Stability Of AuNPs Research Articles

Synthesis and Stabilization of Gold Nanoparticles Using Water-Soluble Synthetic and Natural Polymers.

Gold nanoparticles (AuNPs) were synthesized and stabilized using the one-pot method and growth seeding, through utilization of synthetic polymers, including poly(N-vinylpyrrolidone) (PVP), poly(ethylene glycol) (PEG), and poly(vinylcaprolactame) (PVCL), as well as natural polysaccharides, including gellan, welan, pectin, and κ-carrageenan. The absorption spectra, average hydrodynamic size, ζ-potential, and morphology of the gold nanoparticles were evaluated based on various factors, such as polymer concentration, molecular mass of polymers, temperature, and storage time. The optimal polymer concentration for stabilization of AuNPs was found to be 4.0 wt % for PVP, 0.5 wt % for gellan, and 0.2 wt % for pectin, welan, and κ-carrageenan. The values of the ζ-potential of polymer-stabilized AuNPs show that their surfaces are negatively charged. Most of the AuNPs are polydisperse particles, though very monodisperse AuNPs were detected in the presence of a 0.5 wt % gellan solution. At a constant polymer concentration of PVP (4 wt %), the average size of the PVP–AuNPs decreased with the decrease of molecular weight, and in the following order: PVP 350 kDa (~25 nm) > PVP 40 kDa (~8 nm) > PVP 10 kDa (~4 nm). The combination of Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy revealed that the functional groups of polymers that are responsible for stabilization of AuNPs are lactam ring in PVP, carboxylic groups in gellan and welan, esterified carboxylic groups in pectin, and SO2 groups in κ-carrageenan. Viscometric and proton nuclear magnetic resonance (1H NMR) spectroscopic measurements showed that the temperature-dependent change in the size of AuNPs, and the gradual increase of the intensity of AuNPs at 550 nm in the presence of gellan, is due to the rigid and disordered conformation of gellan that affects the stabilization of AuNPs. The AuNPs synthesized in the presence of water-soluble polymers were stable over a period of 36 days. Preliminary results on the synthesis and characterization of gold nanorods stabilized by polymers are also presented.

Dual-Product Synergistically Enhanced Colorimetric Assay for Sensitive Detection of Lipid Transferase Activity.

Lipid transferase-catalyzed protein lipidation plays critical roles in many physiological processes and it has been an increasingly attractive therapeutic target from cancer to neurodegeneration, while sensitive detection of lipid transferase activity in biological samples remains challenging. Here, we presented an AuNP-based colorimetric method with dual-product synergistically enhanced sensitivity for convenient detection of lipid transferase activity. Homo sapiens N-myristoyltransferase 1 (HsNMT1), a key lipid transferase, was selected as the model. Accordingly, positively charged substrate peptides (Pep) of HsNMT1 can induce the aggregation of AuNPs through disrupting their electrostatic repulsion, while the HsNMT1-catalyzed lipid modification generates aggregated lipidated peptides (C14-Pep) and negatively charged HS-CoA, which will eliminate the disruption and stabilize the AuNPs by the formation of Au-S bonds, respectively. Consequently, charge reversal of the biomolecules and the formation of Au-S bonds synergistically contribute to the stability of AuNPs in the presence of HsNMT1. Therefore, the HsNMT1 activity can be visually detected by the naked eye through the color change of the AuNPs originated from the change in their distance-dependent surface plasmon resonance absorptions. Here, the A520/A610 ratio can sensitively reflect the activity of HsNMT1 in the linear range of 2-75 nM with a low detection limit of 0.56 nM. Moreover, the method was successfully applied for probing the HsNMT1 activities in different cell lysates and inhibitor screening. Furthermore, given the replaceability of the substrate peptide, the proposed assay is promising for universal application to other lipid transferases and exhibits great potential in lipid transferase-targeted drug development.

