Artificial nano-and microcapsules that seek to mimic their natural counterparts can be constructed in different ways, leading to a variety of properties, as will be discussed in this review. [6][7][8] Enzymatic conversions can take place in the lumen of such capsules, and their membranes can be used to confine and tune reaction pathways. Synthetic capsules are also attracting a lot of attention because of their promising applications in the controlled release of pharmaceuticals. Capsules that bear recognition elements have been targeted to specific tissues or organs, providing a desirable vehicle for the aforementioned release of drugs. 9 For a chemist, the successful exploitation of capsules begins with their tailormade design and synthesis, for which cells and their organelles are the primary source of inspiration. In order to be able to do so, one needs insight into the design principles of nature to endow function to a molecule and to direct its self-assembly to a preset architecture. Although spectacular progresshasbeenmadeinthefieldofbioinspiredself-assembly, [10][11][12][13] unfortunately, the construction of an artificial cell is still not much more than a fantasy. Fortunately, more simple systems such as micelles, vesicles, and other assemblies of molecules may already partly solve the problem by providing a capsule that can be geared toward a desired application, e.g. the controlled release of drugs, as was demonstrated in the literature already quite a long time ago. [14][15][16] The view of life as being the result of a nanoscale phenomenon 17 is of more recent date and should rouse the interest in capsules for any chemist. Stijn F. M. van Dongen (group, center) was born in Goirle, The Netherlands, and studied chemistry at the Radboud University Nijmegen. He received his master's degree in 2006 after traineeships in the physical organic chemistry group of Prof. R. J. M. Nolte and the synthetic biology group of Prof. D. M. Hilvert at the ETH in Zu ¨rich, Switzerland. He is currently a Ph.D. student in the group of Profs.' R. J. M. Nolte and J. C. M. van Hest, working on the exploration of polymersomes as nanoreactors in a biological setting. Hans-Peter M. de Hoog (group, second from left) was born in Arnhem, The Netherlands, and graduated in chemistry at Utrecht University in 1998, specializing in the analysis of complex biomolecules. After a short stay at The Netherlands Organisation for Applied Scientific Research (TNO), he moved to the Radboud University Nijmegen in 2005 to pursue a Ph.D. in supramolecular and physical organic chemistry in the group of Prof. R. J. M. Nolte and J. J. L. M. Cornelissen. His research involves a collaborative project with Delft University of Technology (Prof. I. W. C. E. Arends) on the applicationdriven encapsulation of enzymes in polymersomes. Ruud J. R. W. Peters (group, right) obtained his bachelor's degree in molecular life sciences at the Radboud University Nijmegen in 2008. He is currently performing his master's research on the interactions between polymersomes a...

Porous polymersomes based on block copolymers of isocyanopeptides and styrene have been used to anchor enzymes at three different locations, namely, in their lumen (glucose oxidase, GOx), in their bilayer membrane (Candida antarctica lipase B, CalB) and on their surface (horseradish peroxidase, HRP). The surface coupling was achieved by click chemistry between acetylene-functionalised anchors on the surface of the polymersomes and azido functions of HRP, which were introduced by using a direct diazo transfer reaction to lysine residues of the enzyme. To determine the encapsulation and conjugation efficiency of the enzymes, they were decorated with metal-ion labels and analysed by mass spectrometry. This revealed an almost quantitative immobilisation efficiency of HRP on the surface of the polymersomes and a more than statistical incorporation efficiency for CalB in the membrane and for GOx in the aqueous compartment. The enzyme-decorated polymersomes were studied as nanoreactors in which glucose acetate was converted by CalB to glucose, which was oxidised by GOx to gluconolactone in a second step. The hydrogen peroxide produced was used by HRP to oxidise 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to ABTS(.+). Kinetic analysis revealed that the reaction step catalysed by HRP is the fastest in the cascade reaction.

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Polystyrene(40)-b-poly(isocyanoalanine(2-thiophen-3-yl-ethyl)amide)(50) (PS-PIAT) polymersomes have the unique property of being sufficiently porous to allow diffusion of small (organic) substrates while retaining large biomolecules such as enzymes inside. Herein we report on the encapsulation and protection of glucose oxidase (GOx) and horse radish peroxidase (HRP) in PS-PIAT polymersomes and the successful employment of these functionalised nanoreactors in a cascade reaction. The demonstrated concept allows for further application in other enzymatic cascade reactions, bio-organic hybrid systems and biosensing devices.

Hybrid phospholipid/block copolymer vesicles, in which the polymeric membrane is blended with phospholipids, display interesting self-assembly behavior, incorporating the robustness and chemical versatility of polymersomes with the softness and biocompatibility of liposomes. Such structures can be conveniently characterized by preparing giant unilamellar vesicles (GUVs) via electroformation. Here, we are interested in exploring the self-assembly and properties of the analogous nanoscale hybrid vesicles (ca. 100 nm in diameter) of the same composition prepared by film-hydration and extrusion. We show that the self-assembly and content-release behavior of nanoscale polybutadieneb-poly(ethylene oxide) (PB-PEO)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) hybrid phospholipid/block copolymer vesicles can be tuned by the mixing ratio of the amphiphiles. In brief, these hybrids may provide alternative tools for drug delivery purposes and molecular imaging/sensing applications and clearly open up new avenues for further investigation. OPEN ACCESSPolymers 2013, 5 1103