Tobias Halthur - Academia.edu (original) (raw)

Papers by Tobias Halthur

Colloids and surfaces. A, Physicochemical and engineering aspects, May 1, 2024

Journal of Colloid and Interface Science, Oct 1, 2010

Delmopinol is a tertiary amine surfactant that is used to counteract dental plaque formation. As ... more Delmopinol is a tertiary amine surfactant that is used to counteract dental plaque formation. As it is of interest to understand the interfacial behavior from both fundamental and applied perspectives the adsorption of delmopinol to model surfaces was investigated. Adsorption on Teflon, titanium and stainless steel was studied by radioactive labeling and adsorption on silica was studied by quartz crystal microbalance (QCM), ellipsometry and particle electrophoresis. It was shown that the adsorption of delmopinol was complex and strongly influenced by pH and concentration. Pronounced peak values were detected in the adsorption curves (adsorbed amount versus concentration) exceeding the expected value for a bilayer type of structure. To account for this behavior two surface active component were assumed to be present. Accordingly, the high amounts result from the deposition of the component with lower solubility and the decrease at the critical micelle concentration can be explained by solubilization of this component. Based on data from several experimental methods and the pH dependence of the effect we propose an explanation in which the protonated and non-protonated forms of delmopinol represent the two components. However, it cannot be excluded that the component with the lower solubility could be a compound chemically different from delmopinol in the sample.

Journal of environmental chemical engineering, Jun 1, 2016

Monolithic composites of Polyphepan 1 or Kraft lignin embedded in a poly(vinyl alcohol) (PVA) mat... more Monolithic composites of Polyphepan 1 or Kraft lignin embedded in a poly(vinyl alcohol) (PVA) matrix were synthesized using cryogelation technique and studied as flow permeable adsorbents for bisphenol A and erythromycin removal from water. Adsorption isotherms of bisphenol A on pristine Polyphepan provided the equilibrium dissociation constant K L = 2.6 Â 10 À6 M and the maximal binding capacity Q max = 20 mmol/g; for erythromycin K L was in the 9.6 Â 10 À6 M to 5.8 Â 10 À5 M range, and Q max was between 55 mmol/g and 94 mmol/g. Embedment of lignins into PVA cryogels resulted in monoliths with adequate flow permeability and the composites essentially retained the binding capacity for both bisphenol A and erythromycin. Percolation of contaminated water through the monoliths resulted in 10fold reduction of the pollutant concentrations within 12-70 column volumes of the effluent. Due to the higher loading of lignin, the Kraft lignin-PVA composite showed higher adsorption capacity for erythromycin than Polyphepan-PVA. Stability and reversible compression of the monoliths in the flow of water were studied. Limitations are associated with leakage of soluble lignin, strongly expressed in the case of Kraft lignin-containing composites.

Biofouling, Jul 17, 2010

The adsorption of proteins from human whole saliva (HWS) onto silica and hydroxyapatite surfaces ... more The adsorption of proteins from human whole saliva (HWS) onto silica and hydroxyapatite surfaces (HA) was followed by quartz crystal microbalance with dissipation (QCM-D) and ellipsometry. The influence of different surface properties and adsorption media (water and PBS) on the adsorption from saliva was studied. The viscoelastic properties of the salivary films formed on the solid surfaces were estimated by the use of the Voigt-based viscoelastic film model. Furthermore, the efficiency of SDS and delmopinol to elute the adsorbed salivary film from the surfaces was investigated at different surfactant concentrations. A biphasic kinetic regime for the adsorption from saliva on the silica and HA surfaces was observed, indicating the formation of a rigidly coupled first layer corresponding to an initial adsorption of small proteins and a more loosely bound second layer. The results further showed a higher adsorption from HWS onto the HA surfaces compared to the silica surfaces in both adsorption media (PBS and water). The adsorption in PBS led to higher adsorbed amounts on both surfaces as compared to water. SDS was found to be more efficient in removing the salivary film from both surfaces than delmopinol. The salivary film was found to be less tightly bound onto the silica surfaces since more of the salivary film could be removed with both SDS and delmopinol compared to that from the HA surface. When adsorption took place from PBS the salivary layer formed at both surfaces seemed to have a similar structure, with a high energy dissipation implying that a softer salivary layer is built up in PBS as opposed to that in water. Furthermore, the salivary layers adsorbed from water solutions onto the HA were found to be softer than those on silica.

