Size, Shape, and Protein Corona Determine Cellular Uptake and Removal Mechanisms of Gold Nanoparticles

A Metabolomic Approach for the In Vivo Study of Gold Nanospheres and Nanostars after a Single-Dose Intravenous Administration to Wistar Rats

Gold nanoparticles (AuNPs) are promising nanoplatforms for drug therapy, diagnostic and imaging. However, biological comparison studies for different types of AuNPs fail in consistency due to the lack of sensitive methods to detect subtle differences in the expression of toxicity. Therefore, innovative and sensitive approaches such as metabolomics are much needed to discriminate toxicity, specially at low doses. The current work aims to compare the in vivo toxicological effects of gold nanospheres versus gold nanostars (of similar ~40 nm diameter and coated with 11-mercaptoundecanoic acid) 24 h after an intravenous administration of a single dose (1.33 × 10¹¹ AuNPs/kg) to Wistar rats. The biodistribution of both types of AuNPs was determined by graphite furnace atomic absorption spectroscopy. The metabolic effects of the AuNPs on their main target organ, the liver, were analyzed using a GC-MS-based metabolomic approach. Conventional toxicological endpoints, including the levels of ATP and reduced and oxidized glutathione, were also investigated. The results show that AuNPs preferentially accumulate in the liver and, to a lesser extent, in the spleen and lungs. In other organs (kidney, heart, brain), Au content was below the limit of quantification. Reduced glutathione levels increased for both nanospheres and nanostars in the liver, but ATP levels were unaltered. Multivariate analysis showed a good discrimination between the two types of AuNPs (sphere- versus star-shaped nanoparticles) and compared to control group. The metabolic pathways involved in the discrimination were associated with the metabolism of fatty acids, pyrimidine and purine, arachidonic acid, biotin, glycine and synthesis of amino acids. In conclusion, the biodistribution, toxicological, and metabolic profiles of gold nanospheres and gold nanostars were described. Metabolomics proved to be a very useful tool for the comparative study of different types of AuNPs and raised awareness about the pathways associated to their distinct biological effects.

pH-triggered endosomal escape of pore-forming Listeriolysin O toxin-coated gold nanoparticles

Background

A major bottleneck in drug delivery is the breakdown and degradation of the delivery system through the endosomal/lysosomal network of the host cell, hampering the correct delivery of the drug of interest. In nature, the bacterial pathogen Listeria monocytogenes has developed a strategy to secrete Listeriolysin O (LLO) toxin as a tool to escape the eukaryotic lysosomal system upon infection, allowing it to grow and proliferate unharmed inside the host cell.

Results

As a “proof of concept”, we present here the use of purified His-LLO H311A mutant protein and its conjugation on the surface of gold nanoparticles to promote the lysosomal escape of 40 nm-sized nanoparticles in mouse embryonic fibroblasts. Surface immobilization of LLO was achieved after specific functionalization of the nanoparticles with nitrile acetic acid, enabling the specific binding of histidine-tagged proteins.

Conclusions

Endosomal acidification leads to release of the LLO protein from the nanoparticle surface and its self-assembly into a 300 Å pore that perforates the endosomal/lysosomal membrane, enabling the escape of nanoparticles.

Decoding Live Cell Interactions with Multi-Nanoparticle Systems: Differential Implications for Uptake, Trafficking, and Gene Regulation

