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The determination of lactic acid content has a guiding significance for disease diagnosis or food supervision. Herein, a hydrogel-based three-dimensional photonic crystal (PC) sensor for specific detection of lactic acid is introduced. The hydrogel was prepared by one-step copolymerization of N-isopropylacrylamide and acrylamide in the presence of oxamate derivative 2-((6-acrylamidohexyl) amino)-2-oxoacetic acid (AOA). An obvious color change from orange-red to purple and a 45-nm redshift of the reflection peak were obtained in 3 min when lactic acid concentration increased from 0 to 20 mM. The detection limit was confirmed as 0.1 mM, and the prepared sensor can be reused more than 20 times. Moreover, the affinity and selectivity of AOA to lactic acid were proven by both the interaction energy from density functional theory (DFT) study and the comparison to those of pyruvate and propionic acid. This sensor was proven to be cost-effective and convenient with rapid response time, good reusability, and selectivity., (© 2022. Springer-Verlag GmbH Germany, part of Springer Nature.)

A novel polymerized crystalline colloidal array (PCCA) sensing material for the detection of urine glucose was developed by embedding a two-dimensional (2-D) polystyrene crystalline colloidal array (CCA) in 3-acrylamidophenylboronic acid (3-APBA)-functionalized hydrogel. After adjusting the cross-linker concentration, this material showed significant sensitivity for glucose under lab conditions, the particle spacing of the PCCA changed from 917 to 824 nm (93 nm) within 3 min as the glucose concentration increased from 0 to 10 mM, and the structural color of the PCCA changed from red through orange, to green, and finally, to cyan. In further experiments, this material was used to semi-quantitatively detect glucose in 20 human urine (HU) samples. Compared with the traditional dry-chemistry method, which was applied widely in clinical diagnosis, the PCCA method was more accurate and cost-effective. Moreover, this method can efficiently avoid the errors induced by most of the urine-interfering elements like vitamin C and ketone body. With a homemade portable optical detector, this low-cost intelligent sensing material can provide a more convenient and efficient strategy for the urine glucose detection in clinical diagnosis and point-of-care monitoring.

Photonic crystal has become a powerful technique for regulating electromagnetic waves due to its excellent features, such as structure designability and dynamic adjustability; in addition, it has great application value. In this paper, we visualize colors on the Ostwald color model and analyze the color differences of each group of color patches via the minimum color difference model. The manipulation law of particle size, temperature, and humidity on the color change of photonic crystal hydrogel is verified by these color analyses. [ABSTRACT FROM AUTHOR]

Bletilla striata is an herb with a good medicinal value whose main active ingredient is Bletilla striata polysaccharide (BSP) in the tuber of Bletilla striata. In this study, a polysaccharide-based semi-interpenetrating network hydrogel was constructed by introducing BSP into polyacrylamide (PAM) hydrogel. The introduction of the BSP chain no only maintains the excellent mechanical properties of PAM, but also endows it with good biocompatibility. By implanting the colloidal crystal array into the above hydrogels, we obtained a novel biomass-based photonic crystal with good stimulus responsiveness that is sensitive to volatile organic compounds (VOCs), especially alcohol vapor. In addition, due to the scavenging ability of BSP to hydroxyl radicals, the photonic crystal hydrogel also has a good response to hydrogen peroxide ( H 2 O 2 ). [ABSTRACT FROM AUTHOR]

G-series nerve agents, such as sarin, tabun, and soman, would cause tremendous harm in military and terrorist attacks, so it is necessary to develop a simple method for the rapid and efficient detection of these hazardous substances. We have developed a tunable acetylcholinesterase (AChE)-functionalized two-dimensional photonic crystal (2D PhC) for the detection of a real nerve agent, sarin. In accordance with the 2D PhC previously prepared by our group, the AChE-functionalized 2D PhC was optimized by adjustment of the amount of monomer in the hydrogel, which not only increased the sensitivity of the 2D PhC, with the detection limit decreasing by two orders of magnitude, but also ensured the structural color spanned the whole visible region in the detection range. A linear relationship between the logarithm of the sarin concentration and the particle spacing of the AChE-functionalized 2D PhC was observed from 7.1 × 10-17 to 7.1 × 10-4 mol/L. The AChE-functionalized 2D PhC also responded to mimics of G-series nerve agents, including dimethyl methylphosphonate, diisopropyl methylphosphonate, and isodipropyl methylphosphonate, to various degrees. The proposed 2D-PhC hydrogel has potential for low-cost, trace-level, and on-site monitoring of other G-series nerve agents. Graphical abstract [ABSTRACT FROM AUTHOR]