effect was observed when the fluorophore (5-(and-6)-carboxyfluorescein-succinimidyl ester) was conjugated to the modified nanoparticle surface. Cellular imaging assay of the nanoparticles in folic acid receptor-positive cancer cells showed their excellent biocompatibility and selectivity. The as-prepared functional nanoparticles demonstrate the efficiency of the metal-enhanced fluorescence effect and provide an alternative approach for the cellular imaging and targeting of cancer cells

Time trends in the percentage (%) of Western fast food consumers among Chinese children of the same age between 2004 and 2009, by age group (those aged 6–10 vs 13–17 years old), socio-demographics, lifestyles and weight status: China Health and Nutrition Survey.

<p>Time trends in the percentage (%) of Western fast food consumers among Chinese children of the same age between 2004 and 2009, by age group (those aged 6–10 vs 13–17 years old), socio-demographics, lifestyles and weight status: China Health and Nutrition Survey.</p

Linear and logistic regression analysis for cross-sectional and longitudinal associations between Chinese children’s Western fast food consumption and their BMI z-scores and weight status: China Health and Nutrition Survey 2004–2009.

<p>Linear and logistic regression analysis for cross-sectional and longitudinal associations between Chinese children’s Western fast food consumption and their BMI z-scores and weight status: China Health and Nutrition Survey 2004–2009.</p

Socio-demographic characteristics of children aged 6–17 years in nine provinces in China: China Health and Nutrition Survey 2004–2009 (cross-sectional analysis).

<p>Socio-demographic characteristics of children aged 6–17 years in nine provinces in China: China Health and Nutrition Survey 2004–2009 (cross-sectional analysis).</p

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<p>Human–robot collaboration could be advanced by facilitating the intuitive, gaze-based control of robots, and enabling robots to recognize human actions, infer human intent, and plan actions that support human goals. Traditionally, gaze tracking approaches to action recognition have relied upon computer vision-based analyses of two-dimensional egocentric camera videos. The objective of this study was to identify useful features that can be extracted from three-dimensional (3D) gaze behavior and used as inputs to machine learning algorithms for human action recognition. We investigated human gaze behavior and gaze–object interactions in 3D during the performance of a bimanual, instrumental activity of daily living: the preparation of a powdered drink. A marker-based motion capture system and binocular eye tracker were used to reconstruct 3D gaze vectors and their intersection with 3D point clouds of objects being manipulated. Statistical analyses of gaze fixation duration and saccade size suggested that some actions (pouring and stirring) may require more visual attention than other actions (reach, pick up, set down, and move). 3D gaze saliency maps, generated with high spatial resolution for six subtasks, appeared to encode action-relevant information. The “gaze object sequence” was used to capture information about the identity of objects in concert with the temporal sequence in which the objects were visually regarded. Dynamic time warping barycentric averaging was used to create a population-based set of characteristic gaze object sequences that accounted for intra- and inter-subject variability. The gaze object sequence was used to demonstrate the feasibility of a simple action recognition algorithm that utilized a dynamic time warping Euclidean distance metric. Averaged over the six subtasks, the action recognition algorithm yielded an accuracy of 96.4%, precision of 89.5%, and recall of 89.2%. This level of performance suggests that the gaze object sequence is a promising feature for action recognition whose impact could be enhanced through the use of sophisticated machine learning classifiers and algorithmic improvements for real-time implementation. Robots capable of robust, real-time recognition of human actions during manipulation tasks could be used to improve quality of life in the home and quality of work in industrial environments.</p

Flexible Antibacterial Film Based on Conjugated Polyelectrolyte/Silver Nanocomposites

In this work, we report a flexible film based on conjugated polyelectrolyte/silver nanocomposites with efficient antibacterial activity. A flexible poly­(dimethylsiloxane) film served as a substrate for deposition of nanostructured silver. A light-activated antibacterial agent, based on the cationic conjugated polyelectrolyte poly­({9,9-bis­[6′-(<i>N,N</i>-trimethylamino)­hexyl]-2,7-fluorenyleneethynylene}-<i>alt</i>-<i>co</i>-1,4-(2,5-dimethoxy)­phenylene)­dibromide (PFEMO) was self-assembled on the negatively charged substrate. By changing the thickness of the poly­(l-lysine)/poly­(acrylic acid) multilayers between the metal substrate and PFEMO, we obtained concomitant enhancement of PFEMO fluorescence, phosphorescence, and reactive oxygen species generation. These enhancements were induced by surface plasmon resonance effects of the Ag nanoparticles, which overlapped the PFEMO absorption band. Owing to the combination of enhanced bactericidal effects and good flexibility, these films have great potential for use as novel biomaterials for preventing bacterial infections

Synthesis of Polycyclic Benzo[<i>b</i>]indolo[3,2,1-<i>de</i>]acridines via Sequential Allenylation, Diels–Alder Cyclization, and Hydrogen Migration Reaction

A novel methodology for stereoselective synthesis of benzo­[<i>b</i>]­indolo­[3,2,1-<i>de</i>]­acridines through the tandem reaction of propargylic compounds with organoboron is described, and only one diastereoisomer was obtained. The sequential procedure was triggered by Pd(0)-catalyzed allenylation of propargyl carbonate. Then, Diels–Alder cyclization and hydrogen migration processes proceeded successively to furnish the polycyclic target molecules. Control reactions suggested the base (Cs₂CO₃) was indispensable for the hydrogen migration

2D-Metal–Organic-Framework-Nanozyme Sensor Arrays for Probing Phosphates and Their Enzymatic Hydrolysis

The detection of phosphates and their enzymatic hydrolysis is of great importance because of their essential roles in various biological processes and numerous diseases. Compared with individual sensors for detecting one given phosphate at a time, sensor arrays are able to discriminate multiple phosphates simultaneously. Although nanomaterial-based sensor arrays have shown great promise for the discrimination of phosphates, very few of them have been explored for probing phosphates involved enzymatic hydrolysis. To fill this gap, herein we fabricated two-dimensional-metal–organic-framework (2D-MOF)-nanozyme-based sensor arrays by modulating their peroxidase-mimicking activity with various phosphates, including AMP, ADP, ATP, pyrophosphate (PPi), and phosphate (Pi). The sensor arrays were used to successfully discriminate the five phosphates not only in aqueous solutions but also in biological samples. The practical application of the sensor arrays was then validated with blind samples, where 30 unknown samples containing phosphates were accurately identified. Moreover, the sensor arrays were successfully applied to probing hydrolytic processes involving ATP and PPi that are catalyzed by apyrase and PPase, respectively. This work demonstrates a nanozyme-based sensor array as a convenient and reliable analytical platform for probing phosphates and their related enzymatic processes, which could be applied to other analytes and enzymatic reactions