Transferrin-conjugated quasi-cubic SPIONs for cellular receptor profiling and detection of brain cancer

The high biocompatibility, unique magnetic properties and significant biomedical potential of superparamagnetic iron oxide nanoparticles (SPIONs) have spurred a major interest in developing new strategies to synthesise aqueous-phase dispersible SPIONs. In parallel, the rapidly growing field of enzyme-mimicking catalytic nanomaterials, referred to as NanoZymes, has seen immense interest in utilising the unique properties of NanoZymes for new applications. Here, we report a new strategy for the large-scale synthesis of water dispersible quasi-cubic γ-Fe2O3 SPIONs. This strategy provides a unique way to control the morphological characteristics of SPIONs through the in-situ formation of sodium oleate complex. Notably, our approach eliminates the need for high temperatures, complex cleaning protocols and post-synthesis phase-transfer strategies that are typically required during the well-established thermal decomposition synthesis approaches. We further establish the peroxidase-mimic NanoZyme activity of these quasi-cubic SPIONs and use them as an effective transducer platform to generate a unique colour through efficient oxidation of peroxidase substrates. By combining these inorganic enzymes with transferrin (Tf) as a brain cancer-specific targeting agent, we create a simple yet effective colorimetric biosensing platform that allows us to monitor the cellular expression profile of transferrin receptors (TfR). The difference in the expression profile of TfR in the U87MG glioblastoma cells and the fibroblast cells generates a distinct tonality of the colorimetric response. This not only allows cell surface receptor profiling but also allows robust identification of brain cancer cells. The high accuracy and precision of the proposed biosensor outlines the robustness of the NanoZyme-based catalysts in colorimetric detection of various targets.