Ultrasmall gold nanorods: synthesis and glycocalyx-related permeability in human endothelial cells

Abstract

BackgroundClinical data show shed endothelial glycocalyx (GCX) components in blood samples of atherosclerotic patients, linking atherosclerotic development to endothelial GCX integrity. Healthy GCX has pores no >7 nm, and shed GCX has even larger pores. Therefore, we suggest targeting and treating atherosclerosis-prone blood vessels by using nanoscale vehicles to deliver drugs via the nanoscale GCX as it becomes dysfunctional.Materials and methodsTo test our idea, we investigated permeability of nanoparticles in endothelium, as related to a GCX expression. The present work involves nanorods, which are expected to interact with larger portions of endothelial cell (EC) membranes, due to surface area of the nanorod long axis. Conventional nanorod diameters are orders of magnitude larger than the GCX pore size, so we adapted conventional synthesis methods to fabricate ultrasmall gold nanorods (GNRs). Our ultrasmall GNRs have an aspect ratio of 3.4, with a length of 27.9±3.1 nm and a diameter of 8.2±1.4 nm. In addition, we produced GNRs that are biocompatible and fluorescently visible, by coating the surface with functionalized polyethylene glycol and Alexa Fluor 647. To study GNR–GCX interactions, we used human ECs, for species relevance.ResultsUnder life-like flow conditions, the human ECs are densely covered with a 1.3 µm thick layer of GCX, which coincides with minimal GNR permeability. When the GCX is weakened from lack of flow (static culture) or the presence of GCX degradation enzyme in the flow stream, the GCX shows 40% and 60% decreased thickness, respectively. GCX weakness due to lack of flow only slightly increases cellular permeability to GNRs, while GCX weakness due to the presence of enzyme in the flow leads to substantial increase in GNR permeability.ConclusionThese results clarify that the GCX structure is an avenue through which drug-carrying nanoparticles can be delivered for targeting affected blood vessels to treat atherosclerosis.

Metastatic cancer cell attachment to endothelium is promoted by endothelial glycocalyx sialic acid degradation

“…For example, in critical control experiments, we have confirmed that untreated human umbilical vein endothelial cells (HUVEC; Figure a) highly express GCX components such as those targeted by WGA (Figure b) (Mensah et al, manuscript in review), similar to what we observed in healthy RFPEC (Figure e,f). Other GCX components such as HS show low expression (Figure c) in HUVEC, particularly in the absence of physiological flow stimulation, which is usually required for in vitro human EC studies of the GCX . This was contrary to what we observed in RFPEC where HS expression was prominent without flow stimulation (Figure g).…”

Improvement of Gold Nanorods in Photothermal Therapy: Recent Progress and Perspective

“…However, the low yield and unsatisfied size of GNRs synthesized in this original way make it inappropriate for applications (Scarabelli et al, 2015;Allen et al, 2017), so there appears an endless stream of improvements in accordance with the requirements based on GNRs applications in PTT. GNRs suitable for PTT require good monodispersity, small size (An et al, 2017;Cheng et al, 2019), anisotropy, no toxicity, and the need to be produced in high yields. To obtain ideal GNRs, previous studies have discussed the influence of various factors on the synthesis process (Scarabelli et al, 2015) and adopted different improvement methods, including silver-assisted seeded growth (Nikoobakht and El-Sayed 2003), using CTAB-capped seeds instead of citrate-capped ones, etc., which can help grow GNRs to the desired length (He et al, 2017).…”

“…Larger GNRs represent the higher scattering/absorption ratio, allowing scattering-based applications, such as imaging, whereas smaller GNRs exhibit great potential in PTT toward tumors due to their comparably larger absorption cross-sections. However, traditional synthesis methods of ultrasmall GNRs, by increasing the concentration of seeds added in the growth solution, show a lot of inevitable problems, such as the decreased growth yield and the more by-products, such as nanospheres (Tatini et al, 2014;Chang and Murphy 2018;Cheng et al, 2019;Mbalaha et al, 2019). Therefore, new synthesis strategies of small-sized GNRs should be put forward as soon as possible.…”

Flow‐regulated endothelial glycocalyx determines metastatic cancer cell activity

“…ECs are covered by endothelial glycocalyx (GCX), which is a complex sugar coat. Due to its unique position, the GCX lines the luminal side of blood vessels and plays an essential role as a vasculoprotective barrier . While there have been numerous studies focusing on DF‐induced endothelial dysfunction, only a few studies have paid attention to DF regulation of the GCX structure and function despite its importance in vascular homeostasis.…”