Contamination of surface water and drinking water with pharmaceuticals presents an environmental concern. It has been shown to affect aquatic organisms and have adverse health effects on humans. One of the most common pharmaceutical contaminants is the opioid analgesic tramadol. In this communication, we report on the first surface plasmon resonance biosensor-based detection of tramadol in water. The biosensor utilizes a binding inhibition format and enables detection of tramadol at a wide range of concentrations (5 orders of magnitude) with a limit of detection of 0.52 µg/L. The results of a small-scale environmental study are reported in which the biosensor was used to analyze river water samples. The results were found to agree well with those obtained using the liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

• Keywords
• Biosensor, Surface plasmon resonance, Tramadol, Water quality monitoring,
• MeSH
• Biosensing Techniques * methods   MeSH
• Water Pollutants, Chemical * analysis   MeSH
• Limit of Detection MeSH
• Environmental Monitoring * methods   MeSH
• Analgesics, Opioid * analysis   MeSH
• Surface Plasmon Resonance * methods   MeSH
• Rivers chemistry   MeSH
• Tandem Mass Spectrometry MeSH
• Tramadol * analysis   MeSH
• Chromatography, High Pressure Liquid MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Water Pollutants, Chemical * MeSH
• Analgesics, Opioid * MeSH
• Tramadol * MeSH

Calmodulin (CaM) is a ubiquitous calcium-sensitive messenger in eukaryotic cells. It was previously shown that CaM possesses an affinity for diverse lipid moieties, including those found on CaM-binding proteins. These facts, together with our observation that CaM accumulates in membrane-rich protrusions of HeLa cells upon increased cytosolic calcium, motivated us to perform a systematic search for unmediated CaM interactions with model lipid membranes mimicking the cytosolic leaflet of plasma membranes. A range of experimental techniques and molecular dynamics simulations prove unambiguously that CaM interacts with lipid bilayers in the presence of calcium ions. The lipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) hold the key to CaM-membrane interactions. Calcium induces an essential conformational rearrangement of CaM, but calcium binding to the headgroup of PS also neutralizes the membrane negative surface charge. More intriguingly, PE plays a dual role-it not only forms hydrogen bonds with CaM, but also destabilizes the lipid bilayer increasing the exposure of hydrophobic acyl chains to the interacting proteins. Our findings suggest that upon increased intracellular calcium concentration, CaM and the cytosolic leaflet of cellular membranes can be functionally connected.

• Keywords
• calcium, calmodulin, lipid membrane, phosphatidylethanolamine, phosphatidylserine,
• MeSH
• Cell Membrane * metabolism   MeSH
• Cytosol * metabolism   MeSH
• Phosphatidylethanolamines metabolism   MeSH
• Phosphatidylserines * metabolism   MeSH
• HeLa Cells MeSH
• Calmodulin * metabolism   chemistry   MeSH
• Humans MeSH
• Lipid Bilayers * metabolism   MeSH
• Molecular Dynamics Simulation * MeSH
• Calcium * metabolism   MeSH
• Protein Binding * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phosphatidylethanolamines MeSH
• Phosphatidylserines * MeSH
• Calmodulin * MeSH
• Lipid Bilayers * MeSH
• phosphatidylethanolamine MeSH Browser
• Calcium * MeSH

The analysis of low-abundance protein molecules in human serum is reported based on counting of the individual affinity-captured analyte on a solid sensor surface, yielding a readout format similar to digital assays. In this approach, a sandwich immunoassay with rolling circle amplification (RCA) is used for single molecule detection (SMD) through associating the target analyte with spatially distinct bright spots observed by fluorescence microscopy. The unspecific interaction of the target analyte and other immunoassay constituents with the sensor surface is of particular interest in this work, as it ultimately limits the performance of this assay. It is minimized by the design of the respective biointerface and thiol self-assembled monolayer with oligoethylene (OEG) head groups, and a poly[oligo(ethylene glycol) methacrylate] (pHOEGMA) antifouling polymer brush was used for the immobilization of the capture antibody (cAb) on the sensor surface. The assay relying on fluorescent postlabeling of long single-stranded DNA that are grafted from the detection antibody (dAb) by RCA was established with the help of combined surface plasmon resonance and surface plasmon-enhanced fluorescence monitoring of reaction kinetics. These techniques were employed for in situ measurements of conjugating of cAb to the sensor surface, tagging of short single-stranded DNA to dAb, affinity capture of the target analyte from the analyzed liquid sample, and the fluorescence readout of the RCA product. Through mitigation of adsorption of nontarget molecules on the sensor surface by tailoring of the antifouling biointerface, optimizing conjugation chemistry, and by implementing weak Coulombic repelling between dAb and the sensor surface, the limit of detection (LOD) of the assay was substantially improved. For the chosen interleukin-6 biomarker, SMD assay with LOD at a concentration of 4.3 fM was achieved for model (spiked) samples, and validation of the ability of detection of standard human serum samples is demonstrated.

