An anisotropic propagation technique for synthesizing hyperbranched polyvillic gold nanoparticles

Of late, many synthesis processes have been studied to develop irregular nano-morphologies of gold nanostructures for biomedical applications in order to increase the efficacy of nanoparticle theranostics, tune the plasmonic absorbance spectra, and increase the sensitivity of biomolecule detection through surface enhanced Raman spectroscopy. Here we report, a novel, non-seed mediated versatile single pot synthesis method capable of producing hyperbranched gold “nano-polyvilli” with more than 50–90 branching nanowires propagating from a single origin within each structure. The technique was capable of achieving precise tuning of the branch propagation where the branching could be controlled by varying the duration of incubation, temperature, and hydrogen ion concentration.

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分子印迹聚合物在分离领域的应用

分子印迹技术是近年来集高分子合成、分子设计、分子识别、仿生生物工程等众多学科优势发展起来的一种应用广泛的新型技术.阐述了分子印迹方法的基本原理,介绍了分子印迹聚合物在分离领域的应用.综述了该技术的研究现状,并展望了其发展趋势.     

核-壳型罗丹明6G磁性分子印迹固相萃取材料的合成与表征

采用化学共沉淀法制备Fe3O4磁性纳米粒子,以3-氨丙基三乙氧基硅烷(APTES)对其表面进行氨基硅烷化改性,形成Fe3O4@SiO2-NH2纳米粒子。以其作为磁性核,采用表面印迹技术,以罗丹明6G为模板,丙烯酰胺(AM)为功能单体,三羟甲基丙烷三甲基丙烯酸酯(TRIM)为交联剂,在Fe3O4@SiO2-NH2表面形成罗丹明6G分子印迹聚合膜,制备了核-壳型罗丹明6G磁性分子印迹聚合物(Fe3O4@MIPs),对合成条件进行了优化。分别采用红外光谱(FT-IR)、场发射扫描电镜(FESEM)、振动样品磁强分析(VSM)和热重分析(TGA)等仪器分析手段,对Fe3O4@MIPs的结构进行表征。结果表明,所制备的核-壳型磁性分子印迹聚合物具有高吸附容量及显著选择性;在外加磁场作用下Fe3O4@MIPs可快速与样品基质分离,大大提高了实验效率。Fe3O4@MIPs作为一种新型固相萃取材料,可以从样品中选择性分离和富集违规添加的罗丹明6G,可应用于食品的安全检测。     

A new approach to solution-phase gold seeding for SERS substrates

Surface-enhanced Raman scattering (SERS) vastly improves signal-to-noise ratios as compared to traditional Raman scattering, making sensitive assays based upon Raman scattering a reality. However, preparation of highly stable SERS-active gold substrates requires complicated and expensive methodologies and instrumentation. Here, a general and completely solution-phase, seed-based approach is introduced, which is capable of producing gold films for SERS applications on a variety of substrates, not requiring surface modification or functionalization. SERS enhancement factors of ≈10(7) were observed. Moreover, solution-phase gold film deposition on highly complex surfaces, such as protein-coated bioassays, is demonstrated for the first time. Protein bioassays coated with such SERS-active gold films are combined with bioconjugated single-walled carbon nanotube Raman labels, affording highly sensitive detection of the cancer biomarker, carcinoembryonic antigen in serum, with a limit of detection of ≈5 fM (1 pg mL(-1) ).     

Development of an active packaging with molecularly imprinted polymers for beef preservation

To develop molecularly imprinted polymers (MIPs) for new food packaging material, a new active antibacterial packaging material was prepared with allyl isothiocyanate MIPs (AITC‐MIPs) and chitosan (CS) for beef preservation. AITC‐MIPs were prepared with AITC as template, β‐CD as the functional monomer, and TDI as the cross‐linker by the non‐covalent method, and the release characteristics were evaluated under different relative humidities and temperatures. The AITC‐MIPs active packaging film was obtained by uniform coating with CS coating solution and AITC‐MIPs based on the surface of the original low‐density polyethylene packaging film, and its role in delaying muscle metamorphism was thoroughly explored. According to the N‐hexane extraction method, the AITC content in AITC‐MIPs was determined to be 73.9 μL/g. The release behaviors of AITC‐MIPs under different humidities could be obtained by fitting with Avrami's Equation. The release of AITC‐MIPs under the relative humidities of 98% and 75% is a restricted dynamic diffusion process, while the release behaviors of AITC‐MIPs under the relative humidity of 50% are between those of a diffusion process and those of a first‐order mode dynamic process. The AITC‐MIPs could endure the heat stress, and the lower temperature was conducive to the stability of the AITC‐MIPs. A series of physicochemical and microbiological indicators fully illustrated that muscle deterioration could be significantly (P < 0.05) postponed by AITC‐MIPs active packaging film compared with the original low‐density polyethylene packaging film.     

