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[Display omitted] • A novel fluorescence sensing material based on upconversion nanoparticles (UCNPs), Metal-organic frameworks (MOFs) and molecularly imprinted polymer was prepared. • UCNPs were introduced as fluorophores to provide fluorescent signal. • MOFs were introduced to increase the rate mass transfer and adsorption capacity. A novel strategy for sensing protein was proposed through combining the high selectivity of molecular imprinting technology with the excellent upconversion fluorescence of upconversion nanoparticles (UCNPs) and high specific surface area of metal–organic frameworks (MOFs). Herein, the UCNPs acted as signal reporter and MOFs were introduced to increase the rate of mass transfer. The UCNPs@MIL-100 as support material was prepared via a step-by-step method. The imprinted material-coated UCNPs@MIL-100 (UCNPs@MIL-100@MIPs) were obtained by sol–gel technique. The results showed that as the increase of the template protein concentration, the fluorescence intensity of UCNPs@MIL-100@MIPs quenched gradually, and the imprinting factor was 2.90. The linear in the range of 1.00 to 8.00 μM, and the detection limit was 0.59 μM. Therefore, the novel optosensing material is very promising for future applications. [ABSTRACT FROM AUTHOR]

A novel fluorescence material with thermo-sensitive for the enrichment and sensing of protein was successfully prepared by combining molecular imprinting technology with upconversion nanoparticles (UCNPs) and metal-organic frameworks (MOFs). Herein, the UCNPs acted as signal reporter for composite materials because of its excellent fluorescence property and chemical stability. MOFs were introduced to molecularly imprinted polymer (MIP) due to its high specific surface area which increases the rate of mass transfer relative to that of traditional bulk MIP. The thermo-sensitive imprinted material which allows for swelling and shrinking with response to temperature changes was prepared by choosing Bovine hemoglobin (BHB) as the template, N-isopropyl acrylamide (NIPAAM) as the temperature-sensitive functional monomer and N,N-methylenebisacrylamide (MBA) as the cross-linker. The recognition characterizations of imprinted material-coated UCNPs/MOFs (UCNPs/MOFs/MIP) were evaluated, and the results showed that the fluorescence intensity of UCNPs/MOFs/MIP reduced gradually with the increase of BHB concentration. The fluorescence material was response to the temperature. The adsorption capacity was as much as 167.6 mg/g at 28 °C and 101.2 mg/g at 44 °C, which was higher than that of traditional MIP. Therefore, this new fluorescence material for enrichment and sensing protein is very promising for future applications. [ABSTRACT FROM AUTHOR]

Based on the mesoporous silica nanoparticles (MSN), a novel, simple and label-free aptamer biosensor was designed for the detection of aflatoxin B 1 (AFB 1). Here, the aptamers were used as molecular recognition probes and "gated molecules" while Rh6G was loaded into the interior of the particles as the signal probe. In the absence of AFB 1 , the "gate" was closed to prevent the leakage of the signal probe because of the immobilization of aptamers on the surface of MSN-NH 2. With the presence of AFB 1 , the "gate" could be opened to release the signal probe for the specifical binding of aptamers to AFB 1. Our results showed that the fluorescence intensity was positively correlated with the concentration of AFB 1 (0.5–50 ng mL−1), with the detection limit as low as 0.13 ng mL−1. What's more, this design provides a new approach for rapid, sensitive and selective detection based on aptamers and it could be applied to numerous other analytes if appropriate aptamers are available. Image 1 • High amino-modified concentration of mesoporous silica nanomaterials (MSN-NH 2) was synthesized. • MSN-NH 2 loaded with label-free signal probe (Rh6G) could be regulated by gated molecular (AFB 1 -aptamers). • This aptasensor is designed by MSN-NH 2 , Rh6G and AFB1-aptamers to detect AFB1 with the detection limit of 0.13 ng mL−1. • This design could be applied to other mycotoxins and contaminants if appropriate aptamers are available. [ABSTRACT FROM AUTHOR]

