Nanoparticles could induce micron sized gaps between endothelial cells which we coined as nanoparticles induced endothelial leakiness (nanoEL effect) even without any tumor cells in the vicinity of the blood vessels cells; thus NanoEL is a novel nanoparticle driven effect distinct from the EPR effect. This presents an opportunistic window to control access of nanomedicine and drugs to tumors and other tissues without relying on the uncontrollable EPR effect. Nanoparticle parameters that determine NanoEL are slowly emerging but under intense investigation. In this study, we showed that the negatively charged Au nanoparticles could induce the NanoEL effect several fold more effectively than positively charged Au nanoparticles of the same size. This effect occurred in the absence of any cellular uptake of the particles which suggested that the action occurs external to the cells. We showed with in silico modelling that negatively charged particles were repelled successively from the negatively charged glycocalyx surface of the endothelial cells towards the cell-cell junction. The high density of the Au particles disrupted the critical VE-cadherin interactions that hold neighbouring endothelial cells together and resulted in gaps that are at least 1000 fold larger in the hundreds of micron ranges.