Construction of self-assembled nanogel as mulitenzyme mimics for bioresponsive tandem-catalysis imaging

Abstract

The self-assembled phospholipid- or cytosol-associated multienzyme complexes constitute necessary components of the foundation of life. As a proof of concept, metal-coordinated supramolecular nanogels (MCSGs) have been designed, with the self-assembly of di-lysine coordinated iron (Fe(Lys)2)-functionalized peptide gelators on the interface by an in situ amidation-induced protonation process. The monoatomic and highly dispersed active centers of Fe(Lys)2 offered the nanogel mimics with excellent reaction rates due to the high density and nano compartmental structure similar to the natural matrix-associated multienzyme complex. SiO2@MCSGs show both superoxide dismutase (SOD) activity and peroxidase (POD) activity, and the higher activities compared with the activity of free Fe(Lys)2 molecules can be detected. After loading the substrate 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), SiO2@MCSGsABTS can responsively convert O2− · in the tumor microenvironment into H2O2 intermediates and then tandem catalyzed the oxidization of ABTS for contrast photoacoustic (PA) imaging of tumor by the SOD-POD mimic activity, showing their great potential as the efficient enzymatic agents for pathological theranostics.