Nanoparticle-Assisted Diagnosis and Treatment for Abdominal Aortic Aneurysm

An abdominal aortic aneurysm (AAA) is a localized dilatation of the aorta related to the regional weakening of the wall structure, resulting in substantial morbidity and mortality with the aortic ruptures as complications. Ruptured AAA is a dramatic catastrophe, and aortic emergencies constitute one of the leading causes of acute death in older adults. AAA management has been centered on surgical repair of larger aneurysms to mitigate the risks of rupture, and curative early diagnosis and effective pharmacological treatments for this condition are still lacking. Nanoscience provided a possibility of more targeted imaging and drug delivery system. Multifunctional nanoparticles (NPs) may be modified with ligands or biomembranes to target agents' delivery to the lesion site, thus reducing systemic toxicity. Furthermore, NPs can improve drug solubility, circulation time, bioavailability, and efficacy after systemic administration. The varied judiciously engineered nano-biomaterials can exist stably in the blood vessels for a long time without being taken up by cells. Here, in this review, we focused on the NP application in the imaging and treatment of AAA. We hope to make an overview of NP-assisted diagnoses and therapy in AAA and discussed the potential of NP-assisted treatment.

A Nanoradiomics Approach for Differentiation of Tumors Based on Tumor-Associated Macrophage Burden

Objective

Tumor-associated macrophages (TAMs) within the tumor immune microenvironment (TiME) of solid tumors play an important role in treatment resistance and disease recurrence. The purpose of this study was to investigate if nanoradiomics (radiomic analysis of nanoparticle contrast-enhanced images) can differentiate tumors based on TAM burden.

Materials and Methods

In vivo studies were performed in transgenic mouse models of neuroblastoma with low (N = 11) and high (N = 10) tumor-associated macrophage (TAM) burden. Animals underwent delayed nanoparticle contrast-enhanced CT (n-CECT) imaging at 4 days after intravenous administration of liposomal-iodine agent (1.1 g/kg). CT imaging-derived conventional tumor metrics (tumor volume and CT attenuation) were computed for segmented tumor CT datasets. Nanoradiomic analysis was performed using a PyRadiomics workflow implemented in the quantitative image feature pipeline (QIFP) server containing 900 radiomic features (RFs). RF selection was performed under supervised machine learning using a nonparametric neighborhood component method. A 5-fold validation was performed using a set of linear and nonlinear classifiers for group separation. Statistical analysis was performed using the Kruskal-Wallis test.

Results

N-CECT imaging demonstrated heterogeneous patterns of signal enhancement in low and high TAM tumors. CT imaging-derived conventional tumor metrics showed no significant differences (p > 0.05) in tumor volume between low and high TAM tumors. Tumor CT attenuation was not significantly different (p > 0.05) between low and high TAM tumors. Machine learning-augmented nanoradiomic analysis revealed two RFs that differentiated (p < 0.002) low TAM and high TAM tumors. The RFs were used to build a linear classifier that demonstrated very high accuracy and further confirmed by 5-fold cross-validation.

Conclusions

Imaging-derived conventional tumor metrics were unable to differentiate tumors with varying TAM burden; however, nanoradiomic analysis revealed texture differences and enabled differentiation of low and high TAM tumors.

Early Detection of Aortic Degeneration in a Mouse Model of Sporadic Aortic Aneurysm and Dissection Using Nanoparticle Contrast-Enhanced Computed Tomography

[Figure: see text].

Recent progress on nanoparticles for targeted aneurysm treatment and imaging

An abdominal aortic aneurysm (AAA) is a localized dilatation of the aorta that plagues millions. Its rupture incurs high mortality rates (~80-90%), pressing an urgent need for therapeutic methods to prevent this deadly outcome. Judiciously designed nanoparticles (NPs) have displayed a unique potential to fulfill this need. Aneurysms feature excessive inflammation and extracellular matrix (ECM) degradation. As such, typically inflammatory cells and exposed ECM proteins have been targeted with NPs for therapeutic, diagnostic, or theranostic purposes in experimental models. NPs have been used not only for encapsulation and delivery of drugs and biomolecules in preclinical tests, but also for enhanced imaging to monitor aneurysm progression in patients. Moreover, they can be readily modified with various molecules to improve lesion targeting, detectability, biocompatibility, and circulation time. This review updates on the progress, limitations, and prospects of NP applications in the context of AAA.

Cell-Penetrating Peptide-Functionalized Persistent Luminescence Nanoparticles for Tracking J774A.1 Macrophages Homing to Inflamed Tissues

Recruitment of leukocytes exhibiting arguable and ambiguous processes is involved in the inflammatory response, a specific reaction of organisms to tissue damage. Tracking leukocytes is of great importance for understanding the recruitment of leukocytes. Here, we report the fabrication of carboxyl silane and TAT cell-penetrating peptide-functionalized near-infrared-emitting persistent luminescence nanoparticles (PLNP-TAT) with deep tissue penetration in bioimaging for autofluorescence-free tracking of J774A.1 macrophages homing to inflamed tissues. The PLNP-TAT enables effective labeling of the J774A.1 macrophages and the tracking of the migration of cells to the simulated endothelial inflammatory microenvironment in vitro. Moreover, the PLNP-TAT also allows the tracking of J774A.1 macrophages homing to inflamed tissues in vivo under discontinuous illumination with a red light-emitting diode light. The PLNP-TAT allows in vivo tracking of leukocytes without the need for conventional continuous excitation and offers great potential in cell-tracking and diagnostic applications without the autofluorescence background and thermal damages brought about by continuous excitation.

