Glutathione-coated Gold Research Articles

Glutathione-Coated Gold Nanoparticles Enabling Bifunctional Therapy at the Buried Interface for Efficient and UV-Resistant Perovskite Solar Cells.

Very recently, the poor contact between the perovskite and carrier selective layer has been regarded as a critical issue for improving the performance and stability of perovskite solar cells (PSCs). In this study, the buried interface of regularly structured PSCs has been targeted. Glutathione-coated gold nanoparticles (GSH-AuNPs) are used as double-sided passivating agents to improve the quality of the perovskite films. It has been demonstrated that the GSH-AuNPs interact strongly with the SnO2 underlayer and the upper perovskite layer, significantly reducing the defect densities of this interface. Thus, the power conversion efficiency (PCE) of the PSCs can be increased from 20.46% (control, 19.38%, IPCE corrected) to 22.22% (GSH-AuNPs modified, 21.10%, IPCE corrected) with notable enhancement in Voc and FF. Moreover, the strong interaction between the C═O groups of GSH-AuNPs and the undercoordinated Pb2+ species of the perovskite films inhibits the formation of metallic Pb0. As a result, the unencapsulated GSH-AuNPs-modified devices retained 80% of their initial PCEs after 1000 h at ambient conditions, with a relative humidity (RH) of 60 ± 5%. UV-resistant PSCs have also been demonstrated after introducing GSH-AuNPs. Therefore, our findings demonstrate the bidirectional therapy strategy as a feasible approach for achieving efficient and UV-resistant PSCs.

Soft scaffold aided plasmon-enhanced upconversion luminescence and its application in vascular endothelial growth factor (VEGF) detection

The dimensioning of glutathione-coated gold nanoparticles (GSH-Au NPs) greatly enhanced the luminescence intensity of upconversion nanoparticles (UCNPs) in close proximity and offered significant implications for biomedicine and materials science. According to systematic studies, the luminescence changes between UCNPs and AuNPs are enhanced by a well-tuned electric field-induced absorption, especially when the distance between the two is approximately 5 nm. At this distance, an upconversion enhancement factor of approximately 4.4 is achieved at a wavelength of 361 nm. This maximized plasmonic enhancement effect was subsequently employed for the quantification of Vascular Endothelial Growth Factor (VEGF) with the well-fabricated plasmon-enhanced luminescence complex (PELC) by replacing the ssDNA with the corresponding aptamer. This complex provides a basis for the rational design of a hybrid metal-upconversion complex to enhance luminescence for bioimaging and sensing applications.

Sensitive Near-Infrared Fluorescent Determination of Hydrogen Peroxide and Glucose Using Glutathione-Coated Gold Nanoparticles

Near-infrared luminescence glutathione-coated gold nanoparticles (NGS-AuNPs) were synthesized and employed as fluorescent probes for the selective determination of hydrogen peroxide and glucose. This approach was based upon the coordination-induced fluorescence quenching of tris(2-carboxyethyl)phosphine (TCEP) with the NGS-AuNPs and its reduction of H2O2. The NGS-AuNPs possessed a highly monodispersed spherical morphology with a uniform diameter of 2.1 ± 0.5 nm and a maximal fluorescence emission wavelength of 810 nm. The results of the H2O2 determination demonstrate the excellent selectivity of this strategy with a limit of detection of 5.4 μM. This system was also employed for the selective determination of glucose which generated H2O2 by the catalytic oxidation of glucose oxidase with a limit of detection of 0.42 μM. This strategy exhibited excellent performance for the test of H2O2 and glucose in urine with recoveries from 93% to 103%. This methodology may allow the analysis of biological samples and clinical diagnosis.

Fluorescent Labeling of Human Serum Albumin by Thiol-Cyanimide Addition and Its Application in the Fluorescence Quenching Method for Nanoparticle-Protein Interactions.

A boron-dipyrromethene (BODIPY)-based fluorescent probe, BDP-CN, was synthesized in this work. It had a fluorescence emission maximum at 512 nm and a high quantum yield (48%). As evidenced by agarose gel electrophoresis and liquid chromatography-mass spectrometry, it could realize the fluorescent labeling of human serum albumin (HSA) through a thiol-cyanimide addition. Interestingly, f-HSA, defined as HSA labeled by BDP-CN, had an even higher quantum yield (77%). In addition, BDP-CN would not affect the secondary structure of HSA. Based on the successful formation of f-HSA, it was further applied to study the interactions with nanoparticles. The fluorescence quenching of f-HSA by dihydrolipoic acid-coated gold nanoclusters (DHLA-AuNCs) obeyed a dynamic mechanism, consistent with the intrinsic fluorescence quenching of HSA by DHLA-AuNCs. The association constant Ka between f-HSA and DHLA-AuNCs at 298 K was 1.5 × 105 M-1, which was the same order of magnitude as that between HSA and DHLA-AuNCs. Moreover, the interactions of f-HSA with glutathione-coated gold nanoclusters confirmed that the labeled fluorescence could replace the intrinsic fluorescence to monitor the interactions between proteins and nanoparticles. By this method, strong fluorescence ensures better stability and reproducibility, excitation at a longer wavelength reduces the damage to the proteins, and covalent conjugation with cysteine residues eliminates the inner filter effects to a great extent. Therefore, the strategy for the fluorescent labeling of HSA can be expanded to investigate a broad class of nanoparticle-protein interactions and inspire even more fluorescent labeling methods with organic dyes.

