Serum Gold Research Articles

Dried blood spot improves global access to aquaporin-4-IgG testing for neuromyelitis optica.

This study aimed to evaluate the diagnostic accuracy of dried blood spot (DBS) compared with conventional serum Aquaporin-4-IgG (AQP4-IgG) testing. Prospective multicenter diagnostic study was conducted between April 2018 and October 2023 across medical centers in the United States, Uganda, and the Republic of Guinea. Neuromyelitis optica spectrum disorder (NMOSD) patients and controls collected blood on filter paper cards along with concurrent serum samples. These samples underwent analysis using flow cytometric live-cell-based assays (CBA) and enzyme-linked immunosorbent assay (ELISA) to determine AQP4 serostatus. The accuracy of AQP4-IgG detection between DBS and serum (gold standard) was compared. Among 150 participants (47 cases, 103 controls), there was a strong correlation between DBS and serum samples (Spearman's correlation coefficient of 0.82). The AUC was 0.97 (95% CI: 0.92-0.99). AQP4-IgG detection through DBS showed 87.0% sensitivity (95% CI: 0.74-0.95) and 100% specificity (95% CI: 0.96-1.00) using CBA, and 65.2% sensitivity (95% CI: 0.43-0.84) and 95.2% specificity (95% CI: 0.76-0.99) using ELISA. Serum ELISA demonstrated 69.6% sensitivity (95% CI: 0.47-0.87) and 98.4% specificity (95% CI: 0.91-0.99). The stability of DBS in detecting AQP4-IgG persisted over 24 months for most cases. The DBS represents a viable alternative for detecting AQP4-IgG in resource-limited settings to diagnose NMOSD, offering high sensitivity and specificity comparable to serum testing. Moreover, DBS has low shipping costs, is easy to administer, and is suitable for point-of-care testing.

Anticancer photodynamic activities of triphenylphosphine-labelled phthalocyanines and their bovine serum albumin-gold nanoparticles- complexes on melanoma A375 cell lines in vitro

This work reports on the synthesis of triphenylphosphine-labelled cationic phthalocyanines (Pc) complexed with bovine serum albumin (BSA) and gold nanoparticles (Au NPs). This nano-complex (Pc-BSA-Au) is studied for its photodynamic therapy (PDT) activity compared to the non-complexed Pc counterpart. The photochemical properties and in vitro PDT efficacies of the Pc and the nano-complex were determined and are compared herein. The singlet oxygen (1O2) yields of the Pcs were determined and are reported in DMF. A singlet oxygen quantum yield of 0.47 was obtained for the Pcs. The PDT efficacies of the complexes were thereafter determined using malignant melanoma A375 cancer cell line in vitro. An increase in the cell toxicity was observed for cells treated with Pc-BSA-Au compared to those treated with the Pc alone. The cell survival percentages were 23.1% for cells treated with Pc-BSA-Au and 48.7% for those treated with Pc alone under PDT treatments.

Chemical equilibria in aqueous solutions of H[AuCl4] and bovine or human serum albumin

Interaction of metals with serum albumins is of special interest as it may mediate the toxic or beneficial action of metal ions and their complexes that are often considered (pro)drugs. Among metals, gold(III) draws special attention because of the antibacterial activity of its complexes reported recently. The paper focuses on the interactions between bovine and human serum albumins and gold(III) species in aqueous solutions. Tetrachloroaurate(III) hydrolysis, protein self-association and interactions involving chloride ions are accounted for to determine the most probable stoichiometric composition of gold(III) associated with proteins and the related binding constants. The data obtained are used to calculate the equilibrium composition of the solution containing [AuCl4]−, biologically active hydrazone derived from pyridoxal 5′-phosphate and bovine serum albumin at different pH values.

Theoretical investigation on the effect of volume fraction in the optical trapping of gold nanoparticles

Stable optical trapping of gold nanoparticles is essential and desirable because of its wide applications in nanotechnology. While several factors have been proposed to affect optical trapping stability, the sample’s volume fraction during optical trapping has often been neglected. To address this, by utilizing the effective medium theory, we analyze the stability of optical trapping of a gold nanoparticle in human serum albumin solutions, HIV-1,virus solutions, and gold nanoparticle solutions in this article. Our comparative analysis of the optical force and potential on a single gold nanoparticle in solutions of varying volume fractions reveals that both parameters decrease with increasing volume fraction. This finding can aid in more effective control of gold nanoparticles in various applications.

