Engineering theranostic nanovehicles capable of targeting cerebrovascular amyloid deposits

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid beta (Aβ) proteins within the walls of the cerebral vasculature with subsequent aggressive vascular inflammation leading to recurrent hemorrhagic strokes. The objective of the study was to develop theranostic nanovehicles (TNVs) capable of a) targeting cerebrovascular amyloid; b) providing magnetic resonance imaging (MRI) contrast for the early detection of CAA; and c) treating cerebrovascular inflammation resulting from CAA. The TNVs comprised of a polymeric nanocore made from Magnevist (MRI contrast agent) conjugated chitosan. The nanocore was also loaded with cyclophosphamide (CYC), an immunosuppressant shown to reduce the cerebrovascular inflammation in CAA. Putrescine modified F(ab')2 fragment of anti-amyloid antibody, IgG4.1 (pF(ab')24.1) was conjugated to the surface of the nanocore to target cerebrovascular amyloid. The average size of the control chitosan nanoparticles (conjugated with albumin and are devoid of Magnevist, CYC, and pF(ab')24.1) was 164±1.2 nm and that of the TNVs was 239±4.1 nm. The zeta potential values of the CCNs and TNVs were 21.6±1.7 mV and 11.9±0.5 mV, respectively. The leakage of Magnevist from the TNVs was a modest 0.2% over 4 days, and the CYC release from the TNVs followed Higuchi's model that describes sustained drug release from polymeric matrices. The studies conducted in polarized human microvascular endothelial cell monolayers (hCMEC/D3) in vitro as well as in mice in vivo have demonstrated the ability of TNVs to target cerebrovascular amyloid. In addition, the TNVs provided contrast for imaging cerebrovascular amyloid using MRI and single photon emission computed tomography. Moreover, the TNVs were shown to reduce pro-inflammatory cytokine production by the Aβ challenged blood brain barrier (BBB) endothelium more effectively than the cyclophosphamide alone.

Multimodal nanoprobes to target cerebrovascular amyloid in Alzheimer's disease brain

Cerebral amyloid angiopathy (CAA) results from the accumulation of Aβ proteins primarily within the media and adventitia of small arteries and capillaries of the cortex and leptomeninges. CAA affects a majority of Alzheimer's disease (AD) patients and is associated with a rapid decline in cognitive reserve. Unfortunately, there is no pre-mortem diagnosis available for CAA. Furthermore, treatment options are few and relatively ineffective. To combat this issue, we have designed nanovehicles (nanoparticles-IgG4.1) capable of targeting cerebrovascular amyloid (CVA) and serving as early diagnostic and therapeutic agents. These nanovehicles were loaded with Gadolinium (Gd) based (Magnevist(®)) magnetic resonance imaging contrast agents or single photon emission computed tomography (SPECT) agents, such as (125)I. In addition, the nanovehicles carry either anti-inflammatory and anti-amyloidogenic agents such as curcumin or immunosuppressants such as dexamethasone, which were previously shown to reduce cerebrovascular inflammation. Owing to the anti-amyloid antibody (IgG4.1) grafted on the surface, the nanovehicles are capable of specifically targeting CVA deposits. The nanovehicles effectively marginate from the blood flow to the vascular wall as determined by using quartz crystal microbalance with dissipation monitoring (QCM-D) technology. They demonstrate excellent distribution to the brain vasculature and target CVA, thus providing MRI and SPECT contrast specific to the CVA in the brain. In addition, they also display the potential to carry therapeutic agents to reduce cerebrovascular inflammation associated with CAA, which is believed to trigger hemorrhage in CAA patients.

Chitosan enhances the stability and targeting of immuno-nanovehicles to cerebro-vascular deposits of Alzheimer's disease amyloid protein

Alzheimer's disease amyloid β (Aβ) proteins accumulate in the cerebral vasculature and cause cerebral amyloid angiopathy (CAA). The objective of this study was to resolve critical formulation issues in developing nanoparticles (NPs) capable of permeating the blood brain barrier (BBB) and targeting cerebrovascular Aβ proteins. To achieve this objective we designed immuno-nanovehicles, which are chitosan-coated poly lactic-co-glycolic acid (PLGA) NPs conjugated with a novel anti-Aβ antibody. Measurements made according to Derjaguin-Landau-Verwey-Overbeek (DLVO) theory indicated that the immuno-nanovehicles have a much lower propensity to aggregate than the control nanovehicles. Immuno-nanovehicles showed enhanced uptake at the BBB and better targeting of the Aβ proteins deposited in the CAA model in vitro in comparison with the control nanovehicles. In addition, chitosan enhanced aqueous dispersibility and increased the stability of immuno-nanovehicles during lyophilization, thus transforming them into ideal vehicles for delivering therapeutic and diagnostic agents to the cerebral vasculature ridden with vascular amyloid.

FROM THE CLINICAL EDITOR

In this study, the authors report the development of chitosan-coated PLGA nanoparticles conjugated with anti-amyloid antibody to be used as immuno-nanovehicles to image cerebral amyloid angiopathy deposits in vivo. This method enables delivering therapeutic and diagnostic agents to the cerebral vasculature ridden with vascular amyloid.