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A novel hydrogel film with a highly ordered macropore monolayer on its surface was prepared by templated photo-polymerization of hydrogel monomers on a two-dimensional (2D) polystyrene colloidal array. The 2D inverse opal hydrogel has prominent advantages over traditional three-dimensional (3D) inverse opal hydrogels. First, the formation of the 2D array template through a self-assembly method is considerably faster and simpler. Second, the stable ordering structure of the 2D array template makes it easier to introduce the polymerization solution into the template. Third, a simple measurement, a Debye diffraction ring, is utilized to characterize the neighboring pore spacing of the 2D inverse opal hydrogel. Acrylic acid was copolymerized into the hydrogel; thus, the hydrogel responded to pH through volume change, which resulted from the formation of the Donnan potential. The 2D inverse opal hydrogel showed that the neighboring pore spacing increased by about 150 nm and diffracted color red-shifted from blue to red as the pH increased from pH 2 to 7. In addition, the pH response kinetics and ionic strength effect of this 2D mesoporous polymer film were also investigated. [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]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • A pH-responsive discoloration photonic crystal sensor was proposed for amniotic fluid recognition. • The sensor showed the high accuracy and sensitivity, rapid response and visual detection. • Compared with pH test paper, a noticeable color difference and extraordinary accuracy were obtained. In this study, we proposed a pH-responsive photonic crystal hydrogel sensor (PCHs) to conveniently and accurately recognize the amniotic fluid from urine of parturient women, which was constituted by three-dimensional polymethyl acrylamide (PMMA) array and optimized hydrogel. PMMA array was self-assembled by 180 nm monodispersed nanoparticles with vertical sedimentation method. The functional hydrogel containing N-acryloyl phenylalanine (APA), acrylamide (AM) and N, N'-methylene bis(acrylamide) (BIS) as co-monomer and crosslinking agent respectively, was photo-polymerized by the precursor under 365 nm UV light. This hydrogel significantly shrank or swelled corresponding to the acidity and alkalinity of the aqueous solution, which resulted in both the reflection peak position (λ max) of the prepared sensor and its structural color changing with the pH value. The λ max of PCHs redshifted from 514 nm to 606 nm in 60 s while the pH value of testing solution increased from 4.5 to 8.0, which exactly covered the pH value of amniotic fluid and urine. Correspondingly, its structure color gradually changed from pale-green to red ensuring their naked-eye determination. Furthermore, an extremely high sensitivity as 26.3 nm/pH of Δ λ max was obtained which was linearly related to pH value. The prepared sensor possessed steady accuracy and extraordinary sensitivity compared with the pH test strip which was generally used in amniorrhexis diagnosis nowadays besides the advantages of the low cost, simple operation, rapid response and visual detection mode. The reliability of this PCHs was further confirmed by the real sample detection which relative standard deviation was below 5.0 %, suggesting its potential clinical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogel nanoparticles were applied in ssDNA fragments isolation in CE. • The thermosensitive NPs were confirmed as rational medium with high sieving ability. • NPs possess hydrophilic and hydrophobic performance, low viscosity, good solubility. • Separation was accomplished with theoretical plate number over 108,000 (plates m−1). Nowadays, research on single-stranded DNA (ssDNA) requires a quick, effective and easy operation method to separate small ssDNA fragments from the organism and ssDNA production process to realize their application in gene therapy and drug diagnosis. Herein, a novel separation matrix of thermosensitive hydrogel nanoparticles (NPs) was proposed, which has been successfully applied to the isolation of biomacromolecules such as enzymes, peptides and proteins, based on the desirable properties of various monomers and advantages, such as high sieving capacity, tunability of hydrophilic and hydrophobic performance and non-toxicity. The flexible particles were prepared by precipitation polymerization