Controlled assembly of gold and albumin nanoparticles to form hybrid multimeric nanomaterials

AbstractMultimeric nanoparticles (MNP) possess unique physical, chemical, and biological properties compared to monomeric NP thus, being used in applications ranging from photonic devices to cancer therapy. Despite the potential, the synthesis of well‐defined MNP poses a significant challenge to scientists and remains elusive. One commonly used synthetic methodology to generate these structures is the self‐assembly of individual particles. However, the surface of the individual particles in this assembly is saturated, so the esthetically beautiful structure would lack functional utility. Direct reaction of different NP is yet another way to synthesize multimeric structure. Nevertheless, the inherent reactivity of NP always results in a statistical mixture of different clusters—varying from dimeric to multimeric structure. However, the process is facile and provides opportunities to synthesize a well‐defined mixture of MNP. Therefore, we used this approach to synthesize hybrid MNP composed of human serum albumin nanoparticles (HSA‐NP) and gold nanoparticles (AuNP). In this MNP, each HSA‐NP is attached with a median of five AuNP. The process is robust, and even the covalent attachment of dye to the surface of HSA‐NP did not deter the controlled assembly. The well‐defined MNP internalize within the cancer cells, whereas the aggregated nonspecific assembly failed to enter. The quantification of fluorescence in cells treated with MNP or pristine dye‐labeled HSA‐NP showed similar values, inferring that AuNP in MNP exhibit minimal or no influence in internalization. In summary, the synthetic process reported in this study can be used to develop MNP wherein each NP can potentially carry a drug or a reporter to combat diseases.

Nanotechnology-Based Strategies to Develop New Anticancer Therapies.

The blooming of nanotechnology has made available a limitless landscape of solutions responding to crucial issues in many fields and, nowadays, a wide choice of nanotechnology-based strategies can be adopted to circumvent the limitations of conventional therapies for cancer. Herein, the current stage of nanotechnological applications for cancer management is summarized encompassing the core nanomaterials as well as the available chemical–physical approaches for their surface functionalization and drug ligands as possible therapeutic agents. The use of nanomaterials as vehicles to delivery various therapeutic substances is reported emphasizing advantages, such as the high drug loading, the enhancement of the pay-load half-life and bioavailability. Particular attention was dedicated to highlight the importance of nanomaterial intrinsic features. Indeed, the ability of combining the properties of the transported drug with the ones of the nano-sized carrier can lead to multifunctional theranostic tools. In this view, fluorescence of carbon quantum dots, optical properties of gold nanoparticle and superparamagnetism of iron oxide nanoparticles, are fundamental examples. Furthermore, smart anticancer devices can be developed by conjugating enzymes to nanoparticles, as in the case of bovine serum amine oxidase (BSAO) and gold nanoparticles. The present review is aimed at providing an overall vision on nanotechnological strategies to face the threat of human cancer, comprising opportunities and challenges.

Probing protein-nanorod aggregates

Plasmonics The interaction of proteins with nanoparticles can enhance circular dichroism signals and provide a route for sensitive biodetection. However, ensemble measurements are insufficient for resolving the origin of plasmon-coupled circular dichroism (PCCD). Zhang et al. used single-particle circular differential scattering spectroscopy along with correlated tomographic reconstruction and electromagnetic simulations to study individual aggregates of bovine serum albumin and gold nanorods (see the Perspective by Kim and Kotov). Aggregates contribute to PCCD activity through formation of plasmonic hotspots, but single nanoparticles do not contribute. The protein does not function simply as a chiral chromophore but enables assembly of the chiral nanorod-protein complexes. Science , this issue p. [1475][1]; see also p. [1378][2] [1]: /lookup/doi/10.1126/science.aax5415 [2]: /lookup/doi/10.1126/science.aay7776

Unraveling the origin of chirality from plasmonic nanoparticle-protein complexes.

