Antibody-conjugated, dual-modal, near-infrared fluorescent iron oxide nanoparticles for antiamyloidgenic activity and specific detection of amyloid-ß fibrils.

Amyloid-ß (Aß) peptide is the main fibrillar component of plaque deposits found in brains affected by Alzheimer's disease (AD) and is related to the pathogenesis of AD. Passive anti-Aß immunotherapy has emerged as a promising approach for the therapy of AD, based on the administration of specific anti-Aß monoclonal antibodies (aAßmAbs) to delay Aß aggregation in the brain. However, the main disadvantage of this approach is the required readministration of the aAßmAbs at frequent intervals. There are only a few reports describing in vitro study for the immobilization of aAßmAbs to nanoparticles as potential targeting agents of Aß aggregates. In this article, we report the immobilization of the aAßmAb clone BAM10 to near-infrared fluorescent maghemite nanoparticles for the inhibition of Aß40 fibrillation kinetics and the specific detection of Aß40 fibrils. The BAM10-conjugated iron oxide nanoparticles were well-characterized, including their immunogold labeling and cytotoxic effect on PC-12 (pheochromocytoma cell line). Indeed, these antibody-conjugated nanoparticles significantly inhibit the Aß40 fibrillation kinetics compared with the same concentration, or even five times higher, of the free BAM10. This inhibitory effect was confirmed by different assays such as the photo-induced crosslinking of unmodified proteins combined with sodium dodecyl sulfate- polyacrylamide gel electrophoresis. A cell viability assay also confirmed that these antibody-conjugated nanoparticles significantly reduced the Aß40-induced cytotoxicity to PC-12 cells. Furthermore, the selective labeling of the Aß40 fibrils with the BAM10-conjugated near-infrared fluorescent iron oxide nanoparticles enabled specific detection of Aß40 fibrils ex vivo by both magnetic resonance imaging and fluorescence imaging. This study highlights the immobilization of the aAßmAb to dual-modal nanoparticles as a potential approach for aAßmAb delivery, eliminating the issue of readministration, and contributes to the development of multifunctional agents for diagnosis and therapy of AD.