Pure hydrophilic block copolymer vesicles with redox- and pH-cleavable crosslinks

Abstract

The self-assembly of a novel double hydrophilic block copolymer consisting of biocompatible blocks, namely pullulan-b-poly(N-vinylpyrrolidone), is presented. Completely hydrophilic spherical structures with an average apparent radius of 800 nm at increased concentrations in water are observed via dynamic light scattering as well as cryo scanning electron microscopy and confocal laser scanning microscopy techniques. Moreover, the pullulan block is converted to present aldehyde groups acting as anchor point for crosslinker attachments. It is demonstrated, that the oxidized self-assembled particles could be crosslinked via the bifunctional crosslinker cystamine forming dynamic covalent imine linkages with aldehyde groups. The afforded vesicles with an average diameter of 700 nm are stable upon high dilution and could be observed via cryo scanning electron microscopy and transmission electron microscopy. Furthermore, it is possible to cleave the crosslinking bonds with the treatment of acid or the application of a reducing agent. The responsivity is a key feature taking future applications in the biomedical sector into account.

Poly(ethylene glycol) brush-b-poly(N-vinylpyrrolidone)-based double hydrophilic block copolymer particles crosslinked via crystalline α-cyclodextrin domains

“…Conclusively, the a-CD induced selfassembly process at 2.0 wt% is partially reversible when the sample is diluted, which strongly differs from other previous reported DHBC crosslinking systems where the crosslinking agent could stabilize the particles against dilution. 21,36 In contrast, the present supramolecular crosslinking strategy introduces an additional equilibrium to enhance the selfassembly process but sustaining the dynamics of the DHBC system.…”

“…In order to gain control over the equilibrium and stabilize the DHBC particles for further uses, it is inevitable to crosslink the DHBC particles as reported recently. 35,36 In general, there are several crosslinking approaches: covalent, dynamic covalent and physical/supramolecular crosslinking. Covalent bonding is non-reversible, which enhances the longterm stability of crosslinks but excludes adaptivity of the system.…”

Polysaccharide nanoparticles: from fabrication to applications

“…For example, the native charges of polysaccharides can be exploited for the synthesis of polysaccharide NPs [88][89][90] or covalent crosslinking can be implemented. [91][92][93] Mizrahy and Peer discussed the main mechanisms during the synthesis of polysaccharide NPs in their review in detail, which are categorised as chemical (covalent) crosslinking, physical (ionic) crosslinking, polyelectrolyte-complexation and self-assembly (Scheme 2). 25 Due to the repeated number of monomer units on the polysaccharide a full network can be achieved.…”

Double Hydrophilic Block Copolymer Self‐Assembly in Aqueous Solution

“…Dynamic covalent crosslinking was recently described by Willersinn and Schmidt. [119] The Pull phase was crosslinked due its high density of functional groups. Therefore, Pull building blocks were partially oxidized to introduce aldehyde functionalities that can be crosslinked via imine formation employing a diamine (Figure 7f).…”