No abstract

Magnetically labelled cells are finding a wealth of applications for in vitro analysis as well as in vivo treatments. Sorting of cells into subpopulations based on their magnetite loading is an important step in such procedures. Here, we study the sorting of monocytes and macrophages which internalise nanoparticles to different extents based on their endocytotic capacity. Macrophages featured a high endocytotic activity and were found to internalise between 4 and 60 pg of iron per cell. They were successfully sorted into five subpopulations of narrow iron loading distributions via on-chip free-flow magnetophoresis, thus demonstrating the potential of sorting of relatively similarly loaded cells. Monocytes featured a low endocytotic capacity and took on 1 to 4 pg of iron per cell. Mixtures of monocytes and macrophages were successfully sorted within the free-flow magnetophoresis chip and good purity (>88%), efficacy (>60%) and throughput (from 10 to 100 cells s(-1)) could be achieved. The introduced method constitutes a viable tool for studies of endocytotic capacity and sorting/selection of cells based on this functionality.

An extremely versatile microfluidic device is demonstrated in which multi-step (bio)chemical procedures can be performed in continuous flow. The system operates by generating several co-laminar flow streams, which contain reagents for specific (bio)reactions across a rectangular reaction chamber. Functionalized magnetic microparticles are employed as mobile solid-supports and are pulled from one side of the reaction chamber to the other by use of an external magnetic field. As the particles traverse the co-laminar reagent streams, binding and washing steps are performed on their surface in one operation in continuous flow. The applicability of the platform was first demonstrated by performing a proof-of-principle binding assay between streptavidin coated magnetic particles and biotin in free solution with a limit of detection of 20 ng mL(-1) of free biotin. The system was then applied to a mouse IgG sandwich immunoassay as a first example of a process involving two binding steps and two washing steps, all performed within 60 s, a fraction of the time required for conventional testing.

in Wiley InterScience (www.interscience.wiley.com).In this work a simple method is described for depositing a robust yet highly porous film of anatase titania nanoparticles with a very high surface area onto the inside walls of microfluidic devices. A very high loading of 66 g of titania per liter of reactant solution was achieved. The effectiveness is demonstrated of this deposition method by producing functionalized microfluidic reactor devices and using them to photocatalytically degrade air-saturated methylene blue solutions. Experiments were performed with and without the addition of gaseous oxygen to the microreactors. The addition of oxygen dramatically enhanced the degradation rate. This highlights the necessity for supplying additional oxygen to microsystems during photocatalysis since dissolved oxygen can be rapidly depleted within the small confined space inside microreactors. With additional gaseous oxygen, the conversion rate for the photodegradation reaction of 0.1mM methylene blue at a flow rate of 12 ml min À1 was 10.6 % s À1 .