Validation by Magnetic Resonance Imaging of the Diagnostic Potential of a Heptapeptide-Functionalized Imaging Probe Targeted to Amyloid-β and Able to Cross the Blood-Brain Barrier

Abstract

The diagnosis of Alzheimer's disease (AD) is a critical step in the management of patients. We have developed a non-invasive diagnosis tool based on magnetic resonance molecular imaging (MRMI) of amyloid-β peptide using ultra-small particles of iron oxide (USPIO) functionalized with a disulfide constrained cyclic heptapeptide (PHO) identified by phage display (USPIO-PHO). After previously demonstrating the optimal pharmacologic properties of USPIO-PHO and its capacity to cross the blood-brain barrier (BBB), the ability of USPIO-PHO to target amyloid plaques (AP) by MRMI has been validated in the present work on AD transgenic mice. The immunohistochemistry and immunofluorescent detection of USPIO-PHO on brain sections collected after in vivo MRMI studies enabled its colocalization with AP, confirming the BBB passage and specific targeting. The AP targeting by USPIO-PHO has been moreover corroborated by the good correlation between the number of AP detected with anti-amyloid β antibody and Perls'-DAB staining. Finally, the crossing mechanism of USPIO-PHO through the BBB was elucidated, revealing the involvement of non-degradation pathway of caveolae, while the control contrast agent USPIO-PEG was not endocytosed by the human brain endothelial cells.

Application of Iron Oxide Nanoparticles in the Diagnosis and Treatment of Neurodegenerative Diseases With Emphasis on Alzheimer’s Disease

“…The colocalization of USPIO-PHO with amyloid plaques on brain sections was demonstrated by immunohistochemistry and immunofluorescent experiment (André et al, 2017). Moreover, the amount of amyloid plaques detected by USPIO-PHO was in good correlation with that of plaques detected with anti-amyloid β antibody and Perls'-DAB staining (André et al, 2017).…”

“…Based on magnetic resonance molecular imaging (MRMI), ultrasmall particles of iron oxide (USPIO) functionalized with a disulfide constrained cyclic heptapeptide (PHO) was able to target Aβ plaques and cross the BBB in AD transgenic mice (André et al, 2017). The colocalization of USPIO-PHO with amyloid plaques on brain sections was demonstrated by immunohistochemistry and immunofluorescent experiment (André et al, 2017). Moreover, the amount of amyloid plaques detected by USPIO-PHO was in good correlation with that of plaques detected with anti-amyloid β antibody and Perls'-DAB staining (André et al, 2017).…”

Magnetic Nanoparticles Applications for Amyloidosis Study and Detection: A Review

“…This important aspect needs to be taken into account from the beginning of the development of these targeted MNPs. A large variety of SPIONs has been designed for MRI because they present a certain efficiency to cross the BBB and act as promising in vivo contrast agents [ 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 ]. On AD mice models, Anti-AβPP antibodies-coated SPIONS doubled the number of MRI-visible plaques with suggested spontaneous crossing of the BBB [ 94 ].…”

“…Poduslo et al shows specific dark spots on T 2 *-weighted images located in cortical arterioles thanks to monoclonal antibody IgG4.1-targeted MIONS [ 72 ]. Some other iron oxide NPs grafted with peptides having a hydrophobic character and selected through a library of small peptides, termed USPIO-PHO, remain a high contrast tool for transgenic mice using T 2 -weighted MRI sequences [ 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 ]. MNPs grafted with the polyphenolic curcumin, and stabilized by an amphiphilic copolymer, have shown great detection of amyloid deposits in ex vivo brain scanned by T 2 *-weighted MRI [ 39 ].…”

“…Some, i.e., AGuIX ® , show high r 1 relaxivity due to their high paramagnetism [ 103 ], stability, and clearance from the body [ 104 ]. Regarding AD and cerebral amyloid angiopathy, the combination of Gd-based NPs with several targeting molecules, i.e., PIB, polyphenols, peptides, and antibodies, remains the common strategy [ 98 , 104 , 105 , 106 , 107 , 108 ]. Most of these works attempt to prove the in vivo concept, but the concept also needs ex vivo confirmation.…”