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We report here a colorimetric method for rapid detection of norovirus based on the valence-driven peptide-AuNP interactions. We engineered a peptide sequence named K1 with a cleavage sequence in between two lysine residues. The positively charged lysine groups aggregated the negatively charged nanoparticles leading to a purple color change. There was a red color when the cleavage sequence was digested by the Southampton norovirus 3C-like protease (SV3CP)—a protease involved in the life cycle of Human norovirus (HNV). The limit of detection was determined to be 320 nM in Tris buffer. We further show that the sensor has good performance in exhaled breath condensate, urine, and faecal matter. This research provides a potential easy and quick way to selectively detect HNV. [ABSTRACT FROM AUTHOR]

Noroviruses are highly contagious and are one of the leading causes of acute gastroenteritis worldwide. Due to a lack of effective antiviral therapies, there is a need to diagnose and surveil norovirus infections to implement quarantine protocols and prevent large outbreaks. Currently, the gold standard of diagnosis uses reverse transcription polymerase chain reaction (RT-PCR), but PCR can have limited availability. Here, we propose a combination of a tunable peptide substrate and gold nanoparticles (AuNPs) to colorimetrically detect the Southampton norovirus 3C-like protease (SV3CP), a key protease in viral replication. Careful design of the substrate employs a zwitterionic peptide with opposite charged moieties on the C- and N- termini to induce a rapid color change visible to the naked eye; thus, this color change is indicative of SV3CP activity. This work expands on existing zwitterionic peptide strategies for protease detection by systematically evaluating the effects of lysine and arginine on nanoparticle charge screening. We also determine a limit of detection for SV3CP of 28.0 nM with comparable results in external breath condensate, urine, and fecal matter for 100 nM of SV3CP. The key advantage of this system is its simplicity and accessibility, thus making it an attractive tool for qualitative point-of-care diagnostics. [ABSTRACT FROM AUTHOR]

A new microfluidic paper-based analytical device, a (Ag-μPAD)-based chemiresistor composed of silver ink, has been developed for the selective, sensitive, and quantitative determination of nitrite ions in environmental analysis. The silver ink acts as an efficient transducer in terms of resistance changes due to nitrite initiating a diazo reaction and further reacting with the ink. The silver ink is synthesized onto the μPADs by pulsed light sintering from silver nanoparticles, a mixture of silver nanowires and nanoparticles. The resistance changes show two linear response ranges to nitrite in the concentration ranges of 1.0 × 10−8 M to 5.0 × 10−6 M and 1.0 × 10−5 M to 3.2 × 10−3 M, with a limit of detection of 8.5 × 10−11 M (S/N = 3). The sensor displays a wider linear range, a lower detection limit, a higher stability, high selectivity, low-volume sampling, and disposability for nitrite with respect to other nanoparticle- and paper-based sensors. The characterization of silver ink was verified by SEM, EDS, and IR studies, and the sensing mechanism is discussed. In addition, this paper-based sensor has been successfully employed to determine the nitrite content in tap, river and lake water samples. [ABSTRACT FROM AUTHOR]

In this work, we present a facile preparation of a paper-based glucose assay for rapid, sensitive, and quantitative measurement of glucose in blood plasma and urine. Two copper phosphorescent complexes [Cu(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu1) and [Cu(2,9-dimethyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu2) and a new silver congener [Ag(P3)CNAg(P3)][B(C6H3(CF3)2)4] (Ag3) (P3 = PPh2C6H4-PPh-C6H4PPh2 [bis(o-diphenylphosphinophenyl)phenylphosphine]) have been synthesized and their oxygen sensing abilities were investigated. The dimetallic phosphine-based Ag3 complex, having a high oxygen sensing ability, was employed as an efficient signal transducer in enzymatic reactions to recognize blood plasma glucose and urine glucose, which provided a wide linear response for a concentration range between 1.0 and 35 mM and a rapid response, with a limit of detection (LOD) of 0.09 mM for glucose. In practical application, this Ag3 paper-based device offers great analytical reliability and accuracy upon monitoring glucose concentrations in blood plasma. [ABSTRACT FROM AUTHOR]

Four novel photochromic metal–organic frameworks (MOFs) self-assembled from a naphthalenediimide-based ligand and different metal cations, [Zn2(BINDI)(DMA)2]·2DMA (1), [Cd(H4BINDI)(H2BINDI)]·4DMF (2), [Ca2(HBINDI)Cl(DMA)3]·DMA (3), [Ba4(BINDI)2(DMF)7]·7DMF (4) (H4BINDI = N,N′-bis(5-isophthalic acid)naphthalenediimide), have been synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, IR spectroscopy and TG analyses. Compound 1 exhibits a 3D porous framework with an lvt topology based on paddle-wheel Zn2(COO)4 clusters and BINDI as four-connected nodes. Compound 2 features a porous threefold interpenetrating diamondoid framework. Compound 3 shows a microporous 2D double-layer architecture and compound 4 displays a porous twofold interpenetrated 3D network. Interestingly, these four MOFs exhibit reversible photochromic behaviors with a concomitant eye-detectable color change, but different coloration degrees. The comparison of these MOFs indicates that the electron-withdrawing capabilities of metal cations play a significant role in tuning the photosensitive properties of photochromic MOFs; this result may provide a feasible route for the design and synthesis of photochromic MOFs with controllable photoinduced electron-transfer properties. Moreover, the photomodulated photoluminescence properties of compounds 1–4, as well as the solvatochromic behaviors of 3 and 4 were also investigated. Additionally, compounds 1–3 are found to be useful as indicators for the qualitative detection of nitrite by naked eye recognition of color change. [ABSTRACT FROM AUTHOR]

