Tetraphenylethene-based highly emissive metallacage as a component of theranostic supramolecular nanoparticles

A theranostic agent combines diagnostic reporter with therapeutic activity in a single entity, an approach that seeks to increase the efficacy of cancer treatment. Herein, we describe the synthesis of a highly emissive tetraphenylethene-based metallacage using multicomponent coordination-driven self-assembly that exhibits a coordination-triggered aggregation-induced emission (AIE) enhancement. The formation of metallacage-loaded nanoparticles (MNPs) occurs when the assembly is treated with two variants of a 1,2-distearoyl-phosphatidylethanolamine (DSPE)/polyethylene glycol (PEG) conjugate, mPEG-DSPE, and biotin-PEG-DSPE. This combination endows the resultant MNPs with excellent stability and targeting ability, specifically enabling selective delivery of the metallacages to cancer cells that overexpress biotin receptors via receptor-mediated endocytosis. Although the mechanism of activity is based on existing Pt(II) anticancer drugs such as oxaliplatin, carboplatin, and cisplatin, in vitro and in vivo studies indicate that the MNPs are more active and show low systemic activity while also possessing emissive properties that allow for fluorescence-based imaging. This pioneering example of a metallacage that combines biologically active components with AIE imaging establishes supra-molecular coordination complexes imbedded within nanoparticles as a promising potential theranostic platform for cancer treatment.