A variety of fluorescence probes have been developed for fluorescence imaging of metals in biological cells. However, accurate quantification of metals with fluorescent approaches is challenging due to the difficulty in establishing a standard calibration curve in living cells. Herein, a fluorescence imaging protocol is developed for imaging intracellular Cu2+ and its correlation with the cellular uptake of copper. The total amount of intracellular Cu is detected by inductively coupled plasma mass spectrometry (ICP-MS) in parallel. Fluorescence imaging of Cu2+ is accomplished with Rhodamine B derivative modified carbon dots (CDs-Rbh) based on fluorescence resonance energy transfer (FRET) from CDs to rhodamine. Intracellular Cu2+ is correlated with fluorescence ratio at λ em 500–600 nm (rhodamine) to λ em 425–475 nm (CDs) with excitation at λ ex 405 nm. It is found that Cu2+ is linearly correlated with the total intracellular uptaken copper content, with a linear correlation between the relative fluorescence ratio in fluorescence imaging and intracellular Cu derived from ICP-MS, including both Cu(I) and Cu(II) species. The linear calibration equation is lg(F 2 /F 1) = 0.00148 m[Cu]-0.3622. This approach facilitates further investigation and elucidation of copper transition in live cells and the evaluation of their cytotoxicity. Fluorescence imaging of intracellular free cationic copper is correlated with the intracellular uptaken copper by live cells. Image 1 • Fluorescence imaging is developed for intracellular Cu2+ and its correlation with total uptake of copper derived by ICP-MS. • Fluorescence imaging of intracellular Cu2+ is accomplished with a CDs conjugate based on FRET. • It facilitates investigation and elucidation of copper transition in live cells. [ABSTRACT FROM AUTHOR]

5-butyl-3,9-difluoro-5 H -benzimidazo[1,2- a ]benzimidazole was designed and synthesized, its structure was characterized by infrared spectroscopy (IR) and nuclear magnetic resonance ( 1 H NMR, 13 C NMR) spectroscopy. Optical properties including UV–vis absorption and fluorescence emission spectra of the title compound were investigated experimentally. The results showed the title compound can absorb UV light at 314 nm and exhibit UV fluorescence emission at 341 nm. Theoretical studies on molecular structure, IR, 1 H NMR, 13 C NMR, frontier molecular orbitals, UV–vis absorption and fluorescence emission of the synthesized compound had been carried out by using Gaussian 09 program with DFT method. Calculations on molecular structure and vibrational frequency were carried out at B3LYP/6-311G(d,p) level. Nuclear magnetic resonance chemical shifts were performed by DFT MPW1PW91/6-311 + G(2d,p) method. UV–vis absorption and fluorescence emission were simulated with TD-DFT method at PBEPBE/6-311 + G(d,p) level. The comparison between experimental and theoretical results indicates good coincidences between them, which prove that the chosen theoretical methods are reliable for the properties prediction of other structurally similar compounds, especially for those whose properties are difficult to be measured experimentally. The results also clue the title compound a candidate dye with high fluorescence quantum yield for its small Stokes' shift and structural stacking protection. [ABSTRACT FROM AUTHOR]

Abstract: In 10mM N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (Hepes), pH 7.4, 25°C, the conformational change of the truncated form of ciliate Euplotes Octocarinatus centrin (P23) induced by metal ions were investigated using 2-p-toluidinylnaphthalene-6-sulfonate (TNS) as a probe. The results show that upon metal ions binding, P23 undergo a conformational change and the contributions to the conformational change from the two EF-hands are different, and Tb3+ has more larger influence than Ca2+ with the same concentration metal ions, which provide possible the evidence that the different EF-hands play distinct biological functions. Meanwhile, the conditional binding constants of TNS and Ca2-loaded or Tb2-loaded P23 were obtained, K (Ca2-P23 +TNS)=(7.49±0.88)×105 mol−1 L, K (Tb2-P23 +TNS)=(8.24±0.49)×105 mol−1 L. [Copyright &y& Elsevier]