Non-specific surface adsorption of bio-macromolecules (e.g. proteins) on nanoparticles, known as biofouling, and the uptake of nanoparticles by the mononuclear phagocyte system (MPS) and reticuloendothelial system (RES) lead to substantial reduction in the efficiency of target-directed imaging and delivery in biomedical applications of engineered nanomaterials in vitro and in vivo. In this work, a novel copolymer consisting of blocks of poly ethylene glycol and allyl glycidyl ether (PEG-b-AGE) was developed for coating magnetic iron oxide nanoparticles (IONPs) to reduce non-specific protein adhesion that leads to formation of “protein corona” and uptake by macrophages. The facile surface functionalization was demonstrated by using targeting ligands of a small peptide of RGD or a whole protein of transferrin (Tf). The PEG-b-AGE coated IONPs exhibited anti-biofouling properties with significantly reduced protein corona formation and non-specific uptake by macrophages before and after the surface functionalization, thus improving targeting of RGD-conjugated PEG-b-AGE coated IONPs to integrins in U87MG glioblastoma and MDA-MB-231 breast cancer cells that overexpress αvβ3 integrins, and Tf-conjugated PEG-b-AGE coated IONPs to transferrin receptor (TfR) in D556 and Daoy medulloblastoma cancer cells with high overexpression of transferrin receptor, compared to respective control cell lines. Magnetic resonance imaging (MRI) of cancer cells treated with targeted IONPs with or without anti-biofouling PEG-b-AGE coating polymers demonstrated the target specific MRI contrast change using anti-biofouling PEG-b-AGE coated IONP with minimal off-targeted background compared to the IONPs without anti-biofouling coating, promising the highly efficient active targeting of nanoparticle imaging probes and drug delivery systems and potential applications of imaging quantification of targeted biomarkers.

As an emerging zero-dimensional nanomaterial, MXene quantum dots (MQDs) have aroused the interest of researchers because of their unique physical and chemical characteristics. Here, a straightforward hydrothermal strategy was used to successfully produce the amino-functionalized Ti 3 C 2 MQDs. The functionalized Ti 3 C 2 MQDs exhibited bright blue fluorescence (FL), which was derived from its size effect and surface defects. In addition, Ni 2+ can bind to the amino groups on the surface of Ti 3 C 2 MQDs. The absorption of the excitation light by the light-absorbing substance causes nickel ions to effectively quench the photoluminescence of Ti 3 C 2 MQDs, which can be explained by the internal filter effect (IFE). At the same time, the strong affinity of histidine (His) for Ni 2+ , which is absorbed by His to form a stable complex, causes Ni 2+ to dissociate from the Ti 3 C 2 MQD surface and restore the FL. Thus, a fluorescent sensor for detecting the His content in serum was developed. Overall, this work provides a method for the detection of His and shows that the Ti 3 C 2 MQDs have great potential in biomedical and biosensing applications.

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