Glyco disulfide capped gold nanoparticle synthesis: cytotoxicity studies and effects on lung cancer A549 cells.

Background: Glyco disulfide gold nanoparticles (GDAuNPs) were prepared by three methods: direct, photochemical irradiation and ligand substitution. Glyco disulfide acted as reducing and capping agents of gold ions, to produce AuNPs GD1-GD16. Results: Shorter chains of glyco disulfides (n = 1 and 2) offered monodispersed and stable GDAuNPs in physiological pH, while longer chains (n = 3) furnished unstable nanoparticles. ζ-potential study of direct method GDAuNPs revealed surface charge dependency on the alkyl unit length. Transmission electron microscope imaging indicated that sizes/shapes of the ligand exchange AuNPs remained post-exchange step. The mechanism of GDAuNP formation was forecast as the Ostwald ripening effect at low pH of ligand (5.1-8.9) and reinforcement of static stabilization at high pH (12.4-13.0). Conclusion: GDAuNPs recorded moderately anticancer activity against the A549 cancer cell line, with IC50 between 14.95 and 64.95 µg/ml.

Development and characterization of functionalized glyco thiolate capped gold nanoparticles for biological applications.

Glyco-gold nanoparticles (AuNPs) in aqueous dispersions were prepared by two approaches, namely direct reduction and ligand substitution methods. In the direct method, potassium salts of glyco thiols, with the general formula (C6H11O6)NH(CH2) n CH2SK (where L1, n = 1; L2, n = 2; L3, n = 3, L4, n = 4; L5, n = 5), were used as reducing and capping agents to give the glyco thiolate capped gold nanoparticles (AuNPs G1-G5); meanwhile in the ligand exchange experiments, L1-L5 and their acetylated forms (L6-L8) replaced citrate ions in citrate-capped gold nanoparticles to give additional AuNPs G6-G11. UV-visible spectroscopy, surface charge (ζ-potential,) measurements and transmission electron microscopy (TEM) were used for physical and chemical characterization of all the resultant AuNPs. The ζ-potential studies of AuNPs prepared through the direct method revealed that the surface charge is dependent on the length of the alkyl unit of (C6H11O6)NH(CH2) n CH2S- ligands. TEM images of the acetylated and non-acetylated glyco thiolate capped gold nanoparticles (AuNPs G6-G11) prepared via the ligand exchange method indicate that the size and shape of the gold nanoparticles remained the same as those of the citrate-capped gold nanoparticles used to prepare them. Selected AuNPs were tested on peripheral blood mononuclear cells (PBMCs) and the A549 cancer cell line to investigate their respective toxicity and cytotoxicity profiles. All AuNPs showed indiscriminate activity against both PBMCs and A4549 cells, although the gold nanoparticles having an acetylated glyco moiety with an amino propyl thiol linker as the ligand (G10) prepared via the citrate exchange method had better selectivity (PBMCs >59 mg mL-1 and for A549 ∼7 µg mL-1).

Cytotoxicity, intracellular localization and exocytosis of citrate capped and PEG functionalized gold nanoparticles in human hepatocyte and kidney cells.

Surface-modified gold nanoparticles (AuNPs) are nanomaterials that hold promise in drug delivery applications. In this study, the cytotoxicity, uptake, intracellular localization, and the exocytosis of citrate-stabilized (Cit-AuNP) and polyethylene glycol (PEG)-modified gold nanoparticles with the carboxyl (COOH) terminal functional group were assessed in human embryonic kidney (HEK 293) and the human caucasian hepatocytes carcinoma (Hep G2) cell systems, representing two major accumulation sites for AuNPs. The zeta (ζ)-potential measurements confirmed the negative surface charge of the AuNPs in water and in cell growth medium. The transmission electron microscopy confirmed the size and morphology of the AuNPs. Both types of AuNPs were shown to induce cytotoxic effects in cells. The Hep G2 cells were more sensitive cell type, with the COOH-PEG-AuNPs inducing the highest toxicity at higher concentrations. Dark field microscopy and TEM images revealed that the AuNPs were internalized in cells, mostly as agglomerates. TEM micrographs further revealed that the AuNPs were confined as agglomerates inside vesicle-like compartments, likely to be endosomal and lysosomal structures as well as in the cytosol, mostly as individual particles. The AuNPs were shown to remain in cellular compartments for up to 3 weeks, but thereafter, clearance of the gold nanoparticles from the cells by exocytosis was evident. The results presented in this study may therefore give an indication on the fate of AuNPs on long-term exposure to cells and may also assist in safety evaluation of AuNPs.

Facile Attachment of TAT Peptide on Gold Monolayer Protected Clusters: Synthesis and Characterization.

High affinity thiolate-based polymeric capping ligands are known to impart stability onto nanosized gold nanoparticles. Due to the stable gold-sulfur bond, the ligand forms a protective layer around the gold core and subsequently controls the physicochemical properties of the resultant nanogold mononuclear protected clusters (AuMPCs). The choice of ligands to use as surfactants for AuMPCs largely depends on the desired degree of hydrophilicity and biocompatibility of the MPCs, normally dictated by the intended application. Subsequent surface modification of AuMPCs allows further conjugation of additional biomolecules yielding bilayer or multilayered clusters suitable for bioanalytical applications ranging from targeted drug delivery to diagnostics. In this study, we discuss our recent laboratory findings on a simple route for the introduction of Trans-Activator of Transcription (TAT) peptide onto the surface of biotin-derivatised gold MPCs via the biotin-strepavidin interaction. By changing the surface loading of biotin, controlled amounts of TAT could be attached. This bioconjugate system is very attractive as a carrier in intercellular delivery of various delivery cargoes such as antibodies, proteins and oligonucleotides.

