PEGylated iridium-based nano-micelle: Self-assembly, selective tumor fluorescence imaging and photodynamic therapy

Poly(ethylene glycol) (PEG) as a key role can significantly affect the bio-application of imaging sensors or drugs. In this study, iridium (Ir) complexes decorated with PEG chain from 600 Da to 4000 Da were synthesized. Four amphiphilic Ir-based molecules could self-assemble to form micellar nanoparticles (IP600 NPs-IP4000 NPs). TEM results revealed that the size decreased from 76 to 34 nm with the increased PEG length, and the micellar stability increased with longer PEG length. The longer blood circulation time of IP2000 NPs and IP4000 NPs could be ascribed to the decreased serum protein adsorption in theoretically and experimentally. Fluorescence imaging study further exhibited selective tumor accumulation enhancement. Cell fluorescence imaging results revealed that cellular uptake decreased with the PEG length increase. Take multi-factors into consideration, PEG (2000 Da) is suitable for decorating a small molecule. Photodynamic therapy study also exhibited that IP2000 NPs qualified higher therapeutic effect. Biosafety study uncovered the excellent biocompatibility of IP2000 and IP4000 NPs. Our study not only proved that 2000 Da PEG is suitable for the PEGylation of small molecules to fabricate micellar nanoparticles but also supplied a self-assembled strategy for constructing a metabolizable fluorescence-imaging nano-sensors and drug delivery system.