Abstract
Aggregation-induced quenching of porphyrin molecules as photosensitizer significantly reduces the quantum yield of the singlet oxygen generation, and it is able to decrease the efficacy of photodynamic therapy. We utilized amphiphilic copolymers in this work to precisely control porphyrin H-type and J-type aggregations in water. The amphiphilic copolymer bearing azobenzene, β-cyclodextrin, and porphyrin was successfully synthesized by the atom transfer radical polymerization technique. The azobenzene and β-cyclodextrin complex, as a host–guest supramolecular interaction, has great potential in the design of light-responsive nanocarriers. The amphiphilic block copolymer can be self-assembled into polymersomes, whose application in the generation of singlet oxygen has been also tested. We further demonstrate that, due to the stable H- and J-aggregates of porphyrin, which act as noncovalent cross-linking points, the structure of polymersomes can be reversible under light-stimulus. This formation method has the advantage of allowing for both the encapsulation of hydrophilic and hydrophobic molecules and release upon external light without any distinguishable changes in the structure. Furthermore, the morphology and particle size distribution of the polymersomes were also investigated by using transition electron microscopy, dynamic light scattering, and field emission scanning electron microscopy.
Highlights
The construction of organic supramolecular assemblies based on porphyrin has attracted great attention in cancer therapy, especially photodynamic therapy (PDT)[1,2,3]
In which the hydrophilic part is constructed by a natural polymer-like dextran (Dex), modified to possess controlled functional positions on the polymer chain, and the hydrophobic part consists of an amphiphilic polymer, synthesized through controlled radical polymerization p rocesses[17,18]
We synthesized an amphiphilic copolymer based on dextran/poly(methyl methacrylate) that contains Azo and β-CD groups for supramolecular interactions, as well as porphyrin units for dedicating the stability to these carriers as a consequence of π–π stacking (Fig. 1)
Summary
The construction of organic supramolecular assemblies based on porphyrin has attracted great attention in cancer therapy, especially photodynamic therapy (PDT)[1,2,3]. Much effort has been devoted to improve their poor biocompatibility, low hydrophilicity, and high tendency to aggregate via π–π stacking, resulting in quenching of the excitation energy which decreases the quantum yield of the singlet oxygen generation (aggregation-induced quenching)[7,8]. To address these limitations, a variety of strategies have been reported to improve the therapeutic efficacy of porphyrin photosensitizers, such as liposomes and polymeric n anoparticles[9,10]. Compared with large π-conjugate, H-type and J-type aggregates with side-by-side and head-to-tail molecular packing, respectively, have attracted more attention for featuring a deeper and stronger absorption[25,26]
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