Inulinase immobilized gold-magnetic nanoparticles as a magnetically recyclable biocatalyst for facial and efficient inulin biotransformation to high fructose syrup

To date, the high cost of enzyme production, lack of enzyme reusability and operational stability are the main limitations of the enzyme's application in industry. In this work, inulinase was covalently immobilized on the surface of glutathione-coated gold magnetic nanoparticles (GSH-AuMNPs). The synthesized NPs were fully characterized. The effects of different restriction factors such as substrate concentration, temperature, and pH on the performance and stability of the enzyme were examined. The maximum activity and immobilization yield were estimated 83% and 93%, respectively. The immobilized inulinase showed maximum activity at pH 4.5 and 60 °C. The kinetic parameters of the immobilized enzyme were not changed significantly after the immobilization process. The reusability assessment indicated that approximately 78% of the initial activity of immobilized inulinase remained after ten times recycling. The storage stability of inulinase was improved by the immobilization process. The inulin hydrolysates were checked by HPLC and the end products only contained two components, 98% of fructose and up to 2% of glucose in both free enzyme and immobilized enzyme systems. This study introduced a simple, effective and inexpensive immobilization process, which is applicable in different biomedical, biotechnological and food industries.

Dually emitting gold-silver nanoclusters as viable ratiometric fluorescent probes for cysteine and arginine.

Glutathione coated gold and silver nanoclusters (GSH-Au/AgNCs) were synthesized by one-pot reduction methods and are found to be viable fluorescent nanoprobes for cysteine (Cys) and arginine (Arg), with good selectivity over other amino acids. The GSH-Au/AgNCs have two emissions at 616nm and 412nm when excited at 360nm. With the increased concentration of Cys, the ratio of the emission intensities (I616/I412) linearly decreases with Cys inconcentration ranging from 0.05 to 10μM and from 10 to 50μM, respectively. With increased concentrations of Arg, the ratio of I616/I412 linearly decreases with Arg concentration ranging from 0 to 50μM and from 50 to 100μM, respectively. The probe was applied to the determination of Cys and Arg in spiked samples of serum and urine where it gave good recoveries. Graphical abstract Glutathione-coated gold and silver nanoclusters (GSH-Au/AgNCs) were synthesized by one-pot reduction and are found to be viable fluorescent nanoprobes for cysteine (Cys) and arginine (Arg).

Physiological stability and renal clearance of ultrasmall zwitterionic gold nanoparticles: Ligand length matters

Efficient renal clearance has been observed from ultrasmall zwitterionic glutathione-coated gold nanoparticles (GS-AuNPs), which have broad preclinical applications in cancer diagnosis and kidney functional imaging. However, origin of such efficient renal clearance is still not clear. Herein, we conducted head-to-head comparison on physiological stability and renal clearance of two zwitterionic luminescent AuNPs coated with cysteine and glycine-cysteine (Cys-AuNPs and Gly-Cys-AuNPs), respectively. While both of them exhibited similar surface charges and the same core sizes, additional glycine slightly increased the hydrodynamic diameter of the AuNPs by 0.4 nm but significantly enhanced physiological stability of the AuNPs as well as altered their clearance pathways. These studies indicate that the ligand length, in addition to surface charges and size, also plays a key role in the physiological stability and renal clearance of ultrasmall zwitterionic inorganic NPs.

Targeting orthotopic gliomas with renal-clearable luminescent gold nanoparticles.

