Water is a matter of vital importance for all developed countries due to the strong impact on human health and aquatic, wetlands and terrestrial environments. Therefore, the monitoring of water ...quality is of tremendous importance. The enormous advantages that Surface-enhanced Raman scattering (SERS) spectroscopy offers, such as fingerprint recognition, multiplex capabilities, high sensitivity, and selectivity or non-destructive testing, make this analytical tool very attractive for this purpose. This minireview aims to provide a summary of current approaches for the implementation of SERS sensors in monitoring organic and inorganic pollutants in water. In addition, we briefly highlight current challenges and provide an outlook for the application of SERS in environmental monitoring.
Microbes produce bioactive chemical compounds to influence the physiology and growth of their neighbors, and our understanding of their biological activities may be enhanced by our ability to ...visualize such molecules in vivo. We demonstrate here the application of surface-enhanced Raman scattering spectroscopy for simultaneous detection of quorum-sensing-regulated pyocyanin and violacein, produced respectively by Pseudomonas aeruginosa and Chromobacterium violaceum bacterial colonies, grown as a coculture on agar-based plasmonic substrates. Our plasmonic approach allowed us to visualize the expression and spatial distribution of the microbial metabolites in the coculture taking place as a result of interspecies chemical interactions. By combining surface-enhanced Raman scattering spectroscopy with analysis of gene expression we provide insight into the chemical interplay occurring between the interacting bacterial species. This highly sensitive, cost-effective, and easy to implement approach allows spatiotemporal imaging of cellular metabolites in live microbial colonies grown on agar with no need for sample preparation, thereby providing a powerful tool for the analysis of microbial chemotypes.
Most bacteria in nature exist as biofilms, which support intercellular signalling processes such as quorum sensing (QS), a cell-to-cell communication mechanism that allows bacteria to monitor and ...respond to cell density and changes in the environment. As QS and biofilms are involved in the ability of bacteria to cause disease, there is a need for the development of methods for the non-invasive analysis of QS in natural bacterial populations. Here, by using surface-enhanced resonance Raman scattering spectroscopy, we report rationally designed nanostructured plasmonic substrates for the in situ, label-free detection of a QS signalling metabolite in growing Pseudomonas aeruginosa biofilms and microcolonies. The in situ, non-invasive plasmonic imaging of QS in biofilms provides a powerful analytical approach for studying intercellular communication on the basis of secreted molecules as signals.
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•Living cells are sensor/actuator entities that perceive and process chemical and physical stimuli by receptor-mediated cell signaling, which in turn modulates cellular function and ...behavior.•Gold nanoparticles and gold nanostructured substrates have unique chemical and physical properties that allow targeted modulation of cell receptor function at the nanoscale.•Multifunctional gold-based nanodevices enable biochemical, plasmonic (e.g. optothermal) and electrical manipulation of cell activities at the nanoscale.
The cell possesses the remarkable ability to perceive and process chemical and physical stimuli, which in turn modulate cellular behavior. One of the great wonders about nanotechnology is that it enables the fabrication of tools on the same length scale as biomolecules, thereby providing us with a unique handle for characterizing and controlling basic cellular processes. Owing to their tunable size and shape dependent physical properties, biocompatibility and facile surface modification, gold nanoparticles become potentially powerful tools to probe fundamental aspects of cell biology. Consequently, innovative approaches based on gold nanoparticles are under development toward the manipulation of cell function and improvement of techniques currently used in biomedicine and biotechnology. In this review we provide an overview of recent applications based on gold nanoparticles and nanostructured materials for the modulation of cellular activity and behavior, mediated by their interactions with cell surface receptors.
Zeolitic imidazolate framework-8 (ZIF-8) is a metal organic framework with exceptional intrinsic properties, high tunability, cost effectiveness, and producibility, which has boosted the research ...development of the field. ZIF-8-based materials have shown high capabilities for multiple purposes as catalysts, capacitors, electrodes, drug delivery systems, or adsorption/separation membranes. Herein, we report the synergistic combination of ZIF-8, plasmonic nanoparticles, and rationally designed protein adaptors and antibodies for fabricating novel surface-enhanced Raman scattering (SERS) tags with enhanced sensing capabilities. The SERS tags consist of Au@Ag core–shell nanorods individually encapsulated within a multifunctional ZIF-8 matrix encoded with Raman reporters. While the role of the plasmonic core is to enhance the Raman, the ZIF-8 traps the Raman active molecules and, more importantly, facilitates the active targeting of the SERS tag surface through the modular assembly with conventional (i.e., immunoglobulins) and recombinant antibodies (i.e., nanobodies) mediated by the specific interaction of Zn2+ with polyhistidine-tagged protein G and SpyCatcher. Evidence of the capabilities of the Au@Ag@ZIF-8 nanotags for the SERS detection of EGFR and CD44 cell surface receptors in vitro illustrates the potential of these optical nanoprobes for imaging and multiplex biodetection. The reported modular assembly approach for the functionalization of ZIF-8 SERS nanotags with different classes of antibodies based on polyhistidine-tagged peptides and protein–protein interactions can not only be applied to the ever-increasing number of reported MOFs structures but also can be further exploited as a universal means for the functionalization of other transition metal surfaces.
This review provides an overview of current progress in Pd nanoparticles supporting localized surface plasmon resonance and their applications. We begin by analyzing briefly the optical properties of ...Pd putting particular focus on outlining the origin of its size- and shape-dependent LSPR, high refractive index sensitivity, and high absorption contribution. The differences in the optical behavior with Au and Ag, the primary plasmonic materials, are highlighted. The main strategies to synthesize Pd nanoparticles, pure or hybrid, with well-defined optical properties are then reviewed. In this section, we include only those works that carry out the study of the optical properties of the nanoparticles. The applications of plasmonic Pd nanoparticles are also discussed in detail. This review is concluded with a section devoted to the future perspectives highlighting the most relevant challenges to be addressed to take Pd nanoparticles from the laboratory to real applications.
