Surface-enhanced Raman scattering (SERS) signals strongly rely on the interactions and distance between analyte molecules and metallic nanostructures. In this work, the use of a gold nanoparticle (AuNP)-embedded metal-organic framework was introduced for the highly sensitive SERS detection. The AuNPs were in situ grown and encapsulated within the host matrix of MIL-101 by a solution impregnation strategy. The as-synthesized AuNPs/MIL-101 nanocomposites combined the localized surface plasmon resonance properties of the gold nanoparticles and the high adsorption capability of metal-organic framework, making them highly sensitive SERS substrates by effectively preconcentrating analytes in close proximity to the electromagnetic fields at the SERS-active metal surface. We discussed the fabrication, physical characterization, and SERS activity of our novel substrates by measuring the Raman signals of a variety of model analytes. The SERS substrate was found to be highly sensitive, robust, and amiable to several different target analytes. A SERS detection limit of 41.75 and 0.54 fmol for Rhodamine 6G and benzadine, respectively, was demonstrated. The substrate also showed high stability and reproducibility, as well as molecular sieving effect thanks to the protective shell of the metal-organic framework. Subsequently, the potential practical application of the novel SERS substrate was evaluated by quantitative analysis of organic pollutant p-phenylenediamine in environmental water and tumor marker alpha-fetoprotein in human serum. The method showed good linearity between 1.0 and 100.0 ng/mL for p-phenylenediamine and 1.0-130.0 ng/mL for alpha-fetoprotein with the correlation coefficients of 0.9950 and -0.9938, respectively. The recoveries ranged from 80.5% to 114.7% for p-phenylenediamine in environmental water and 79.3% to 107.3% for alpha-fetoprotein in human serum. These results foresee promising application of the novel metal-organic framework based composites as sensitive SERS-active substrates in both environmental and clinical samples.

The use of microwave heating for preparation in organic synthesis has been accepted as an effective technique in synthesis due to the significant advantages over the conventional method. In the present work, microwave heating was applied to the preparation of atrazine (template molecule) magnetic molecularly imprinted polymer (mag-MIP) beads by suspension polymerization. The term of the polymerization was dramatically shortened by using microwave heating in polymerization, which was less than (1)/(10) that by conventional heating. The resultant polymers incorporating molecular recognition and magnetic separation can provide a highly selective material for trace analysis in complicated samples. The mag-MIP beads were demonstrated with a narrow diameter distribution (80-250 microm) and cross-linking, spherical shape, and porous morphologies and exhibited magnetic property (M(s) = 0.491 emicro/g) and thermal stability under 260 degrees C. An improvement of imprinted efficiency is obtained in comparison to the mag-MIP beads prepared by conventional heating. A method for the determination of triazines in complicated samples by the mag-MIP beads extraction coupled with high-performance liquid chromatography (HPLC) was developed. The results indicated that the mag-MIP beads can be favorably used for the extraction of the triazines in spiked soil, soybean, lettuce, and millet samples. The reused beads displayed a long-term stability after undergoing extraction of 100 times.

A facile and efficient strategy about the synthesis of a novel kind of hybrid magnetic metal-organic framework (MOF)-5 via chemical bonding assembly was reported. The covalent bonding established between the amino functionalized Fe3O4 nanoparticles and the surface of the metal organic framework improved the chemical stability and structure uniformity of the hybrid microcrystals. Combination of MOF-5 with Fe3O4 nanoparticles allows for facile withdrawal of the porous materials by magnetic decantation. The powder X-ray diffraction patterns of the hybrid magnetic MOF-5 showed the structure of the metal organic framework was not disturbed with the decoration of magnetic nanoparticles. The as-synthesized materials combine the favorable attributes of both magnetic characteristics of Fe3O4 nanoparticles and high porosity of metal organic framework, making them excellent candidates as adsorbents for magnetic enrichment of trace analytes. Their potential applications were explored by preconcentrating polycyclic aromatic hydrocarbons and gibberellic acids from environmental, food, and plant samples prior to gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The results showed that the magnetic MOF-5 exhibited superior enrichment capacity for both of these nonpolar and polar analytes. The method demonstrated good precision (relative standard deviations (RSDs) of 1.7-9.7%), low detection limits (0.91-1.96 ng·L(-1) for polycyclic aromatic hydrocarbons and 0.006-0.08 μg L(-1) for gibberellic acid), and good linearity (correlation coefficients higher than 0.9949). The RSDs of batch-to-batch extraction were 2.9-11.2%. The magnetic MOF-5 was robust enough for repeatable use without damage of extraction performance.

