Synthesis, characterization and self-assembly of hybrid pH-sensitive block copolymer containing polyhedral oligomeric silsesquioxane (POSS)

Peptide 18-4/chlorin e6-conjugated polyhedral oligomeric silsesquioxane nanoparticles for targeted photodynamic therapy of breast cancer

Chlorin e6 (Ce6), with its high phototoxic potential, has wide applications in photodynamic therapy (PDT) for many human diseases. However, poor cancer cell localization of Ce6 has limited its direct application for PDT. Here, we developed cancer-targeting peptide p 18-4/chlorin e6 (Ce6)-conjugated polyhedral oligomeric silsesquioxane (PPC) nanoparticles for improving the targeting ability of Ce6 to breast cancer cells, thereby enhancing PDT efficacy. The synthesized PPC nanoparticles exhibited a spherical shape with an average diameter of 127.2 ± 11.3 nm in aqueous solution. Compared with free Ce6, the immobilization of p 18-4 enhanced the in vitro cellular uptake and targeting ability of PPC nanoparticles in breast cancer cell line MDA-MB-231. In addition, the intracellular uptake of PPC nanoparticles in MDA-MB-231 cells was dramatically increased compared with other cancer cells, indicating an obvious targeting ability of PPC nanoparticles on breast cancer cells. Upon light irradiation, PPC nanoparticles revealed significantly improved phototoxicity to MDA-MB-231 cells, mainly due to apoptotic cell death. In vivo PDT study suggested that PPC nanoparticles exhibited increased retention in tumor tissues and effectively inhibited the growth of MDA-MB-231 tumors in a target-specific manner. Overall, these results indicate that PPC nanoparticles are highly effective PDT agents for breast cancer therapy.

Self-Assembly and Applications of Amphiphilic Hybrid POSS Copolymers

Understanding the mechanism of molecular self-assembly to form well-organized nanostructures is essential in the field of supramolecular chemistry. Particularly, amphiphilic copolymers incorporated with polyhedral oligomeric silsesquioxanes (POSSs) have been one of the most promising materials in material science, engineering, and biomedical fields. In this review, new ideas and research works which have been carried out over the last several years in this relatively new area with a main focus on their mechanism in self-assembly and applications are discussed. In addition, insights into the unique role of POSSs in synthesis, microphase separation, and confined size were encompassed. Finally, perspectives and challenges related to the further advancement of POSS-based amphiphilics are discussed, followed by the proposed design considerations to address the challenges that we may face in the future.

Self-Assembly Behavior and pH-Stimuli-Responsive Property of POSS-Based Amphiphilic Block Copolymers in Solution

Stimuli-responsive polymeric systems containing special responsive moieties can undergo alteration of chemical structures and physical properties in response to external stimulus. We synthesized a hybrid amphiphilic block copolymer containing methoxy polyethylene glycol (MePEG), methacrylate isobutyl polyhedral oligomeric silsesquioxane (MAPOSS) and 2-(diisopropylamino)ethyl methacrylate (DPA) named MePEG-b-P(MAPOSS-co-DPA) via atom transfer radical polymerization (ATRP). Spherical micelles with a core-shell structure were obtained by a self-assembly process based on MePEG-b-P(MAPOSS-co-DPA), which showed a pH-responsive property. The influence of hydrophobic chain length on the self-assembly behavior was also studied. The pyrene release properties of micelles and their ability of antifouling were further studied.