Gold nanoparticle based Tuberculosis immunochromatographic assay: the quantitative ESE Quanti analysis of the intensity of test and control lines.

A rapid dual channel lateral flow assay for the detection of Mycobacterium Tuberculosis antibodies (MTB 38 kDa monoclonal antibody) in human blood was developed. The MTB 6-14-38 kDa fusion antigen and anti-Protein A were used as the capture proteins for test and control lines respectively. Protein A labeled 40 nm gold nanoparticles were used as the detection conjugate. Whole blood and serum were spiked with MTB 38 kDa monoclonal antibody to make a positive sample model. The developed lateral flow was used to test MTB 38 kDa monoclonal antibody, and a detection limit of 5 ng/ml was used as a cut-off concentration of the analytes. The effect of the analyte concentration on the MTB lateral flow assay was studied using the variation of the intensity obtained from a ESE Quanti reader. There was a direct correlation between the analyte (MTB 38 kDa monoclonal antibody) concentration and the intensity of the test line. The intensity increased with an increase in the concentration of MTB 38 kDa monoclonal antibody, while in contrast, an increase in analyte concentration decreased the intensity of the control line.

Label-free in vitro toxicity and uptake assessment of citrate stabilised gold nanoparticles in three cell lines.

BACKGROUND: Reliable in vitro toxicity testing is needed prior to the commencement of in vivo testing necessary for hazard identification and risk assessment of nanoparticles. In this study, the cytotoxicity and uptake of 14 nm and 20 nm citrate stabilised gold nanoparticles (AuNPs) in the bronchial epithelial cell line BEAS-2B, the Chinese hamster ovary cell line CHO, and the human embryonic kidney cell line HEK 293 were investigated. METHODS: Cytotoxicity of the AuNPs was assessed via traditional XTT-, LDH-, and ATP-based assays, followed by cell impedance studies. Dark-field imaging and hyperspectral imaging were used to confirm the uptake of AuNPs into the cells. RESULTS: Interference of the AuNPs with the XTT- and ATP-based assays was overcome through the use of cell impedance technology. AuNPs were shown to be relatively non-toxic using this methodology; nevertheless CHO cells were the most sensitive cell type with 20 nm AuNPs having the highest toxicity. Uptake of both 14 nm and 20 nm AuNPs was observed in all cell lines in a time- and cell type-dependent manner. CONCLUSIONS: Using the cell impedance and dark-field hyperspectral imaging technologies, it was possible to study the toxicity of AuNPs in different cell lines and show that these cells could internalize AuNPs with their subsequent intracellular aggregation. It was also possible to show that this toxicity would not correlate with the level of uptake but it would correlate with cell-type and the size of the AuNPs. Therefore, these two label-free methodologies used in this study are suitable for in vitro studies on the effects of AuNPs, and could present themselves as appropriate and valuable methodologies for future nanoparticle toxicity and uptake studies.

Gold nanoparticles show electroactivity: counting and sorting nanoparticles upon impact with electrodes.

Gold nanoparticles (AuNPs) in aqueous 0.10 M HCl are shown to be electroactive at oxidising potentials greater than 1.0 V (vs. Ag/AgCl) by means of voltammetric monitoring of AuNP-electrode collisions. The method promises the use of anodic particle coulometry for the detection and characterisation of the AuNPs.

Monolayer-protected clusters of gold nanoparticles: impacts of stabilizing ligands on the heterogeneous electron transfer dynamics and voltammetric detection.

Surface electrochemistry of novel monolayer-protected gold nanoparticles (MPCAuNPs) is described. Protecting ligands, (1-sulfanylundec-11-yl)tetraethylene glycol (PEG-OH) and (1-sulfanylundec-11-yl)poly(ethylene glycol)ic acid (PEG-COOH), of three different percent ratios (PEG-COOH:PEG-OH), 1:99 (MPCAuNP-COOH(1%)), 50:50 (MPCAuNP-COOH(50%)), and 99:1 (MPCAuNP-COOH(99%)), were studied. The electron transfer rate constants (k(et)/s(-1)) in organic medium decreased as the concentration of the surface-exposed -COOH group in the protecting monolayer ligand is increased: MPCAuNP-COOH(1%) (approximately 5 s(-1)) > MPCAuNP-COOH(50%) (approximately 4 s(-1)) > MPCAuNP-COOH(99%) (approximately 0.5 s(-1)). In aqueous medium, the trend is reversed. The surface pK(a) was estimated as approximately 8.2 for the MPCAuNP-COOH(1%), while both MPCAuNP-COOH(50%) and MPCAuNP-COOH(99%) showed two pK(a) values of about 5.0 and approximately 8.0. These results have been interpreted in terms of the quasi-solidity and quasi-liquidity of the terminal -OH and -COOH head groups, respectively. MPCAuNP-COOH(99%) excellently suppressed the voltammetric response of the ascorbic acid but enhanced the electrocatalytic detection of epinephrine compared to the other MPCAuNPs studied. This study reveals important factors that should be considered when designing electrode devices that employ monolayer-protected gold nanoparticles and possibly for some other redox-active metal nanoparticles.