Matthias Franzreb | Karlsruhe Institute of Technology (KIT) (original) (raw)

Papers by Matthias Franzreb

Biotechnology and Bioengineering, 2019

A 3D printed ultrafiltration/diafiltration (UF/DF) module is presented allowing the continuous, s... more A 3D printed ultrafiltration/diafiltration (UF/DF) module is presented allowing the continuous, simultaneous concentration of retained (bio-)molecules and reduction or exchange of the salt buffer. Differing from the single-pass UF concepts known from the literature, DF operation does not require the application of several steps or units with intermediating dilution. In contrast, the developed module uses two membranes confining the section in which the molecules are concentrated while the sample is passing. Simultaneously to this concentration process, the two membranes allow a perpendicular in and outflow of DF buffer reducing the salt content in this section. The module showed the continuous concentration of a dissolved protein up to a factor of 4.6 while reducing the salt concentration down to 47% of the initial concentration along a flow path length of only 5 cm. Due to single-pass operation the module shows concentration polarization effects reducing the effective permeability of the applied membrane in case of higher concentration factors. However, because of its simple design and the capability to simultaneously run UF and DF processes in a single module, the development could be economically beneficial for small scale UF/DF applications.

Electroanalysis, 2021

We demonstrate a novel impedimetric approach providing unprecedented insight into characteristic ... more We demonstrate a novel impedimetric approach providing unprecedented insight into characteristic properties of dielectric thin films covering electrode surfaces. The concept is based on the joint interpretation of electrochemical impedance spectroscopy (EIS) together with dielectrometry (DEM) whose informative value is mutually interconnected. The advantage lies in the synergistic compensation of individual shortcomings adversely affecting conventional impedimetric analysis strategies relying exclusively on either DEM or the traditional EIS approach, which in turn allows a reliable determination of thickness and permittivity values. The versatility of the method proposed is showcased by an in-situ growth-monitoring of a nanoporous, crystalline thin film (HKUST-1) on an interdigitated electrode geometry.

Chemie Ingenieur Technik, 2018

Dem Wunsch nach umfassenden Einsichten in zelluläre Prozesse kommen multiparametrische Analytikve... more Dem Wunsch nach umfassenden Einsichten in zelluläre Prozesse kommen multiparametrische Analytikverfahren immer besser nach. Sie liefern den Life Sciences immer sensitivere Messtechniken, mit denen zelluläre und subzelluläre Abläufe online und in Echtzeit erfasst werden. Eine zentrale Rolle spielen dabei Mikrosysteme wie Mikrofluidik-Chips und Multiwell-Mikroelektroden-Chips. Deren Anwendungsbereiche reichen von der Wirkstoffentwicklung über chemische Synthese bis zur Toxikologie. So vielfältig die Einsatzbereiche sind, so zahlreich sind die Anforderungen an solche Chips. Man muss sie in großer Stückzahl und hoher Qualität fertigen können, aber auch kostengünstig. Sie müssen robust, oft auch transparent sein, und immer in Echtzeit hohe Datenqualität liefern. Dieser Vortrag stellt den ,,Werkzeugkasten'' zur Entwicklung modernster Biochips vor. Er enthält diverse Designformate, verschiedene Substrate, optisch transparente und (halb)leitende Elektrodenmaterialien. Beispiele aus den Berei-chen Enzymregeneration [1] und Bioanalytik/Toxikologie [2] erläutern den Weg vom Anforderungsprofil zum fertigen Biochip.

Acta Hydrochimica et Hydrobiologica, 1996

ABSTRACT

New Biotechnology, 2016

SC are atypical protein ligands because they bind outside of the protein's active site (related w... more SC are atypical protein ligands because they bind outside of the protein's active site (related with conformational changes resulting from function-related destabilization of the protein) 3) in vivo interactions between SC and Ag-Ab complexes (local inflammatory conditions), followed by their progressive elimination from the organism. Research methodology include spectrophotometry, microscopic and dynamic light scattering technique and molecular modelling of interactions between carbon nanotubes, SC and drugs. Results show the ability of SC to disperse hydrophobic CNT in aqueous solution and form capacious drug carriers. Results show pH-dependent release of drugs and accumulate on the cell surface.

