Unexpected intracellular biodegradation and recrystallization of gold nanoparticles

Abstract

Gold nanoparticles are used in an expanding spectrum of biomedical applications. However, little is known about their long-term fate in the organism as it is generally admitted that the inertness of gold nanoparticles prevents their biodegradation. In this work, the biotransformations of gold nanoparticles captured by primary fibroblasts were monitored during up to 6 mo. The combination of electron microscopy imaging and transcriptomics study reveals an unexpected 2-step process of biotransformation. First, there is the degradation of gold nanoparticles, with faster disappearance of the smallest size. This degradation is mediated by NADPH oxidase that produces highly oxidizing reactive oxygen species in the lysosome combined with a cell-protective expression of the nuclear factor, erythroid 2. Second, a gold recrystallization process generates biomineralized nanostructures consisting of 2.5-nm crystalline particles self-assembled into nanoleaves. Metallothioneins are strongly suspected to participate in buildings blocks biomineralization that self-assembles in a process that could be affected by a chelating agent. These degradation products are similar to aurosomes structures revealed 50 y ago in vivo after gold salt therapy. Overall, we bring to light steps in the lifecycle of gold nanoparticles in which cellular pathways are partially shared with ionic gold, revealing a common gold metabolism.

Plasticised Regenerated Silk/Gold Nanorods Hybrids as Sealant and Bio-Piezoelectric Materials

“…Such organisms have the capability to stick on wet interfaces (for example, mussel and spider-web glues) by removing water from the contact surfaces. Gold (Au) nanoparticles were thought to be stable in biologic environments but it has been recently demonstrated that they can undergo intracellular biodegradation and recrystallisation, with a faster degradation of the smallest size particle [15]. Gold nanoparticles maintain stability on solid silk fibroin and promote the dissolution of degummed silk fibres into silk fibroin in a certain CaCl 2 composition [16].…”

Selective shortening of gold nanorods: when surface functionalization dictates the reactivity of nanostructures

“…1 On the other hand, oxidative degradation is an integral part of the life cycle of nanomaterials, especially when used in fuel cells 2,3 and biological media. [4][5][6][7][8] Therefore, understanding the atomicscale mechanisms of nanomaterial dissolution in liquid electrolyte is of primary importance to design more efficient nanotechnologies. In that regards, liquid cell transmission electron microscopy (LCTEM) has become a method of choice to observe the oxidative etching of individual nanostructures such as metallic nanoparticles [9][10][11][12][13][14][15][16][17] and nanoalloys [18][19][20][21] and it has provided a unique observation window on the intermediate nanostructures formed during these dynamic processes.…”

Endocytosis-driven gold nanoparticle fractal rearrangement in cells and its influence on photothermal conversion

“…Aggregation-induced plasmon coupling can be efficient enough to generate photoacoustic signals, even for small sizes of AuNP (<30 nm) with the advantages of better penetrating the tumor and facilitating elimination or degradation, as compared to larger NIR-absorbing gold nanorods or nanostars. [33][34][35] Since AuNP endocytosis can lead to highly dense clustering within intracellular compartments, 36,37 it might narrow interparticle gaps (<2 nm) 26 and facilitate the plasmon coupling phenomenon only in situ inside the cells. The plasmon coupling effect and its association with the appearance of a secondary LSPR were well demonstrated by the conformation of discrete AuNP-based structures, i.e., dimers and trimers, 38 or more complex self-assemblies of gold nanoparticles into linear, globular, or fractal clusters.…”