method in aqueous solution while N-isopropylacrylamide (NIPAm), acrylic acid (AAc) and N-t-butyl acrylamide (TBAm) was performed as co-monomer, which were first used as the dynamic coating to separate small fragments of ssDNA in capillary electrophoresis (CE). The synthesized NPs were bound to the inner wall of the capillary through non-covalent interactions forming stable dynamic coating to affect the electroosmotic flow and improve the separation reproducibility of ssDNA fragments. Based on the formulation design of NPs and condition optimization of electrophoresis, the running buffer TG (25 mM Tris, 192 mM glycine, pH 8.3) was modified by 4 mg·mL−1 optimized NPs aqueous suspension addition while its molar feed ratio of NIPAm /AAc /TBAm /BIS was 83/5/10/2 and particle size was about 214 nm. Both the formulation design and temperature sensitivity of hydrogel nanoparticles contributed to the DNA separation efficiency. The designed NPs with low viscosity provide an approach to increase their capability as the separation medium for small fragment DNA with important physiological functions great potential and promise. [ABSTRACT FROM AUTHOR]

The detection of the human immunodeficiency virus-1 (HIV) at an early stage is vital and could be realized through its cell surface glycoprotein-120 (gp120) without virus preprocessing. Here, we present an ssDNA-aptamer-linked photonic crystal (APC) hydrogel sensor for HIV detection which is comprised of photonic crystals (PCs) made of polystyrene nanoparticles embedded in the polyacrylamide hydrogel. ssDNA aptamers specific for gp120 are crosslinked in the hydrogel which can selectively bind to gp120 by hydrogen bonding increasing the PCs particle spacing and swelling of the hydrogel. The binding response can be visually monitored as a color change due to the diffraction of light from PCs and can eventually be measured (1–1000 ng mL−1 of gp120) and 100 to 108 VP mL−1 of HIV by the Debye's ring diameter or a UV/Vis spectrometer. APC-hydrogel can be regenerated by Tris-HCl and EDTA washing buffer system. The sensor demonstrates LOD of 7.1 ± 1.55 ng mL−1 for gp120 and 4 VP mL−1 for the whole HIV, a rapid response of 5 min, reusability up to 70 % (in fifth use), and recovery of 95.4 ± 0.1 % to 99.0 ± 0.2 % in plasma samples. The sensor is cost-effect and stable compared to antibody-based sensors and can be utilized to develop point-of-care testing (POCT) devices for HIV diagnosis. [Display omitted] • A novel ssDNA aptamer linked photonic crystal sensor for rapid, sensitive, and onsite quantitative detection of HIV. • Specific binding of the aptamer to gp120 results in reversible swelling of the hydrogel. • Photonic crystals embedded in the polyacrylamide hydrogel provide a vibrant optical response visible to the naked eye. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A label free and easy-to-prepare optical sensor with high mechanical strength for the fast and visible response to tension and pH variables was reported. An elastic nanocomposite hydrogel was successfully fabricated by in situ free-radical co-polymerization of N , N -dimethylacrylamide (DMAA), acrylic acid (AA) and aluminum oxide nanoparticles (Al 2 O 3 NPs). DMAA and AA could form effective cross-linkage with Al 2 O 3 NPs via hydrogen binding, electrostatic interaction and bidentate bridging. By encapsulating polymethyl methacrylate (PMMA) colloidal arrays into the hydrogels, the optical nanocomposite hydrogels (ONHs) can be easily obtained. This three-dimensionally ordered array exhibits a stop band, and the optical hydrogels can tune the bright color from blue to cyan, green, yellow green, yellow, orange and then finally red by mechanical stimulation of uniaxial tension within 50% strain following Bragg’s law. The mechanical and optical properties can be adjusted via changing the fraction of AA and polymerization time. Meanwhile, the mechanical and optical responses were reversible for more than 10 times without deterioration. Besides, this material has rapid response to the changing of pH and the full-color change was observed. Owing to the high biocompatibility of nanocomposite hydrogel (NC gel) system and the excellent mechanical strength and water-stability of these ONHs, this optical sensor has high potential to be applied in biomedical field as tension or pH sensor for the intraocular pressure measurement and tonometry and blood gas analysis. [ABSTRACT FROM AUTHOR]