Langmuir, Jan 21, 2004

The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and tit... more The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces, with and without an initial layer of polyethyleneimine (PEI), was investigated and characterized by means of in situ ellipsometry and quartz crystal microbalance with dissipation. A two-regime buildup was found in all systems, where the length of the first slow-growing regime is dependent on the structure of the initial layers. In the second fast-growing regime, the film thickness grows linearly while the mass increases more than linearly (close to exponentially) with the number of deposited layers. The film refractive indices as well as the water contents indicate that the film density changes as the multilayer film builds up. The change in film density was proposed to be due to polypeptides diffusing into the multilayer film as they attach. Furthermore, the use of PEI as the initial layer was found to induce a difference in the thickness increments for PGA and PLL.

Langmuir, Nov 8, 2006

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on ... more The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.

Biomacromolecules, Mar 3, 2005

We have used a novel polyelectrolyte multilayer (PEM) coating consisting of the polyelectrolytes ... more We have used a novel polyelectrolyte multilayer (PEM) coating consisting of the polyelectrolytes collagen and hyaluronic acid. The build-up by the layer-by-layer deposition technique is outlined by ex situ and in situ ellipsometric measurements. When collagen was added, the thickness of the PEM was increased, and the refractive index was decreased. Corresponding but opposite effects were noted when hyaluronic acid was added. These changes are considered to be explained by a diffusion mechanism. It was also found that the PEM layers were unstable at physiological pH. However, by cross-linking using N-(3-di-methylaminopropyl)-N&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-ethylcarbodiimide together with N-hydroxysuccinimide, a stable PEM layer resulted. These tissue friendly PEM layers are expected to have a great impact in the design of artificial extracellular matrixes. Also, the insertion of fluorescence labels demonstrates the potential for incorporation of other functionalities.

Pharmaceutics, Apr 5, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surfa... more The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surface properties, and can thus be altered by the introduction of a surface coating. In this thesis the buildup of a biomacromolecule-based coating formed by layerby-layer (LbL) deposition of the charged polypeptides poly(-lysine) (PLL) and poly(glutamic acid) (PGA) has been studied. In an attempt to make these coatings bioactive and useful for bone-anchored implants, an amelogenin protein mixture (EMD), has been immobilized in these thin polyelectrolyte multilayer (PEM) films. Multilayers were also built by LbL deposition of the natural biomacromolecules collagen (Col) and hyaluronic acid (HA). Multilayer films of these two extra-cellular biomacromolecules should be of interest for use as a scaffold for tissue engineering. The buildup of the multilayer films has been followed in situ, using ellipsometry, quartz crystal microbalance with dissipation (QCM-D), and dual polarization interfero...

Journal of Environmental Chemical Engineering, 2016

Abstract Monolithic composites of Polyphepan ® or Kraft lignin embedded in a poly(vinyl alcohol) ... more Abstract Monolithic composites of Polyphepan ® or Kraft lignin embedded in a poly(vinyl alcohol) (PVA) matrix were synthesized using cryogelation technique and studied as flow permeable adsorbents for bisphenol A and erythromycin removal from water. Adsorption isotherms of bisphenol A on pristine Polyphepan provided the equilibrium dissociation constant K L = 2.6 × 10 −6 M and the maximal binding capacity Q max = 20 μmol/g; for erythromycin K L was in the 9.6 × 10 −6 M to 5.8 × 10 −5 M range, and Q max was between 55 μmol/g and 94 μmol/g. Embedment of lignins into PVA cryogels resulted in monoliths with adequate flow permeability and the composites essentially retained the binding capacity for both bisphenol A and erythromycin. Percolation of contaminated water through the monoliths resulted in 10-fold reduction of the pollutant concentrations within 12–70 column volumes of the effluent. Due to the higher loading of lignin, the Kraft lignin–PVA composite showed higher adsorption capacity for erythromycin than Polyphepan–PVA. Stability and reversible compression of the monoliths in the flow of water were studied. Limitations are associated with leakage of soluble lignin, strongly expressed in the case of Kraft lignin-containing composites.

