Bifunctional colorimetric oligonucleotide probe based on a G-quadruplex DNAzyme molecular beacon

A label-free bifunctional colorimetric oligonucleotide probe for DNA and protein detection has been developed on the basis of a novel catalytic molecular beacon consisting of two hairpin structures and a split G-quadruplex DNAzyme in the middle. The two loops of this molecular beacon consist of thrombin aptamer sequence and the complementary sequence of target DNA, which are utilized to sense single-stranded DNA and thrombin. The G-quadruplex DNAzyme can effectively catalyze the H(2)O(2)-mediated oxidation of 3,3',5,5'-tetramethylbenzidine sulfate to generate colorimetric signal. Upon addition of the target, the DNA or protein combines with one loop of the hairpin structures, and meanwhile drives the middle G-quadruplex DNAzyme to dissociate. This results in a decrease of catalytic activity, enabling the separate analysis of DNA and thrombin.     

Nanomaterial-based optical indicators: Promise,opportunities, and challenges in the development of colorimetric systems for intelligent packaging

Nano Research - The market and the future trends of smart packaging show a tendency towards a continuous increase. Several reports have revealed about the increase of consumer concern for food...     

A new approach towards controlled synthesis of multifunctional core-shell nano-architectures: luminescent and superparamagnetic

We have developed a two-step method for synthesis of multifunctional core-shell nanoparticles with an improved structure as compared with those prepared by traditional methods used independently. The nanoparticles comprise a superparamagnetic core, an inner insulating dye-free silica shell, an outer luminescent silica shell encapsulating thousands of dye molecules and a functionalizeable surface. The innovative insertion of the isolating silica shell benefits the nanoparticles' architecture in two ways. Firstly, by keeping the dye molecules away from the magnetic core, the silica shell prevents dye luminescence quenching. Secondly, the non-magnetic shell decreases magnetic interparticle coupling, which, by reducing aggregation and preventing agglomeration, facilitates the formation of the high-quality luminescent shell in the second step of the process. The final nanoparticles being both superparamagnetic and luminescent have a great potential for theranostic applications such as ultra-sensitive detection, and in-vitro and in-vivo imaging.     

DNAzyme molecular beacon probes for target-induced signal-amplifying colorimetric detection of nucleic acids

A novel DNAzyme molecular beacon (DNAzymeMB) strategy was developed for target-induced signal-amplifying colorimetric detection of target nucleic acids. The DNAzymeMB, which exhibits peroxidase activity in its free hairpin structure, was engineered to form a catalytically inactive hybrid through hybridization with a blocker DNA. The presence of target DNA leads to dissociation of the DNAzymeMB from the inactive hybrid through hybridization with the blocker DNA. This process results in recovery of the catalytically active DNAzymeMB, which can catalyze a colorimetric reaction that signals the presence of the target DNA. In addition, a primer was rationally designed to anneal to the blocker DNA of the blocker/target DNA duplex and displace the bound target DNA during the extension reaction. The released target DNA triggers the next cycle involving hybridization with blocker DNA, DNAzymeMB dissociation, primer extension, and target displacement. This unique amplifying strategy leads to the generation of multiple numbers of active DNAzymeMB molecules from a single target molecule and gives a detection limit down to 1 pM, a value that is nearly 3 or 5 orders of magnitude lower than those of previously reported DNAzyme molecular beacon-based DNA detection methods.     

Effects of initial precursor and microwave irradiation on step-by-step synthesis of zinc oxide nano-architectures

ZnO nano-architectures were produced with the aid of a fast, simple and low cost microwave-assisted synthesis method. Solid semispherical ZnO nanoparticles on the order of 600 nm in diameter along with rice-like ZnO nanorods 95 nm thick were produced from butanol, triethanolamine (TEA), and zinc acetate dihydrate. Solid spherical ZnO nano-architectures with an average diameter of 250 nm were produced from the same starting materials in addition to NaOH. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the ZnO nano-architectures as well as the precursor. This method is cheap, fast and simple; capable of producing large quantities of each ZnO nanostructure. Investigation of the step-by-step formation mechanism for each ZnO nanostructure was conducted.     

卟啉聚集行为的研究进展

卟啉是一类特殊的大环共轭芳香化合物,在不同条件下能通过非共价键相互作用形成不同形式的聚集体。综述了国内外学者对卟啉化合物聚集行为的研究,详细介绍了不同类型的卟啉分子在不同条件下所形成的聚集体,重点介绍了卟啉所形成聚集体的结构以及影响卟啉聚集体形成的主要因素,并对卟啉聚集体的研究前景进行了展望。     

Detection of possible economically motivated adulterants in heparin sodium and low molecular weight heparins with a colorimetric microplate based assay

