Colorimetric detection of the potent carcinogen aflatoxin B1 based on the aggregation of L-lysine-functionalized gold nanoparticles in the presence of copper ions.

L-lysine functionalized gold nanoparticles (AuNPs-Lys) have been widely used for the detection of worldwide interest analytes. In this work, a colorimetric assay for the detection of the carcinogen aflatoxin B1 (AFB1) based on the aggregation of AuNPs-Lys in the presence of copper ions was developed. For this purpose, AuNPs were synthesized in citrate aqueous solution, functionalized, and further characterized by UV-Vis, fluorescence, Fourier transform infrared spectroscopy (FTIR), nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). In general, AuNPS-Lys (~2.73 × 1011 particles) offered a clear colorimetric response in the presence of AFB1 and Cu2+ ions showing linearity in the range of 6.25 to 200 ng AFB1/mL, with a detection limit of 4.18 ng AFB1/mL via photometric inspection. Moreover, the performance of the proposed methodology was tested using the 991.31 AOAC official procedure based on monoclonal antibodies in maize samples artificially contaminated with AFB1. There was a good agreement between the measured AFB1 concentrations in both assays, the average recoveries for the colorimetric and immunoaffinity assays were between 91.2-98.4% and 96.0-99.2%, respectively. These results indicated that the colorimetric assay could be used as a rapid, eco-friendly, and cost-effective platform for the quantification of AFB1 in maize-based products.

PDDA induced step-pyramidal growth of nickel-platinum (Ni-Pt) nanoparticles for enhanced 4-nitrophenol reduction.

Herein, we report the synthesis of novel platinum-based nanoparticles with step-pyramidal growth induced by poly(diallyldimethylammonium chloride) (PDDA). The complex stepped pyramidal shape became the central point for outstanding catalytic reduction of 4-nitrophenol, overcoming the activity of bare Pt nanoparticles. These results are valuable for the catalytic degradation of reactive molecules.

The ionophore thiomaltol induces rapid lysosomal accumulation of copper and apoptosis in melanoma.

In this report, we investigate the toxicity of the ionophore thiomaltol (Htma) and Cu salts to melanoma. Divalent metal complexes of thiomaltol display toxicity against A375 melanoma cell culture resulting in a distinct apoptotic response at submicromolar concentrations, with toxicity of Cu(tma)2 > Zn(tma)2 >> Ni(tma)2. In metal-chelated media, Htma treatment shows little toxicity, but the combination with supplemental CuCl2, termed Cu/Htma treatment, results in toxicity that increases with suprastoichiometric concentrations of CuCl2 and correlates with the accumulation of intracellular copper. Electron microscopy and confocal laser scanning microscopy of Cu/Htma treated cells shows a rapid accumulation of copper within lysosomes over the course of hours, concurrent with the onset of apoptosis. A buildup of ubiquitinated proteins due to proteasome inhibition is seen on the same timescale and correlates with increases of copper without additional Htma.

Determination of Salivary Sialic Acid Through Nanotechnology: A Useful Biomarker for the Screening of Breast Cancer.

PURPOSE: To demonstrate the usefulness of sialic acid (SA) in saliva as a biomarker for breast cancer (BC) and develop a new tool for early detection. METHODS: Considering that the amount of SA in human saliva is limited, the levels of SA were measured using surface-enhanced Raman spectroscopy (SERS) with tailored citrate-reduced silver nanoparticles. We calibrated the spectrum using analytical reagent SA. The 164 patients included in this study were undergoing screening mammography and/or ultrasound testing. The SA test was performed in the absence of previous information regarding the health of the subjects. Biopsies were performed to determine the diagnosis of cancer condition. The biopsy studies determined that 35 patients are BC affected and 129 gave negative results. RESULTS: SERS showed a sensitivity and specificity of 80 and 93%, respectively. The cut-off value for SA (12.5 mg/dL) was established through a receiver operating characteristic (ROC) curve analysis. The area under the curve of the ROC analysis resulted in 95% with this SA level cut-off. Our results suggest that SA may be a useful biomarker for the screening of breast cancer in women. CONCLUSIONS: Our results suggest that the SA levels measured from saliva may be highly sensitive and specific markers for the presence of breast cancer.

Determination of sialic acid in saliva by means of surface-enhanced Raman spectroscopy as a marker in adnexal mass patients: ovarian cancer vs benign cases.