Surface modification with oligonucleotides renders gold nanoparticles to endocytose through very different pathways as compared to unmodified ones. Such oligonucleotide-modified gold nanoparticles (OGNs) have been exploited as effective nanocarriers for gene regulation therapies. Notably, in an effort to reduce overall dosage and provide safer transition to the clinic, cooperative systems composed of two or more discrete nanomaterials have been recently proposed as an alternative to intrinsically multifunctional nanoparticles. Yet, our understanding of such systems designed to synergistically cooperate in their diagnostic or therapeutic functions remains acutely limited. Specifically, cellular interactions and uptake of OGNs are poorly understood when the cell simultaneously interacts with other types of nanoparticles. Here, we investigated the impact of simultaneous uptake of similar-sized iron oxide nanoparticles (IOPs) on the endocytosis and gene regulation function of OGNs, whose analogues have been proposed for sensitization, targeting, and treatment of tumors. We discovered that both the OGN uptake amount and, remarkably, the gene regulation function remained stable when exposed to a very wide range of extracellular concentrations of IOPs. Additionally, the co-localization analysis showed that a proportion of OGNs was co-localized with IOPs inside cells, which hints at the presence of similar trafficking pathways for OGNs and IOPs following endocytosis. Taken together, our observations indicate that while the OGN endocytosis is highly independent of the IOP endocytosis, it shares transport pathways inside cells-but does so without affecting the gene regulation behavior. These results provide key insights into concomitant interactions of cells with diverse nanoparticles and offer a basis for the future design and optimization of cooperative nanomaterials for diverse theranostic applications.

Internalization Characterization of Si Nanorod with Camouflaged Cell Membrane Proteins Reveals ATXN2 as a Negative Regulator

The fabrication of shape-controlled nanocarriers is critical for efficient delivery of biomolecules across the cell membrane. Surface coating of the nanocarrier can improve internalization efficiency. Here, we developed a facile method of silicon nanorod fabrication leading to a controlled size and shape. We then systematically evaluated five surface modifications with membrane proteins from different cancer cell lines including MCF7, MD231, Hela, Panc-PDX, and Panc-1. We demonstrated that silicon nanorods coated with either a homolytic or heterolytic membrane protein coating have significantly improved internalization efficiency as compared with uncoated Si nanorods. To elucidate the molecular mechanism of the improved efficiency associated with a modified coating, we analyzed the coating membrane proteins derived from five cell lines with proteomics and identified 601 proteins shared by different cell sources. These proteins may function as cell-substrate adhesion molecules that contribute to the enhanced internalization. We also tested the internalization efficiency of nanorods with different coatings in each of the five cell lines to determine the influencing factors from target cells. We found that the internalization efficiency varied among different target cells, and the ranking of the average efficiency was as follows: Hela > Panc-PDX > MD231 > MCF7 > Panc-1. The bioinformatics analysis suggested that the low internalization efficiency in Panc-1 cells might be associated with the upregulation of ATXN2, which is a negative regulator of endocytosis. We further demonstrated that ATXN2 knockdown with specific siRNA significantly improved nanorod internalization efficiency in Panc-1 cells suggesting that ATXN2 can be a reference for efficiency prediction of nanoparticle delivery to tumor cells. Thus, we studied the effect of different cancer cell membrane proteins on nanorod uptake efficiencies. These results can improve nanorod internalization to cancer cells, including a fundamental understanding of the internalization efficiency of cancer cells.

Presence of Gold Nanoparticles in Cells Associated with the Cell-Killing Effect of Modulated Electro-Hyperthermia

The efficacy of gold nanoparticle (AuNP)-assisted radiofrequency (RF)-induced hyperthermia employing the Kanzius device remains controversial. Different from the Kanzius device, modulated electro-hyperthermia (mEHT) utilizes the capacitive-impedance coupled 13.56 MHz radiofrequency (RF) current and has been approved for clinical cancer treatment. In this study, we investigated the heating characteristics of spherical-, urchin-, and rod-like AuNPs of a similar 50 nm size upon exposure to a 13.56 MHz radiofrequency using the LabEHY-105CL, an in vivo mEHT device. We found that, regardless of the AuNPs' sphere-, urchin- or rod-like shape, purified gold nanoparticle solution would not promote heat generation. The temperature elevation during radiofrequency irradiation was solely attributed to the ionic background of the solution. The AuNPs present in the medium (≤25 ppm) showed no effect on selective cell killing of malignant cells, whereas the AuNPs incorporated in the cells diminished the cell selectivity as well as cell death and acted as protectors in mEHT cancer treatment. Our study suggested that (1) the temperature elevation induced by 50 nm AuNPs in the 13.56 MHz radiofrequency field was negligible and was shape-independent, and (2) the presence of AuNPs would alter the cell-killing effect of modulated electro-hyperthermia.

