Review of Label-Free Monitoring of Bacteria: From Challenging Practical Applications to Basic Research Perspectives.

Novel biosensors already provide a fast way to detect the adhesion of whole bacteria (or parts of them), biofilm formation, and the effect of antibiotics. Moreover, the detection sensitivities of recent sensor technologies are large enough to investigate molecular-scale biological processes. Usually, these measurements can be performed in real time without using labeling.

Natural Compounds as Target Biomolecules in Cellular Adhesion and Migration: From Biomolecular Stimulation to Label-Free Discovery and Bioactivity-Based Isolation.

Plants and fungi can be used for medical applications because of their accumulation of special bioactive metabolites. These substances might be beneficial to human health, exerting also anti-inflammatory and anticancer (antiproliferative) effects. We propose that they are mediated by influencing cellular adhesion and migration via various signaling pathways and by directly inactivating key cell adhesion surface receptor sites.

Rapid inactivation of SARS-CoV-2 by titanium dioxide surface coating.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission occurs via airborne droplets and surface contamination. Titanium dioxide (TiO ) coating of surfaces is a promising infection control measure, though to date has not been tested against SARS-CoV-2. : Virus stability was evaluated on TiO - and TiO -Ag (Ti:Ag atomic ratio 1:0.

Data evaluation for surface-sensitive label-free methods to obtain real-time kinetic and structural information of thin films: A practical review with related software packages.

Interfacial layers are important in a wide range of applications in biomedicine, biosensing, analytical chemistry and the maritime industries. Given the growing number of applications, analysis of such layers and understanding their behavior is becoming crucial. Label-free surface sensitive methods are excellent for monitoring the formation kinetics, structure and its evolution of thin layers, even at the nanoscale.

Staphylococcus aureus resists UVA at low irradiance but succumbs in the presence of TiO photocatalytic coatings.

The aim of this study was to evaluate the bactericidal effect of reactive oxygen species (ROS) generated upon irradiation of photocatalytic TiO surface coatings using low levels of UVA and the consequent killing of Staphylococcus aureus. The role of intracellular enzymes catalase and superoxide dismutase in protecting the bacteria was investigated using mutant strains. Differences were observed in the intracellular oxidative stress response and viability of S.

How Does a Photocatalytic Antimicrobial Coating Affect Environmental Bioburden in Hospitals?

BACKGROUND The healthcare environment is recognized as a source for healthcare-acquired infection. Because cleaning practices are often erratic and always intermittent, we hypothesize that continuously antimicrobial surfaces offer superior control of surface bioburden. OBJECTIVE To evaluate the impact of a photocatalytic antimicrobial coating at near-patient, high-touch sites in a hospital ward.

Enhanced protein adsorption and cellular adhesion using transparent titanate nanotube thin films made by a simple and inexpensive room temperature process: application to optical biochips.

A new type of titanate nanotube (TNT) coating is investigated for exploitation in biosensor applications. The TNT layers were prepared from stable but additive-free sols without applying any binding compounds. The simple, fast spin-coating process was carried out at room temperature, and resulted in well-formed films around 10nm thick.

Sample handling in surface sensitive chemical and biological sensing: a practical review of basic fluidics and analyte transport.

This paper gives an overview of the advantages and associated caveats of the most common sample handling methods in surface-sensitive chemical and biological sensing. We summarize the basic theoretical and practical considerations one faces when designing and assembling the fluidic part of the sensor devices. The influence of analyte size, the use of closed and flow-through cuvettes, the importance of flow rate, tubing length and diameter, bubble traps, pressure-driven pumping, cuvette dead volumes, and sample injection systems are all discussed.

Dependence of cancer cell adhesion kinetics on integrin ligand surface density measured by a high-throughput label-free resonant waveguide grating biosensor.

A novel high-throughput label-free resonant waveguide grating (RWG) imager biosensor, the Epic® BenchTop (BT), was utilized to determine the dependence of cell spreading kinetics on the average surface density (v(RGD)) of integrin ligand RGD-motifs. v(RGD) was tuned over four orders of magnitude by co-adsorbing the biologically inactive PLL-g-PEG and the RGD-functionalized PLL-g-PEG-RGD synthetic copolymers from their mixed solutions onto the sensor surface. Using highly adherent human cervical tumor (HeLa) cells as a model system, cell adhesion kinetic data of unprecedented quality were obtained.

Optical anisotropy of flagellin layers: in situ and label-free measurement of adsorbed protein orientation using OWLS.

The surface adsorption of the protein flagellin was followed in situ using optical waveguide lightmode spectroscopy (OWLS). Flagellin did not show significant adsorption on a hydrophilic waveguide, but very rapidly formed a dense monolayer on a hydrophobic (silanized) surface. The homogeneous and isotropic optical layer model, which has hitherto been generally applied in OWLS data interpretation for adsorbed protein films, failed to characterize the flagellin layer, but it could be successfully modeled as an uniaxial thin film.

Adhesive properties and inflammatory potential of citrullinated myelin basic protein peptide 45-89.

