Analysis and preparation of (bio)nanoobjects in nano-microfluidic devices

Viefhues M. Analysis and preparation of (bio)nanoobjects in nano-microfluidic devices. Bielefeld: Universität Bielefeld; 2012

DNA dielectrophoresis: Theory and applications a review

Viefhues M, Eichhorn R. DNA dielectrophoresis: Theory and applications a review. ELECTROPHORESIS. 2017;38(11: SI):1483-1506

Parallelized continuous flow dielectrophoretic separation of DNA

Derksen J, Viefhues M. Parallelized continuous flow dielectrophoretic separation of DNA. Electrophoresis. 2022.Numerous microfluidic separation applications have been shown in the past years providing a fast analysis of biological samples like DNA or proteins. Microfluidic separation based on dielectrophoresis (DEP), i.e., migration of a polarizable object in an inhomogeneous electric field, provides numerous advantages. However, the main drawback of DEP separation devices is that they are not sufficient for large scale sample purification due to the lack of high sample throughput. In this work, we present for the first time a microfluidic device with two parallelized dielectrophoretic separations of (biological) samples smaller than 1 mum. The separation is carried out by means of insulator based DEP, i.e., an insulating ridge reduced the flow through height and thus created a nanoslit at which the selective DEP forces occur. The device consists of a cross injector, two parallel operation regions, and separate harvesting reservoirs where the samples are collected. Each DEP operation region contains an insulating ridge. We successfully demonstrate separation of 100 nm and 40 nm beads and 10 kbp and 5 kbp DNA with a separation purity of more than 80%. This states the proof of concept for up-scaling of dielectrophoretic separation by parallelization. Since the present technique is virtually label-free, it offers a fast purification, for example in the production of gene vaccines. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved

Microfluidic Devices for Biotechnological Applications

Viefhues M, Anselmetti D. Microfluidic Devices for Biotechnological Applications. Materials Today: Proceedings. 2017;4:S208-S213

Integrated Microfluidics for Single‐Cell Separation and On‐Chip Analysis: Novel Applications and Recent Advances

From deciphering infection and disease mechanisms to identifying novel biomarkers and personalizing treatments, the characteristics of individual cells can provide significant insights into a variety of biological processes and facilitate decision-making in biomedical environments. Conventional single-cell analysis methods are limited in terms of cost, contamination risks, sample volumes, analysis times, throughput, sensitivity, and selectivity. Although microfluidic approaches have been suggested as a low-cost, information-rich, and high-throughput alternative to conventional single-cell isolation and analysis methods, limitations such as necessary off-chip sample pre- and post-processing as well as systems designed for individual workflows have restricted their applications. In this review, a comprehensive overview of recent advances in integrated microfluidics for single-cell isolation and on-chip analysis in three prominent application domains are provided: investigation of somatic cells (particularly cancer and immune cells), stem cells, and microorganisms. Also, the use of conventional cell separation methods (e.g., dielectrophoresis) in unconventional or novel ways, which can advance the integration of multiple workflows in microfluidic systems, is discussed. Finally, a critical discussion related to current limitations of integrated microfluidic single-cell workflows and how they could be overcome is provided

Fast and continuous-flow separation of DNA-complexes and topological DNA variants in microfluidic chip format

Viefhues M, Regtmeier J, Anselmetti D. Fast and continuous-flow separation of DNA-complexes and topological DNA variants in microfluidic chip format. The Analyst. 2013;138(1):186-196.The efficient detection, separation and purification of topological and (protein-) complexed DNA variants is mandatory for many state-of-the-art molecular medicine technologies, like medical diagnostics, gene- and cancer-therapy as well as plasmid vaccination. Here, we present the proof-of-concept of a novel micro-nanofluidic device for a fast and efficient, continuous-flow, and virtually label-free detection/purification protocol that goes beyond the standard methods of electrophoretic mobility shift assays, capillary electrophoresis and affinity chromatography. Based on dielectrophoretic trapping, analyte mixtures of small linear DNA-fragments (2.868 kbp and 6.0 kbp), topological DNA variants like plasmids (6.766 kbp) and minicircle-DNA (2.257 kbp), or cytostatic- and protein-DNA complexes were separated in the vicinity of a channel-spanning bowed ridge (creating a nanoslit). One analyte is continuously deflected due to dielectrophoretic trapping at the ridge whereas other species pass the nanoslit unhindered, resulting in two molecule specific pathways with baseline separated resolution. This offers one-step real-time separation of low analyte volumes on a one-minute timescale at low-costs. The underlying dielectrophoretic mechanism was quantified by determining the electrical polarizabilities of the molecules. Additionally, we compared the continuous-flow detection of DNA-complexes with well-established electrophoretic mobility shift assays. Future analytical and preparative applications, such as for plasmid pharmaceuticals as well as continuous sample harvesting in parallel microchip format, are discussed

