Construction of Somatostatin-Based Multiphase "Core-Shell" Coacervates as Photodynamic Biomimetic Organelles

Biomimetic coacervates have recently attracted great interest in biomedical fields, especially for drug delivery and as protocells. However, these membraneless structures are easily coalesced and poorly targetable, limiting their real biomedical applications. Here multiphase "core-shell" coacervate (CSC) constructed by dsDNA and somatostatin (SST), a 14-mer cyclopeptide is designed. The CSC shows enhanced tumor targetability through SST binding to SST receptors on the tumor cells' surface. G4 quadruplex-hemin complex can be embedded in the CSC by interaction with SST, as demonstrated by molecular simulation and isothermal titration calorimetry. The G4-hemin embedded CSC can further recruit photosensitizers such as tetracarboxyphenyl porphyrin to form the CSC-GHT composite for photodynamic therapy (PDT). As photodynamic biomimetic organelles, CSC-GHT can convert oxygen to singlet oxygen (catalyzed by the catalase-mimetic activity of G4-hemin), resulting in enhanced PDT effect, which allows the inhibition of cellular migration in vitro and tumor growth in vivo. Owing to high stability, targetability, and biosafety, the proposed CSC can recruit various cargos from small dyes to large biomacromolecules (up to 430 kDa), providing promising theranostic applications.