Colorimetric assay for the determination of molecular weight distribution and branching characteristics of starch hydrolysates

Here, we present a gold nanoparticle-based colorimetric assay for the determination of molecular weight distribution and branching characteristics of enzymatically hydrolyzed starch. The steric stabilization effect of starch hydrolysate on the colloidal stability of AuNPs was found to be proportional to the ratio of high molecular weight amylopectins, which was clearly reflected by the intensity of the characteristic surface plasmonic resonance (SPR) absorbance peak of the AuNPs. The fractional change of high molecular weight amylopectin over the course of enzymatic hydrolysis reaction could be measured based on the intensity of SPR peak, in which the results correlated well with those obtained by conventional gel permeation chromatography. With the proper calibration of a specific set of enzyme and starch type, this method would provide a fairly simple and fast means of analyzing the molecular weight distribution of starch hydrolysate on site as well as the amylose content in native starch.

Star-shaped amino-functionalized poly(glycerol methacrylate)-stabilized gold nanoparticle composites with catalytic activity for reduction of 4-nitrophenol

Polymers containing amine moieties reduce Au(III) and stabilize gold nanoparticles (AuNPs). Such polymers can be used to synthesize AuNPs with controlled sizes and shapes, providing high stability to the colloidal solutions. A star amino-functionalized poly(glycidyl methacrylate) (PGMA) can quickly be prepared by epoxide ring-opening reactions. We functionalized the β-cyclodextrin-(PGMA)7 with diethanolamine (DEA) to create a star polymer (β-CD-(PGDEA)7) by atom transfer radical polymerization (ATRP), using β-cyclodextrin (β-CD) as macroinitiator. We determined the tertiary amine content (-NR2 = 0.63 mmol/g; R = -CH2-CH2-OH) on the star polymer by gravimetric analysis. The material β-CD-(PGDEA)7 reduces Au(III) and stabilize AuNPs, following a strategy in-situ. AuNPs (7.8 nm) were created by controlling the tertiary amine content/Au(III) molar ratio. The ratio 5 at pH 5.2 supports protonated -NR2H+ (that binds [AuCl4]−) and -NR2 (that stabilize AuNPs) on the star polymer structure, providing colloidal stability over 70 days at room temperature due to the high Zeta potential (+30 mV). The catalytic activity of the colloidal suspension containing the star polymer-capped AuNPs was investigated in the conversion of 4-nitrophenol to 4-aminophenol, using sodium borohydride as a hydrogen donor agent. A high catalyst activity (knor = 65.11 L/min μmol) was obtained at 0.0043 μmol/L AuNPs. The result is assigned to the excellent AuNPs stability imparted by star polymer coatings, showing that the star polymer does not influence the catalytic activity of the covered AuNPs.

Sponge-templating synthesis of sandwich-like reduced graphene oxide nanoplates with confined gold nanoparticles and their enhanced stability for solar evaporation

Solar evaporation based on plasmonic metal nanoparticles (MNPs) is emerging as a promising technology. However, the fine structure of MNPs is unstable, and both the high temperature generated by intensive light and corrosive ions in water could damage them. The performance will decline after recycling and long-time usage. To address these issues, we adopted a sponge-templating method for preparing sandwich-like nanoplates with the gold nanoparticles (Au NPs) confined in reduced graphene oxide (rGO) nanosheets. Due to the confinement effect, both the surface melting and ion diffusion were suppressed. The solar evaporator based on the sandwich-like nanoplates showed a high solar-vapor conversion efficiency of 85.2% under a high light intensity of 10 kW. After 30 times recycle of seawater desalination, the conversion efficiency scarcely decreased. These sandwich-like nanoplates with enhanced thermal and chemical stability of Au NPs are promising in the practical application of seawater desalination.

