Assembly of Photochromic Molecules into Multiple Stimuli-Responsive Hollow Microparticles via Templating Coordination

Abstract

Supramolecular multifunctional metal-organic networks offer immense potential in drug delivery, bioimaging, catalysis, and therapeutics. However, the creation of multiple stimuli-responsive fluorescent hollow nano/microparticles is a formidable challenge in this field. In this study, a novel strategy is reported for synthesizing photochromic hollow microparticles that exhibit responsiveness to light, pH, and glutathione (GSH). With the assistance of templating coordination from zeolitic imidazolate framework-8 microparticles, bisphosphonate-merocyanine ligands are successfully assembled to create hollow bisphosphonate-spiropyran (BPSP)-Zn2+ microparticles. The photochromic and pH responses stem from the reversible conversion between spiropyran and zwitterionic merocyanine components and between merocyanine and protonated merocyanine, respectively. The GSH response is attributed to the stronger affinity of Zn2+ to thiol groups than to phosphonate groups. These remarkable features render the hollow BPSP-Zn2+ microparticles highly suitable for applications in stimulus-triggered drug delivery, and these findings provide a platform for developing innovative materials that have the potential to transform the biomedical field. The synthesis of multiple stimuli-responsive fluorescent hollow nano/microparticles by templating coordination is reported. With this strategy, bisphosphonate-merocyanine ligands are successfully assembled to hollow bisphosphonate-spiropyran (BPSP)-Zn2+ microparticles that exhibit responsiveness to light, pH, and glutathione. These remarkable features render the hollow BPSP-Zn2+ microparticles to show high promise in the field of stimulus-triggered drug delivery.image