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

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. SiO 2 @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), SiO 2 @MCSGs ABTS can responsively convert O 2 − · in the tumor microenvironment into H 2 O 2 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.