The enhanced and polarized Raman spectra on the spherical aluminum powders encapsulated within graphene nanosheets

This article deals with the Raman spectroscopic research of aluminum–graphene (Al–Gr) composites obtained by aqueous suspension-based mixing to improve dispersion of graphene sheets in composite powders. Raman spectra of composite powders reflect encapsulated nanostructure of Al–Gr composite powders and chemical interaction of oxygen groups on graphene oxide (GO) with magnesium ions (Mg²⁺), depending on the added Mg²⁺ content. First, the enhanced Raman signal for our composite powders is an apparent evidence of that graphene sheets with uniform dispersion on Al matrix are in close contact with the spherical surface of Al powders. The polarization dependence of the Raman spectra, which are dependent on the incident laser spot, also confirms that the graphene sheets surrounded the spherical powder. SEM image, XPS and FT-IR spectra for the composite powders provide additional data to decipher the Raman analysis results.     

Convective assembly of linear gold nanoparticle arrays at the micron scale for surface enhanced Raman scattering

A convective assembly technique at the micron scale analogous to the writing action of a “pipette pen” has been developed for the linear assembly of gold nanoparticle strips with micron scale width and millimeter scale length for surface enhanced Raman scattering (SERS). The arrays with interparticle gaps smaller than 3 nm are hexagonally stacked in the vicinity of the pipette tip. Variable numbers of stacked layers and clean surfaces of the assembled nanoparticles are obtained by optimizing the velocity of the pipette tip. The SERS properties of the assembled nanoparticle arrays rely on their stacking number and surface cleanliness.      

Plasmonic coupling interference (PCI) nanoprobes for nucleic acid detection

A label-free approach using plasmonic coupling interference (PCI) nanoprobes for nucleic acid detection using surface-enhanced Raman scattering (SERS) is described. To induce a strong plasmonic coupling effect, a nanonetwork of silver nanoparticles with the Raman label located between adjacent nanoparticles is assembled by Raman-labeled DNA-locked nucleic acid (LNA) duplexes. The PCI method then utilizes specific nucleic acid sequences of interest as competitor elements for the Raman-labeled DNA strands to interfere the formation of nanonetworks in a competitive binding process. As a result, the plasmonic coupling effect induced through the formation of the nanonetworks is significantly diminished, resulting in a reduced SERS signal. The potential of the PCI technique for biomedical applications is illustrated by detecting single-nucleotide polymorphism (SNP) and microRNA sequences involved in breast cancers. The results of this study could lead to the development of nucleic acid diagnostic tools for biomedical diagnostics and biosensing applications using SERS detection.     

Functional Femtoliter Droplets for Ultrafast Nanoextraction and Supersensitive Online Microanalysis

A universal femtoliter surface droplet‐based platform for direct quantification of trace of hydrophobic compounds in aqueous solutions is presented. Formation and functionalization of femtoliter droplets, concentrating the analyte in the solution, are integrated into a simple fluidic chamber, taking advantage of the long‐term stability, large surface‐to‐volume ratio, and tunable chemical composition of these droplets. In situ quantification of the extracted analytes is achieved by surface‐enhanced Raman scattering (SERS) spectroscopy by nanoparticles on the functionalized droplets. Optimized extraction efficiency and SERS enhancement by tuning droplet composition enable quantitative determination of hydrophobic model compounds of rhodamine 6G, methylene blue, and malachite green with the detection limit of 10^?9 to 10^?11 m and a large linear range of SERS signal from 10^?9 to 10^?6 m of the analytes. The approach addresses the current challenges of reproducibility and the lifetime of the substrate in SERS measurements. This novel surface droplet platform combines liquid–liquid extraction and highly sensitive and reproducible SERS detection, providing a promising technique in current chemical analysis related to environment monitoring, biomedical diagnosis, and national security monitoring.     