Interaction of Gold Nanorods with Human Dermal Fibroblasts: Cytotoxicity, Cellular Uptake, and Wound Healing

Herein, the cytotoxicity, cellular uptake and wound healing of human dermal fibroblasts were investigated upon treatment with gold nanorods (GNR) decorated with different ligands. Neutral and cationic poly ethylene glycol (PEG)-decorated GNR demonstrated the least cytotoxicity and cellular internalization, while anionic- and bovine serum albumin (BSA)-coated GNR revealed significant cytotoxicity and cellular uptake into human dermal fibroblasts. The cell scratch test demonstrated that neutral, cationic PEGylated GNR and anionic-decorated GNR have accelerated the wound healing rate in vitro after 24 h of incubation with scratched human dermal fibroblasts compared to control, while there was a drastic retardation of wound healing rate of scratched fibroblasts upon exposure to BSA-GNR accompanied with a significant release of the inflammatory cytokine; interlukin-1β (IL-1β). The cytotoxicity of GNR against the dermal cells and their ability to enhance the wound healing in vitro are greatly linked to their surface modifications.

Fluorescence correlation spectroscopy as a tool for the study of the intracellular dynamics and biological fate of protein corona

In biological fluids, nanoparticles (NPs) are in contact with proteins and other biomolecules. Proteins adsorb to NPs and form a coating called a protein corona (PC). The PC is known to greatly affect the interaction of NPs with biological systems. A comprehensive knowledge of the protein nanoparticle interaction is essential to understand the biological fate of NPs and for the design of NPs for biomedicine. Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) are sensitive spectroscopy techniques that measure fluorescence intensity fluctuations of single molecules inside a femtoliter confocal volume. Both techniques are suitable for studying the formation of protein corona around NPs and for examining corona stability in situ in biological matrixes. In this review we provide a short description of FCS/FCCS and their application in PC studies, highlighting results from our work about the impact of surface chemistry of NPs on corona formation and NP intracellular fate.

Key Role of Microtubule and Its Acetylation in a Zinc Oxide Nanoparticle-Mediated Lysosome-Autophagy System

Autophagy is a biological process that has attracted considerable attention as a target for novel therapeutics. Recently, nanomaterials (NMs) have been reported to modulate autophagy, which makes them potential agents for the treatment of autophagy-related diseases. In this study, zinc oxide nanoparticles (ZNPs) are utilized to evaluate NM-induced autophagy and debate the mechanisms involved. It is found that ZNPs undergo pH-dependent ion shedding and that intracellular zinc ions (Zn²⁺ ) play a crucial role in autophagy. Autophagy is activated with ZNPs treatment, which is inhibited after Zn²⁺ sequestration via ethylenediamine tetra-acetic acid. Lysosome-based autophagic degradation is halted after ZNPs treatment for more than 3 h and is accompanied by blockage of lysophagy, which renews impaired lysosomes. Furthermore, the microtubule (MT) system participates in ZNP-induced lysosome-autophagy system changes, especially in the fusion between autophagosomes and lysosomes. MT acetylation is helpful for protecting from ZNP-induced MT disruption, and it promotes the autophagic degradation process. In conclusion, this study provides valuable information on NM-induced lysosome-autophagy system changes, particularly with respect to the role of lysophagy and the MT system, which point to some attractive targets for the design of engineered nanoparticles.