Plasmon-coupled circular dichroism has emerged as a promising approach for ultrasensitive detection of biomolecular conformations through coupling between molecular chirality and surface plasmons. Chiral nanoparticle assemblies without chiral molecules present also have large optical activities. We apply single-particle circular differential scattering spectroscopy coupled with electron imaging and simulations to identify both structural chirality of plasmonic aggregates and plasmon-coupled circular dichroism induced by chiral proteins. We establish that both chiral aggregates and just a few proteins in interparticle gaps of achiral assemblies are responsible for the ensemble signal, but single nanoparticles do not contribute. We furthermore find that the protein plays two roles: It transfers chirality to both chiral and achiral plasmonic substrates, and it is also responsible for the chiral three-dimensional assembly of nanorods. Understanding these underlying factors paves the way toward sensing the chirality of single biomolecules.

Adsorption of proteins on gold nanoparticles: One or more layers?

Adsorption of proteins on nanoparticles is a complex and poorly studied process. The mechanisms of protein layer formation can fundamentally differ depending on the composition of the medium, the nanoparticles' structure, the protein's nature, and other factors. In particular, monolayer or multilayer immobilization may occur. In the present work, the composition of conjugates of bovine serum albumin and immunoglobulin G with gold nanoparticles obtained by the Turkevich-Frens method are analyzed. The composition was studied by protein fluorescence measurement for particles ranging in size from 20 to 48 nm, depending on the pH of the immobilization medium (from 4 to 5 to 8-10). It was found that a pH shift of the immobilization medium from acidic to alkaline values is accompanied by a change in the mechanism of protein adsorption on the gold surface. In acidic pH conditions (4-5), effective binding of bovine serum albumin and gold nanoparticles occurs throughout the entire range of studied protein concentrations. In alkaline pH conditions (8-10), however, effective binding occurs only at concentrations of >10 μg/mL. This effect is not observed for immunoglobulin G, which is efficiently adsorbed onto nanoparticles throughout the entire range of studied concentrations and pH values. For acidic pH values, the surface of the particles is saturated with the amount of bound proteins, which approximately corresponds to the amount the monolayer is filled. For neutral and alkaline pH values, saturation is not observed and the amount of adsorbed protein certainly exceeds the monolayer filling, leading to multilayer immobilization.

Complexation of bovine serum albumin and gold nanorods revealed by plasmon-enhanced light scattering spectroscopy

ABSTRACTComplexation of bovine serum albumin (BSA) and gold nanorods has been investigated by plasmon-enhanced light scattering spectroscopy under external stimuli such as the changes in hydrogen ion concentration value and ionic strength, with addition of ethanol. The results indicated that the BSA chains tend to adopt a coil conformation by decreasing hydrogen ion concentration value. Scattering intensity of the gold nanorods–BSA system gradually decreases because BSA chains tend to adopt a coil conformation with addition of sodium chloride. This work will further extend the application range of this method due to its simplicity, rapidity, and sensitivity.

Enantioselective discrimination of l-/d-phenylalanine by bovine serum albumin and gold nanoparticles modified glassy carbon electrode

A new chiral biosensor able to discriminate and detect phenylalanine (Phe) enantiomers was fabricated by immobilizing bovine serum albumin (BSA) on gold-nanoparticle-modified glassy carbon electrodes.

Effects of surface compositional and structural heterogeneity on nanoparticle-protein interactions: different protein configurations.

As nanoparticles (NPs) enter into biological systems, they are immediately exposed to a variety and concentration of proteins. The physicochemical interactions between proteins and NPs are influenced by the surface properties of the NPs. To identify the effects of NP surface heterogeneity, the interactions between bovine serum albumin (BSA) and gold NPs (AuNPs) with similar chemical composition but different surface structures were investigated. Different interaction modes and BSA conformations were studied by dynamic light scattering, circular dichroism spectroscopy, fluorescence quenching and isothermal titration calorimetry (ITC). Depending on the surface structure of AuNPs, BSA seems to adopt either a "side-on" or an "end-on" conformation on AuNPs. ITC demonstrated that the adsorption of BSA onto AuNPs with randomly distributed polar and nonpolar groups was primarily driven by electrostatic interaction, and all BSA were adsorbed in the same process. The adsorption of BSA onto AuNPs covered with alternating domains of polar and nonpolar groups was a combination of different interactions. Overall, the results of this study point to the potential for utilizing nanoscale manipulation of NP surfaces to control the resulting NP-protein interactions.