A major clinical translational challenge in nanomedicine is the potential of toxicity associated with the uptake and long-term retention of non-degradable nanoparticles (NPs) in major organs. The development of inorganic NPs that undergo renal clearance could potentially resolve this significant biosafety concern. However, it remains unclear whether inorganic NPs that can be excreted by the kidneys remain capable of targeting tumors with poor permeability. Glioblastoma multiforme, the most malignant orthotopic brain tumor, presents a unique challenge for NP delivery because of the blood-brain barrier and robust blood-tumor barrier of reactive microglia and macroglia in the tumor microenvironment. Herein, we used an orthotopic murine glioma model to investigate the passive targeting of glutathione-coated gold nanoparticles (AuNPs) of 3 nm in diameter that undergo renal clearance and 18-nm AuNPs that fail to undergo renal clearance. Remarkably, we report that 3-nm AuNPs were able to target intracranial tumor tissues with higher efficiency (2.3× relative to surrounding non-tumor normal brain tissues) and greater specificity (3.0×) than did the larger AuNPs. Pharmacokinetics studies suggested that the higher glioma targeting ability of the 3-nm AuNPs may be attributed to the longer retention time in circulation. The total accumulation of the 3-nm AuNPs in major organs was significantly less (8.4×) than that of the 18-nm AuNPs. Microscopic imaging of blood vessels and renal-clearable AuNPs showed extravasation of NPs from the leaky blood-tumor barrier into the tumor interstitium. Taken together, our results suggest that the 3-nm AuNPs, characterized by enhanced permeability and retention, are able to target brain tumors and undergo renal clearance.

The molecular mechanism of the ligand exchange reaction of an antibody against a glutathione-coated gold cluster

The labeling of proteins with heavy atom clusters is of paramount importance in biomedical research, but its detailed molecular mechanism remains unknown. Here we uncover it for the particular case of the anti-influenza N9 neuraminidase NC10 antibody against a glutathione-coated gold cluster by means of ab initio QM/MM calculations. We show that the labeling reaction follows an associative double SN2-like reaction mechanism, involving a proton transfer, with low activation barriers only if one of the two distinct peptide/peptidic ligands (the one that occupies the side position) is substituted. Positively charged residues in the vicinity of the incoming thiol result in strong interactions between the antibody and the AuMPC, favoring the ligand exchange reaction for suitable protein mutants. These results pave the way for future investigations aimed at engineering biomolecules to increase their reactivity towards a desired gold atom cluster.

Biointeractions of ultrasmall glutathione-coated gold nanoparticles: effect of small size variations.

Recent in vivo studies have established ultrasmall (<3 nm) gold nanoparticles coated with glutathione (AuGSH) as a promising platform for applications in nanomedicine. However, systematic in vitro investigations to gain a more fundamental understanding of the particles' biointeractions are still lacking. Herein we examined the behavior of ultrasmall AuGSH in vitro, focusing on their ability to resist aggregation and adsorption from serum proteins. Despite having net negative charge, AuGSH particles were colloidally stable in biological media and able to resist binding from serum proteins, in agreement with the favorable bioresponses reported for AuGSH in vivo. However, our results revealed disparate behaviors depending on nanoparticle size: particles between 2 and 3 nm in core diameter were found to readily aggregate in biological media, whereas those strictly under 2 nm were exceptionally stable. Molecular dynamics simulations provided microscopic insight into interparticle interactions leading to aggregation and their sensitivity to the solution composition and particle size. These results have important implications, in that seemingly small variations in size can impact the biointeractions of ultrasmall AuGSH, and potentially of other ultrasmall nanoparticles as well.

Ultrasensitive microfluidic array for serum pro-inflammatory cytokines and C-reactive protein to assess oral mucositis risk in cancer patients.

In addition to disease diagnostics, there is a need for biomarkers to predict severity of cancer therapy side effects such as oral mucositis. Oral mucositis is an inflammatory lesion of oral mucosa caused by high-dose chemotherapy and/or radiation that is especially prevalent during oral cancer treatment. We describe here a semi-automated, modular microfluidic immunoarray optimized for ultrasensitive detection of pro-inflammatory cytokines involved in pathobiology of oral mucositis. Our goal is to methodologically identify risk of mucositis early in oral cancer treatment, before the onset of lesions. Biomarkers include tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and C-reactive protein (CRP). Protein analytes were captured from serum in a capture chamber by 1-μm magnetic beads coated with antibodies and enzyme labels. Beads are then transported downstream to a detection chamber containing an eight-sensor array coated with glutathione-coated gold nanoparticles (GSH-AuNP) and a second set of antibodies to capture the beads with analyte proteins. In this first application of the immunoarray to four-protein multiplexed measurements, ultralow detection limits of 10-40 fg mL(-1) in 5 μL serum were achieved for simultaneous detection in 30 min. Mass detection limits were 2.5-10 zmol, as few as 1500 molecules. Accuracy and diagnostic utility of the arrays were demonstrated by correlation of levels of the four biomarker proteins in serum from head and neck cancer patients with results from standard ELISA. This approach may lead to rapid, low-cost estimates of projected risk for severity of oral mucositis in cancer patients to enable improved therapeutic management.