Biochemical Changes in Human Cells Exposed to Low Concentrations of Gold Nanoparticles Detected by Raman Microspectroscopy

The toxicological implications of nanoparticles deserve accurate scientific investigation for the protection of human health. Although toxic effects involve specific organs, the events that cause them have their origin from biochemical modifications of some cellular constituents. Therefore, a first analysis to evaluate the effects due to the action of nanoparticles is achieved by investigation of in vitro cells, which allows the identification of the cellular modifications caused by nanoparticles (NPs) even at much lower doses than the lethal ones. This work evaluated the Raman microspectroscopy capability to monitor biochemical changes occurring in human cells as a consequence of exposure to a suspension of gold nanoparticles with a non-cytotoxic concentration. Human keratinocyte cells were used as a model cell line, because they are mainly involved in environmental exposure. A trypan blue assay revealed that the investigated concentration, 650 ng/mL, is non-cytotoxic (about 5% of cells died after 48 h exposure). Specific Raman spectral markers to represent the cell response to nanoparticle exposure were found (at 1450 and 2865 cm^-1) in the cytoplasm spectra, with the aid of ratiometric and principal component analysis.

Au nanoparticle-decorated aragonite microdumbbells for enhanced antibacterial and anticancer activities

The present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications.

An erythrocyte membrane coated mimetic nano-platform for chemo-phototherapy and multimodal imaging

The tumor variability and low efficiency associated with conventional chemical drugs provide an impetus to develop drug-carrying systems with targeted accumulation and controllable release behavior.

Advances in nanoparticle development for improved therapeutics delivery: nanoscale topographical aspect

Nanoparticle-based therapeutics delivery holds great promise for the treatment of intractable diseases. The high loading of drug molecules and their precise delivery to target sites are needed to gain optimal therapeutic functions of the nanoparticle delivery system. In this communication, we highlight, among other properties of nanoparticles (e.g. size, shape, surface chemistry, and degradation), the nanoscale topography, which has recently been shown to be an important parameter, ultimately determining drug loading, cell penetration, and body clearance. This nanotopographical aspect is considered to offer a new effective strategy to the development of nanoparticles for drug and gene delivery with enhanced therapeutic outcome.

Assembly of DNA Probes into Superstructures for Dramatically Enhancing Enzymatic Stability and Signal-to-Background Ratio

DNA fluorescent probes are versatile tools that are widely used for biological detection in tubes. Using DNA probes in living systems, however, represents a significant challenge because of the endogenous nuclease-induced DNA degradation and strong background fluorescence in complex biological environments. Here, we show that assembling DNA probes into core-satellite gold nanoparticle (AuNP) superstructures could unprecedentedly enhance enzymatic stability and reduce background interference. The embedded DNA probes are protected from interaction with nuclease, eliminating the enzymatic degradation. In the meantime, the AuNP superstructures show extremely high quenching efficiency (>98%) toward the embedded DNA probes, whose fluorescence can be instantly turned on by the target binding, resulting in high signal-to-background ratio. To demonstrate these distinct properties, we made use of the assembled nanoprobes to monitor the ATP levels under different stimuli in living cells. The assembly strategy leads to a new opportunity for accurately sensing targets in living systems.

Influence of size and surface capping on photoluminescence and cytotoxicity of gold nanoparticles

Hydrophilic and homogeneous sub-10 nm blue light-emitting gold nanoparticles (NPs) functionalized with different capping agents have been prepared by simple chemical routes. Structure, average, size, and surface characteristics of these NPs have been widely studied, and the stability of colloidal NP solutions at different pH values has been evaluated. Au NPs show blue PL emission, particularly in the GSH capped NPs, in which the thiol-metal core transference transitions considerably enhance the fluorescent emission. The influence of capping agent and NP size on cytotoxicity and on the fluorescent emission are analyzed and discussed in order to obtain Au NPs with suitable features for biomedical applications. Cytotoxicity of different types of gold NPs has been determined using NPs at high concentrations in both tumor cell lines and primary cells. All NPs used show high biocompatibility with low cytotoxicity even at high concentration, while Au-GSH NPs decrease viability and proliferation of both a tumor cell line and primary lymphocytes.