The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.

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Minimal information for studies of extracellular vesicles 2018 (MISEV2018) : a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

Plasmons in strongly coupled metallic nanostructures.

http://pubs.acs.org/doi/pdf/10.1021/cr400546e

Fluorescent Sensors for Measuring Metal Ions in Living Systems

Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

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Present and Future of Surface-Enhanced Raman Scattering

Owing to their excellent multiplexing ability, high sensitivity, and large dynamic range, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal have found prosperous applications in fields such as disease diagnosis, environmental surveillance, and food safety supervision. Various ever-increasing demands have promoted SERS-based immunoassays from the classical sandwich-type ones to those integrated with fascinating automatic platforms (e.g., test strips and microfluidic chips). As recent years have witnessed impressive progress in SERS immunoassays, we try to comprehensively cover SERS-based immunoassays from their basic working principles to specific applications. Focusing on several basic elements in SERS immunoassays, typical structures of SERS nanoprobes, productive optical spectral encoding strategies, and popular immunoassay platforms are highlighted, followed by their representative biological applications in the last 5 years. Moreover, despite the vast advances achieved ...

SERS-Activated Platforms for Immunoassay: Probes, Encoding Methods, and Applications

A new concept of optical encoding approach, surface enhanced Raman scattering (SERS)-fluorescence joint spectral encoding method (SFJSE), was demonstrated by using organic-metal-quantum dot (QD) hybrid nanoparticles (OMQ NPs) with a nanolayered structure. This method has two distinct characteristics, which make it more feasible to achieve enormous codes in practice, compared with a sole fluorescence- or SERS-based encoding protocol. One of the two characteristics is to use the joint SERS and fluorescence spectra as the encoding elements instead of an individual optical signal, resulting in a broadened optical spectrum range for efficient encoding. The other is to assemble SERS reporters and fluorescent agents onto different layers of OMQ NPs, leading to an easier fabrication protocol when a large number of agents need to be involved into encoding carriers. By conjugating different antibodies to OMQ NPs with varied codes, the potential application of such an encoding system in high-throughput detection has been investigated by multiplex sandwich immunoassays. The high specificity and sensitivity of the assays suggest that the SFJSE method could be developed as a powerful encoding tool for high-throughput bioanalysis with the use of OMQ NPs.

SERS-fluorescence joint spectral encoding using organic-metal-QD hybrid nanoparticles with a huge encoding capacity for high-throughput biodetection: putting theory into practice.

Unlike widely used postsynthetic halide exchange for CsPbX3 (X is halide) perovskite nanocrystals (NCs), cation exchange of Pb is of a great challenge due to the rigid nature of the Pb cationic sublattice. Actually, cation exchange has more potential for rendering NCs with peculiar properties. Herein, a novel halide exchange-driven cation exchange (HEDCE) strategy is developed to prepare dually emitting Mn-doped CsPb(Cl/Br)3 NCs via postsynthetic replacement of partial Pb in preformed perovskite NCs. The basic idea for HEDCE is that the partial cation exchange of Pb by Mn has a large probability to occur as a concomitant result for opening the rigid halide octahedron structure around Pb during halide exchange. Compared to traditional ionic exchange, HEDCE is featured by proceeding of halide exchange and cation exchange at the same time and lattice site. The time and space requirements make only MnCl2 molecules (rather than mixture of Mn and Cl ions) capable of doping into perovskite NCs. This special molecular doping nature results in a series of unusual phenomenon, including long reaction time, core–shell structured mid states with triple emission bands, and dopant molecules composition-dependent doping process. As-prepared dual-emitting Mn-doped CsPb(Cl/Br)3 NCs are available for ratiometric temperature sensing.

Postsynthetic Doping of MnCl2 Molecules into Preformed CsPbBr3 Perovskite Nanocrystals via a Halide Exchange-Driven Cation Exchange.

As a kind of most important cancer biomarker, exosomes are getting more frequently investigated in cancer diagnosis. In this study, we proposed an SERS-based method for the screening and simultaneous multiple detection of exosomes using magnetic substrates and SERS probes. Specifically, the capturing substrates are achieved using gold shell magnetic nanobeads modified by aptamers, which can capture most kinds of exosomes by recognizing the generic surface protein CD63. Moreover, the SERS probes are made of gold nanoparticles decorated with a Raman reporter and a specific aptamer for targeting exosomes. Further, for the simultaneous detection of multiple kinds of exosomes, three kinds of SERS probes were designed using different SERS reporters. While detecting specific kinds of exosomes, the capturing substrates were mixed with these three kinds of SERS probes. When the target exosome is present, an apta-immunocomplex can be formed among the target exosomes, the substrate, and the corresponding kind of SERS probes, and the other non-specific SERS probes remain in the suspension. Hence, an SERS signal with a decreased intensity will be detected in the supernatant, indicating the presence of the target exosomes. Finally, this detection method has also been successfully employed for the detection of exosomes in real blood samples; this proves that the proposed SERS-based method is a promising tool for clinical cancer screening based on exosomes.

Screening and multiple detection of cancer exosomes using an SERS-based method.

We report an intracellular pH sensor based on surface enhanced Raman scattering (SERS) using the hydrochloric acid (HCl) treated gold nanorods (GNRs) as the SERS substrates and p-aminothiophenol (pATP) as the Raman reporter. Using the HCl treated GNRs previously reported by us, the biocompatibility and the SERS performance of GNRs have been greatly improved. Meanwhile, the adsorbed reporters are allowed to be directly exposed to the surrounding environments, which is very important for biosensors. It is found that the SERS spectrum of pATP is strongly dependent on the pH value. The intensities of SERS bands at 1142 cm–1, 1390 cm–1, and 1432 cm–1 increased obviously with the pH value varying from 3.0 to 8.0. This pH-dependent SERS performance of pATP-functionalized HCl treated GNRs was well retained after the incorporation of the GNRs into living HeLa cells. Our experimental results indicate that such pATP-functionalized HCl treated GNRs can be used as an effective intracellular pH sensor. Thus, we show a ...

Zhuyuan Wang

Papers

SERS-Activated Platforms for Immunoassay: Probes, Encoding Methods, and Applications

SERS-fluorescence joint spectral encoding using organic-metal-QD hybrid nanoparticles with a huge encoding capacity for high-throughput biodetection: putting theory into practice.

Postsynthetic Doping of MnCl2 Molecules into Preformed CsPbBr3 Perovskite Nanocrystals via a Halide Exchange-Driven Cation Exchange.

Screening and multiple detection of cancer exosomes using an SERS-based method.

Intracellular pH sensing using p-aminothiophenol functionalized gold nanorods with low cytotoxicity.