A highly sensitive Golgi-targeted fluorescent probe for the simultaneous detection of malondialdehyde and formaldehyde in living systems and foods.

Malondialdehyde (MDA) and formaldehyde (FA) are highly active carbonyl substances widely present in both biological and abiotic systems. The detection of MDA and FA is of great significance for disease diagnosis and food safety monitoring. However, due to the similarity in structural properties between MDA and FA, very few probes for synergistically detecting MDA and FA were reported. In addition, functional abnormalities in the Golgi apparatus are closely related to MDA and FA, but currently there are no fluorescent probes that can detect MDA and FA in the Golgi apparatus. Therefore, we constructed a simple Golgi-targetable fluorescent probe GHA based on hydrazine moiety as the recognition site to produce a pyrazole structure after reaction with MDA and to generate a CN double bond after reaction with FA, allowing MDA and FA to be distinguished due to different emission wavelengths during the recognition process. The probe GHA has good specificity and sensitivity. Under the excitation of 350 nm, the blue fluorescence was significantly enhanced at 424 nm when the probe reacted with MDA, and the detection limit was 71 nM. At the same time, under the same excitation of 350 nm, the reaction with FA showed a significant enhancement of green fluorescence at 520 nm, with a detection limit of 12 nM for FA. And the simultaneous and high-resolution imaging of MDA and FA in the Golgi apparatus of cells was achieved. In addition, the applications of the probe GHA in food demonstrated it can provide a powerful method for food safety monitoring. In summary, this study offers a promising tool for the synergistic identification and determination of MDA and FA in the biosystem and food, facilitating the revelation of their detailed functions in Golgi apparatus and the monitoring of food safety.

A Carbamoyl Oxime-Based Highly Specific Fluorescent Chemodosimeter for Monitoring Labile Fe2+ in Food and Living Organisms.

Iron is an essential element in the composition of living organisms and plays a crucial role in a wide range of biological activities. The human body primarily obtains essential iron through the consumption of food. Therefore, it is vital for the health of human body to maintain iron homeostasis. The reducing character of the cellular microenvironment enables Fe2+ to occupy a dominant position within the cell. Hence, there is an urgent need for a simple and sensitive tool that can detect a large amount of Fe2+ in organisms. In this work, a highly specific fluorescent chemodosimeter NPCO ("NP" represents the naphthalimide fluorophore, and "CO" represents the carbamoyl oxime structure) for the detection of Fe2+ with excellent sensitivity (LOD = 82 nM) was constructed by incorporating a novel carbamoyl oxime structure as the recognition group. NPCO can be effectively employed for the detection of Fe2+ in food samples, living cells, and zebrafish. Furthermore, by using soybean sprouts as a model plant, the application of NPCO was expanded to detect Fe2+ in plants. Therefore, NPCO could be used as an excellent assay tool for detecting Fe2+ in organisms and is expected to be an important aid in exploring the mechanism of iron regulation.

Corrigendum: Flexible biosensors based on colorimetry, fluorescence, and electrochemistry for point-of-care testing.

[This corrects the article DOI: 10.3389/fbioe.2021.753692.].

Flexible Biosensors Based on Colorimetry, Fluorescence, and Electrochemistry for Point-of-Care Testing.

With the outbreak and pandemic of COVID-19, point-of-care testing (POCT) systems have been attracted much attention due to their significant advantages of small batches of samples, user-friendliness, easy-to-use and simple detection. Among them, flexible biosensors show practical significance as their outstanding properties in terms of flexibility, portability, and high efficiency, which provide great convenience for users. To construct highly functional flexible biosensors, abundant kinds of polymers substrates have been modified with sufficient properties to address certain needs. Paper-based biosensors gain considerable attention as well, owing to their foldability, lightweight and adaptability. The other important flexible biosensor employs textiles as substrate materials, which has a promising prospect in the area of intelligent wearable devices. In this feature article, we performed a comprehensive review about the applications of flexible biosensors based on the classification of substrate materials (polymers, paper and textiles), and illustrated the strategies to design effective and artificial sensing platforms, including colorimetry, fluorescence, and electrochemistry. It is demonstrated that flexible biosensors play a prominent role in medical diagnosis, prognosis, and healthcare.

Mechanical Behavior and Failure Mode of Steel-Concrete Connection Joints in a Hybrid Truss Bridge: Experimental Investigation.

The core part of a hybrid truss bridge is the connection joint which combines the concrete chord and steel truss-web members. To study the mechanical behavior and failure mode of steel-concrete connection joints in a hybrid truss bridge, static model tests were carried out on two connection joints with the scale of 1:3 under the horizontal load which was provided by a loading jack mounted on the vertical reaction wall. The specimen design, experimental setup and testing procedure were introduced. In the experiment, the displacement, strain level, concrete crack and experimental phenomena were factually recorded. Compared with the previous study results, the experimental results in this study demonstrated that the connection joints had the excellent bearing capacity and deformability. The minimum ultimate load and displacement of the two connection joints were 5200 kN and 59.01 mm, respectively. Moreover, the connection joints exhibited multiple failure modes, including the fracture of gusset plates, the slippage of high-strength bolts, the local buckling of compressive splice plates, the fracture of tensile splice plates and concrete cracking. Additionally, the strain distribution of the steel-concrete connection joints followed certain rules. It is expected that the findings from this paper may provide a reference for the design and construction of steel-concrete connection joints in hybrid truss bridges.