Combination of UV–vis spectroscopy and chemometrics to understand protein–nanomaterial conjugate: A case study on human serum albumin and gold nanoparticles

Study of the interactions between proteins and nanomaterials is of great importance for understanding of protein nanoconjugate. In this work, we choose human serum albumin (HSA) and citrate-capped gold nanoparticles (AuNPs) as a model of protein and nanomaterial, and combine UV-vis spectroscopy with multivariate curve resolution by an alternating least squares (MCR-ALS) algorithm to present a new and efficient method for comparatively comprehensive study of evolution of protein nanoconjugate. UV-vis spectroscopy coupled with MCR-ALS allows qualitative and quantitative extraction of the distribution diagrams, spectra and kinetic profiles of absorbing pure species (AuNPs and AuNPs-HSA conjugate are herein identified) and undetectable species (HSA) from spectral data. The response profiles recovered are converted into the desired thermodynamic, kinetic and structural parameters describing the protein nanoconjugate evolution. Analysis of these parameters for the system gives evidence that HSA molecules are very likely to be attached to AuNPs surface predominantly as a flat monolayer to form a stable AuNPs-HSA conjugate with a core-shell structure, and the binding process takes place mainly through electrostatic and hydrogen-bond interactions between the positively amino acid residues of HSA and the negatively carboxyl group of citrate on AuNPs surface. The results obtained are verified by transmission electron microscopy, zeta potential, circular dichroism spectroscopy and Fourier transform infrared spectroscopy, showing the potential of UV-vis spectroscopy for study of evolution of protein nanoconjugate. In parallel, concentration evolutions of pure species resolved by MCR-ALS are used to construct a sensitive spectroscopic biosensor for HSA with a linear range from 1.8 nM to 28.1 nM and a detection limit of 0.8 nM.

Detection of Aflatoxin M1 in Milk by Dynamic Light Scattering Coupled with Superparamagnetic Beads and Gold Nanoprobes

This study aimed to develop a rapid and sensitive method for detection of aflatoxin M1 (AFM) by dynamic light scattering (DLS) coupled with superparamagnetic beads and gold nanoprobes. The nanoprobes were synthesized by the conjugate of AFM and bovine serum albumin (AFM-BSA), BSA, and gold nanoparticles. Magnetic beads-based immunosorbent assay (MBISA) was used to measure the concentration of AFM by direct competition between AFM and nanoprobes. DLS was used to determine the concentration of unattached nanoprobes that was positively proportional to the concentration of AFM in the sample. TEM images prove that the as-prepared nanoprobes were able to attach on the magnetic beads through the antibody-antigen reaction. Compared to conventional ELISA, MBISA could effectively reduce the incubation time to 15 min in buffer solution and completely eliminate the color development step, thus simplifying the analysis of AFM. A linear relationship was observed between the inhibition values and the concentrations of AFM in both buffer solution (0-1000 ng·L(-1)) and spiked milk samples (0-400 ng·L(-1)). The limit of detection was found to be 37.7 ng·L(-1) for AFM in buffer solution and 27.5 ng·L(-1) in milk samples. These results demonstrate that DLS coupled with magnetic beads and gold nanoprobes is a rapid and effective method to detect AFM. This method could also be easily extended to rapid detection of other mycotoxins and biological species.

