Bioorthogonal SERS Nanoprobes for Mulitplex Spectroscopic Detection,Tumor Cell Targeting,and Tissue Imaging

A surface‐enhanced Raman scattering (SERS) technique shows extraordinary features for a range of biological and biomedical applications. Herein, a series of novel bioorthogonal SERS nanoprobes were constructed with Gold nanoflower (AuNF) and Raman reporters, the signals of which were located in a Raman‐silent region of biological samples. AS1411 aptamer was also co‐conjugated with AuNF through a self‐assembled monolayer coverage strategy. Multiplex SERS imaging using these nanoprobes with three different bioorthogonal small‐molecule Raman reporters is successfully achieved with high multiplexing capacity in a biologically Raman‐silent region. These Raman nanoprobes co‐conjugated with AS1411 showed high affinity for tumor cells with overexpressed nucleolin and can be used for selective tumor cell screening and tissue imaging.     

1,3-Sulfinate Migration Triggered by α-Imino Carbene and Divergent Zwitterion Cyclization: Synthesis of Cyclopropane,Dihydropyrrole, and Azepane Ring Systems

Cyclopropane, dihydropyrrole, and azepane ring systems were synthesized conveniently from sulfinate-tethered triazoles. The divergent synthetic strategy started with the unique 1,3-sulfinate migration of an α-imino carbene. The efficient reaction allowed control of the zwitterion bearing multiple reactive sites depending on the increased stability of the resulting carbocation and anion. The sulfinate was converted to a sulfone after the group migration, and a stable anion bearing two electron-withdrawing groups was thus formed. Catalytic amounts of iodide acted as a switch for the synthesis of cyclopropanes and dihydropyrroles. The reaction merits including readily available substrates, mild reaction conditions, and excellent functional group compatibility qualified this protocol a possible synthetic tool for cyclic compounds, especially for N-heterocycles.     

硫脲修饰Cd掺杂ZnO水溶性量子点的制备及表征

在非水稀溶液中以聚乙烯吡咯烷酮K-30为稳定剂,硫脲为表面修饰剂,制备Cd掺杂ZnO水溶性量子点荧光体;同时研究了基质的优化及硫脲含量对ZnO量子点发光性能的影响,Eu和Li的共掺杂对ZnO:Cd量子点发光性能的影响.采用紫外光谱、荧光发射光谱、红外光谱和透射电镜、XRD对样品进行表征.结果表明:经Cd优化基质后、Eu和Li的共掺杂使量子点荧光强度明显增强;硫脲修饰后纳米颗粒分布更加均匀、晶粒更小、荧光光谱蓝移、量子点产率增加;该样品XRD衍射峰是馒头峰.属于无定形态;红外光谱图中因硫脲引起的NH2和C-NH2伸缩振动吸收峰分别为3189.0,1088.2 cm-1,硫脲修饰的最佳浓度大约为32 mg/mL.该量子点制备方法简单易行,具有较好的稳定性及高荧光量子效率,为进一步应用于生物标记奠定基础.     

Location of Si vacancies and [Ti(OSi)4] and [Ti(OSi)3OH] sites in the MFI framework: a large cluster and full ab initio study

Titanium silicalite-1 (TS-1) is an important catalyst for selective oxidation reactions. However, the nature and structure of the active sites and the mechanistic details of the catalytic reactions over TS-1 have not been well-understood, leaving a continuous debate on the genesis of active sites on the TS-1 surface in the literature. In this work, the location of Si vacancies and [Ti(OSi)(4)] and [Ti(OSi)(3)OH] sites in the MFI (Framework Type Code of ZSM-5 (Zeolite Socony Mobile-Five)) framework has been studied using a full ab initio method with 40T clusters with a Si:Ti molar ratio of 39:1. It was shown that the former four energetically favorable sites for Si vacancies are T6, T12, T4, and T8 and for Ti centers of [Ti(OSi)(4)] are T10, T4, T8 and T11, being partially the same sites. Whether by replacing Si vacancies or substituting the fully coordinated Si sites, the most preferential site for Ti is T10, which indicates that the insertion mechanism does not affect the favorable sites of Ti in the MFI lattice. For the defective [Ti(OSi)(3)OH] sites, it was found that the Si vacancy at T6 with a Ti at its neighboring T9 site (T6-def-T9-Ti pair) is the most energetically favorable one, followed by a T6-def-T5-Ti pair with a small energy gap. These findings are significant to elucidate the nature of the active sites and the mechanism of reactions catalyzed by TS-1 and to design the TS-1 catalyst.     

Aptamer-functionalized magnetic nanoparticle-based bioassay for the detection of ochratoxin A using upconversion nanoparticles as labels

A sensitive luminescent bioassay for the detection of ochratoxin A (OTA), a small molecular mycotoxin, was developed using aptamer-conjugated magnetic nanoparticles (MNPs) as the recognition and concentration element and upconversion nanoparticles (UCNPs) as highly sensitive labels. The bioassay system was fabricated by immobilizing aptamer DNA 1 sequence onto the surface of Fe(3)O(4) MNPs, which were implemented to capture and concentrate OTA from bulk samples. The aptamer DNA 1 sequence then hybridized with UCNPs modified with DNA 2 sequence, which could dissociate from DNA 1 and result in a decreased luminescent signal when aptamer DNA 1 recognized and bound to target OTA. Under the optimal conditions, the decreased luminescent intensity (ΔI) is proportional to the concentration of OTA in the range of 1 × 10(-13) to 1 × 10(-9) g mL(-1) with a detection limit of 1 × 10(-13) g mL(-1). The proposed method then was successfully applied to measure OTA in naturally contaminated maize samples and validated by a commercially available enzyme-linked immunosorbent assay (ELISA) method. Benefiting from the magnetic separation and concentration effect of MNPs, the high sensitivity of UCNPs, as well as the selectivity and stability of the aptamer, the present upconversion luminescent bioassay offers a promising approach for the screening of small molecular mycotoxins because it is simple, rapid, highly sensitive, specific, does not require sample pre-concentration and lacks interference from autofluorescence of other biomolecules.