Reported here is a 2D, interfacial microcompartmentalization strategy governed by 3D phase separation. In aqueous polyethylene glycol (PEG) solutions doped with biotinylated polymers, the polymers spontaneously accumulate in the interfacial layer between the oil-surfactant-water interface and the adjacent polymer phase. In aqueous two-phase systems, these polymers first accumulated in the interfacial layer separating two polymer solutions and then selectively migrated to the oil-PEG interfacial layer. By using polymers with varying photopolymerizable groups and crosslinking rates, kinetic control and capture of spatial organisation in a variety of compartmentalized macroscopic structures, without the need of creating barrier layers, was achieved. This selective interfacial accumulation provides an extension of 3D phase separation towards synthetic compartmentalization, and is also relevant for understanding intracellular organisation.

We report a flexible single-cell isolation method by imaging-assisted hydrogel formation. Our approach consists of imaging-aided selective capture of cells of interest by encasing them into a polymeric hydrogel, followed by removal of unwanted cells and subsequent release of isolated cells by enzymatic hydrogel degradation, thus offering an opportunity for further analysis or cultivation of selected cells. We achieved high sorting efficiency and observed excellent viability rates (>98%) for NIH/3T3 fibroblasts and A549 carcinoma cells isolated using this procedure. The method presented here offers a mask-free, cost-efficient and easy-to-use alternative to many currently existing surface-based cell-sorting techniques, and has the potential to impact the field of cell culturing and isolation, e.g. single cell genomics and proteomics, investigation of cellular heterogeneity and isolation of best performing mutants for developing new cell lines.

Hydrogel microparticles are important in materials engineering, but their applications remain limited owing to the difficulties associated with their manipulation. Herein, we report the self-orientation of crescent-shaped hydrogel microparticles and elucidate its mechanism. Additionally, the microparticles were used, for the first time, as micro-buckets to carry living cells. In aqueous solution, the microparticles spontaneously rotated to a preferred orientation with the cavity facing up. We developed a geometric model that explains the self-orienting behavior of crescent-shaped particles by minimizing the potential energy of this specific morphology. Finally, we selectively modified the particles’ cavities with RGD peptide and exploited their preferred orientation to load them with living cells. Cells could adhere, proliferate, and be transported and released in vitro. These micro-buckets hold a great potential for applications in smart materials, cell therapy, and biological engineering.

Extracellular vesicles (EVs) are a family of small membrane vesicles that carry information about cells by which they are secreted. Growing interest in the role of EVs in intercellular communication, but also in using their diagnostic, prognostic and therapeutic potential in (bio) medical applications, demands for accurate assessment of their biochemical and physical properties. In this review, we provide an overview of available technologies for EV analysis by describing their working principles, assessing their utility in EV research and summarising their potential and limitations. To emphasise the innovations in EV analysis, we also highlight the unique possibilities of emerging technologies with high potential for further development.

The last decade has witnessed great progress in understanding and manipulating self-assembly of block copolymers in solution. A wide variety of micellar structures can be created and many promising applications in bioscience have been reported. In particular, nano-fibrous micelles provide a great platform to mimic the filamentous structure of native extracellular matrix (ECM). However, the evaluation of this kind of filomicellar system with potential use in tissue engineering is virtually unexplored. The question behind it, such as if the block copolymer nano-fibrous micelles can regulate cellular response, has lingered for many years because of the difficulties in preparation and 3D manipulation of these tiny objects. Here, by using a combination approach of self-assembly of block copolymers and soft lithography, we establish a novel and unique nano-fibrous 2D platform of organized micelles and demonstrate that patterned micelles enable control over the cellular alignment behavior. The area density and orientation of fibrous micelles determine the alignment degree and directionality of cells, respectively. Furthermore, when cells were cultured on multi-directionally aligned micelles, a competitive response was observed. Due to the virtually infinite possibilities of functionalization of the micelle corona, our work opens a new route to further mimic the native fibrous networks with artificial micelles containing various functionalities.

We report the continuous production of microcapsules composed of an aqueous core and permeable hydrogel shell, made stable by the controlled photo-cross-linking of the shell of an all-aqueous double emulsion. While most previous work on water-based emulsions focused on active droplet formation, here double emulsion droplets were spontaneously generated at a three-dimensional flow-focusing junction through the break-up of a double jet formed by immiscible aqueous solutions of polyethylene glycol and cross-linkable dextrans. The capsules obtained with this lipid-free, organic-solvent-free, and surfactant-free approach displayed excellent stability under a variety of harsh conditions (3 <pH <13, high salinity). Drying and rehydration experiments demonstrate the permeability of the shell, which may enable molecular-weight-dependent release and uptake of polar solutes.

Self-assembly provides access to a variety of molecular materials, yet spatial control over structure formation remains difficult to achieve. Here we show how reaction-diffusion (RD) can be coupled to a molecular self-assembly process to generate macroscopic free-standing objects with control over shape, size, and functionality. In RD, two or more reactants diffuse from different positions to give rise to spatially defined structures on reaction. We demonstrate that RD can be used to locally control formation and self-assembly of hydrazone molecular gelators from their non-assembling precursors, leading to soft, free-standing hydrogel objects with sizes ranging from several hundred micrometres up to centimeters. Different chemical functionalities and gradients can easily be integrated in the hydrogel objects by using different reactants. Our methodology, together with the vast range of organic reactions and self-assembling building blocks, provides a general approach towards the programmed fabrication of soft microscale objects with controlled functionality and shape.

Researchers investigated the effect of various (bio)polymeric crosslinkers on the self-assembly process of this reaction-coupled hydrazide-aldehyde gelator into hydrogel materials as a model system. They selected duplex DNA, which acted as a stiff, negatively charged rigid rod below its persistence length ideal for the construction of (nano)materials,[38–40] and compared it against a soft, neutral poly(ethylene glycol) (PEG) polymer of comparable size. Aldehyde moieties were specifically incorporated at the terminal ends of the (bio)polymers to introduce them during the self-assembly of the reaction-coupled network composed another set of (bio)polymers. The researchers also examined the effect of these two crosslinkers on the gelation of the reaction-coupled monomers into hydrogels over several length scales and compared their resultant materials properties.

A generic method is used for compartmentalization of supramolecular hydrogels by using water-in-water emulsions based on aqueous multi-phase systems (AMPS). By forming the low-molecular-weight hydrogel throughout all phases of all-aqueous emulsions, distinct, micro-compartmentalized materials were created. This structuring approach offers control over the composition of each type of the compartments by directing the partitioning of objects to be encapsulated. Moreover, this method allows for barrier-less, dynamic exchange of even large hydrophilic solutes (MW≈60kDa) between separate aqueous compartments. These features are expected to find use in the fields of, for instance, micro-structured catalysts, templating, and tissue engineering.

In this contribution we show that biological membranes can catalyze the formation of supramolecular hydrogel networks. Negatively charged lipid membranes can generate a local proton gradient, accelerating the acid-catalyzed formation of hydrazone-based supramolecular gelators near the membrane. Synthetic lipid membranes can be used to tune the physical properties of the resulting multicomponent gels as a function of lipid concentration. Moreover, the catalytic activity of lipid membranes and the formation of gel networks around these supramolecular structures are controlled by the charge and phase behavior of the lipid molecules. Finally, we show that the insights obtained from synthetic membranes can be translated to biological membranes, enabling the formation of gel fibers on living HeLa cells.