Deimination of arginyl residue of myelin basic protein (MBP) reduces cationicity of MBP and impedes the normal myelin membrane assembly. Less ordered structure of MBP is more susceptible to proteolytic attack that may lead to the release of highly immunogenic deiminated peptides into extracellular milieu. We have studied the association of peptides 45-89 derived from citrullinated MBP (C8 isomer) and phosphorylated MBP (C3 isomer) with the myelin lipids in a model membrane system using optical waveguide lightmode spectrometry.

Optical biosensors for cell adhesion.

Planar optical waveguides offer an ideal substratum for cells on which to reside. The materials from which the waveguides are made--high refractive index transparent dielectrics--correspond to the coatings of medical implants (e.g.

Polyphenol control of cell spreading on glycoprotein substrata.

Cell-surface contacts are vital for many eukaryotic cells. The surface provides anchorage (facilitating spreading and proliferation), is involved in sensation, i.e.

Optical monitoring of stem cell-substratum interactions.

Modulation of the coupling of light into a waveguide via a grating, together with a novel approach to analyzing the data, is used to investigate the attachment of human embryonal carcinoma stem cells to three substrata: silica-titania (representative of artificial implants); poly-lysine (a commonly used laboratory cell culture substrate); and mucin (the coating of the mucosae). By considering both in-coupling peak width and position, the secretion of microexudate by the cells, the formation of filopodia, and the overall change in their shape (spreading) can be distinguished. This cannot be achieved by the conventional microscopic imaging approach.

Viscous boundary lubrication of hydrophobic surfaces by mucin.

The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin "Orthana" (Mw=0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces.

Self-assembly of rodlike receptors from bulk solution.

Optical waveguide lightmode spectroscopy has been used to observe the deposition of bacterial flagellar filaments of mean length 350 nm from bulk solution onto a smooth planar substratum, chemically modified to covalently bind the flagellar filaments on contact. At the highest practicable bulk concentration, the filaments follow the theoretically predicted kinetics of random sequential addition of highly elongated rigid rods to the substratum, but addition terminates with the rods almost perpendicular to the substratum. Rod-rod correlations in the bulk anomalously accelerate the rate of arrival of the filaments at the surface of the substratum, relative to spheres.

Structural hysteresis and hierarchy in adsorbed glycoproteins.

The adsorption and desorption of the giant heavily glycosylated protein mucin from solutions of different bulk concentrations have been followed at the nanometer scale using high resolution molecular microscopy based on optical waveguide lightmode spectroscopy. Modeling the layer as a uniaxial thin film allowed the in situ determination of adsorbed mass, mean layer thickness, and structural anisotropy. These parameters manifest highly significant adsorption-desorption hysteresis, indicating at least two dominant glycoprotein conformational types (i.

Multidepth screening of living cells using optical waveguides.

The use of planar optical waveguides as substrata for label-free, non-invasive monitoring of cells growing on them is demonstrated. Different submicrometre depths (measured from and perpendicular to the substratum surface) can be selected for monitoring. The so-called symmetry waveguide configuration with a low refractive index waveguide support (nanoporous silica with refractive index approximately 1.

Temperature dependence of mucin adsorption.

The kinetics of adsorption and desorption on a silica-like surface of the large glycoprotein mucin have been measured across a range of temperatures from 25 to 60 degrees C. The area occupied per molecule diminishes with increasing temperature both in the bulk and adsorbed states, implying that the glycoprotein belongs to the "natively open" conformational class. Due to the conformational rearrangement, the specific interaction energy governing desorption greatly increases with temperature, resulting in an impressively regulated temperature-invariant dynamic surface coating.

Quasi-isotropic analysis of anisotropic thin films on optical waveguides.

Thin films assembled on a substrate are often anisotropic. Nevertheless, because of experimental limitations, sufficient parameters to characterize the anisotropy, even in the simplest (and perhaps most common) case of uniaxial thin films, which are birefringent, are not usually available. This paper examines the consequences of treating them as isotropic thin films, with particular reference to their characterization via perturbation of the propagation constants (effective refractive indices) of optical waveguides.

Complex desorption of mucin from silica.

Complex solutes may adsorb from solution onto solid surfaces in a concentration-dependent manner. In other words, the adsorption behavior is qualitatively different in different bulk concentration regimes. Here we show that the large glycoprotein mucin not only adsorbs in distinctively different ways according to the bulk concentration but also, strikingly, that the law of desorption, established with the help of high-resolution molecular microscopy, depends on the bulk concentration during adsorption.

Integrated optical switching based on the protein bacteriorhodopsin.

According to our earlier pioneering study, a dry film containing native bacteriorhodopsin (bR) shows unique nonlinear optical properties (refractive index change, controllable by light of different colors, greater than 2 x 10(-3)) that are in many respects superior to those of the materials presently applied in integrated optics. Here, we report on the first integrated optical application based on a miniature Mach-Zehnder interferometer (see Figs. 1 and 2) demonstrating a real switching effect by bR (efficiency higher than 90%) due to the M-state.

Guidelines: From artificial evolution to computational evolution: a research agenda.

Computational scientists have developed algorithms inspired by natural evolution for at least 50 years. These algorithms solve optimization and design problems by building solutions that are 'more fit' relative to desired properties. However, the basic assumptions of this approach are outdated.