Programming an enhanced uptake and the intracellular fate of magnetic microbeads

This study compares two kinds of magnetic microbeads with different surface features and cell entry pathways, aiming to provide insights into how to program their cell uptake and intracellular fate. It is found that a rougher surface enhances the cell uptake of the microbeads, regardless of whether they are pulled by a magnetic field gradient or adsorbed by the cell membrane. However, the entry route affects the intracellular localization of the microbeads: The magnetically dragged microbeads reach the cytoplasm, while the adsorbed microbeads stay in the late endosomes and lysosomes. This suggests that different strategies can be used to target different cellular compartments with magnetic microbeads. Moreover, it is demonstrated that the cells containing the microbeads can be moved and regrown at specific locations by applying a magnetic field gradient, showing the potential of these magnetic microbeads for cell delivery and manipulation.Agencia Estatal de Investigación | Ref. PID2019-109669RB-I00Agencia Estatal de Investigación | Ref. PID2020-119242RB-I00Xunta de GaliciaUniversidade de Vigo/CISU

Sunlight‐sensitive plasmonic nanostructured composites as photocatalytic coating with antibacterial properties

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.Universidade de Vigo/CISU

Using Surface Enhanced Raman Scattering to Analyze the Interactions of Protein Receptors with Bacterial Quorum Sensing Modulators

Many members of the LuxR family of quorum sensing (QS) transcriptional activators, including LasR of Pseudomonas aeruginosa, are believed to require appropriate acyl-homoserine lactone (acyl-HSL) ligands to fold into an active conformation. The failure to purify ligand-free LuxR homologues in nonaggregated form at the high concentrations required for their structural characterization has limited the understanding of the mechanisms by which QS receptors are activated. Surface-enhanced Raman scattering (SERS) is a vibrational spectroscopy technique that can be applied to study proteins at extremely low concentrations in their active state. The high sensitivity of SERS has allowed us to detect molecular interactions between the ligand-binding domain of LasR (LasRLBD) as a soluble apoprotein and modulators of P. aeruginosa QS. We found that QS activators and inhibitors produce differential SERS fingerprints in LasRLBD, and in combination with molecular docking analysis provide insight into the relevant interaction mechanism. This study reveals signal-specific structural changes in LasR upon ligand binding, thereby confirming the applicability of SERS to analyze ligand-induced conformational changes in proteinsS

Recent progress in surface-enhanced raman scattering for the detection of chemical contaminants in water

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 monitoringMinisterio de Economía y Competitividad | Ref. MAT2016-77809-RXunta de Galicia | Ref. ED431C 2016-04

Plasmonic Au@Ag@mSiO2 nanorattles for In situ imaging of bacterial metabolism by surface-enhanced raman scattering spectroscopy

It is well known that microbial populations and their interactions are largely influenced by their secreted metabolites. Noninvasive and spatiotemporal monitoring and imaging of such extracellular metabolic byproducts can be correlated with biological phenotypes of interest and provide new insights into the structure and development of microbial communities. Herein, we report a surface-enhanced Raman scattering (SERS) hybrid substrate consisting of plasmonic Au@Ag@mSiO2 nanorattles for optophysiological monitoring of extracellular metabolism in microbial populations. A key element of the SERS substrate is the mesoporous silica shell encapsulating single plasmonic nanoparticles, which furnishes colloidal stability and molecular sieving capabilities to the engineered nanostructures, thereby realizing robust, sensitive, and reliable measurements. The reported SERS-based approach may be used as a powerful tool for deciphering the role of extracellular metabolites and physicochemical factors in microbial community dynamics and interactions.Xunta de Galicia | Ref. 2019-2022Xunta de Galicia | Ref. ED431C 2020/09Agencia Estatal de Investigación | Ref. PID2019-109669RB-I00Agencia Estatal de Investigación | Ref. PID2019-108954RB-I00Ministerio de Economía, Industria y Competitividad | Ref BES-2017-08167

An expanded surface-enhanced raman scattering tags library by combinatorial rncapsulation of reporter molecules in metal nanoshells

Raman-encoded gold nanoparticles (NPs) have been widely employed as photostable multifunctional probes for sensing, bioimaging, multiplex diagnostics, and surfaceenhanced 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 closedshell 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.Ministerio de Ciencia, Innovación y Universidades | Ref. MDM-2017-0720Ministerio de Economía, Industria y Competitividad | Ref. MAT2016-77809-RAgencia Estatal de Investigación | Ref. PID2019-108954RB-100Xunta de Galicia | Ref. ED431G 2019/07Fundación Ramón Areces | Ref. SERSforSAFETYResearch Foundation Flanders | Ref. G038116