The effects of road building on arbuscular mycorrhizal fungal diversity in Huangshan Scenic Area.

Arbuscular mycorrhizal (AM) fungi are vital soil microbes that connect many individual plants into a large functional organism via a vast mycelial network under the ground. In this study, the changes of soil AM fungal community in response to road-building disturbance caused by tourism development in Huangshan (Yellow Mountain) Scenic Area are assessed. Road building have brought negative effects on AM fungal community, inducing lower diversity parameters, including species number, spore density and diversity indices. However, the dominant genus and species of AM fungi which play key roles in the AM fungal community composition are quite similar before and after road building. Moreover, there are no significant differences in species richness of AM fungi associated with plants, suggesting the tolerance of AM fungal community to the disturbance of road building.

Raman photostability of off-resonant gap-enhanced Raman tags.

Surface-enhanced Raman scattering (SERS) nanoprobes show promising potential for biosensing and bioimaging applications due to advantageous features of ultrahigh sensitivity and specificity. However, very limited research has been reported on the SERS photostability of nanoprobes upon continuous laser irradiation, which is critical for high-speed and time-lapse microscopy. The core-shell off-resonant gap-enhanced Raman tags (GERTs) with built-in Raman reporters, excited at near-infrared (NIR) region but with a plasmon resonance at visible region, allow decoupling the plasmon resonance behaviors with the SERS performance and therefore show ultrahigh Raman photostability during continuous laser irradiation. In this work, we have synthesized five types of off-resonant GERTs with different embedded Raman reporters, numbers of shell layer, or nanoparticle shapes. Via thorough examination of time-resolved SERS trajectories and quantitative analysis of photobleaching behaviors, we have demonstrated that double metallic-shell GERTs embedded with 1,4-benzenedithiol molecules show the best photostability performance, to the best of our knowledge, among all SERS nanoprobes reported before, with a photobleaching time constant up to 4.8 × 105 under a laser power density of 4.7 × 105 W cm-2. Numerical calculations additionally support that the local plasmonic heating effect in fact can be greatly minimized using the off-resonance strategy. Moreover, double-shell BDT-GERTs are highly potential for high-speed and high-resolution Raman-based cell bioimaging.

Rational Design of Ultrabright SERS Probes with Embedded Reporters for Bioimaging and Photothermal Therapy.

Plasmonic nanoparticles can be utilized as surface-enhanced Raman scattering (SERS) probes for bioimaging and as photothermal (PT) agents for cancer therapy. Typically, their SERS and PT efficiencies reach maximal values under the on-resonant condition, when the excitation wavelength overlaps the localized surface plasmon resonance (LSPR) wavelength preferably in the near-infrared (NIR) biological window. However, the photogenerated heat may inevitably disturb or even destroy biological samples during the imaging process. Herein, we develop ultrabright SERS probes composed of metallic Au@Ag core-shell rodlike nanomatryoshkas (RNMs) with embedded Raman reporters. By rationally controlling the Ag shell thickness, the LSPR of RNMs can be tuned from UV to NIR range, resulting in highly tunable SERS and PT properties. As bright NIR SERS imaging nanoprobes, RNMs with a thick Ag shell are designed for minimal PT damage to the biological targets under the off-resonance condition, as illustrated through monitoring the changes in mitochondrial membrane potential of cancer cells during SERS imaging procedure. By contrast, RNMs with a thin Ag shell are designed as multifunctional NIR theranostic probes that combine enhanced photothermal therapy capability, as exemplified by efficient PT killing of cancer cells, with reduced yet still efficient imaging properties at the on-resonance excitation.

Plasmonic nanoshells enhanced laser desorption/ionization mass spectrometry for detection of serum metabolites.

