Paramagnetic albumin decorated CuInS₂/ZnS QDs for CD133⁺ glioma bimodal MR/fluorescence targeted imaging

Glioma stem cells (GSCs) are considered the key to the occurrence, development, invasion, recurrence and sensitivity to treatment of brain tumors. Precise molecular imaging of GSCs by means of probes in vivo has therefore become a premise of solving the above problems. Herein, a sensitive, specific, accurate and biocompatible molecular nanoprobe is reported with MR/fluorescence imaging modalities for CD133⁺ glioma tumor bimodal targeted imaging. Cd-free high quality CuInS₂/ZnS core/shell quantum dots (QDs) were synthesized for fluorescence imaging; DTPA-coupled BSA with Gd³⁺ chelation (BSA-DTPA^Gd) were prepared and used both for phase transfer of hydrophobic CuInS₂/ZnS QDs and MR imaging modality. The resulting hydrophilic paramagnetic QDs (pQDs) were then linked with anti-CD133 monoclonal antibody, pQDs-CD133mAb denoting the framework of the entire molecular probe, for tumor targeting. The obtained pQDs-CD133mAb has a proper size (ca. 45 nm) and good colloidal stability. It exhibits a high quality fluorescent emission (ca. 630 nm) together with high longitudinal relaxivity (r₁ = 15.2 mM^-1 s^-1) compared with that of commercial Magnevist (r₁ = 3.12 mM^-1 s^-1). Dual modal imaging in vitro and in vivo shows potent tumor enhancement with administration of pQDs-CD133mAb. A biodistribution study indicates hepatobiliary and renal processing of pQDs-CD133mAb with no obvious toxicity. It could be therefore concluded, with a dual-modal imaging and targeting strategy, pQDs-CD133mAb presents a great potential as an alternative for accurate diagnosis of glioma.