Nanoscale, 2016

In this study the wet adhesion between Layer-by-Layer (LbL) assembled films of triblock copolymer... more In this study the wet adhesion between Layer-by-Layer (LbL) assembled films of triblock copolymer micelles was investigated. Through the LbL assembly of triblock copolymer micelles with hydrophobic, low glass transition temperature (T g) middle blocks and ionic outer blocks, a network of energy dissipating polymer chains with electrostatic interactions serving as crosslinks can be built. Four triblock copolymers were synthesized through Atom Transfer Radical Polymerisation (ATRP). One pair had a poly(2-ethyl-hexyl methacrylate) middle block with cationic or anionic outer blocks. The other pair contained the same ionic outer blocks but poly(n-butyl methacrylate) as the middle block. The wet adhesion was evaluated with colloidal probe AFM. To our knowledge, wet adhesion of the magnitude measured in this study has not previously been measured on any polymer system with this technique. We are convinced that this type of block copolymer system grants the ability to control the geometry and adhesive strength in a number of nano-and macroscale applications. † Electronic supplementary information (ESI) available: Additional characterisation of the synthesised materials. See

Pharmaceutics

A novel formulation technology called AKVANO® has been developed with the aim to provide a tuneab... more A novel formulation technology called AKVANO® has been developed with the aim to provide a tuneable and versatile drug delivery system for topical administration. The vehicle is based on a water-free lipid formulation where selected lipids, mainly phospholipids rich in phosphatidylcholine, are dissolved in a volatile solvent, such as ethanol. With the aim of describing the basic properties of the system, the following physicochemical methods were used: viscometry, dynamic light scattering, NMR diffusometry, and atomic force microscopy. AKVANO formulations are non-viscous, with virtually no or very minute aggregates formed, and when applied to the skin, e.g., by spraying, a thin film consisting of lipid bilayer structures is formed. Standardized in vitro microbiological and irritation tests show that AKVANO formulations meet criteria for antibacterial, antifungal, and antiviral activities and, at the same time, are being investigated as a non-irritant to the skin and eye. The ethanol...

Water Resources and Industry

The use of recycled process water in steam crackers leads to the accumulation of corrosive impuri... more The use of recycled process water in steam crackers leads to the accumulation of corrosive impurities, hence the need for adequate treatment. Two corrosion inhibitor formulations containing N-[(9Z)−9-octadecen-1-yl]−1,3-propanediamine (N-oleyl-1,3-propanediamine) with either cyclohexanamine (CHA) or 2-(diethylamino)ethanol (DEAE) were compared for their performance. Electrochemical impedance spectroscopy and visual observations showed that the two formulations offered comparable protection against corrosion. Bengal Rose testing and experiments conducted using a quartz-crystal microbalance with dissipation monitoring (QCM-D) indicated that the two formulations yielded similar coverage of the metal surfaces, and that the kinetics of mass adsorption were also similar. QCM-D data further suggested that the films formed with the two formulations had similar rigidity, and contact angle measurements indicated that they formed films with comparable hydrophobicity, which were equally effective in isolating the metal surfaces from water.

Biofouling, 2010

Langmuir, 2010

Mucin and lactoperoxidase are both natively present in the human saliva. Mucin provides lubricati... more Mucin and lactoperoxidase are both natively present in the human saliva. Mucin provides lubricating and antiadhesive function, while lactoperoxidase has antimicrobial activity. We propose that combined films of the two proteins can be used as a strategy for surface modification in biomedical applications such as implants or biosensors. In order to design and ultilize mixed protein films, it is necessary to understand the variation in adsorption behavior of the proteins onto different surfaces and how it affects their interaction. The quartz crystal microbalance with dissipation (QCM-D) technique has been used to extract information of the adsorption properties of bovine mucin (BSM) and lactoperoxidase (LPO) to gold, silica, and hydrophobized silica surfaces. The information has further been used to retrieve information of the viscoelastic properties of the adsorbed film. The adsorption and compaction of BSM were found to vary depending on the nature of the underlying bare surface, adsorbing as a thick highly hydrated film with loops and tails extending out in the bulk on gold and as a thinner film with much lower adsorbed amount on silica; and on hydrophobic surfaces, BSM adsorbs as a flat and much more compact layer. On gold and silica, the highly hydrated BSM film is cross-linked and compacted by the addition of LPO, whereas the compaction is not as pronounced on the already more compact film formed on hydrophobic surfaces. The adsorption of LPO to bare surfaces also varied depending on the type of surface. The adsorption profile of BSM onto LPO-coated surfaces mimicked the adsorption to the underlying surface, implying little interaction between the LPO and BSM. The interaction between the protein layers was interpreted as a combination of electrostatic and hydrophobic interactions, which was in turn influenced by the interaction of the proteins with the different substrates.

Journal of Colloid and Interface Science, 2010