Dual-Functionality PAR@HP-NU-66 Nanoplatforms for Colorimetric Sensing and Adsorption of Cu2+ Ions for Theranostics Application

Abstract The maintenance of human physiological homeostasis is crucial for public health, as the abnormal accumulation of Cu2+ ions in the body can lead to severe physiological damage. However, achieving both convenient, reliable detection and efficient removal of excess Cu2+ ions in vivo remains a challenge. Herein, a series of PAR@HP-NU-66 nanocomposites are synthesized by postgrafting 4-(2-pyridylazo)resorcinol (PAR) onto HP-NU-66 frameworks for selective Cu2+ ion detection and elimination. As a tridentate chromogenic ligand, PAR forms stable Cu2+ chelates via metal-to-ligand charge transfer, inducing a spectral red shift and a visible color change. This property enables PAR@HP-NU-66 nanocomposite to colorimetrically detect Cu2+ ions at a low limit of 0.25 mg L–1 in aqueous solutions, which is below normal physiological levels. The nanocomposite exhibits outstanding anti-interference performance against high-concentration coexisting metal cations, amino acids, proteins and other endogenous biomolecules; even under excess physiological interferents, its colorimetric signal retention exceeds 90%. Moreover, a smartphone-assisted colorimetric platform was developed to facilitate the rapid, on-site, and quantitative detection of Cu2+ ions. Meanwhile, the nanocomposite achieved a superior adsorption capacity of up to 577.6 mg of Cu2+ per gram of PAR@HP-NU-66, outperforming most previously reported metal–organic framework (MOF)-based adsorbents. In vivo murine therapeutic assays on copper-overload models confirm that PAR@HP-NU-66 reduces serum Cu2+ levels by 41% with minimal histopathological effects on tissues and organs. Density functional theory (DFT) calculations confirm that the functionalization of HP-NU-66 with PAR introduces electron-rich regions and dual synergistic chelation sites, thereby boosting the adsorption capacity and eliciting a distinct colorimetric response. These results highlight a promising dual-functional material for Cu2+ ion detection and removal, with great potential for clinical diagnosis and treatment of Cu2+ overload diseases.