Redox-responsive maltoheptaose-b-polystyrene nanoparticles containing zinc phthalocyanine: Formulation, photophysical properties, release kinetic and toxicity

Sugar-based nanoparticles with redox responsive properties are an emerging class of nanovehicles designed to boost photodynamic therapy (PDT) in the treatment of neoplastic and non-neoplastic diseases. In this paper, it was synthesized a maltoheptaose-b-polystyrene [MH1.2k-b-PS5k)] block copolymer using metal-free click reaction, containing a redox-cleavable linker. The glyconanoparticles, loaded with photosensitizer zinc phthalocyanine (ZnPc) were produced by block copolymer self-assembly in an appropriate solvent mixture. The hydrodynamic radius of the nanoparticles (MH1.2k-b-PS5k@ZnPc) was dependent on copolymer concentration and method of nanoprecipitation (standard or reverse). The polymeric micelles displayed a spherical morphology, suitable values of efficiency encapsulation and kinetics profile showed a burst release at first stage, followed by a sustained release controlled by diffusion. The nanocarriers were able to produce cytotoxic singlet oxygen (O-1(2)) and displayed appropriate values of singlet oxygen quantum yields ( Phi(Delta)). The MH1.2k-b-PS5k@ZnPc nanoparticles were non-toxic towards Caernohabditis elegans and do not induced delay on larval development on dark conditions. The redox-responsive cleavage of block copolymer by N-bromosuccinimide (NBS) and MH1.2k-b-PS5k@ZnPc nanoparticles by NBS or reduced glutathion (GSH) was evidenced through by several techniques. These outcomes highlight that glyconanoparticles are stimuli-responsive and can contribute to the development of third-generation photosensitizers for use in PDT.