Pd as an alternative material for nanoplasmonics.
Detection technologies employing optically encoded particles have gained much interest toward clinical diagnostics and drug discovery, but the portfolio of available systems is still limited. The ...fabrication and characterization of highly stable surface‐enhanced resonance Raman scattering (SERRS)‐encoded colloids for the identification and imaging of proteins expressed in cells are reported. These plasmonic nanostructures are made of gold octahedra coated with poly(N‐isopropylacrylamide) microgels and can be readily encoded with Raman active dyes while retaining high colloidal stability in biofluids. A layer‐by‐layer polyelectrolyte coating is used to seal the outer surface of the encoded particles and to provide a reactive surface for covalent conjugation with antibodies. The targeted multiplexing capabilities of the SERRS tags are demonstrated by the simultaneous detection and imaging of three tumor‐associated surface biomarkers: epidermal growth factor receptor (EGFR), epithelial cell adhesion molecule (EpCAM), and homing cell adhesion molecule (CD44) by SERRS spectroscopy. The plasmonic microgels are able to discriminate tumor A431 (EGFR+/EpCAM+/CD44+) and nontumor 3T3 2.2 (EGFR−/EpCAM−/CD44+) cells while cocultured in vitro.
Surface‐enhanced resonance Raman scattering (SERRS) tags with a multiplex capability for targeted identification of cellular receptors are prepared by dye encoding poly(N‐isopropylacrylamide)‐encapsulated Au nanooctahedra. Upon irradiation with a single laser line, the plasmonic microgels are able to discriminate tumor and nontumor cells while co‐cultured in vitro. Hence, these SERRS labels may be applied to high‐throughput, multiplex assays for in vitro screening and diagnostics.
Raman-encoded gold nanoparticles (NPs) have been widely employed as photostable multifunctional probes for sensing, bioimaging, multiplex diagnostics, and surface-enhanced Raman scattering ...(SERS)-guided tumor therapy. We report a strategy toward obtaining a particularly large library of Au nanocapsules encoded with Raman codes defined by the combination of different thiol-free Raman reporters, encapsulated at defined molar ratios. The fabrication of SERS tags with tailored size and predefined codes is based on the in situ incorporation of Raman reporter molecules inside Au nanocapsules during their formation via galvanic replacement coupled to seeded growth on Ag NPs. The hole-free closed-shell structure of the nanocapsules is confirmed by electron tomography. The unusually wide encoding possibilities of the obtained SERS tags are investigated by means of either wavenumber-based encoding or Raman frequency combined with signal intensity, leading to an outstanding performance as exemplified by 26 and 54 different codes, respectively. We additionally demonstrate that encoded nanocapsules can be readily bioconjugated with antibodies for applications such as SERS-based targeted cell imaging and phenotyping.
Infections caused by microorganisms are a global public health problem that continually demands new antimicrobial strategies. The generation of reactive oxygen species (ROS) by photocatalytic ...materials is an attractive approach to combat microbes. Along these lines, titanium dioxide (TiO2) constitutes an outstanding light‐driven ROS generator. However, the wide bandgap of this semiconductor limits its use to the ultraviolet range of the spectral region. Herein, nanostructured materials composed of TiO2 nanoparticles and plasmonic gold nanorods (AuNRs) are presented for the photoinactivation of bacteria by means of sunlight irradiation, aiming to extend the photocatalytic action of the nanocomposite to the visible and near‐infrared ranges. It is shown that, upon simulated sunlight irradiation, the different composites as coating films show photodegradation of rhodamine B, ROS production, photocatalytic inactivation of protein function in bacterial biofilms, and strong antimicrobial activity. This approach involving AuNRs/TiO2 photocatalytic composites may pave the way for the fabrication of visible light‐responsive surfaces with antimicrobial activity.
Nanostructured materials composed of TiO2 nanoparticles and gold nanorods (AuNR) disposed as a coating film for the killing of bacteria by reactive oxygen species generation through sunlight irradiation are presented. The AuNR@TiO2 composites extend the photocatalytic action to the visible and near‐infrared ranges, thereby improving the development of sunlight‐responsive surfaces and coatings with integrated antimicrobial activity and self‐sterilizing properties.
Abstract
The immunoglobulin (Ig) protein domain is widespread in nature having a well-recognized role in proteins of the immune system. In this review, we describe the proteins containing Ig-like ...domains in Escherichia coli and enterobacteria, reporting their structural and functional properties, protein folding, and diverse biological roles. In addition, we cover the expression of heterologous Ig domains in E. coli owing to its biotechnological application for expression and selection of antibody fragments and full-length IgG molecules. Ig-like domains in E. coli and enterobacteria are frequently found in cell surface proteins and fimbrial organelles playing important functions during host cell adhesion and invasion of pathogenic strains, being structural components of pilus and nonpilus fimbrial systems and members of the intimin/invasin family of outer membrane (OM) adhesins. Ig-like domains are also found in periplasmic chaperones and OM usher proteins assembling fimbriae, in oxidoreductases and hydrolytic enzymes, ATP-binding cassette transporters, sugar-binding and metal-resistance proteins. The folding of most E. coliIg-like domains is assisted by periplasmic chaperones, peptidyl–prolyl cis/trans isomerases and disulfide bond catalysts that also participate in the folding of antibodies expressed in this bacterium. The technologies for expression and selection of recombinant antibodies in E. coli are described along with their biotechnological potential.
This review describes the proteins containing Ig-like domains in E coli and other enterobacterial species and the expression of heterologous Ig domains of antibody fragments and full-length IgGs in this microorganism.
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