The level of endothelial glycocalyx maturity modulates interactions with charged nano-materials

Nanomaterials have been extensively investigated for their potential in delivering therapeutics to target tissues, but few have advanced to clinical application. The luminal surface of endothelial cells that line blood vessels are covered by a glycocalyx, a complex extracellular matrix rich in anionic glycans. However, the role of this glycocalyx in governing nanomaterial-cell interactions is often overlooked. In this study, we demonstrate that gold nanoparticles functionalized with branched polyethyleneimine (AuNP+) bind to primary human endothelial cells expressing either a developing or mature glycocalyx, with the interaction involving hyaluronan and heparan sulfate. Notably, the mature glycocalyx decreases the toxicity of AuNP+. In contrast, lipoic acid-functionalized gold nanoparticles (AuNP-) bind to endothelial cells with a developing glycocalyx, but not a mature glycocalyx. To further investigate this phenomenon, we studied charged polymers, including poly(arginine) (polyR) and poly(glutamic acid) (polyE). PolyE does not associate with endothelial cells regardless of glycocalyx maturity, but when glycans are enzymatically degraded, it can bind to the cells. Conversely, polyR associates with endothelial cells irrespective of glycocalyx maturity or glycan degradation. These findings highlight the intricate relationship between nanomaterial charge and presentation in interactions with endothelial cells, offering insights for modulating nanomaterial interactions with the blood vessel wall.