Stijn F. M. van Dongen

Biohybrid Polymer Capsules

An overview of the wide range of polymer-based capsules that have been constructed from synthetic and biological building blocks or from biological building blocks that are taken out of their natural environment, using both hyperbranched and self-assembly approaches, was reviewed. The capsules that are discussed can be considered as the simplest mimics of an organelle or cell and contain a cavity in which chemical reactions can take place or cargo can be stored. The chemical tool box available for constructing polymer micelles and polymersomes is much larger, and natural motifs have been actively incorporated into their designs. Regarding LbL, polymersome, or polymeric micelle nanoreactors, it can be predicted that natures biocatalysts will be increasingly used for encapsulation in these synthetic systems, holding promise for future nanoscale diagnostic devices. One of the main challenges in this field will be the effective stimulation of responsive polymersomes since most stimuli reported thus far cannot be applied in living organisms.

Cellular integration of an enzyme-loaded polymersome nanoreactor.

Cells with implants: Porous enzyme-loaded polymersomes were constructed that display the cell-penetrating peptide tat on their surfaces. These nanoreactors are taken up by mammalian cells through macropinocytosis. Inside the cells, the polymersomes are only partially routed to acidic compartments. Polymersomes with horseradish peroxidase as a model cargo enzyme displayed sustained intracellular activity.

Single-Step Azide Introduction in Proteins via an Aqueous Diazo Transfer

The controlled introduction of azides in proteins provides targetable handles for selective protein manipulation. We present here an efficient diazo transfer protocol that can be applied in an aqueous solution, leading to the facile introduction of azides in the side chains of lysine residues and at the N-terminus of enzymes, e.g. horseradish peroxidase (HRP) and the red fluorescent protein DsRed. The effective introduction of azides was verified by mass spectrometry, after which the azido-proteins were used in Cu(I)-catalyzed [3 + 2] cycloaddition reactions. Azido-HRP retained its catalytic activity after conjugation of a small molecule. This modified protein could also be successfully immobilized on the surface of an acetylene-covered polymersome. Azido-DsRed was coupled to an acetylene-bearing protein allowing it to act as a fluorescent label, demonstrating the wide applicability of the diazo transfer procedure.

A DNA-based strategy for dynamic positional enzyme immobilization inside fused silica microchannels

A three-enzyme cascade reaction was successfully realized in a continuous flow microreactor. The first enzyme (Candida antarctica lipase B, also known as Pseudozyma antarctica lipase B) and the third enzyme (horseradish peroxidase) of the cascade process were immobilized in a mild non-contact manner via ssDNA-ssDNA interaction in discrete zones on the capillary wall, whereas the second enzyme (glucose oxidase) was kept in the mobile phase. The unique combined feature of patterning, possibility of loading and stripping, and modularity in a fused silica microchannel is demonstrated. By changing the distance between the two enzyme patches, the reaction time available for glucose oxidase could be independently and modularly varied. The reusability of the enzymatic microfluidic system was shown by using the hybridization and dehybridization capabilities of DNA as a tool for subsequent enzyme immobilization and removal.

Sorting Catalytically Active Polymersome Nanoreactors by Flow Cytometry

Enzyme-filled stable polymeric capsules (polymersomes) that are permeable to low-molecular-weight (pro-fluorescent) substrates can be sorted based on the activity of encapsulated enzymes using flow cytometry (see image). Enzymatic activity is screened by the build-up of fluorescent product that is prevented from leaking out by co-encapsulation of a trapping agent.

Correction: Structure–delivery relationships of lysine-based gemini surfactants and their lipoplexes

Correction for ‘Structure–delivery relationships of lysine-based gemini surfactants and their lipoplexes’ by Mark Damen et al., Soft Matter, 2014, 10, 5702–5714.