Pen‐on‐Paper Approach Toward the Design of Universal Surface Enhanced Raman Scattering Substrates

The translation of a technology from the laboratory into the real world should meet the demand of economic viability and operational simplicity. Inspired by recent advances in conductive ink pens for electronic devices on paper, we present a “pen‐on‐paper” approach for making surface enhanced Raman scattering (SERS) substrates. Through this approach, no professional training is required to create SERS arrays on paper using an ordinary fountain pen filled with plasmonic inks comprising metal nanoparticles of arbitrary shape and size. We demonstrate the use of plasmonic inks made of gold nanospheres, silver nanospheres and gold nanorods, to write SERS arrays that can be used with various excitation wavelengths. The strong SERS activity of these features allowed us to reach detection limits down to 10 attomoles of dye molecules in a sample volume of 10 μL, depending on the excitation wavelength, dye molecule and type of nanoparticles. Furthermore, such simple substrates were applied to pesticide detection down to 20 ppb. This universal approach offers portable, cost effective fabrication of efficient SERS substrates at the point of care. This approach should bring SERS closer to the real world through ink cartridges to be fixed to a pen to create plasmonic sensors at will.     

Selective Surface Enhanced Raman Scattering for Quantitative Detection of Lung Cancer Biomarkers in Superparticle@MOF Structure

Surface enhanced Raman scattering (SERS) is a trace detection technique that extends even to single molecule detection. Its potential application to the noninvasive recognition of lung malignancies by detecting volatile organic compounds (VOCs) that serve as biomarkers would be a breakthrough in early cancer diagnostics. This application, however, is currently limited by two main factors: (1) most VOC biomarkers exhibit only weak Raman scattering; and (2) the high mobility of gaseous molecules results in a low adsorptivity on solid substrates. To enhance the adsorption of gaseous molecules, a ZIF‐8 layer is coated onto a self‐assembly of gold superparticles (GSPs) in order to slow the flow rate of gaseous biomarkers and depress the exponential decay of the electromagnetic field around the GSP surfaces. Gaseous aldehydes that are released as a result of tumor‐specific tissue composition and metabolism, thereby acting as indicators of lung cancer, are guided onto SERS‐active GSPs substrates through a ZIF‐8 channel. Through a Schiff base reaction with 4‐aminothiophenol pregrafted onto gold GSPs, gaseous aldehydes are captured with a 10 ppb limit of detection, demonstrating tremendous prospects for in vitro diagnoses of early stage lung cancer.     

Quantitative and Specific Detection of Exosomal miRNAs for Accurate Diagnosis of Breast Cancer Using a Surface‐Enhanced Raman Scattering Sensor Based on Plasmonic Head‐Flocked Gold Nanopillars

MicroRNAs in exosomes (exosomal miRNAs) have attracted increased attention as cancer biomarkers for early diagnosis and prognosis owing to their stability in body fluids. Since strong association exists between exosomal miRNA expression levels and breast cancer, the development of effective methods that can monitor exosomal miRNA expression both over broad concentration ranges and in ultralow amounts is critical. Here, a surface‐enhanced Raman scattering (SERS)‐based sensing platform is developed for the quantitative determination of exosomal miRNAs. Ultrasensitive exosomal miRNA detection with single‐nucleotide specificity is obtained from enhanced SERS signals from a uniform plasmonic head‐flocked gold nanopillar substrate, which generates multiple hotspots and enables hybridization between short oligonucleotides, i.e., miRNAs and locked nucleic acid probes. The proposed SERS sensor shows an extremely low detection limit without any amplification process, a wide dynamic range (1 am to 100 nm ), multiplex sensing capability and sound miRNA recovery in serum. Furthermore, this sensor allows reliable observation of exosomal miRNA expression patterns from breast cancer cell lines and can discriminate breast cancer subtype based on the difference between these patterns. The results suggest that this sensor can be used for universal cancer diagnosis and further biomedical applications through the quantitative measurement of exosomal miRNAs in bodily fluids.