A naked eye aggregation assay for Pb2+ detection based on glutathione-coated gold nanostars

Gold nanostars (AuNS) with a mean hydrodynamic size of 40 nm, obtained with a seed-growth approach using a zwitterionic surfactant (laurylsulfobetaine, LSB), were successfully coated with glutathione (GSH), obtaining a stable and purified solid product which can be easily stored and re-dissolved on need in 0.1 M aqueous solution of Hepes buffered at pH 7. Upon exposure to micromolar concentrations of Pb2+ cation, the GSH-coated nano-objects undergo a fast aggregation followed by sedimentation leading to complete precipitation in about an hour. The subsequent disappearing of the intense LSPR extinction can of course be followed spectrophotometrically but, most importantly, can be easily detected with the naked eye. No signs of this event are noticed when other divalent cations are added to the colloidal suspension in the same condition. A careful investigation was performed to study this selectivity and the behaviour of aggregation as a function of time and Pb2+ cation concentration. We demonstrate that an easy, rapid, instrument-free, visual detection of micromolar levels of Pb2+ is thus possible with this assay, showing a good selectivity towards other investigated metal cations.

The Impact of Surface Ligands and Synthesis Method on the Toxicity of Glutathione-Coated Gold Nanoparticles.

Gold nanoparticles (AuNPs) are increasingly used in biomedical applications, hence understanding the processes that affect their biocompatibility and stability are of significant interest. In this study, we assessed the stability of peptide-capped AuNPs and used the embryonic zebrafish (Danio rerio) as a vertebrate system to investigate the impact of synthesis method and purity on their biocompatibility. Using glutathione (GSH) as a stabilizer, Au-GSH nanoparticles with identical core sizes were terminally modified with Tryptophan (Trp), Histidine (His) or Methionine (Met) amino acids and purified by either dialysis or ultracentrifugation. Au-GSH-(Trp)2 purified by dialysis elicited significant morbidity and mortality at 200 µg/mL, Au-GSH-(His)2 induced morbidity and mortality after purification by either method at 20 and 200 µg/mL, and Au-GSH-(Met)2 caused only sublethal responses at 200 µg/mL. Overall, toxicity was significantly reduced and ligand structure was improved by implementing ultracentrifugation purifications at several stages during the multi-step synthesis and surface modification of Au-GSH nanoparticles. When carefully synthesized at high purity, peptide-functionalized AuNPs showed high biocompatibility in biological systems.

In vivo toxicity, biodistribution, and clearance of glutathione-coated gold nanoparticles

Gold nanoparticles are emerging as promising materials from which to construct nanoscale therapeutics and therapeutic delivery systems. However, animal studies have shown that gold nanoparticles modified with certain thiol monolayers such as tiopronin can cause renal complications and morbidity. Although these effects may be eliminated by coadsorbing small amounts of polyethylene glycol (PEG) onto the nanoparticle surface, PEG can also lower cellular internalization efficiency and binding interactions with protein disease targets, significantly reducing the potential for using gold nanoparticles as therapeutics. Using ICP-MS analysis of blood, urine, and several organs, we show in this article that glutathione-coated gold nanoparticles (1.2 nm ± 0.9 nm) cause no morbidity at any concentration up to and including 60 μM and target primary organs although providing gradual dissipation and clearance over time. This study suggests that glutathione may be an attractive alternative to PEG in the design of gold nanoparticle therapeutics. From the Clinical EditorThis study describes the utility and toxicity of glutathione coated gold nanoparticles in comparison to PEGylated counterparts that are commonly used to increase “Stealth” properties and lower cytotoxicity. Too much PEG on the NPs can lead to lower cellular internalization efficiency and less efficient binding interactions with protein disease targets, significantly reducing the potential for using gold nanoparticles as therapeutics.

The influence of ligand organization on the rate of uptake of gold nanoparticles by colorectal cancer cells

We have explored the uptake of different hydrophilic mono- and dual-ligand gold nanoparticles in colorectal cancer cells in vitro and find that the rate of uptake is dependent on the structural organization of the ligands on the surface of the particles rather than their charge or chemical properties. Gold nanoparticles with 50%PEG-NH 2/50% glucose are taken up eighteen fold faster than nanoparticles carrying only PEG-NH 2 or glucose. Glutathione-coated gold particles are by far the most efficiently internalized; however, glucose-glutathione dual-ligand nanoparticles are taken up at a thirty fold reduced rate. We found furthermore that the rates are influenced by the cell density and concentration of glucose in the growth medium. Rather than being internalized through a conventional receptor-mediated mechanism the particles appear to be taken up by the cells via an energy-independent diffusion across the cell membrane through pre-existing pores or openings in the lipid bi-layer created by ligands on the gold nanoparticles.