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PH-responsive non-ionic diblock copolymers: ionization of carboxylic acid end-groups induces an order-order morphological transition.

ABSTRACT: A carboxylic acid based reversible additionfragmentation transfer (RAFT) agent is used to prepare gels composed of worm-like diblock copolymers using two non-ionic monomers, glycerol monomethacrylate (GMA) and 2-hydroxypropyl methacrylate (HPMA). Ionization of the carboxylic acid end-group on the PGMA stabilizer block induces a worm-to-sphere transition, which in turn causes immediate degelation. This morphological transition is fully reversible as determined by TEM and rheology studies and occurs because of a subtle change in the packing parameter for the copolymer chains. A control experiment where the methyl ester derivative of the RAFT agent is used to prepare the same diblock copolymer confirms that no pH-responsive behavior occurs in this case. This end-group ionization approach is important for the design of new pH-responsive copolymer nano-objects as, unlike polyacids or polybases, only a minimal amount of added base (or acid) is required to drive the morphological transition.

SUBMITTER: Lovett JR

PROVIDER: S-EPMC4312895 | biostudies-other | 2015 Jan

REPOSITORIES: biostudies-other

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pH-responsive non-ionic diblock copolymers: ionization of carboxylic acid end-groups induces an order-order morphological transition.

Lovett Joseph R JR Warren Nicholas J NJ Ratcliffe Liam P D LP Kocik Marzena K MK Armes Steven P SP

Angewandte Chemie (International ed. in English) 20141121 4

A carboxylic acid based reversible additionfragmentation transfer (RAFT) agent is used to prepare gels composed of worm-like diblock copolymers using two non-ionic monomers, glycerol monomethacrylate (GMA) and 2-hydroxypropyl methacrylate (HPMA). Ionization of the carboxylic acid end-group on the PGMA stabilizer block induces a worm-to-sphere transition, which in turn causes immediate degelation. This morphological transition is fully reversible as determined by TEM and rheology studies and occu ...[more]

PMID: 25418214

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Project description:INTRODUCTION:Intracellular delivery is a key step for many applications in medicine and for investigations into cellular function. This is particularly true for immunotherapy, which often requires controlled delivery of antigen and adjuvants to the cytoplasm of immune cells. Due to the complex responses generated by the stimulation of diverse immune cell populations, it is critical to monitor which cells are targeted during treatment. To address this issue, we have engineered an immunotheranostic polymersome delivery system that fluorescently marks immune cells following intracellular delivery. METHODS:N-(3-bromopropyl)phthalimide end-capped poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS-PI) was synthesized by anionic ring opening polymerization and linked with PEG-PPS-NH2 via a perylene bisimide (PBI) bridge to form a tetrablock copolymer (PEG-PPS-PBI-PPS-PEG). Block copolymers were assembled into polymersomes by thin film hydration in phosphate buffered saline and characterized by dynamic light scattering, cryogenic electron microscopy and fluorescence spectroscopy. Polymersomes were injected subcutaneously into the backs of mice, and draining lymph nodes were extracted for flow cytometric analysis of cellular uptake and disassembly. RESULTS:Modular self-assembly of tetrablock / diblock copolymers in aqueous solutions induced ?-? stacking of the PBI linker that both red-shifted and quenched the PBI fluorescence. Reactive oxygen species within the endosomes of phagocytic immune cell populations oxidized the PPS blocks, which disassembled the polymersomes for dequenching and shifting of the PBI fluorescence from 640 nm to 550 nm emission. Lymph node resident macrophages and dendritic cells were found to increase in 550 nm emission over the course of 3 days by flow cytometry. CONCLUSIONS:Immunotheranostic polymersomes present a versatile platform to probe the contributions of specific cell populations during the elicitation of controlled immune responses. Flanking PBI with two oxidation-sensitive hydrophobic PPS blocks enhanced ? stacking and introduced a mechanism for disrupting ?-? interactions to shift PBI fluorescence in response to oxidative conditions. Shifts from red (640 nm) to green (550 nm) fluorescence occurred in the presence of physiologically relevant concentrations of reactive oxygen species and could be observed within phagocytic cells both in vitro and in vivo.

Dataset Information

PH-responsive non-ionic diblock copolymers: ionization of carboxylic acid end-groups induces an order-order morphological transition.

Publications

pH-responsive non-ionic diblock copolymers: ionization of carboxylic acid end-groups induces an order-order morphological transition.

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