Spectroscopic investigation of the interactions between gold nanoparticles and bovine serum albumin

The interactions between bovine serum albumin (BSA) and gold nanoparticles (AuNPs), and the conformational changes of BSA induced by this interaction, were investigated by UV-visible absorption spectroscopy, fluorescence spectroscopy, and Fourier transform infrared in combination with attenuated total reflection spectroscopy (ATR-FTIR). The critical adsorption density for preventing AuNP aggregation in 0.1 mol/L phosphate buffered saline (pH 7.2) was 23 BSA molecules per gold particle or 3.8×1012 BSA molecules/cm2. BSA bound to the AuNPs with high affinity (binding constant Ks=7.59×108 L/mol), and the intrinsic fluorescence of BSA was quenched by the AuNPs in accordance with the static quenching mechanism. Both fluorescence spectroscopy and ATR-FTIR showed that AuNPs induced conformational changes in BSA, which resulted in it becoming less compact and increased the polarity of the microenvironment around the tryptophan residue Trp-212.

Seleno-Auranofin (Et3PAuSe-tagl): Synthesis, Spectroscopic (EXAFS, 197Au Mössbauer, 31P, 1H, 13C, and 77Se NMR, ESI-MS) Characterization, Biological Activity, and Rapid Serum Albumin-Induced Triethylphosphine Oxide Generation

Seleno-auranofin (SeAF), an analogue of auranofin (AF), the orally active antiarthritic gold drug in clinical use, was synthesized and has been characterized by an array of physical techniques and biological assays. The Mössbauer and extended X-ray absorption fine structure (EXAFS) parameters of the solid compound demonstrate a linear P-Au-Se coordination environment at a gold(I) center, analogous to the structure of auranofin. The (31)P, (13)C, and (1)H NMR spectra of SeAF in chloroform solution closely resemble those of auranofin. The (77)Se spectrum consists of a singlet at 481 ppm, consistent with a metal-bound selenolate ligand. The absence of (2)J(PSe) coupling in the (31)P and (77)Se spectra may arise from dynamic processes occurring in solution or because the (2)J(PSe) coupling constants are smaller than the observed bandwidths. Electrospray ionization mass spectrometry (ESI-MS) spectra of SeAF in 50:50 methanol-water exhibited strong signals for [(Et(3)P)(2)Au](+), [(Et(3)PAu)(2)-mu-Se-tagl](+), and [Au(Se-tagl)(2)](-), which arise from ligand scrambling reactions. Three assays of the anti-inflammatory activity of SeAF allowed comparison to AF. SeAF exhibited comparable activity in the topically administered murine arachadonic acid-induced and phorbol ester-induced anti-inflammatory assays but was inactive in the orally administered carrageenan-induced assay in rats. However, in vivo serum gold levels were comparable in the rat, suggesting that differences between the in vivo metabolism of the two compounds, leading to differences in transport to the inflamed site, may account for the differential activity in the carrageenan-induced assay. Reactions of serum albumin, the principal transport protein of gold in the serum, demonstrated formation of AlbSAuPEt(3) at cysteine 34 and provided evidence for facile reduction of disulfide bonds at cysteine 34 and very rapid formation of Et(3)P=O, a known metabolite of auranofin.

Development and Validation of a Gold Nanoparticle Immunochromatographic Assay (ICG) for the Detection of Zearalenone

A monoclonal antibody (mAb)-based gold nanoparticle immunochromatographic assay (ICG) for zearalenone detection was developed, optimized, and validated. The detection limits of ICG optimized with appropriate amounts of zearalenone-bovine serum albumin and gold nanoparticle-mAb to zearalenone were 2.5 ng/mL and 30 μg/kg for the standard solution and spike sample, respectively, and a weak cross-reaction for α-zearalenol and β-zearalenol was observed. The assay required only 15 min to obtain results and one step to perform the assay. In validation, the results obtained from spiked corn (10, 20, 30, 50, and 100 μg/kg) and naturally contaminated corn samples by the ICG were in good agreement with those obtained by direct competitive enzyme-linked immunosorbent assay (DC-ELISA) and high-performance liquid chromatography (HPLC). Therefore, the results obtained in this study could be used as basic research for the development of zearalenone-ICG, and the ICG developed could be a useful on-site screening tool for the rapid detection of zearalenone in corn without special instrumentation.