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The unregulated activities of matrix metalloproteinases (MMPs) are implicated in disease processes including arthritis and tumor cell invasion and metastasis. MMP activities are controlled by four homologous endogenous protein inhibitors, tissue inhibitors of metalloproteinases (TIMPs), yet different TIMPs show little specificity for individual MMPs. The large interaction interface in the TIMP-1⅐MMP-3 complex includes a contiguous region of TIMP-1 around the disulfide bond between Cys 1 and Cys 70 that inserts into the active site of MMP-3. The effects of fifteen different substitutions for threonine 2 of this region reveal that this residue makes a large contribution to the stability of complexes with MMPs and has a dominant influence on the specificity for different MMPs. The size, charge, and hydrophobicity of residue 2 are key factors in the specificity of TIMP. Threonine 2 of TIMP-1 interacts with the S1 specificity pocket of MMP-3, which is a key to substrate specificity, but the structural requirements in TIMP-1 residue 2 for MMP binding differ greatly from those for the corresponding residue of a peptide substrate. These results demonstrate that TIMP variants with substitutions for Thr 2 represent suitable starting points for generating more targeted TIMPs for investigation and for intervention in MMP-related diseases.The matrix metalloproteinases (MMPs) 1 are a family of about twenty Zn 2ϩ -dependent endopeptidases that have important roles in connective tissue turnover during physiological processes including development, morphogenesis, and wound healing (1, 2). Their activities in the extracellular matrix are stringently regulated through transcriptional control, zymogen activation, and the actions of four endogenous inhibitory proteins, tissue inhibitors of metalloproteinases (TIMPs) 1 to 4 (3-7). Normal matrix homeostasis is associated with an appropriate balance between the levels of TIMPs and active MMPs, whereas an imbalance involving excess MMP activity is linked with disease processes including arthritis, tumor cell metastasis, and tissue invasion and atherosclerosis (1, 2).Mammalian TIMPs have an N-terminal domain of about 125 amino acids and a smaller C-terminal domain of about 65 amino acids; each domain is stabilized by three disulfide bonds (8). The N-terminal domains of different TIMPs fold into a correct native structure which carries the inhibitory activity against MMPs (9 -11). Although correctly folded and functional C-terminal domains have not been described, truncation experiments indicate that this region is responsible for the interactions of TIMPs with pro-MMPs (12, 13). There is little specificity in the inhibitory actions of TIMPs on metalloproteinases, with the exception of the ability of TIMP-2 and TIMP-3 to inhibit membrane-type metalloproteinases-1 and -2, whereas TIMP-1 is a poor inhibitor of these enzymes (12-14). However, the interactions of TIMPs with pro-MMPs are more specific. For example, TIMP-2 and TIMP-4 form specific complexes with pro-MMP-2 (progelatinase A), whe...

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Conjugated microporous polymers (CMPs), linked by a covalent bond to form an extension of the aromatic ring skeleton, are microporous materials characterized by a highly conjugated structure and high stability. The present study reported on a novel strategy for the synthesis of CMPs with built-in magnetic nanoparticles for excellent enrichment of trace hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in human urine. We modified Fe3O4 nanoparticles with boronic acid groups and then reacted the nanoparticles with reactive monomers of polyphenylene conjugated microporous polymer (PP-CMP) to anchor the magnetic components in the PP-CMP framework. Chemical bonding between Fe3O4 nanoparticles and PP-CMP networks, together with equally firm covalent linkage and rigidity of the PP-CMP network, endows the magnetic PP-CMP with remarkable chemical stability and durability, even in harsh conditions. Magnetic PP-CMP has the characteristics of high conjugation ability, highly porous structure, and magnetism, which makes it an ideal magnetic adsorbent for trace analytes with aromatic conjugation structure. The adsorption mechanism of OH-PAHs on magnetic PP-CMP was investigated and demonstrated that hydrophobic interaction was important for the contribution of interaction between adsorbents and target analytes, together with the assistance of π-π stacking interaction. For the application, the magnetic PP-CMP was used for the enrichment of trace OH-PAHs in human urine of both smokers and nonsmokers in combination with high-performance liquid chromatography with fluorescence detection (HPLC-FLD). It showed good selectivity and excellent sensitivity to these OH-PAHs. Their detection limits were low and in the range of 0.01-0.08 μg·L(-1). The OH-PAHs were detected with different amounts from 0.054 to 0.802 μg·L(-1) in urine samples from smokers and nonsmokers. The recoveries were found to be 76.0%-107.8%. The results indicate that the magnetic PP-CMP offers an efficient enrichment method for trace OH-PAHs in human urine.