BACKGROUND: To demonstrate the use of surface-enhanced Raman spectroscopy (SERS) to determine sialic acid (SA) levels in saliva using silver nanoparticles as substrates, in adnexal mass patients scheduled for surgical intervention to remove invasive masses, with the aim to compare SA levels in benign tumor vs ovarian cancer patients. METHODS: Quantification of SA levels was accomplished by measuring their SERS and calibrating with analytical reagent SA. The mean SA concentration in saliva from 37 benign adnexal mass resulted smaller (5.1 mg/dL) than the mean concentration in 15 Ovarium cancer patients (23 mg/dL). The cancer condition was determined by biopsy of the removed adnexal mass. The CA-125 biomarker was also measured. The predictive potential of both biomarkers is discussed, together with the malignity risk index (MRI). RESULTS: Our results showed a sensitivity/specificity of 80%/100% with a cutoff to distinguish between benign/cancer cases of SA 15.5 mg/dL, as established from a ROC analysis. Our results suggest that SA may be a more useful biomarker than CA-125 to detect ovarian cancer. CONCLUSIONS: Our results suggest that the SA levels measured from saliva may be as good predictors as the MRI index for the presence of ovarian cancer in sensitivity/negative predictive value and outperforms it in specificity/positive predictive value.

Metallic Two-Dimensional Nanoframes: Unsupported Hierarchical Nickel-Platinum Alloy Nanoarchitectures with Enhanced Electrochemical Oxygen Reduction Activity and Stability.

Electrochemical oxygen reduction reaction (ORR) catalysts that have both high activities and long-term stabilities are needed for proton-exchange membrane fuel cells (PEMFCs) and metal-air batteries. Two-dimensional (2D) materials based on graphene have shown high catalytic activities, however, carbon-based materials result in significant catalyst degradation due to carbon oxidation that occurs at high electrochemical potentials. Here, we introduce the synthesis and electrochemical performance of metallic 2D nanoframes which represent a new approach to translate 2D materials into unsupported (carbon-free) electrocatalysts that have both significantly higher ORR catalytic activities and stabilities compared with conventional Pt/carbon electrocatalysts. Metallic Ni-Pt 2D nanoframes were synthesized by controlled thermal treatments of Pt-decorated Ni(OH)2 nanosheets. The nanoframes consist of a hierarchical 2D framework composed of a highly catalytically active Pt-Ni alloy phase with an interconnected solid and pore network that results in three-dimensional molecular accessibility. The inclusion of Ni within the Pt structure resulted in significantly smaller Pt lattice distances compared to those of Pt nanoparticles. On the basis of its unique local and extended structure, the ORR specific activity of Ni-Pt 2D nanoframes (5.8 mA cmPt-2) was an order of magnitude higher than Pt/carbon. In addition, accelerated stability testing at elevated potentials up to 1.3 VRHE showed that the metallic Ni-Pt nanoframes exhibit significantly improved stability compared with Pt/carbon catalysts. The nanoarchitecture and local structure of metallic 2D nanoframes results in high combined specific activity and elevated potential stability. Analysis of the ORR electrochemical reaction kinetics on the Ni-Pt nanoframes supports that at low overpotentials the first electron transfer is the rate-determining step, and the reaction proceeds via a four electron reduction process. The ability to create metallic 2D structures with 3D molecular accessibility opens up new opportunities for the design of high activity and stability carbon-free catalyst nanoarchitectures for numerous electrocatalytic and catalytic applications.

SERS-active Au/SiO2 clouds in powder for rapid ex vivo breast adenocarcinoma diagnosis.

In the present work, we report a dry-based application technique of Au/SiO2 clouds in powder for rapid ex vivo adenocarcinoma diagnosis through surface-enhanced Raman scattering (SERS); using low laser power and an integration time of one second. Several characteristic Raman peaks frequently used for the diagnosis of breast adenocarcinoma in the range of the amide III are successfully enhanced by breading the tissue with Au/SiO2 powder. The SERS activity of these Au/SiO2 powders is attributed to their rapid rehydration upon contact with the wet tissues, which promotes the formation of gold nanoparticle aggregates. The propensity of the Au/SiO2 cloud structures to adsorb biomolecules in the vicinity of the gold nanoparticle clusters promotes the necessary conditions for SERS detection. In addition, electron microscopy, together with elemental analysis, have been used to confirm the structure of the new Au/SiO2 cloud material and to investigate its distribution in breast tissues.

Advanced microscopy of star-shaped gold nanoparticles and their adsorption-uptake by macrophages.