Nanofluidic devices for dielectrophoretic mobility shift assays by soft lithography

Viefhues M, Regtmeier J, Anselmetti D. Nanofluidic devices for dielectrophoretic mobility shift assays by soft lithography. Journal Of Micromechanics And Microengineering. 2012;22(11): 115024.We report development and application of 3D structured nano-microfluidic devices that were produced via soft lithography with poly(dimethylsiloxane). The procedure does not rely on hazardous or time-consuming production steps. Here, the nanochannels were created by channel-spanning ridges that reduce the flow height of the microchannel. Several realizations of the ridge layout and nanochannel height are demonstrated, depicting the high potential of this technique. The nanochannels proved to be stable even for width-to-height aspect ratios of 873:1. Additionally, an application of these submicrometer structures is presented with a new technique of a dielectrophoretic mobility shift assay (DEMSA). The DEMSA was used to detect different DNA variants, e.g. protein-DNA-complexes, via a shift in (dielectrophoretically retarded) migration velocities within an array of nanoslits

Microfluidics for Biotechnology: Bridging Gaps to Foster Microfluidic Applications

Ortseifen V, Viefhues M, Wobbe L, Grünberger A. Microfluidics for Biotechnology: Bridging Gaps to Foster Microfluidic Applications. Frontiers in Bioengineering and Biotechnology. 2020;8: 589074.Microfluidics and novel lab-on-a-chip applications have the potential to boost biotechnological research in ways that are not possible using traditional methods. Although microfluidic tools were increasingly used for different applications within biotechnology in recent years, a systematic and routine use in academic and industrial labs is still not established. For many years, absent innovative, ground-breaking and “out-of-the-box” applications have been made responsible for the missing drive to integrate microfluidic technologies into fundamental and applied biotechnological research. In this review, we highlight microfluidics’ offers and compare them to the most important demands of the biotechnologists. Furthermore, a detailed analysis in the state-of-the-art use of microfluidics within biotechnology was conducted exemplarily for four emerging biotechnological fields that can substantially benefit from the application of microfluidic systems, namely the phenotypic screening of cells, the analysis of microbial population heterogeneity, organ-on-a-chip approaches and the characterisation of synthetic co-cultures. The analysis resulted in a discussion of potential “gaps” that can be responsible for the rare integration of microfluidics into biotechnological studies. Our analysis revealed six major gaps, concerning the lack of interdisciplinary communication, mutual knowledge and motivation, methodological compatibility, technological readiness and missing commercialisation, which need to be bridged in the future. We conclude that connecting microfluidics and biotechnology is not an impossible challenge and made seven suggestions to bridge the gaps between those disciplines. This lays the foundation for routine integration of microfluidic systems into biotechnology research procedures

Dielectrophoretic analysis: a tool for studying the impact of organic solvents on whole-cell biocatalysts

S. Epping M, Grundmann A, Gröger H, Viefhues M. Dielectrophoretic analysis: a tool for studying the impact of organic solvents on whole-cell biocatalysts. In: 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS2019). 2019: 1014-1015

Fast and Continous-Flow detection and Separation of DNA-Complexes and DNA in Nanofluidic Chip Format

Viefhues M, Regtmeier J, Anselmetti D. Fast and Continous-Flow detection and Separation of DNA-Complexes and DNA in Nanofluidic Chip Format. In: Van Schepdael A, ed. Microchip Capillary Electrophoresis Protocols. Springer Series: Methods in Molecular Biology. Vol 1274. New York: Springer, Humana Press; 2015: 99-110