| 1. |
- Anderson, Henrik, et al.
(författare)
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Systematic investigation of biomolecular interactions using combined frequency and motional resistance measurements
- 2011
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 153:1, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- The resonance frequency of acoustic biosensors is today used as a label-free technique for detecting mass changes on sensor surfaces. In combination with an appropriate continuous flow system it has earlier been used for affinity and kinetic rate determination. Here, we assess the potential of a modified acoustic biosensor, monitoring also the real-time dissipation through the resistance of the sensor, to obtain additional kinetic information related to the structure and conformation of the molecules on the surface. Actual interaction studies, including an attempt to determine avidity, are presented along with thorough verification of the experimental setup utilizing true viscous load exposure together with protein and DNA immobilizations. True viscous loads show a linear relationship between resistance and frequency as expected. However, in the interaction studies between antibodies and proteins, as well as in the immobilization of DNA and proteins, higher surface concentrations of interacting molecules led to a decrease (i.e. deviation from the linear trend) in the differential resistance to frequency ratio. This is interpreted as increased surface rigidity at higher surface concentrations of immobilized molecules. Consequently, studies that aim at obtaining biological binding information, such as avidity, from real-time resistance and dissipation data should be conducted at low surface concentrations. In addition, the differential resistance to frequency relationship was found to be highly dependent on the rigidity of the preceding layer(s) of immobilized molecules. This dependence can be utilized to obtain a higher signal-to-noise ratio for resistance measurement by using low surface densities of immobilized interaction partners.
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| 2. |
- Bertling, Sofia, et al.
(författare)
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Long-term corrosion-induced copper runoff from natural and artificial patina and its environmental impact
- 2006
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Ingår i: Environmental Toxicology and Chemistry. - 0730-7268 .- 1552-8618. ; 25:3, s. 891-898
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Tidskriftsartikel (refereegranskat)abstract
- The overall objective of this paper is to present an extensive set of data for corrosion-induced copper dispersion and its environmental interaction with solid surfaces in the near vicinity of buildings. Copper dispersion is discussed in terms of total copper flows, copper speciation and bioavailability at the immediate release situation, and its changes during transport from source to recipient. Presented results are based on extensive field exposures (eight years) at an urban site, laboratory investigations of the runoff process, published field data, generated predictive site-specific runoff rate models, and reactivity investigations toward various natural and manmade surfaces, such as those in soil, limestone, and concrete. Emphasis is placed on the interaction of copper-containing runoff water with different soil systems through long-term laboratory column investigations. The fate of copper is discussed in terms of copper retention, copper chemical speciation, breakthrough capacities, and future mobilization based on changes in copper concentrations in the percolate water, computer modeling using the Windermere Humic Aqueous Model, and sequential extractions. The results illustrate that, for scenarios where copper comes in extensive contact with solid surfaces, such as soil and limestone, a large fraction of released copper is retained already in the immediate vicinity of the building. In all, both the total copper concentration in runoff water and its bioavailable part undergo a significant and rapid reduction.
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| 3. |
- Durall, Claudia, et al.
(författare)
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Robust QCM-Based Sensing and Assay Formats in Commercialized Systems
- 2023
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Ingår i: Springer Series on Chemical Sensors and Biosensors. - : Springer.
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Bokkapitel (refereegranskat)abstract
- Attana’s Quartz Crystal Microbalance (QCM) analytical instruments have been developed to study in vitro biological interactions, mimicking the in vivo conditions. Attana’s superior technology for kinetic interaction studies allows to perform different assays, including biochemical, crude, sera, cell, and tissue-based, in vitro diagnostic and material chemistry assays, in real time and label free. With the focus to validate, select, and optimize drug candidates prior to clinical trials, Attana has helped pharmaceutical companies to increase their efficiency and profitability. In addition, the Attana instruments and services have been used in many other applications and research as described in this chapter.
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| 4. |
- Forssén, Patrik, 1966-, et al.
(författare)
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Reliable Strategy for Analysis of Complex Biosensor Data
- 2018
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:8, s. 5366-5374
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Tidskriftsartikel (refereegranskat)abstract
- When using biosensors, analyte biomolecules of several different concentrations are percolated over a chip with immobilized ligand molecules that form complexes with analytes. However, in many cases of biological interest, e.g., in antibody interactions, complex formation steady-state is not reached. The data measured are so-called sensorgram, one for each analyte concentration, with total complex concentration vs time. Here we present a new four-step strategy for more reliable processing of this complex kinetic binding data and compare it with the standard global fitting procedure. In our strategy, we first calculate a dissociation graph to reveal if there are any heterogeneous interactions. Thereafter, a new numerical algorithm, AIDA, is used to get the number of different complex formation reactions for each analyte concentration level. This information is then used to estimate the corresponding complex formation rate constants by fitting to the measured sensorgram one by one. Finally, all estimated rate constants are plotted and clustered, where each cluster represents a complex formation. Synthetic and experimental data obtained from three different QCM biosensor experimental systems having fast (close to steady-state), moderate, and slow kinetics (far from steady-state) were evaluated using the four-step strategy and standard global fitting. The new strategy allowed us to more reliably estimate the number of different complex formations, especially for cases of complex and slow dissociation kinetics. Moreover, the new strategy proved to be more robust as it enables one to handle system drift, i.e., data from biosensor chips that deteriorate over time.
