Delivery of bevacizumab to atheromatous porcine carotid tissue using echogenic liposomes

Abstract

Ultrasound is both a valuable diagnostic tool and a promoter of beneficial tissue bioeffects for the treatment of cardiovascular disease. Vascular effects can be mediated by mechanical oscillations of circulating microbubbles that may also encapsulate and shield therapeutic agents in the bloodstream. Here, the effect of color-Doppler ultrasound exposure on bevacizumab-loaded liposome delivery into the vascular bed was assessed in atheromatous porcine carotids. Bevacizumab, an anti-angiogenic antibody to vascular endothelial growth factor (VEGF-A), was loaded into echogenic liposomes (BEV-ELIP) and confirmed to be immunoreactive. BEV-ELIP flowing within the lumen were exposed to color-Doppler ultrasound at three acoustic pressures for 3.5 min during treatment at physiologic temperature and fluid pressure. To confirm the presence of bubble activity, cavitation was detected within the lumen by a single-element passive cavitation detector. After treatment, the artery was fixed at physiologic pressure and subjected to immunohistochemical analysis to assess the penetration of bevacizumab within the carotid wall. The results suggest that other factors may more strongly influence the deposition of bevacizumab into carotid tissue than color-Doppler ultrasound and cavitation. In both sets of arteries, preferential accumulation of bevacizumab occurred in locations associated with atheroma progression and neointimal thickening: fibrous tissue, necrotic plaque and areas near macrophage infiltration. The delivery of bevacizumab to carotid vascular tissue correlated with the properties of the tissue bed, such as permeability, or affinity for growth-factor binding. Future investigations using this novel therapeutic strategy may focus on characterizing the spatial extent of delivery and bevacizumab colocalization with biochemical markers of atheroma.