An insight into fluorescence and magnetic resonance bioimaging using a multifunctional polyethyleneimine-passivated...

A nanoassembly of PEI-passivated Gd@CDs, a type of aptamer, is presented which was designed and characterized in order to target specific cancer cells based on their recognition of the receptor nucleolin (NCL), which is overexpressed on the cell membrane of breast cancer cells for fluorescence and magnetic resonance imaging and treatment. Using hydrothermal methods, Gd-doped nanostructures were synthesized, then modified by a two-step chemical procedure for subsequent applications: the passivating of Gd@CDs with branched polyethyleneimine (PEI) (to form Gd@CDs-PEI1 and Gd@CDs-PEI2), and using AS1411 aptamer (AS) as a DNA-targeted molecule (to generate AS/Gd@CDs-PEI1 and AS/Gd@CDs-PEI2). Consequently, these nanoassemblies were constructed as a result of electrostatic interactions between cationic Gd@CDs-passivated PEI and AS aptamers, offering efficient multimodal targeting nanoassemblies for cancer cell detection. It has been demonstrated through in vitro studies that both types of AS-conjugated nanoassemblies are highly biocompatible, have high cellular uptake efficiency (equivalent concentration of AS: 0.25 μΜ), and enable targeted fluorescence imaging in nucleolin-positive MCF7 and MDA-MB-231 cancer cells compared to MCF10-A normal cells. Importantly, the as-prepared Gd@CDs, Gd@CDs-PEI1, and Gd@CDs-PEI2 exhibit higher longitudinal relaxivity values (r₁) compared with the commercial Gd-DTPA, equal to 5.212, 7.488, and 5.667 mM^-1s^-1, respectively. Accordingly, it is concluded that the prepared nanoassemblies have the potential to become excellent candidates for cancer targeting and fluorescence/MR imaging agents, which can be applied to cancer imaging and personalized nanomedicine.