• Keywords
• antifouling biointerface, biomarker, digital readout of assay, rolling circle amplification, single molecule detection, surface plasmon resonance, surface plasmon-enhanced fluorescence,
• MeSH
• DNA, Single-Stranded * MeSH
• Humans MeSH
• Surface Plasmon Resonance * methods   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA, Single-Stranded * MeSH

Aberrant glycosylation of glycoproteins has been linked with various pathologies. Therefore, understanding the relationship between aberrant glycosylation patterns and the onset and progression of the disease is an important research goal that may provide insights into cancer diagnosis and new therapy development. In this study, we use a surface plasmon resonance imaging biosensor and a lectin array to investigate aberrant glycosylation patterns associated with oncohematological disease-myelodysplastic syndromes (MDS). In particular, we detected the interaction between the lectins and glycoproteins present in the blood plasma of patients (three MDS subgroups with different risks of progression to acute myeloid leukemia (AML) and AML patients) and healthy controls. The interaction with lectins from Aleuria aurantia (AAL) and Erythrina cristagalli was more pronounced for plasma samples of the MDS and AML patients, and there was a significant difference between the sensor response to the interaction of AAL with blood plasma from low and medium-risk MDS patients and healthy controls. Our data also suggest that progression from MDS to AML is accompanied by sialylation of glycoproteins and increased levels of truncated O-glycans and that the number of lectins that allow discriminating different stages of disease increases as the disease progresses.

• MeSH
• Leukemia, Myeloid, Acute * MeSH
• Biosensing Techniques * MeSH
• Glycoproteins metabolism   MeSH
• Glycosylation MeSH
• Plasma metabolism   MeSH
• Lectins MeSH
• Humans MeSH
• Myelodysplastic Syndromes * therapy   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Glycoproteins MeSH
• Lectins MeSH

Glyphosate is one of the most widely used pesticides, which, together with its primary metabolite aminomethylphosphonic acid, remains present in the environment. Many technologies have been developed to reduce glyphosate amounts in water. Among them, heterogeneous photocatalysis with titanium dioxide as a commonly used photocatalyst achieves high removal efficiency. Nevertheless, glyphosate is often converted to organic intermediates during its degradation. The detection of degraded glyphosate and emerging products is, therefore, an important element of research in terms of disposal methods. Attention is being paid to new sensors enabling the fast detection of glyphosate and its degradation products, which would allow the monitoring of its removal process in real time. The surface plasmon resonance imaging (SPRi) method is a promising technique for sensing emerging pollutants in water. The aim of this work was to design, create, and test an SPRi biosensor suitable for the detection of glyphosate during photolytic and photocatalytic experiments focused on its degradation. Cytochrome P450 and TiO2 were selected as the detection molecules. We developed a sensor for the detection of the target molecules with a low molecular weight for monitoring the process of glyphosate degradation, which could be applied in a flow-through arrangement and thus detect changes taking place in real-time. We believe that SPRi sensing could be widely used in the study of xenobiotic removal from surface water or wastewater.

• Keywords
• aminomethylphosphonic acid, glyphosate, pesticide, photocatalysis, surface plasmon resonance,
• MeSH
• Water Pollutants, Chemical * analysis   MeSH
• Herbicides * analysis   MeSH
• Pesticides * MeSH
• Surface Plasmon Resonance MeSH
• Water MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Water Pollutants, Chemical * MeSH
• Herbicides * MeSH
• Pesticides * MeSH
• Water MeSH

Surface plasmons, the collective oscillation of electrons, enable the manipulation of optical fields with unprecedented spatial and time resolutions. They are the workhorse of a large set of applications, such as chemical/biological sensors or Raman scattering spectroscopy, to name only a few. In particular, the ultrafast optical response configures one of the most fundamental characteristics of surface plasmons. Thus, the rich physics about photon-electron interactions could be retrieved and studied in detail. The associated plasmon-enhanced electric fields, generated by focusing the surface plasmons far beyond the diffraction limit, allow reaching the strong field regime with relatively low input laser intensities. This is in clear contrast to conventional optical methods, where their intrinsic limitations demand the use of large and costly laser amplifiers, to attain high electric fields, able to manipulate the electron dynamics in the non-linear regime. Moreover, the coherent plasmonic field excited by the optical field inherits an ultrahigh precision that could be properly exploited in, for instance, ultraprecision spectroscopy. In this review, we summarize the research achievements and developments in ultrafast plasmonics over the last decade. We particularly emphasize the strong-field physics aspects and the ultraprecision spectroscopy using optical frequency combs.

