Affiliation: | 1. ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia Department of Chemistry, The University of Adelaide, Adelaide, South Australia, 5005 Australia;2. ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia;3. ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia Department of Physiology, Adelaide Medical School, The University of Adelaide, South Australia, Australia;4. The Robinson Research Institute, Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005 Australia;5. ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia CNBP, School of Science, RMIT University, Melbourne, Victoria, 3001 Australia |
Abstract: | A new spiropyran-based stimuli-responsive delivery system is fabricated. It encapsulates and then releases an extraneous compound in response to elevated levels of Zn2+, a critical factor in cell apoptosis. A C12-alkyl substituent on the spiropyran promotes self-assembly into a micelle-like nanocarrier in aqueous media, with nanoprecipitation and encapsulation of added payload. Zn2+ binding occurs to an appended bis(2-pyridylmethyl)amine group at biologically relevant micromolar concentration. This leads to switching of the spiropyran (SP) isomer to the strongly fluorescent ring opened merocyanine-Zn2+ (MC-Zn2+) complex, with associated expansion of the nanocarriers to release the encapsulated payload. Payload release is demonstrated in solution and in HEK293 cells by encapsulation of a blue fluorophore, 7-hydroxycoumarin, and monitoring its release using fluorescence spectroscopy and microscopy. Furthermore, the use of the nanocarriers to deliver a caspase inhibitor, Azure B, into apoptotic cells in response to an elevated Zn2+ concentration is demonstrated. This then inhibits intracellular caspase activity, as evidenced by confocal microscopy and in real-time by time-lapsed microscopy. Finally, the nanocarriers are shown to release an encapsulated proteasome inhibitor ( 5 ) in Zn2+-treated breast carcinoma cell line models. This then inhibits intracellular proteasome and induces cytotoxicity to the carcinoma cells. |