Dirk van Swaay

Doctoral Student

Dirk is currently a PhD student with Prof Andrew deMello in the Institute for Chemical and Bioengineering at ETH Zurich. He has an MEng in Bioengineering from Imperial College London, with the first two years spent taking engineering and medical science courses in the Bioengineering Department, and the third year in the Electrical Engineering Department. His final undergraduate year was spent abroad at University of California, Berkeley, where he worked with Prof Luke Lee in the Bioengineering Department and took classes in BioMEMS, microfluidics, robotics, and molecular biomechanics.

Journal

Claire Stanley, Martina Stöckli, Dirk van Swaay, Jerica Sabotič, Pauli Kallio, Markus Kuenzler, Andrew deMello and Markus Aebi. Probing bacterial-fungal interactions at the single cell level. Integr. Biol., 2014, Accepted Manuscript

Interactions between fungi and prokaryotes are abundant in many ecological systems. A wide variety of biomolecules regulate such interactions and many of them have found medicinal or biotechnological applications. However, studying a fungal-bacterial system at a cellular level is technically challenging. New microfluidic devices provided a platform for microscopic studies and for long-term, time-lapse experiments. Application of these novel tools revealed insights into in the dynamic interactions between the basidiomycete Coprinopsis cinerea and Bacillus subtilis. Direct contact was mediated by polar attachment of bacteria to only a subset of fungal hyphae suggesting a differential competence of fungal hyphae and thus differentiation of hyphae within a mycelium. The fungicidal activity of Bacillus subtilis was monitored at a cellular level and showed a novel mode of action on fungal hyphae.

Simon Berger, Joanna Stawikowska, Dirk van Swaay, and Andrew deMello. Continuous Suspension of Lipids in Oil by the Selective Removal of Chloroform via Microfluidic Membrane Separation. Ind. Eng. Chem. Res., 2014, 53, 9256–9261

A continuous flow method for the suspension of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipids in oil using a microfluidic platform is presented. The system consists of a microfluidic device housing a semipermeable membrane, a vacuum pump, and a syringe pump. Separation is achieved using a counter current flow of chloroform and a lipid containing oil stream, driven by the syringe pump and vacuum. Using such a system, a high efficiency extraction method was realized through the use of a semipermeable polydimethylsiloxane (PDMS) membrane on an anodized aluminum oxide (AAO) support. For a liquid flow rate of 5 μL/min, an air flow rate of 100 mL/min, and initial chloroform concentrations between 0.245 and 1.619 M, extraction rates of 93.5% to 97.9% and a retentate stream purity of between 99.79% and 99.29% were achieved.

Dirk van Swaay, Jean-Pierre Mächler, Claire Stanley and Andrew deMello. A chip-to-world connector with a built-in reservoir for simple small-volume sample injection. Lab Chip, 2013, 14, 178-181

We present a novel connector that allows for easy handling and injection of sample volumes between 1 and 20 μl. All tubing connections between external pumps and the microfluidic device are established before the sample is introduced into a sealable reservoir built into the connector. This approach allows for multiple injections of small sample volumes without the need to dismantle the chip-tubing assembly. We demonstrate that the connector reservoir seal can withstand pressures of up to 6 bar, that opening or closing the reservoir does not dislocate the sample by more than 35 nl, and that the connector can be used for injecting samples into both miscible and immiscible carrier fluids.

Dirk van Swaay and Andrew deMello. Microfluidic methods for forming liposomes. Lab Chip, 2013, 13, 752-767

Liposome structures have a wide range of applications in biology, biochemistry, and biophysics. As a result, several methods for forming liposomes have been developed. This review provides a critical comparison of existing microfluidic technologies for forming liposomes and, when applicable, a comparison with their analogous macroscale counterparts. The properties of the generated liposomes, including size, size distribution, lamellarity, membrane composition, and encapsulation efficiency, form the basis for comparison. We hope that this critique will allow the reader to make an informed decision as to which method should be used for a given biological application.

Conference

Dirk van Swaay. Cell-Free Biofilm Biosensor of Catheter related Urinary Tract Infections, Built using Biobricks that Exploit AHL Signalling Pathways in Biofilms. IET BioSysBio 2008

Urinary catheters are the major source of hospital infections worldwide and the second most common cause for bloodstream infections. Biofilm formation begins by the initial adherence of bacteria to the catheter surface that build a polysaccharide matrix. The internal communication is based on quorum sensing, involving small signaling molecules such as acyl-homoserine lactone (AHL). As part of the 2007 iGEM competition, we combined the principles of synthetic biology and the engineering cycle to produce ‘Infector Detector’. The design of this DNA construct, based on the MIT Biobrick Registry part F2620, consists of 2 main elements. The first is a constitutive Tet promoter, generating transcription factor LuxR. This binds to AHL, from the biofilm, providing the input of our biosensor system. The resulting AHL-LuxR complex activates the second part, a Lux promoter generating a fluorescent signal in the form of GFPmut3b, giving a detectable output. To avoid bacterial exposure in the clinical scenario, the biobrick was incorporated in an S30 E.Coli cell extract chassis - an in vitro transcription/translation system - as opposed to commonly used E.Coli chassis. Watch the presentation: http://scpro.streamuk.com/uk/player/Default.aspx?wid=8989&ptid=22&t=0