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| 5. |
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| 6. |
- Hjalmarsson, Nicklas, et al.
(författare)
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Electro-Responsive Surface Composition and Kinetics of an Ionic Liquid in a Polar Oil
- 2019
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:48, s. 15692-15700
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Tidskriftsartikel (refereegranskat)abstract
- The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence. The measured mass changes cannot be explained only in terms of simple ion exchange; the relative molecular volumes of the ions and the density changes in response to ion exclusion must be considered. The relaxation behavior of the potential between the electrodes upon disconnecting the applied potential is more complex than that observed for pure ionic liquids, but a measure of the surface charge can be extracted from the exponential decay when the rapid initial potential drop is accounted for. The adsorbed film at the gold surface consists predominantly of ionic liquid despite the low concentration, which is unsurprising given the surtactant-like structures of (some of) the ionic liquid ions. Changes in response to potential correspond to changes in the relative numbers of cations and anions, rather than a change in the oil composition. No evidence for an electric field induced change in viscosity is observed. This work shows conclusively that electric potentials can be used to control the surface composition, even in an oil-based system, and paves the way for other ion solvent studies.
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| 7. |
- Hjalmarsson, Nicklas, et al.
(författare)
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Weighing the surface charge of an ionic liquid
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:38, s. 16039-16045
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical quartz crystal microbalance has been used to measure changes in the composition of the capacitive electrical double layer for 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate, an ionic liquid, in contact with a gold electrode surface as a function of potential. The mass difference between the cation and anion means that the technique can effectively "weigh" the surface charge accurately with high temporal resolution. This reveals quantitatively how changing the potential alters the ratio of cations and anions associated with the electrode surface, and thus the charge per unit area, as well as the kinetics associated with these interfacial processes. The measurements reveal that it is diffusion of co-ions into the interfacial region rather than expulsion of counterions that controls the relaxation. The measured potential dependent double layer capacitance experimentally validates recent theoretical predictions for counterion overscreening (low potentials) and crowding (high potentials) at electrode surfaces. This new capacity to quantitatively measure ion composition is critical for ionic liquid applications ranging from batteries, capacitors and electrodeposition through to boundary layer structure in tribology, and more broadly provides new insight into interfacial processes in concentrated electrolyte solutions.
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| 8. |
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| 9. |
- Wei, Zheng, 1988-
(författare)
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Metal release from stainless steel and CoCrMo alloys in protein-rich environments – effects of protein aggregation, friction, and irradiation
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Highly corrosion-resistant alloys are used in sensitive environments such as the human body and food environments. However, even tiny amounts of released metals from these surfaces could potentially cause adverse effects. It is hence important to study the biointerface between corrosion-resistant alloys and protein-rich environments. This licentiate thesis focused on the metal release processes for stainless steels and cobalt-chromium-molybdenum (CoCrMo) alloys in different protein-rich environments. It aimed at investigating the effect of protein displacement (Vroman effect), gamma irradiation, and friction on the metal release processes. Trace metal analysis was the main tool, combined with other solution analytical tools, electrochemical methods, and surface sensitive techniques.The effect of gamma irradiation, of relevance for cancer radiotherapy, on metal release from CoCrMo and stainless steel 316L was investigated in Paper I. The effect was minor, however the released amount of metals increased after irradiation causing an enhanced surface passivation effect. Whether the displacement of surface proteins (Vroman effect) was playing a role on the metal release and corrosion processes of stainless steels 316L and 303, and of CoCrMo, was investigated in Papers II and III. A Vroman effect influencing the metal release could be observed for stainless steel 316L, but not for CoCrMo and stainless steel grade 303. However, the displacement of the smaller protein bovine serum albumin (BSA) from the surface by the larger protein fibrinogen (Fbn) was observed for both stainless steel grades. The Vroman effect also caused a higher corrosion susceptibility of stainless steel 303, probably due to a thicker layer or patches of adsorbed Fbn. Most probably, protein aggregation and precipitation caused an underestimation of the extent of metal release, especially in the case of CoCrMo. Protein aggregation and precipitation were significantly observed in all studies, especially for solutions with high protein concentrations (Papers II-IV). The effect of friction, by using different setups (stirring with physical contact and sliding in a pin-on-disk machine), on metal release from stainless steel 316L and CoCrMo was investigated in Papers II and IV. Friction induced an increased extent of metal release, increased protein aggregation and precipitation, and enhanced metal precipitation. A combined friction and complexation effect was observed for stainless steel 316L, resulting in an etching effect and relatively high amounts of released metals. Due to enhanced precipitation effects and the experimental setup, it is recommended to strongly consider protein aggregation and metal precipitation events in systems where this could be expected and where friction is present. Otherwise, there is a risk to strongly underestimate the extent of metal release in these protein-rich environments.
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