Modular Approach for the Design of Smart Polymeric Nanocapsules

Abstract

embracing layer-by-layer assembly (LBL) methods, [4][5][6] and iii) self-assembly of the amphiphilic block copolymers. [7][8][9] In principle, the formation of the polymer shell that covers the core space is triggered by either covalent or non-covalent bonding depending on the selected method. The heterophase polymerization systems consist of (mini)emulsions and suspensions resulting in the covalently linked polymers covering the core-forming droplets. On the other hand, the miniemulsion technology also provides the opportunity to make capsules from preformed polymers when the polymerization cannot be performed in heterophase systems as shown by Landfester et al. [10][11][12] Miniemulsion polymerization is understood as a polymerization technique where stable droplets are formed prior to polymerization and the droplets are then polymerized. LBL approaches are commonly used in combination with templating methods. The principle is to use an organic or inorganic particle as a support in which the polymers are either adsorbed or grown by surface initiated polymerization (SIP) techniques on the surface of the particle template. [13] In this approach, different types and sized particles made of gold, silica, and carbonate are utilized as platforms. The template particles are further removed through etching procedures such as dissolution in acids to produce hollow capsules having a polymer shell. [6] Another promising way of polymeric nanocapsule formation is to use the self-assembly of specially designed amphiphilic block copolymers in water which in turn leads to polymersomes comprising a bilayer membrane and an aqueous core. [7] These vesicular structures are artificial mimetics of the liposomes that are self-assembled from natural phospholipids. Polymersomes showed various outstanding properties over their lipid counterparts such as higher mechanical strength, enhanced stability as well as a wide range of chemical versatility that enhances application opportunities in nanomedicine. [14,15] Several excellent reviews about polymeric nanocapsules focusing on their synthesis through miniemulsion processes, [1][2][3]16,17] templating approaches including layer-by-layer assemblies [4][5][6]18] as well as self-assembly processes [8,14,[19][20][21][22][23] have been published. Generally, their use in biomedical science including drug delivery and synthetic biology is underlined. However, there are relatively few examples of comparative reviews [13,[24][25][26][27][28][29] to emphasize the application-oriented eligibilities of the polymeric nanocapsules formed by different methods. In this context, we aim to discuss from a modular perspective both self-assembled nanocapsules, so-called polymersomes, and nanocapsules with a covalently formed shell, mainly obtained by the miniemulsion technique (Figure 1). NanocapsulesThe formation of nanocapsules from a modular perspective for self-assembled nanocapsules, so-called polymersomes, and nanocapsules with a covalently formed shell are discussed in this review. It is shown that the...

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The rise of bio-inspired polymer compartments responding to pathology-related signals

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