Laser desorption/ionization mass spectrometry (LDI MS)-based small metabolites detection is fundamentally important for the clinic prognoses and diagnoses. Plasmonic materials have been applied as efficient substrates for LDI MS of these molecules. However, there is no clear understanding of the mechanism of using plasmonic materials for enhanced LDI MS of small metabolites, thus restricting their application for real case serum samples. In this work, we report the use of plasmonic nanoshells for enhanced LDI MS detection of small analytes. The antibonding modes of Au nanoshells provided unique opportunity for the generation of hot carriers in the ultra-violet (UV) optical range. This effect of the Au nanoshells displayed desirable analytical sensitivity and endurance towards small metabolites (e.g. amino acids) in complex protein/mixtures as compared to Au nanorods/nanospheres and conventional organic matrix. Further we achieved LDI MS profiling and detection of small metabolites from complex serum samples by Au nanoshells. Our work not only shed light on the enhancement mechanism of LDI MS detection using plasmonic nanoparticles with hot carriers, but also contributed to the real case application of LDI MS in clinical study.

Strong plasmon coupling in self-assembled superparamagnetic nanoshell chains.

Construction of ordered patterns of plasmonic nanoparticles is greatly important for nanophotonics relevant applications. We have reported a facile and low-cost magnetic field induced self-assembly approach to construct plasmonic superparamagnetic nanoshell (SN) chains up to several hundred micrometers in a few seconds in a large area without templates or other assistance processes. Experimental and theoretical investigations of the near- and far-field optical properties indicate that the super- and sub-radiant modes of the SN chains continuously redshift with the increase of SN number and the Fano resonance emerges in the infinite double- and triple-line SN chains. Strong plasmon coupling effects in the SN chains result in great electric field enhancements at visible and infrared wavelengths, which indicates that these chain structures potentially can be used as a common substrate for both surface enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) application. This fabrication method also offers a general strategy alternative to top-down processing that enables the construction of nanostructures for metamaterials, electromagnetic energy transport, and optical waveguide.

Superparamagnetic plasmonic nanoshells for improved imaging, separation and seeding of co-cultured cells.

A human umbilical vein endothelial cell/human dermal fibroblast (HUVEC/HDF) co-culture system has been widely applied for mimicking the vascularization process in tissue engineering. Here, we have developed plasmonic superparamagnetic nanoshells (SNs) to realize the visualization of cell proliferation behaviour via two-photon luminescence of particle shells and the cell separation via the superparamagnetic properties of particle cores. The cell viability test and gene expression analysis have demonstrated no obvious cytotoxicity and disturbance to cell co-culture. Cell separation efficiency via SNs reaches a value of 94.7%, close to 99.5% in routine methods by magnetic beads. In contrast to the complicated and expensive process using specific antibody-targeted immunofluorescence staining and the magnetic beads separation in routine methods, SNs present a more simple and effective way to achieve both functions with better photo-stability and a negligible photo-bleaching effect via TPL imaging. Furthermore, the combination of the TPL imaging and magnetic manipulation of SNs also offers the potential of spontaneously enhancing the cell seeding and tracking the cell distribution in 3D tissue engineering scaffolds.

Multifunctional superparamagnetic nanoshells: combining two-photon luminescence imaging, surface-enhanced Raman scattering and magnetic separation.

With the increasing need for multi-purpose analysis in the biomedical field, traditional single diagnosis methods cannot meet the requirements. Therefore new multifunctional technologies and materials for the integration of sample collection, sensing and imaging are in great demand. Core-shell nanoparticles offer a unique platform to combine multifunctions in a single particle. In this work, we have constructed a novel type of core-shell superparamagnetic nanoshell (Fe3O4@SiO2@Au), composed of a Fe3O4 cluster core, a thin Au shell and a SiO2 layer in between. The obtained multifunctional nanoparticles combine the magnetic properties and plasmonic optical properties effectively, which were well investigated by a number of experimental characterization methods and theoretical simulations. We have demonstrated that Fe3O4@SiO2@Au nanoparticles can be utilized for two-photon luminescence (TPL) imaging, near-infrared surface-enhanced Raman scattering (NIR SERS) and cell collection by magnetic separation. The TPL intensity could be further greatly enhanced through the plasmon coupling effect in the self-assembled nanoparticle chains, which were triggered by an external magnetic field. In addition, Fe3O4@SiO2@Au nanoparticles may have great potential applications such as enhanced magnetic resonance imaging (MRI) and photo-thermotherapy. Successful combination of multifunctions including magnetic response, biosensing and bioimaging in single nanoparticles allows further manipulation, real-time tracking, and intracellular molecule analysis of live cells at a single-cell level.