• Keywords
• optical frequency comb, photoelectron spectroscopy, strong-field physics, surface plasmons, ultrafast plasmonics,
• Publication type
• Journal Article MeSH
• Review MeSH

Plasmonic nanomaterials have become an integral part of numerous technologies, where they provide important functionalities spanning from extraction and harvesting of light in thin film optical devices to probing of molecular species and their interactions on biochip surfaces. More recently, we witness increasing research efforts devoted to a new class of plasmonic nanomaterials that allow for on-demand tuning of their properties by combining metallic nanostructures and responsive hydrogels. This review addresses this recently emerged vibrant field, which holds potential to expand the spectrum of possible applications and deliver functions that cannot be achieved by separate research in each of the respective fields. It aims at providing an overview of key principles, design rules, and current implementations of both responsive hydrogels and metallic nanostructures. We discuss important aspects that capitalize on the combination of responsive polymer networks with plasmonic nanostructures to perform rapid mechanical actuation and actively controlled nanoscale confinement of light associated with resonant amplification of its intensity. The latest advances towards the implementation of such responsive plasmonic nanomaterials are presented, particularly covering the field of plasmonic biosensing that utilizes refractometric measurements as well as plasmon-enhanced optical spectroscopy readout, optically driven miniature soft actuators, and light-fueled micromachines operating in an environment resembling biological systems.

• MeSH
• Hydrogels * MeSH
• Nanostructures * chemistry   MeSH
• Polymers MeSH
• Spectrum Analysis MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Hydrogels * MeSH
• Polymers MeSH

The ability to detect low concentrations of analytes and in particular low-abundance biomarkers is of fundamental importance, e.g., for early-stage disease diagnosis. The prospect of reaching the ultimate limit of detection has driven the development of single-molecule bioaffinity assays. While many review articles have highlighted the potentials of single-molecule technologies for analytical and diagnostic applications, these technologies are not as widespread in real-world applications as one should expect. This Review provides a theoretical background on single-molecule-or better digital-assays to critically assess their potential compared to traditional analog assays. Selected examples from the literature include bioaffinity assays for the detection of biomolecules such as proteins, nucleic acids, and viruses. The structure of the Review highlights the versatility of optical single-molecule labeling techniques, including enzymatic amplification, molecular labels, and innovative nanomaterials.

• Keywords
• digital assays, immunoassays, optical detection, signal background, single-molecule detection,
• MeSH
• Biomarkers analysis   MeSH
• Enzyme-Linked Immunosorbent Assay MeSH
• Fluorescent Dyes chemistry   MeSH
• Limit of Detection MeSH
• Nanostructures chemistry   MeSH
• Nucleic Acids analysis   MeSH
• Polymerase Chain Reaction methods   MeSH
• Signal-To-Noise Ratio MeSH
• Proteins analysis   MeSH
• Binding Sites MeSH
• Viruses isolation & purification   MeSH
• Single Molecule Imaging methods   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Biomarkers MeSH
• Fluorescent Dyes MeSH
• Nucleic Acids MeSH
• Proteins MeSH

A robust and scalable technology to fabricate ordered gold nanoparticle arrangements on epoxy substrates is presented. The nanoparticles are synthesized by solid-state dewetting on nanobowled aluminum templates, which are prepared by the selective chemical etching of porous anodic alumina (PAA) grown on an aluminum sheet with controlled anodic oxidation. This flexible fabrication technology provides proper control over the nanoparticle size, shape, and interparticle distance over a large surface area (several cm2), which enables the fine-tuning and optimization of their plasmonic absorption spectra for LSPR and SERS applications between 535 and 625 nm. The nanoparticles are transferred to the surface of epoxy substrates, which are subsequently selectively etched. The resulting nanomushrooms arrangements consist of ordered epoxy nanopillars with flat, disk-shaped nanoparticles on top, and their bulk refractive index sensitivity is between 83 and 108 nm RIU-1. Label-free DNA detection is successfully demonstrated with the sensors by using a 20 base pair long specific DNA sequence from the parasite Giardia lamblia. A red-shift of 6.6 nm in the LSPR absorbance spectrum was detected after the 2 h hybridization with 1 μM target DNA, and the achievable LOD was around 5 nM. The reported plasmonic sensor is one of the first surface AuNP/polymer nanocomposites ever reported for the successful label-free detection of DNA.

• Keywords
• DNA biosensor, localized surface plasmon resonance, nanobowled aluminum, nanoparticle lattice, surface nanocomposite,
• MeSH
• Giardia lamblia * MeSH
• Metal Nanoparticles chemistry   MeSH
• Nanocomposites chemistry   MeSH
• Surface Plasmon Resonance * MeSH
• DNA, Protozoan analysis   MeSH
• Gold chemistry   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA, Protozoan MeSH
• Gold MeSH

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematological malignancies with a high risk of transformation to acute myeloid leukemia (AML). MDS are associated with posttranslational modifications of proteins and variations in the protein expression levels. In this work, we present a novel interactomic diagnostic method based on both protein array and surface plasmon resonance biosensor technology, which enables monitoring of protein-protein interactions in a label-free manner. In contrast to conventional methods based on the detection of individual biomarkers, our presented method relies on measuring interactions between arrays of selected proteins and patient plasma. We apply this method to plasma samples obtained from MDS and AML patients, as well as healthy donors, and demonstrate that even a small protein array comprising six selected proteins allows the method to discriminate among different MDS subtypes and healthy donors.

• MeSH
• Principal Component Analysis MeSH
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Protein Interaction Mapping * MeSH
• Young Adult MeSH
• Myelodysplastic Syndromes blood   diagnosis   MeSH
• Surface Plasmon Resonance MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Protein Binding MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH