Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines.

(Oligo)phenothiazinyl thioacetates, synthesized by a one-pot sequence, are electrochemically oxidizable and highly fluorescent. SAMs can be readily formed from thiols prepared by in situ deprotection of the thioacetates in the presence of a gold-coated silicon wafer. Monolayer formation is confirmed by ellipsometry and the results compared to those obtained by force field and DFT calculations.

Optical sensors based on whispering gallery modes in fluorescent microbeads: response to specific interactions.

Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis of the observed shifts in the WGM wavelength positions are applied and used to quantify the adsorbed mass densities, which are then compared with the results of a comparative surface plasmon resonance (SPR) study.

In-vitro sensing of biomechanical forces in live cells by a whispering gallery mode biosensor.

Direct measurement of the biomechanical stress induced by a live cell during endocytosis is reported. Fluorescent dye-doped polystyrene microspheres were used as microscopic remote optical sensors applying whispering gallery modes (WGMs) as transducer mechanism. Monitoring of the WGMs throughout the incorporation of the microsphere into the cell enabled the determination of the deformation experienced by the microsphere, characterized by both a broadening and a blue shift of the resonances, and consequently the stress induced by the cell.

Optical sensors based on whispering gallery modes in fluorescent microbeads: size dependence and influence of substrate.

Whispering gallery modes in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing changes in the refractive index of the beads' environment by exposing them to water/glycerol mixtures of varying composition. The mode positions are analyzed by simultaneous fitting for mode number, bead radius, and environmental index. Down to a diameter of 8 μm, the sensor response follows the index of the bulk solution very well.

Confinement-Induced Enhancement of Antigen-Antibody Interactions within Binary Nanopatterns to Achieve Higher Efficiency of On-Chip Immunosensors.

By combining molecular self-assembly, nanosphere lithography and reactive ion etching, large-scale nanopatterns of antibodies are fabricated for direct application in state-of-the-art on-chip immunosensors. Using in-situ surface plasmon resonance, the patterns are studied in view of their antigen binding capacity, which shows an increase of up to 120% solely in the case of antibody confinement into the nanopatches by means of a nonfouling embedding matrix.

Absorption spectrum of surface-bound cap-shaped gold particles.

A surface-adsorbed monolayer of cap-shaped gold particles upon submicrometer-sized polystyrene spheres exhibits pronounced absorption in the visible region. When the surrounding refractive index was altered by immersion in a fluid, the direction of the shift in the absorption spectrum was dependent on the incidence angle of the irradiation. When a thiol molecule, known to adsorb selectively on gold upon polystyrene, was added, the resultant shift in the absorption spectrum's peak was consistently toward longer wavelengths.

Optically responsive nanoparticle layers for the label-free analysis of biospecific interactions in array formats.

A novel nanocomposite surface is prepared by coating surface-adsorbed dielectric colloidal particles with a contiguous layer of gold nanoparticles. The resulting surface shows pronounced optical extinction in reflection with the extinction peaks located in the UV-Vis and NIR region of the electromagnetic spectrum. The peak positions of these maxima change very sensitively with the adsorption of organic molecules onto the surface.

Reversible protein adsorption and bioadhesion on monolayers terminated with mixtures of oligo(ethylene glycol) and methyl groups.

Surface-grafted, environmentally responsive polymers have shown great promise for controlling adsorption and desorption of macromolecules and cells on solid surfaces. In the paper, we demonstrate that certain mixed self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG) and methyl-terminated alkanethiolates on gold form surfaces with switchable hydrophobicity and tendency for protein adsorption and cellular attachment. At temperatures above 32 degrees C, SAMs with a surface density of approximately 50% OEG adsorbed significant amounts of pyruvate kinase and lysozyme, whereas below this temperature, these same SAMs were resistant to the adsorption of these proteins.

Proteomic profiling of erythrocyte proteins by proteolytic digestion chip and identification using two-dimensional electrospray ionization tandem mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. The bonding of enzyme to SAMs of alkanethiols onto gold surfaces is exploited to produce an enzyme chip. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent.

Characterization of trypsin immobilized on the functionable alkylthiolate self-assembled monolayers: a preliminary application for trypsin digestion chip on protein identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition and other interfacial phenomena. Recently the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N '-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent.

Protein deformation of lipid hybrid bilayer membranes studied by sum frequency generation vibrational spectroscopy.

Structural deformations of lipid hybrid bilayer membranes induced by signal peptideless (SPL) proteins have been studied for the first time using the inherently surface specific nonlinear optical technique of sum frequency generation vibrational spectroscopy. Specifically, deformations of 1,2-distearoylphosphatidylglycerol(DSPG) membranes induced by interaction with FGF-1, a SPL protein which is released asa function of cellular stress through a nonclassical pathway, have been investigated. FGF-1 was found to induce lipid alkyl chain deformations in previously highly ordered DSPG membranes at the extremely low concentration of 1 nM at 60 degrees C.

Proteomic profiling of platelet proteins by trypsin immobilized self-assembled monolayers digestion chip and protein identification using electrospray ionization tandem mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. Recently, the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling agent.