Monitoring the liver status in a convenient and low-cost way is significant for obtaining a warning about drug-indued liver diseases promptly. Herein, we designed a novel colorimetric point-ofcare (POC) platform for the determination of three liver-related biomarkersaspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP). This platform integrated agarose hydrogels into a portable device, where hydrogels were loaded with nanozymes and different reaction substances for triggering specific reactions and generating colorimetric signals. Typically, Au-decorated CoAl-layered double oxide (Au/LDO) was for the first time developed as the nanozyme with peroxidase (POD) mimic activity, which can accelerate the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB with the coexistence of hydrogen peroxide (H 2 O 2 ). The detection mechanism of AST and ALT is based on the fact that they can cause individual cascade reactions to generate H 2 O 2 , and H 2 O 2 further activates the Au/LDO nanozyme to catalyze the chromogenic reaction of TMB. As for ALP, it can catalytically hydrolyze L-ascorbic acid-2-phosphate to ascorbic acid. The latter then discolored the oxTMB that was produced with the assistance of Au/LDO. Teaming up with a smartphone, the color information of hydrogels can be converted to hue values, which allow quantitative analysis of ALT, AST, and ALP with detection limits of 15, 10, and 5 U/L, respectively. Moreover, the simple and cost-effective platform was successfully applied for the simultaneous determination of the three analytes in human plasma. Additionally, since the hydrogel is disposable and can be replaced by new ones loaded with different reaction regents, the platform is expected to serve the POC testing of various chem/bio targets.

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Development of sensors uniting different sensing principles is in line with the concept of reliable, comprehensive, and diversified equipment construction. However, the current exploration in this field is obstructed by compromise of reaction conditions and inevitable mutual interference arising from different sensing modes. This work reported a closed bipolar electrode (c-BPE) strategy for dual-modality detection or dual-target detection. To this end, a c-BPE sensing platform installed in physically separated anode and cathode compartments was well designed and carefully optimized. If luminol was present in the anode section and Prussian blue (PB) was at the cathode part, single stimulation could realize electrochemiluminescence (ECL) from luminol at the anode and conversion of PB to Prussian white (PW) at the cathode. The latter reaction helped elevate the ECL signal and also prepared for colorimetric detection as color change from PW to PB under the trigger of oxidant (like H 2 O 2 ) was used to track the content of the oxidant. Thus, dual signals were obtained for dualmodality detection of single target or the detection of different targets was realized at different poles. Detection of glucose was carried out to validate the application for dual-modality detection, while VLDL/AChE and NADH/H 2 O 2 assays illustrated the potential of dual-target detection. The proposed platform possesses outstanding sensing performance including selectivity, repeatability, long-term stability, accuracy, and so forth. This work implements a breakthrough in designing dual-mode sensors and is expected to present a rational basis for development of a diversified sensing platform.

Transportation of highly viscous solutions at the picoliter level with a rapid dynamic response is paramount for micro/nano-fabrication. With the advantages of a higher length-wall (thickness) ratio and a more stable free surface compared to those of the traditional Weissenberg effect (TWE), the microscale Weissenberg effect (MWE) can continuously and controllably pump high-viscosity solutions at the picoliter scale. Some typical characteristics and behaviors of MWE are investigated as the rotation rod diameter decreases to the microscale of ∼100 μm. The pumped minimum solution volume can reach 167.5 pL per second, and the minimum response time of solution pumping is 0.3 s, which is much shorter than that of pressure driven pumping. Then, a new direct writing with an adjustable jet diameter based on the MWE is proposed to write microstructures on a substrate from a solution with a viscosity of approximately 130.1 Pa s. The stability of the as-spun jet and the deposited structures is improved when a high voltage is applied. To fully demonstrate the advantages of MWE, MWE-based direct writing is performed to successfully fabricate microfluidic channels with variable diameters. Thus, the system can overcome the problems of high transport resistance to the pumping of a high-viscosity solution.