Multifunctional quantum dot-decorated drug-loaded magnetite nanosystem for dual optical-magnetic resonance imaging and drug delivery

Early detection of cancer plays a significant role in the effective prognosis, treatment regimen planning, and patient recovery. The aim of this study was to combine a near-infrared (NIR) contrast agent, a magnetic resonance imaging (MRI) contrast agent and a therapeutic agent in an all-in-one nanosystem. In particular, owing to their excellent properties, Fe₃O₄ magnetic nanoparticles (an MRI contrast agent), CdTe quantum dots (an NIR optical fluorescence agent), and curcumin (an anticancer drug) were incorporated in the nanosystem using carboxymethyl chitosan as the coating polymer. The nanosystem was characterized using DLS, zeta potential analysis, Fourier transform infrared spectroscopy, fluorescence spectroscopy, EDX analysis and TEM analysis. The nanoparticles exhibited average sizes ranging from 100 nm to 170 nm in DI water, PBS and DMEM, with zeta potential in the range of -40 to -64 mV, indicating good stability. The nanoplatform demonstrated potential as a positive MRI contrast agent, exhibiting an <i>r</i> ₂ relaxivity of 78.33 mM^-1 s^-1 and an <i>r</i> ₂/<i>r</i> ₁ ratio of 470.95 ± 15.11 at 7 T, attributed to second-sphere water interactions. The multifunctional nanoplatform showed great <i>in vitro</i> stability and drug encapsulation over two-month period. The MR and NIR optical imaging efficiencies were evaluated <i>in vitro</i> and <i>in vivo</i> on CT26-bearing mice. The <i>ex vivo</i> signal acquisition was also studied for the tumor, liver, spleen, lung and kidney in the mouse model. Results demonstrated the potential of the prepared multifunctional nanosystem in dual optical MR imaging and passive drug delivery applications.