Soft Matter, 2015

High magnetization of spherically shaped superparamagnetic functionalized microgels with 99.9% se... more High magnetization of spherically shaped superparamagnetic functionalized microgels with 99.9% separation efficiency synthesized by a ferrofluid-based miniemulsion procedure.

Water Research, 2013

An innovative nanocomposite material is proposed for phosphate recovery from wastewater using mag... more An innovative nanocomposite material is proposed for phosphate recovery from wastewater using magnetic assistance. Superparamagnetic microparticles modified with layered double hydroxide (LDH) ion exchangers of various compositions act as phosphate adsorbers. Magnetic separation and chemical regeneration of the particles allows their reuse, leading to the successful recovery of phosphate. Based upon the preliminary screening of different LDH ion exchanger modifications for phosphate selectivity and uptake capacity, MgFe-Zr LDH coated magnetic particles were chosen for further characterization and application. The adsorption kinetics of phosphate from municipal wastewater was studied in dependence with particle concentration, contact time and pH. Adsorption isotherms were then determined for the selected particle system. Recovery of phosphate and regeneration of the particles was examined via testing a variety of desorption solutions. Reusability of the particles was demonstrated for 15 adsorption/desorption cycles. Adsorption in the range of 75-97% was achieved in each cycle after 1 h contact time. Phosphate recovery and enrichment was possible through repetitive application of the desorption solution. Finally, a pilot scale experiment was carried out by treating 125 L of wastewater with the particles in five subsequent 25 L batches. Solid-liquid separation on this scale was carried out with a high-gradient magnetic filter (HGMF).

Microelectronic Engineering, 2012

ABSTRACT This paper presents the development of nanoactuators of free-standing Ti beam cantilever... more ABSTRACT This paper presents the development of nanoactuators of free-standing Ti beam cantilevers with integrated superparamagnetic (SPM) beads at their front end that allow a controlled deflection by an external magnetic field gradient. A process flow is investigated based on three-step electron-beam lithography, reactive ion etching and the deposition of functionalized magnetic beads. While the thickness of the beams is 50nm, the lateral dimensions are designed to be 400nm, in order to carry beads of 360nm size. Magnetization measurements confirm the superparamagnetic behaviour of the beads having a saturation magnetization of 63kA/m. The position accuracy of multi-step electron beam lithography is about 10nm, allowing an exact deposition of functionalized beads.

Industrial & Engineering Chemistry Research, 2009

The study focuses on the characterization of platinum-doped titanium dioxide-coated magnetic poly... more The study focuses on the characterization of platinum-doped titanium dioxide-coated magnetic poly(methyl methacrylate) (Pt-TiO 2 /mPMMA) microspheres as a novel photocatalyst. The Pt-TiO 2 /mPMMA microspheres were prepared by a modified suspension polymerization process, followed by titania-coating and Pt-doping. The Pt-TiO 2 /mPMMA microspheres were synthesized with various Pt-doping levels in the range of 0.6-1.5 wt % TiO 2 for comparison. The morphology, composition, Pt-doping content, and magnetic properties of the Pt-TiO 2 /mPMMA microspheres were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum interference device. As a result, the superparamagnetic Pt-TiO 2 /mPMMA microspheres were successfully synthesized with particle sizes of 5-11 µm. The magnetite and TiO 2 contents of the Pt-TiO 2 /mPMMA microspheres were estimated as 7.69 and 16.7 wt %, respectively, while the corresponding saturation magnetization was measured as about 4.39 emu/g. Furthermore, the doped Pt nanoparticles in the metallic state were found to have a particle density of (27.5-33.5) × 10 8 cm-2 on the surface of the Pt-TiO 2 /mPMMA microspheres. This density was found to increase with the synthesized Pt-doping concentration. The photocatalytic activity of the Pt-TiO 2 /mPMMA microspheres was further examined using the photodegradation of dimethyl phthalate in an aqueous solution. Dimethyl phthalate as one of the most common phthalic acid esters has been frequently detected in wastewater effluents and river water. Furthermore, the concentration of total organic carbons was monitored as an index of mineralization. A distinct photocatalytic efficiency improvement was shown with the employment of the Pt-TiO 2 /mPMMA microspheres as compared to the TiO 2 /mPMMA microspheres or direct photolysis.

