Different conjugates of Fe₃O₄ nanoparticles, drug, and dye: optical and magnetic properties for <i>in vivo</i> bimodal imaging

Bioimaging is very important in medicine, especially in cancer diagnosis and treatment. In this study, we determined the impact of different components on the optical and magnetic properties of various conjugates. The three components, <i>i.e.</i>, Fe₃O₄ nanoparticles (NPs), drug (doxorubicin - Dox), and dye (Cyanine 5.5 - Cy 5.5), were incorporated to form the four conjugates of A1 (Fe₃O₄-Cy 5.5), A2 (Fe₃O₄-Dox), A3 (Fe₃O₄-Cy 5.5-Dox), and A4 (Cy 5.5-Dox). The conjugates were characterized by DLS, UV-Vis spectra, fluorescence spectra, VSM, XRD, and TEM methods. After that, <i>in vitro</i> near-infrared (NIR) fluorescence imaging and magnetic resonance imaging (MRI) experiments were carried out to determine the conjugate suitable for bimodal imaging. The results show that A3 exhibits the highest quantum yield and radiance ratio and also has the highest ratio of <i>r</i> ₂/<i>r</i> ₁. The <i>in vivo</i> MRI and NIR fluorescent imaging results of CT26-bearing mice injected with A3 conjugates prove that the conjugate has potential in bimodal cancer imaging applications.