In this study, we present a selective paper-based method for the detection of l-Cys in serum using DTNB-modified Ag nanoprisms (AgP-DTNB). This method is based on the principle that l-Cys reacts with DTNB in AgP-DTNB to release a TNB2− chromophore and etches simultaneously AgP-DTNB to form Ag nanodisks, hence resulting in ratiometric changes of absorbance. Different biothiols have different affinities to etch the AgP surface and cause nanodisks of different sizes, which have slightly different resonance wavelengths. Thus, l-Cys can be discriminated with different biothiols on the basis of the different absorption spectral changes and different absorbance ratios. The linear dynamic range for the determination of l-Cys was 1–1750 μM, and the correlation coefficient (R2) was 0.9968 (y = 3.0859 × 10−4 [Cys] + 0.9376). The limit of detection for l-Cys was calculated to be 0.87 μM from 3 times the standard deviation of the blanks to the slope of the calibration curve. Compared with the other nanoparticle-based sensors in solution and on paper, AgP-DTNB possesses a much wider linear range and a comparable detection limit for l-Cys. This paper-based sensor exhibits selectivity, a wide linear sensing range, low-volume sampling, miniaturization, portability, and disposability. [ABSTRACT FROM AUTHOR]

Seven novel highly connected metal–organic frameworks (MOFs), formulated as [Co7(aobtc)3(bpy)2(μ3-OH)2(μ2-OH2)2(H2O)4]·4H2O (1), [Ni5(aobtc)2(bpy)2(μ3-OH)2(H2O)6]·4H2O (2), [Zn3(aobtc)2]·H2bpy·H2O (3), [Zn3(aobtc)2]·H2bpp·H2O (4), [Cd3(aobtc)2]·[Me2NH2]2·3H2O (5), [Co3(aobtc)2]·H2bpp·H2O (6) and [Mn3(aobtc)2]·H2bpy·2H2O (7) (H4aobtc = azoxybenzene-3,3′,5,5′-tetracarboxylic acid, bpy = 4,4′-bipyridine, bpp = 1,3-bis(4-pyridyl)propane) have been synthesized and characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analyses. Compound 1 is a 3D (4,4,14)-connected self-penetrating framework with (46)2(45·6)(430·526·631·74) topology based on hexanuclear clusters as 14-connected nodes. To our knowledge, compound 1 represents the highest connected self-penetrating topology presently known in the entangled system. Compound 2 displays a trinodal (4,4,10)-connected network with (46)(45·5)(410·518·612·75) topology based on tetranuclear clusters as 10-connected nodes. Compounds 3–7 exhibit (4,8)-connected flu nets based on trinuclear clusters as 8-connected nodes, and these five MOFs show similar structures but different pore volumes mainly associated with the change of the species of guest molecules. Structural analyses of 1–7 demonstrate that increasing the metal nuclearity is a practical method to obtain highly connected coordination networks based on metal clusters as nodes. In addition, the magnetic properties of 1, 2, 6, and 7 and the luminescence properties of compounds 3–5 have also been studied. [ABSTRACT FROM AUTHOR]

In this work, we present a facile preparation of a paper-based glucose assay for rapid, sensitive, and quantitative measurement of glucose in blood plasma and urine. Two copper phosphorescent complexes [Cu(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu1) and [Cu(2,9-dimethyl-1,10-phenanthroline)(2,6-dimethylphenylisocyanide)2][B(C6H3(CF3)2)4] (Cu2) and a new silver congener [Ag(P3)CNAg(P3)][B(C6H3(CF3)2)4] (Ag3) (P3 = PPh2C6H4-PPh-C6H4PPh2 [bis(o-diphenylphosphinophenyl)phenylphosphine]) have been synthesized and their oxygen sensing abilities were investigated. The dimetallic phosphine-based Ag3 complex, having a high oxygen sensing ability, was employed as an efficient signal transducer in enzymatic reactions to recognize blood plasma glucose and urine glucose, which provided a wide linear response for a concentration range between 1.0 and 35 mM and a rapid response, with a limit of detection (LOD) of 0.09 mM for glucose. In practical application, this Ag3 paper-based device offers great analytical reliability and accuracy upon monitoring glucose concentrations in blood plasma.