Recently, we described a 96-well plate format assay for visual detection of oversulfated chondroitin sulfate A (OSCS) contamination in heparin samples based on a water-soluble cationic polythiophene polymer (3-(2-(N-(N'-methylimidazole))ethoxy)-4-methylthiophene (LPTP)) and heparinase digestion of heparin. Here, we establish the specificity of the LPTP/heparinase test with a unique set of reagents that define the structural requirements for significant LPTP chemosensor color change. For example, we observed a biphasic behavior of larger shifts to the red in the UV absorbance spectra with decreasing average molecular weight of heparin chains with a break below 12-mer chain lengths. In addition, the oversulfation of chondroitin sulfate A (CSA) to a partially (PSCS) or fully (OSCS) sulfated form caused progressively less red shift of LPTP solutions. Furthermore, glycosaminoglycans (GAGs) containing glucuronic acid caused distinct spectral patterns compared to iduronic acid containing GAGs. We applied the LPTP/heparinase test to detection of OSCS (≥0.03% (w/w) visually or 0.01% using a plate reader) in 10 μg amounts of low molecular weight heparins (LMWHs; i.e. dalteparin, tinzaparin, or enoxaparin). Furthermore, because other oversulfated GAGs are possible economically motivated adulterants (EMAs) in heparin sodium, we tested the capacity of the LPTP/heparinase assay to detect oversulfated dermatan sulfate (OSDS), heparin (OSH), and heparan sulfate (OSHS). These potential EMAs were visually detectable at a level of ～0.1% when spiked into heparin sodium. We conclude that the LPTP/heparinase test visually detects oversulfated GAGs in heparin sodium and LMWHs in a format potentially amenable to high-throughput screening.     

含偶氮基卟啉大环衍生物的制备及表征

文章介绍了有光、热敏感性能的四（4-重氮基苯基）卟啉及含有偶氮基团的卟啉衍生物的合成,用红外光谱,紫外光谱,飞行质谱等进行了结构表征,并对其光、热稳定性进行了研究。     

基于卟啉及其衍生物的硫化氢检测进展

硫化氢既是有毒 物质又是生物体内重要气体信号分子,所以对硫化氢检测的研究十分重要。卟啉及其衍生物作为传感器材料,具有良好的化学稳定性和光学稳定性,与硫化氢结合后会产生光电变化,是检测硫化氢的优良材料。简述了硫化氢的检测手段、卟啉的性质以及卟啉与硫化氢的反应原理,并按照不同的传感器类别综述了卟啉在硫化氢检测中的应用,同时还对卟啉在硫化氢检测的应用领域进行了展望。     

Porous sheet-like and sphere-like nano-architectures of SnO2 nanoparticles via a solvent-thermal approach and their gas-sensing performances

Porous sheet-like and sphere-like nano-architectures of SnO₂ nanoparticles have been prepared via a solvent-thermal approach in the absence of any surfactant or polymer templates by simply changing the volume ratio of DMF to water. The nano-materials have been characterized by FESEM, XRD, IR, TEM and BET. A mechanism for the formation of nano-architectures is also proposed based on the assembly behaviors of DMF in water. The gas sensors constructed with porous sphere-like SnO₂ nano-architectures exhibit much higher sensitivity to the reduce vapors tested, compared to those from porous sheet-like SnO₂ materials, while the sheet-like materials show better selectivity to ethanol. The nano-architectures fabricated with the facile method are promising candidates for building chemical sensors with tunable performances.     

卟啉分子识别中的非共价键相互作用

卟啉由于其特殊的分子识别性能在超分子材料化学领域得到了广泛的应用。本文综述了近年来卟啉化合物的分子识别研究,详细介绍了卟啉化合物进行分子识别过程中的非共价键相互作用,重点探讨了氢键、配位、π-π堆积以及静电等相互作用在卟啉分子识别中的作用,并对卟啉分子识别的前景进行了展望。     

Porphyrin based hybrid borate glasses: Structure and photophysical investigation

Freebase tetra phenyl porphyrin (H₂TPP) and its derivatives in different concentration ranges (0.5–2.0 mg per 12 g of boric acid) were incorporated into borate glass matrix by melt quenching technique at 230 °C. The formed glasses were stable and in green colour. The optical absorption and emission properties are different from that observed in solutions. The absorption spectrum shows a two line pattern Soret band at 435–454 nm and Q-band at 665–701 nm. The emission spectrum shows strong S₂ → S₀ emission at 490–520 nm region and S₁ → S₀ emission at 725–810 nm. The time resolved fluorescence decay of S₁ → S₀ emission shows three exponential decay. For example, in the case of 2 mg of H₂THP doped glass the lifetimes were found to be τ₁ = 0.511 ns (26.7%), τ₂ = 10 ps (64.68%) and τ₃ = 3.965 ns (8.62%). These unusual photophysical properties were found to arise from different structural motifs of porphyrin in the glass. These structures were further modeled through reactions of porphyrin with BF₃O(C₂H₅) in solution and DFT calculations.