Development of novel radiolabeled antibody-conjugated graphene quantum dots for targeted in vivo breast cancer imaging and biodistribution studies

Nanotechnology-based drug delivery platforms have emerged as one of the promising approaches for the diagnosis and treatment of cancers. Furthermore, significant advancements have been achieved in the development of nanoparticle-antibody conjugates for applications in tumor imaging and immunoassays. Without a doubt, the diagnostic insight garnered from these nanoprobes will prove invaluable in determining rational therapeutic strategies. In the current experiment, we developed a breast cancer imaging probe utilizing graphene quantum dots, these quantum dots were conjugated with pembrolizumab (GQDs–pembrolizumab), a human monoclonal antibody (mAb) targeting the immune checkpoint programmed death receptor (PD-1) and its programmed death ligand-1 (PD-L1). Various techniques were employed for characterization, encompassing transmission electron microscopy (TEM), element mapping, atomic force microscopy (AFM), Fourier-transform infrared spectroscopy, and circular dichroism (CD) spectroscopy. The toxicity of nanoconjugate was evaluated using the MTT assay on HEK-293 and 4T1 cell lines. Subsequently, the synthesized nanoconjugate was radiolabeled with Technetium-99m (99mTc) to produce 99mTc-GQDs–pembrolizumab. Biodistribution and SPECT imaging were conducted to assess the pharmacokinetics and targeting efficacy of the 99mTc-GQDs–pembrolizumab in a BALB/c mouse model bearing with 4T1 tumors. The high Radiochemical purity (RCP > 95 %) and satisfactory in vitro stability demonstrate the significant potential of GQDs–pembrolizumab to form complexes with Technetium-99m. The findings from imaging and biodistribution studies demonstrated the high activity of 99mTc-GQDs–pembrolizumab at the tumor site (8.4 %ID/g), attributed to the presence of the PD-1 receptor. Furthermore, the increased radiotracer uptake was evident in the liver and spleen, both being lymphoid tissues. The suitable properties and behavior of 99mTc-GQDs–pembrolizumab suggest that it holds promise as a novel probe for the development of radiopharmaceutical-based immune checkpoint monoclonal antibodies. Additionally, it has the potential to facilitate immunotherapy for treating a wide range of cancers.