(719d) Engineering Smart Vascular Targeted Carriers: Enzyme-Responsive Hydrogels for Drug Delivery

Vascular targeted carriers (VTCs) are drug-loaded vehicles designed to locally release their payload at regions of diseased vascular tissue. Upon administration into the bloodstream, VTCs navigate the vasculature, localize, and bind to the inflamed endothelial lining of the blood vessel. This precise targeting is usually accomplished through active targeting, using ligands that attach to inflammation markers on the endothelium, such as intracellular adhesion markers (ICAMs). Notably, soft materials such as hydrogels are attractive as VTCs because of their high water content and biocompatibility.

Unsurprisingly, the interest in VTCs as a potential method for site-specific drug delivery continues to grow. This is because VTCs offer a much less invasive treatment option for cardiovascular, neurological, oncological, and inflammatory diseases, which are the leading causes of mortality globally. Cardiovascular diseases (CVDs) are particularly significant, as they alone account for about 33% of all deaths annually.

One of the primary causes of CVDs is coronary artery disease (CAD), which is marked by the accumulation of atherosclerotic plaques in the arteries. These plaques limit blood flow to essential areas of the body. The development of atherosclerotic plaques is notably associated with the buildup of low-density lipoproteins, foam cells, and smooth muscle cells, as well as an increase in inflammatory cytokines and matrix metalloproteinase (MMP) enzymes. Specifically, the MMP-2 enzyme has been found to be upregulated in coronary artery diseases. Consequently, this study focuses on developing hydrogels that can be degraded by MMP-2, enabling them to release drug payloads specifically at the locations of atherosclerotic plaques.

In this work, our enzyme-degradable hydrogels were fabricated by crosslinking MMP-2 cleavable peptides (VPM) with polyethylene-glycol vinyl sulfone (PEGVS), using a water-in-oil emulsion process. The resulting hydrogel particles were 2 µm in size, with a Young’s modulus of 24 kPa. Further, using a scanning electron microscope, we confirmed that the hydrogels are deformable owing to the presence of dimples on their surfaces after they were dehydrated. Additionally, we successfully loaded the hydrogel microparticles with 100 nm polystyrene nanoparticles, demonstrating the hydrogels' capacity to carry therapeutic agents. This was confirmed using fluorescence microscopy.

We also tested the hydrogels’ ability to respond to enzymatic stimulus. Here, we exposed the hydrogel particles to 20 nM MMP-2 enzyme. Our results indicate that the hydrogels degraded in the presence of MMP-2 in a time-dependent manner, with no significant degradation noticed beyond 8 hours. Next, we successfully conjugated the surface of the PEGVS-VPM hydrogels with avidin, and subsequently anti-ICAM-1 (aICAM-1). We then demonstrated that our aICAM-1 conjugated microparticles can bind to inflamed endothelium by incubating the targeted particles with a monolayer of human umbilical vein endothelial cells (HUVECs). Visually, we observed that a significantly greater number of targeted particles adhered to the inflamed endothelium compared to the uninflamed endothelium.