Engineering in Life Sciences, 2011

... kit.edu), Institute of Mechanical Process Engineering and Mechanics, Karlsruhe Institute of T... more ... kit.edu), Institute of Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), Germany. ... working separation device a filter cake easily could be processed on a drum or a ... A., del Bosque, A. et al., Hen egg white fractionation by ion-exchange chro ...

Chemie Ingenieur Technik, 2007

Biotechnology Letters, 2004

The kinetic, selective and stereoselective properties of enzyme immobilised on magnetic polymer b... more The kinetic, selective and stereoselective properties of enzyme immobilised on magnetic polymer beads with diameters in the range 1 µm was studied with penicillin amidase from E. coli. The enzyme was immobilised on epoxy and glutaraldehyde-activated poly(vinyl alcohol), poly(methylmetacrylate) and poly(vinyl acetate-divinylbenzene) magnetic beads. The amount of covalently bound active protein was dependent on the chemical modification of the matrix and increased at higher ionic strength of the immobilisation buffer. The small size of the magnetic beads, that reduces mass transfer limitations, and the decreased charge density in the electric double layer resulted in lower apparent K m values and higher efficiency for benzylpenicillin hydrolysis, higher stereoselectivity in condensation of R-phenylglycine amide with Sand R-Phe and in hydrolysis of racemic phenylacetyl-Phe and higher selectivity in kinetically controlled synthesis of cephalexin compared to the enzyme immobilised on larger and porous carriers.

Biotechnology and Bioengineering, 2013

Cerium (IV) initiated 'graft-from' polymerization reactions were employed to convert M-PVA magnet... more Cerium (IV) initiated 'graft-from' polymerization reactions were employed to convert M-PVA magnetic particles into polyacrylic acid-fimbriated magnetic cation exchange supports displaying ultra-high binding capacity for basic target proteins. The modifications, which were performed at 25 mg and 2.5 g scales, delivered maximum binding capacities (Q max) for hen egg white lysozyme in excess of 320 mg g-1 , combined with sub-micromolar dissociation constants (0.45-0.69 m) and 'tightness of binding' values greater than 49 L g-1. Two batches of polyacrylic acid-fimbriated magnetic cation exchangers were combined to form a 5 g pooled batch exhibiting Q max values for lysozyme, lactoferrin, and lactoperoxidase of 404, 585 and 685 mg g-1 respectively. These magnetic cation exchangers were subsequently employed together with a newly designed 'rotor-stator' type HGMF rig, in five sequential cycles of recovery of lactoferrin and lactoperoxidase from 2 L batches of a crude sweet bovine whey feedstock. Lactoferrin purification performance was observed to remain relatively constant from one HGMF cycle to the next over the 5 operating cycles, with yields between 40% and 49% combined with purification and concentration factors of 37-46 fold and 1.3-1.6 fold respectively. The far superior multi-cycle HGMF performance seen here compared to that observed in our earlier studies can be directly attributed to the combined use of improved high capacity adsorbents and superior particle resuspension afforded by the new 'rotor-stator' HGMS design.

Applied Biochemistry and Biotechnology, 2010

The presented work introduces a novel method to immobilize enzymes either purified or directly ou... more The presented work introduces a novel method to immobilize enzymes either purified or directly out of a crude extract onto magnetic particles in the micrometer range. This method is based on the creation of a fusion protein consisting of the enzyme of choice and a mutant dehalogenase. The dehalogenase gene is commercially available from the company Promega under the name HaloTag TM. When the fusion protein is contacted with magnetic beads having chemically synthesized, chloroalkane ligands on their surface, the dehalogenase and the ligand undergo a covalent coupling leading to stable and spatially defined immobilization. The principle was proved with a lipase fused to the HaloTag TM gene and magnetic poly(methyl)methacrylate beads as carriers. The solubility of the tagged lipase was strongly increased by fusion of the malE gene at the N-terminal end of the HaloTag TM lipase gene. This tripartite protein was purified on amylose resin and used for immobilization. About 13 µg protein could be immobilized per 1 mg of beads within a few minutes. Due to the defined binding site, no activity loss was observed in the course of the immobilization. The resulting enzyme carrier was tested with the same beads up to six times for lipase activity over a storage period of 36 days at 8°C. No loss of activity was found during this time.