A New Enzyme Immobilization Technique Based on Thionine‐Bovine Serum Albumin Conjugate and Gold Colloidal Nanoparticles for Reagentless Amperometric Biosensor Applications

AbstractA novel enzyme immobilization technique based on thionine‐bovine serum albumin conjugate (Th‐BSA) and gold colloidal nanoparticles (nano‐Au) was developed. Thionine was covalently bound onto the BSA film with glutaraldehyde(GA) as cross‐linker to achieve Th‐BSA conjugate. The free amino groups of thionine were then used to attach nano‐Au for the immobilization of horseradish peroxidase (HRP). Such nano‐Au/Th‐BSA matrix shows a favorable microenvironment for retaining the native activity of the immobilized HRP and thionine immobilized in this way can effectively shuttle electrons between the electrode and the enzyme. The proposed biosensor displays excellent catalytic activity and rapid response for H2O2. The linear range for the determination of H2O2 is from 4.9×10−7 to 1.6×10−3 M with a detection limit of 2.1×10−7 M at 3σ and a Michaelies‐Menten constant K$\rm{ {_{M}^{app}}}$ value of 0.023 mM.

Chitosan Reduced Gold Nanoparticles as Novel Carriers for Transmucosal Delivery of Insulin

Colloidal metallic systems have been recently investigated in the area of nanomedicine. Gold nanoparticles have found themselves useful for diagnostic and drug delivery applications. Herein we have reported a novel method for synthesis of gold nanoparticles using a natural, biocompatible and biodegradable polymer; chitosan. Use of chitosan serves dual purpose by acting as a reducing agent in the synthesis of gold nanoparticles and also promotes the penetration and uptake of peptide hormone insulin across the mucosa. To demonstrate the use of chitosan reduced gold nanoparticles as carriers for drug delivery, we report herein the transmucosal delivery of insulin loaded gold nanoparticles. Gold nanoparticles were prepared using different concentrations of chitosan (from 0.01% w/v up to 1% w/v). The gold nanoparticles were characterized for surface plasmon band, zeta potential, surface morphology, in vitro diffusion studies and fluorescence spectroscopy. The in vivo studies in diabetic male Wistar rats were carried out using insulin loaded chitosan reduced gold nanoparticles. Varying concentrations of chitosan used for the synthesis of gold nanoparticles demonstrated that the nanoparticles obtained at higher chitosan concentrations (>0.1% w/v) were stable showing no signs of aggregation. The nanoparticles also showed long term stability in terms of aggregation for about 6 months. Insulin loading of 53% was obtained and found to be stable after loading. Blood glucose lowering at the end of 2 h following administration of insulin loaded gold nanoparticles to diabetic rats was found to be 30.41 and 20.27% for oral (50 IU/kg) and nasal (10 IU/kg), respectively. Serum gold level studies have demonstrated significant improvement in the uptake of chitosan reduced gold nanoparticles. The synthesis of gold nanoparticles using a biocompatible polymer, chitosan would improve its surface properties for binding of biomolecules. Our studies indicate that oral and nasal administration of insulin loaded chitosan reduced gold nanoparticles has led to improved pharmacodynamic activity. Thus, chitosan reduced gold nanoparticles loaded with insulin prove to be promising in controlling the postprandial hyperglycemia.

Study on interaction between gold nanorod and bovine serum albumin

In this work we present the results of the study on the interactions between bovine serum albumin (BSA) and gold nanorod monitored by fluorescence spectroscopy of the intrinsic tryptophans at pH 7.4. Gold nanorod–albumin solution gave an emission spectrum in the wavelength range 300–440 nm with emission maxima at 351 nm when excited at 280 nm. The magnitude of fluorescence intensity increased with increasing nanorod concentration. The interaction of BSA with these nanorods shows an enhancement of fluorescence with binding constants of 0.13 × 10 8 M −1 and 0.27 × 10 8 M −1 for nanorod of aspect ratio 3.0 and 8.0, respectively. On the other hand, the titration of BSA with 14 nm gold nanosphere shows a strong quenching of fluorescence with a binding constant of 1.7 × 10 8 M −1. The fluorescence enhancement is probably due to a direct contact of gold nanorod {1 1 1} face with the bovine serum albumin as determined by DLS, UV–vis and Zeta potential measurements. These results suggest that the technique of fluorescence enhancement can be used successfully to study the nanorod–albumin interaction.