Label-Enhanced Surface Plasmon Resonance: A New Concept for Improved Performance in Optical Biosensor Analysis

Peer reviewe

Elucidating the Signal Responses of Multi-Parametric Surface Plasmon Resonance Living Cell Sensing: A Comparison between Optical Modeling and Drug-MDCKII Cell Interaction Measurements

Peer reviewe

Spin coated chitin films for biosensors and its analysis are dependent on chitin-surface interactions

Chitin, abundant in nature, is a renewable resource with many possible applications in bioengineering. Biosensors, capable of label-free and in-line evaluation, play an important role in the investigation of chitin synthesis, degradation and interaction with other materials. This work presents a comparative study of the usefulness of a chitin surface preparation, either on gold (Au) or on polystyrene (PS). In both cases the most common method to dissolve chitin was used, followed by a simple spin-coating procedure. Multi-parametric surface plasmon resonance (MP-SPR), modeling of the optical properties of the chitin layers, scanning electron microscopy, and contact angle goniometry were used to confirm: the thickness of the layers in air and buffer, the refractive indices of the chitin layers in air and buffer, the hydrophobicity, the binding properties of the chitin binding domain (CBD) of Bacillus circulans, and the split-intein capture process. Binding of the CBD differed between chitin on Au versus chitin on PS in terms of binding strength and binding specificity due to a less homogenous structured chitin-surface on Au in comparison to chitin on PS, despite a similar thickness of both chitin layers in air and after running buffer over the surfaces. The use of the simple method to reproduce chitin films on a thin polystyrene layer to study chitin as a biosensor and for chitin binding studies was obvious from the SPR studies and the binding studies of CBD as moiety of chitinases or as protein fusion partner. In conclusion, stable chitin layers for SPR studies can be made from chitin in a solution of dimethylacetamide (DMA) and lithium chloride (LiCl) followed by spin-coating if the gold surface is protected with PS.Peer reviewe

Kinetics of PKC epsilon Activating and Inhibiting Llama Single Chain Antibodies and Their Effect on PKC epsilon Translocation in HeLa Cells

Peer reviewe

Challenges in land use and transport planning integration in Helsinki metropolitan region—a historical-institutional perspective

Funding Information: The unevenness of resources in metropolitan transport and land use planning also follows from the above differences in their institutionalization. The transport system planning by the HSL is funded by its member municipalities and the state for its institutionally designated duties, while there are no extra funds reserved for metropolitan land use planning. While the HSYK is a light cooperative organ, there is no actual land use planning agency at the metropolitan level. Instead, the municipal land use planners assign the time that is left to metropolitan level land use planning concerns after having to handle their municipal planning duties, institutionally assigned to them. What follows is that the actions of the municipal land use planners are much more closely observed by the municipal decision makers, and the conflict between the metropolitan and municipal land use interests is evident in their everyday planning work. While a metropolitan body to take charge of land use planning at that level has been missing, a logical consequence was that HSL, with its organizational prowess and resources, assumed the coordinating role in the MAL 2019 planning process. This unavoidably also led to an integrated land use and transport planning context where the transport planning approach is more influential and decisive in the MAL 2019 planning process. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Land use and transport integration has been considered a must-have approach in achieving sustainable urban development. However, successful applications of the concept have been few, as institutional reforms to support land use and transport integration have lagged behind. Accordingly, this article argues that understanding difficulties in land use and transport integration requires an analysis of the long-term evolution of formal and informal institutional frameworks in planning practices. For this purpose, this article presents a case study of land use and transport planning in Finland’s Helsinki Metropolitan Region, which combines interview research on planners’ perceptions with a document analysis of the historical trajectories of the region’s plans, policy documents and related institutional and organizational changes. The historical-institutional approach of the article draws on discursive institutionalism as a novel analytical approach for studying how land use and transport integration is institutionally conditioned.Peer reviewe

Supplement 1: Surface plasmon resonance for characterization of large-area atomic-layer graphene film

Supplemental-document Originally published in Optica on 20 February 2016 (optica-3-2-151

Effects of charge ratios of xylan-poly(allylamine hydrochloride) complexes on their adsorption onto different surfaces

The adsorption behavior of polyelectrolyte complexes (PECs) of poly(allylamine hydrochloride) (PAH) and 4-O-methylglucuronoxylan (Xyl) onto silica surface, cellulose nanofibrils (CNFs) model surfaces, and unbleached softwood kraft fibers was studied. Different charge ratios and ionic strengths of the liquid medium (q−/q+: 0.3, 0.5 and 0.8 in 1 mM NaCl, and q−/q+: 0.2, 0.3 and 0.5 in 10 mM NaCl), at pH 7.5 were considered. First, the complexes obtained were characterized by measuring the charge density, the particle size and the zeta potential. Then, the adsorption of PAH alone and PECs on silica and CNF model surfaces were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). The QCM-D test indicated that: (a) adsorbed cationic layers of PECs were soft in 10 mM NaCl, (b) higher adsorption was observed at higher ionic strength and (c) the highest adsorption of complex and coupled water was found at a charge ratio of 0.3. The SPR results analyzed together with the corresponding QCM-D results revealed that a significant portion of the adsorbed layers corresponded to coupled water on the cationic PEC structures. Morphology and structures of the adsorbed PEC layers studied using atomic force microscopy showed that the majority of the PECs were spherical, while some bigger aggregates were also found. Finally, the retention of different PECs on an unbleached softwood pulp was determined and the maximum retention was obtained when the PEC charge ratio was 0.5 in a 10 mM NaCl solution.Fil: Galván, María Verónica. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Peresin, María Soledad. No especifíca;Fil: Mocchiutti, Paulina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Granqvist, Niko. No especifíca;Fil: Zanuttini, Miguel Angel Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; ArgentinaFil: Tammelin, Tekla. No especifíca

