Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles

Abstract

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum(II) supramolecular triangles (1 and 2) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC₅₀ of 6.41 and 2.11 μM). The characteristic ∼570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for 1 and 2, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt(II) polypyridyl fragment swapped for Pt(II) phosphine, the activity may be optimized without a total redesign of the system.