Herein we developed a new “smart” Gd-based MR contrast agent (i.e., 1) which is susceptive to furin, a protease overexpressed in tumor. Under the action of furin, 1 condenses to form dimers (1-Ds) and the latter self-assemble into gadolinium nanparticles (Gd-NPs). Relaxivity of 1-D is more than 2 folds of those of 1 and magnevist at 1.5 T, and 1.4 folds of that of 1 at 3 T. Intracellular condensation of 1 in furin-overexpressed MDA-MB-468 cells was proven with direct two-photon laser microscopy (TPLM) fluorescence imaging of the cells incubated with the europium analog of 1 (i.e., 2). Intracellular Gd-NPs of 1 were uncovered and characterized for the first time. MRI of MDA-MB-468 tumors showed that 1 has enhanced MR contrast within the tumors than that of its scrambled control 1-Scr.

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In this study, oligo(ethylene glycol) (OEG)-based thermoresponsive molecularly imprinted polymers (MIPs) for lysozyme on the surface of magnetic nanoparticles were synthesized. Thermoresponsive monomer 2-(2-methoxyethoxy)ethyl methacrylate, chelate monomer N-(4-vinyl)-benzyl iminodiacetic acid, and acidic monomer methacrylic acid were selected as the ingredients for preparing the MIP layer. The thermoresponsive behavior of the novel imprinted magnetic nanoparticles was evaluated by dynamic light scattering and swelling ratios measurements. Interestingly, in analysis of lysozyme, the capture/release process could be modulated by changing the temperature, avoiding tedious washing steps. Meanwhile, high adsorption capacity (204.1 mg/g) and good selectivity for capturing lysozyme were achieved. Additionally, surface imprinting with magnetic nanoparticles as substrate allowed for short adsorption time (2 h) and rapid magnetic separation. Furthermore, the proposed imprinted magnetic nanoparticles were used to selectively extract lysozyme in human urine with recoveries ranging from 89.2% to 97.3%. The results indicated that the OEG-based monomers are promising for responsive MIP preparation, and the proposed imprinted material is efficient for thermally modulated capture and release of target protein.