RGD targeting of human ferritin iron oxide nanoparticles enhances in vivo MRI of vascular inflammation and angiogenesis in experimental carotid disease and abdominal aortic aneurysm

Purpose

To evaluate Arg‐Gly‐Asp (RGD)‐conjugated human ferritin (HFn) iron oxide nanoparticles for in vivo magnetic resonance imaging (MRI) of vascular inflammation and angiogenesis in experimental carotid disease and abdominal aortic aneurysm (AAA).

Materials and Methods

HFn was genetically engineered to express the RGD peptide and Fe₃O₄ nanoparticles were chemically synthesized inside the engineered HFn (RGD‐HFn). Macrophage‐rich left carotid lesions were induced by ligation in FVB mice made hyperlipidemic and diabetic (n = 14), with the contralateral right carotid serving as control. Murine AAAs were created by continuous angiotensin II infusion in ApoE‐deficient mice (n = 12), while control mice underwent saline infusion (n = 8). All mice were imaged before and after intravenous injection with either RGD‐HFn‐Fe₃O₄ or HFn‐Fe₃O₄ using a gradient‐echo sequence on a whole‐body 3T clinical scanner, followed by histological analysis. The nanoparticle accumulation was assessed by the extent of T2*‐induced carotid lumen reduction (% lumen loss) or aortic T2*‐weighted signal intensity reduction (% SI [signal intensity] loss).

Results

RGD‐HFn‐Fe₃O₄ was taken up more than HFn‐Fe₃O₄ in both the ligated left carotid arteries (% lumen loss; 69 ± 9% vs. 36 ± 7%, P = 0.01) and AAAs (% SI loss; 47 ± 6% vs. 20 ± 5%, P = 0.01). The AAA % SI loss correlated positively with AAA size (r = 0.89, P < 0.001). Histology confirmed the greater accumulation and colocalization of RGD‐HFn‐Fe₃O₄ to both vascular macrophages and endothelial cells.

Conclusion

RGD‐HFn‐Fe₃O₄ enhances in vivo MRI by targeting both vascular inflammation and angiogenesis, and provides a promising translatable MRI approach to detect high‐risk atherosclerotic and aneurysmal vascular diseases.

Level of Evidence: 1

J. Magn. Reson. Imaging 2017;45:1144–1153

2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm

Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro. Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM (p<0.001), thus indicating an increase in MMP activity. Our data suggest that FRET-based proteolytic beacons show promise in assessing MMP activity within the ECM and will therefore allow future studies to identify the heterogeneous distribution of simultaneous ECM remodeling and protease activity in aneurysmal disease.

Decreased reticuloendothelial system clearance and increased blood half-life and immune cell labeling for nano- and micron-sized superparamagnetic iron-oxide particles upon pre-treatment with Intralipid

BACKGROUND

Superparamagnetic iron-oxide nanoparticles are useful as contrast agents for anatomical, functional and cellular MRI, drug delivery agents, and diagnostic biosensors. Nanoparticles are generally cleared by the reticuloendothelial system (RES), in particular taken up by Kupffer cells in the liver, limiting particle bioavailability and in-vivo applications. Strategies that decrease the RES clearance and prolong the circulation residence time of particles can improve the in-vivo targeting efficiency.

METHODS

Intralipid 20.0%, an FDA approved nutritional supplement, was intravenously administered in rats at the clinical dose (2g/kg) 1h before intravenous injection of ultra-small superparamagnetic iron-oxide (USPIO) or micron-sized paramagnetic iron-oxide (MPIO) particles. Blood half-life, monocyte labeling efficiency, and particle biodistribution were assessed by magnetic resonance relaxometry, flow cytometry, inductively-coupled plasma MS, and histology.

RESULTS

Pre-treatment with Intralipid resulted in a 3.1-fold increase in USPIO blood half-life and a 2-fold increase in USPIO-labeled monocytes. A 2.5-fold increase in MPIO blood half-life and a 5-fold increase in MPIO-labeled monocytes were observed following Intralipid pre-treatment, with a 3.2-fold increase in mean iron content up to 2.60pg Fe/monocyte. With Intralipid, there was a 49.2% and 45.1% reduction in liver uptake vs. untreated controls at 48h for USPIO and MPIO, respectively.

CONCLUSIONS

Intralipid pre-treatment significantly decreases initial RES uptake and increases in-vivo circulation and blood monocyte labeling efficiency for nano- and micron-sized superparamagnetic iron-oxide particles.

GENERAL SIGNIFICANCE

Our findings can have broad applications for imaging and drug delivery applications, increasing the bioavailability of nano- and micron-sized particles for target sites other than the liver.