Metallic nanoparticles have diverse applications in biomedicine, as diagnostics, image contrast agents, nanosensors and drug delivery systems. Anisotropic metallic nanoparticles possess potential applications in cell imaging and therapy + diagnostics (theranostics), but controlled synthesis and growth of these anisotropic or branched nanostructures has been challenging and usually require use of high concentrations of surfactants. Star-shaped gold nanoparticles were synthesized in high yield through a seed mediated route using HEPES as a precise shape-directing capping agent. Characterization was performed using advanced electron microscopy techniques including atomic resolution TEM, obtaining a detailed characterization of nanostructure and atomic arrangement. Spectroscopy techniques showed that the particles have narrow size distribution, monodispersity and high colloidal stability, with absorbance into NIR region and high efficiency for SERS applications. Gold nanostars showed to be biocompatible and efficiently adsorbed and internalized by macrophages, as revealed by advanced FE-SEM and backscattered electron imaging techniques of complete unstained uncoated cells. Additionally, low voltage STEM and X-ray microanalysis revealed the ultra-structural location and confirmed stability of nanoparticles after endocytosis with high spatial resolution.

Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques.

Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO(2), TiO(2) and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO(2) and TiO(2), whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution.

Polarization microscopy with stellated gold nanoparticles for robust monitoring of molecular assemblies and single biomolecules.

Advances in plasmonic nanoparticle synthesis afford new opportunities for biosensing applications. Here, we apply a combination of a new type of plasmonic nanomaterial - stellated nanoparticles, and polarization-sensitive darkfield microscopy for detecting molecular assemblies and tracking of individual epidermal growth factor receptors within single live cells with high signal-to-background ratio. Depolarization of linear polarized light by stellated nanoparticles is over 15-fold more efficient than similarly-sized spheroidal nanoparticles. This efficient light depolarization allows robust detection of molecules labeled with stellated nanoparticles in cross-polarized imaging where the intrinsic light scattering from cells is significantly reduced. The imaging can be carried out with single molecule sensitivity for essentially unlimited time with no signal degradation.

Plasmon resonance coupling of metal nanoparticles for molecular imaging of carcinogenesis in vivo.

An effective cancer control strategy requires improved early detection methods, patient-specific drug selection, and the ability to assess response to targeted therapeutics. Recently, plasmon resonance coupling between closely spaced metal nanoparticles has been used to develop ultrasensitive bioanalytical assays in vitro. We demonstrate the first in vivo application of plasmon coupling for molecular imaging of carcinogenesis. We describe molecular-specific gold bioconjugates to image epidermal growth factor receptor (EGFR); these conjugates can be delivered topically and imaged noninvasively in real time. We show that labeling with gold bioconjugates gives information on the overexpression and nanoscale spatial relationship of EGF receptors in cell membranes, both of which are altered in neoplasia. EGFR-mediated aggregation of gold nanoparticles in neoplastic cells results in more than a 100-nm color shift and a contrast ratio of more than tenfold in images of normal and precancerous epithelium in vivo, dramatically increasing contrast beyond values reported previously for antibody-targeted fluorescent dyes.

Noble-metal nanoparticles directly conjugated to globular proteins.

We report the synthesis of gold nanoparticles directly conjugated to bovine serum albumin protein by chemical reduction in aqueous solution. Transmission electron microscopy reveals that the gold nanoparticles are well dispersed with an average diameter less than 2 nm, and elemental analysis verifies the composition of the gold-protein conjugates. Infrared spectroscopy confirms that the polypeptide backbone is not cleaved during the conjugation process and that the side chain functional groups remain intact. Raman spectroscopy demonstrates that the disulfide bonds in the conjugated protein are broken and thus are available for interaction with the nanoparticle surface. This synthesis method is a new technique for directly attaching gold nanoparticles to macromolecular proteins.

Preparation and characterization of individual peptide-wrapped single-walled carbon nanotubes.

Two challenges for effectively exploiting the remarkable properties of single-walled carbon nanotubes (SWNTs) are the isolation of intact individual nanotubes from the raw material and the assembly of these isolated SWNTs into useful structures. In this study, we present atomic force microscopy (AFM) evidence that we can isolate individual peptide-wrapped SWNTs, possibly connected end-to-end into long fibrillar structures, using an amphiphilic alpha-helical peptide, termed nano-1. Transmission electron microscopy (TEM) and well-resolved absorption spectral features further corroborate nano-1's ability to debundle SWNTs in aqueous solution. Peptide-assisted assembly of SWNT structures, specifically in the form of Y-, X-, and intraloop junctions, was observed in the AFM and TEM images.