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The creation of adaptive matter is heavily inspired by biological systems. However, it remains challenging to design complex material responses that are governed by reaction networks, which lie at the heart of cellular complexity. The main reason for this slow progress is the lack of a general strategy to integrate reaction networks with materials. Herein we use a systematic approach to preprogram the response of a hydrogel to a trigger, in this case the enzyme trypsin, which activates a reaction network embedded within the hydrogel. A full characterization of all the kinetic rate constants in the system enabled the construction of a computational model, which predicted different hydrogel responses depending on the input concentration of the trigger. The results of the simulation are in good agreement with experimental findings. Our methodology can be used to design new, adaptive materials of which the properties are governed by reaction networks of arbitrary complexity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The number of circulating tumor cells (CTCs) in blood is strongly correlated with the progress of metastatic cancer. Current methods to detect CTCs are based on immunostaining or discrimination of physical properties. Herein, a label-free method is presented exploiting the abnormal metabolic behavior of cancer cells. A single-cell analysis technique is used to measure the secretion of acid from individual living tumor cells compartmentalized in microfluidically prepared, monodisperse, picoliter (pL) droplets. As few as 10 tumor cells can be detected in a background of 200 000 white blood cells and proof-of-concept data is shown on the detection of CTCs in the blood of metastatic patients., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In recent years, technologies capable of analyzing single cells have emerged that are transforming many fields of biological research. Herein we report how DNA-functionalized hydrogel beads can serve as a matrix to capture mRNA from lysed single cells. mRNA quantification free of pre-amplification bias is ensured by using padlock probes and rolling circle amplification followed by hybridization with fluorescent probes. The number of transcripts in individual cells is assessed by simply counting fluorescent dots inside gel beads. The method extends the potential of existing techniques and provides a general platform for capturing molecules of interest from single cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein, we describe a simple and robust approach to repeatedly modify surfaces with polymer brushes through surface-initiated atomic transfer radical polymerization (SI-ATRP), based on an initiator-embedded polystyrene sheet that does not rely on specific surface chemistries for initiator immobilization. The surface-grafted polymer brushes can be wiped away to expose fresh underlying initiator that re-initiates polymerization. This strategy provides a facile route for modification of molded or embossed surfaces, with possible applications in the preparation of fluidic devices and polymer-embedded circuits., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A wet stamping method to precisely control concentrations of enzymes and inhibitors in place and time inside layered gels is reported. By combining enzymatic reactions such as autocatalysis and inhibition with spatial delivery of components through soft lithographic techniques, a biochemical reaction network capable of recognizing the spatial distribution of an enzyme was constructed. The experimental method can be used to assess fundamental principles of spatiotemporal order formation in chemical reaction networks., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Microdroplets in microfluidics offer a great number of opportunities in chemical and biological research. They provide a compartment in which species or reactions can be isolated, they are monodisperse and therefore suitable for quantitative studies, they offer the possibility to work with extremely small volumes, single cells, or single molecules, and are suitable for high-throughput experiments. The aim of this Review is to show the importance of these features in enabling new experiments in biology and chemistry. The recent advances in device fabrication are highlighted as are the remaining technological challenges. Examples are presented to show how compartmentalization, monodispersity, single-molecule sensitivity, and high throughput have been exploited in experiments that would have been extremely difficult outside the microfluidics platform.

Fully integrated: Mass spectrometry has been integrated into a detection scheme for microdroplets that are created within microfluidic channels (see picture, scale bar 200 microm). This technique allows droplets to be identified based on the compounds they contain, and combines fluorescence screening with MS analysis. These experiments indicate how similar approaches can be applied to the ambitious goals of on-chip protein evolution and chemical synthesis.

The incorporation of dialkyl sulfide side chains in metallodendrimers is a simple method for their insertion into a monolayer of decanethiol formed by self-assembly on a gold surface. The dendrimer binds through the sulfide group to a defect in the monolayer on the gold surface (see picture). The surface concentration of the isolated dendrimer adsorbate can be regulated by the adsorption time (for example, 55 adsorbates on a surface of 200x200 nm(2) after 20 h).