Effects of charge ratios of xylan-poly(allylamine hydrochloride) complexes on their adsorption onto different surfaces

The adsorption behavior of polyelectrolyte complexes (PECs) of poly(allylamine hydrochloride) (PAH) and 4-O-methylglucuronoxylan (Xyl) onto silica surface, cellulose nanofibrils (CNFs) model surfaces, and unbleached softwood kraft fibers was studied. Different charge ratios and ionic strengths of the liquid medium (q - /q +: 0.3, 0.5 and 0.8 in 1 mM NaCl, and q - /q +: 0.2, 0.3 and 0.5 in 10 mM NaCl), at pH 7.5 were considered. First, the complexes obtained were characterized by measuring the charge density, the particle size and the zeta potential. Then, the adsorption of PAH alone and PECs on silica and CNF model surfaces were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). The QCM-D test indicated that: (a) adsorbed cationic layers of PECs were soft in 10 mM NaCl, (b) higher adsorption was observed at higher ionic strength and (c) the highest adsorption of complex and coupled water was found at a charge ratio of 0.3. The SPR results analyzed together with the corresponding QCM-D results revealed that a significant portion of the adsorbed layers corresponded to coupled water on the cationic PEC structures. Morphology and structures of the adsorbed PEC layers studied using atomic force microscopy showed that the majority of the PECs were spherical, while some bigger aggregates were also found. Finally, the retention of different PECs on an unbleached softwood pulp was determined and the maximum retention was obtained when the PEC charge ratio was 0.5 in a 10 mM NaCl solution

Kretschmann configuration and key parameters obtained from the full SPR angular spectra.

<p>A) A simplified chart of the Kretschmann configuration enabling plasmon excitations and SPR measurements. The intensity of the reflected light from a monochromatic light source is measured as a function of incident light angle (θ). The light passes from a high refractive index medium (glass, ε₀) to a low refractive index medium (air or liquid, ε₁+ε_bulk). In between, the light is reflected from an interface containing a metal with a high density of free electrons and an optimal thickness for plasmon excitation (gold 50 nm, ε₂) to a photodetector. The surface plasmons on the metal surface are excited at a certain incident light angle (θ) and the evanescent field created by the plasmon extends to the adjacent low refractive index medium (ε₁) where samples are introduced to the system. B) A schematic full SPR angular spectrum showing the positions of the TIR region, the main SPR peak angular position and the main SPR peak minimum intensity.</p

Simulated full SPR spectra for optical changes within different regions of a cell monolayer.

<p>A) Schematic representation of the sample layer used in simulating full SPR angular spectra of cell monolayers. The cell monolayer was theoretically split into three sections in order to clarify the effect of changing different optical properties in it: 1) a thin section in the magnitude of evanescent field close to the sensor surface (<i>ñ_ef</i>, <i>d_ef</i>  = 500 nm), 2) a thick section consisting of the rest of the cell (<i>ñ_cell</i>, <i>d_cell</i>  = 3000 nm), and 3) an infinite bulk medium layer (<i>ñ_bulk</i>, <i>d_bulk</i>  =  ∞). Simulated full SPR angular spectra when changing; B) the real (<i>n_ef</i>) and C) the imaginary (<i>k_ef</i>) parts of the refractive index for a cell monolayer within the evanescent field, D) the real part of the refractive index (<i>n_cell</i>) for a cell monolayer not within the evanescent field and E) the imaginary part of the refractive index (<i>k_cell</i>) for a cell monolayer not within the evanescent field. Insets in B-E are more detailed views of the TIR regions. The following parameters were used for simulations: B) <i>d_cell</i>  = 3000 nm, <i>k_cell</i>  = 0.002, <i>n_cell</i> varied from 1.340–1.345, <i>d_ef</i>  = 500 nm, <i>n_ef</i>  = 1.34 and <i>k_ef</i>  = 0.002, C) <i>d_cell</i>  = 3000 nm with <i>n_cell</i>  = 1.340, <i>k_cell</i> varied from 0–0.005, <i>d_ef</i>  = 500 nm, <i>n_ef</i>  = 1.34 and <i>k_ef</i>  = 0.002, D) <i>d_cell</i>  = 3000 nm, <i>k_cell</i>  = 0.002, <i>n_cell</i>  = 1.34, <i>d_ef</i>  = 500 nm, <i>k_ef</i>  = 0.002 and <i>n_ef</i> varied from 1.340–1.345, and E) <i>d_cell</i>  = 3000 nm, <i>k_cell</i>  = 0.002, <i>n_cell</i>  = 1.34, <i>d_ef</i>  = 500 nm, <i>n_ef</i>  = 1.34 and <i>k_ef</i> varied from 0–0.005.</p