Abstract
Due to a strong retardation effect of o-nitrobenzyl ester on polymerization, it is still a great challenge to prepare amphiphilic block copolymers for polymersomes with a o-nitrobenzyl ester-based hydrophobic block. Herein, we present one such solution to prepare amphiphilic block copolymers with pure poly (o-nitrobenzyl acrylate) (PNBA) as the hydrophobic block and poly (N,N’-dimethylacrylamide) (PDMA) as the hydrophilic block using bulk reversible addition-fragmentation chain transfer (RAFT) polymerization of o-nitrobenzyl acrylate using a PDMA macro-RAFT agent. The developed amphiphilic block copolymers have a suitable hydrophobic/hydrophilic ratio and can self-assemble into photoresponsive polymersomes for co-loading hydrophobic and hydrophilic cargos into hydrophobic membranes and aqueous compartments of the polymersomes. The polymersomes demonstrate a clear photo-responsive characteristic. Exposure to light irradiation at 365 nm can trigger a photocleavage reaction of o-nitrobenzyl groups, which results in dissociation of the polymersomes with simultaneous co-release of hydrophilic and hydrophobic cargoes on demand. Therefore, these polymersomes have great potential as a smart drug delivery nanocarrier for controllable loading and releasing of hydrophilic and hydrophobic drug molecules. Moreover, taking advantage of the conditional releasing of hydrophilic and hydrophobic drugs, the drug delivery system has potential use in medical applications such as cancer therapy.
Highlights
IntroductionO-nitrosobenzaldehyde is a commonly used molecule in designing drug delivery systems for cancer therapy and nitrosobenzaldehyde shows a low toxicity to the body [26,27]
To fabricate a photosensitive polymer, a photoresponsive monomer Nitrobenzyl Acrylate (NBA) was synthesized according to the literature [28]
The photoresponsive amphiphilic block copolymers were synthesized via Synthesis of PRhAoFtToproelsypmoernizsaitvioen.BThloecdketaCiloedposylnytmheteicrsroute is shown in Scheme 2
Summary
O-nitrosobenzaldehyde is a commonly used molecule in designing drug delivery systems for cancer therapy and nitrosobenzaldehyde shows a low toxicity to the body [26,27] Under light irradiation, they perform irreversible photocleavage isomerization and generate a corresponding o-nitrosobenzaldehyde and a free carboxylic acid. Photocleavage of the o-nitrobenzyl groups disturb the bilayer membrane of the corresponding polymersomes, which re-organize into smaller polymersomes accompanied by the release of the loaded drugs This strategy has been adopted by Katz and Meier to deliver different payloads including biocytin, drugs, and biomolecules [28,29]. Special efforts have been dedicated to the design and synthesis of polymerizable monomers with o-nitrobenzyl far from (meth)acrylate groups [30] He and coworkers have designed a novel photolabile monomer with o- nitrosobenzaldehyde acetal and prepared photoresponsive polymersomes from this photolabile acetal containing amphiphilic block copolymers.
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