Sensitive biosensor for p53 DNA sequence based on the photothermal effect of gold nanoparticles and the signal amplification of locked nucleic acid functionalized DNA walkers using a thermometer as readout

A convenient photothermal biosensor was constructed for p53 DNA sequence detection based on the high discrimination capability of locked nucleic acid and high efficiency of signal amplification strategy of DNA walkers and difference photothermal effect between aggregated and dispersed gold nanoparticles (AuNPs). The presence of target activated the DNA walkers via the high affinity between target and complementary locked nucleic acid in the probe strand, resulting in the hybridization of the walker strand and substrate strand to form a specific enzyme recognition site. Under the cleavage of the endonuclease, single-stranded DNA (ssDNA) was released to the solution. Then the walker strand bound to a new substrate strand, and the next round of cleavage was triggered. The released ssDNA enhanced the stability of AuNPs against salt-induced aggregation. Given difference photothermal effects of the aggregated AuNPs and dispersed AuNPs under the near-infrared laser, the change of the temperature was detected by a common thermometer easily, which had a linear relationship with the target concentration in the range of 2.0–120.0 pM, the detection limit was 1.4 pM (S/N = 3). The proposed photothermal assay has been applied to detect p53 DNA sequence spiked complex samples with satisfying results.

Experimental and theoretical studies of 1-alkanethiols SAMs of various chain-lengths on gold nanoparticles and their effect on SERS, stability and surface properties

1-alkanethiol SAMs on AuNPs have shown great potential towards the development of new functional materials. This is mainly due to the formation of dense, tightly bonded and well-ordered systems on the surface of AuNPs. This work showcases how the chain-length of 1-alkanethiols affects the stability and surface properties of AuNPs and the SERS effect. Using experimental and theoretical studies (by means of DFT), this work shows the interaction between 1-alkanethiols of 3 different chain-lengths and AuNPs. The effects on the optical properties, surface charge, stability and SERS were also investigated. The red shift of surface plasmon resonance band was observed as a result of the interaction between AuNPs and 1-alkanethioals. The Zeta potential indicated a strong electrostatic repulsion between AuNPs which was reduced after functionalizing with 1-alkanethiols. The long chain alkanethiol was found to strongly reduce the surface charge due to strong interaction with AuNPs. The calculated nucleophilic centre cross-sections for all alkanethiols were found to increase with the chain-length, indicating a strong interaction existed between long chain alkanethiol and AuNPs. The SERS data shows an increase in Raman intensities of all 1-alkanethiols adsorbed on the surface of AuNPs. Both the experimental and theoretical data shows that the alkanethiol with short chain-length possesses the strongest Raman signal enhancement.

The Performance of Plasmonic Gold and Silver Nanoparticle-Based SERS Sensors

The influence of different types of plasmonic gold (Au-NPs) and silver (Ag-NPs) nanoparticles as well as aging on the performance of Surface-Enhanced Raman Scattering (SERS) sensors were studied. The average diameters of Au-NPs and Ag-NPs were about 23 nm and 15 nm, respectively, with a number of laser pulses of about 200. plasmonic nanoparticles were synthesized by laser ablation process in distilled water using a fixed energy laser fluence of about 14 J/cm2 of Nd-YAG laser, with 1060 nm wavelength and 1 Hz pulse repetition rate. The SERS sensor was carried out by quick drop casting process of plasmonicplasmonic nanoparticles on glass substrates. The morphological aspects and the performance of SERS sensors were investigated by high resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy. All the results indicated the significant dependence of the performance of the sensor on the types of the plasmonic nanoparticles . The obtained Raman signal intensity of Ag-NPs was about 105a.u. compared with 103a.u. for Au-NPs. While, the stability of Au-NPs was much higher than that of Ag-NPs based on SERS sensors due to the normal oxidation process of Ag-NPs.

Experimental Investigations on Behaviour of Rhamnolipid Biosurfactant as a Green Stabilizer for the Biological Synthesis of Gold Nanoparticles

Use of biosurfactant as a stabilizer for the biological synthesis of gold nanoparticles (AuNPs) is now emerging as a nontoxic and environmentally acceptable green chemistry procedure. Stability of AuNPs at different pHs is very important because our body has different pHs. This paper addresses this issue. In this work, first P. aeruginosa PTCC 13401 was used to produce rhamnolipid biosurfactant. The highest rhamnolipid production occurred at 120 h, achieving a value of 3.1 g/L. The thin layer chromatography (TLC) indicated that the crude product is a mixture of mono-rhamnolipid and di-rhamnolipid with retardation factor (Rf) value of about 0.35 and 0.78, respectively. Moreover, rhamnolipid solutions with different pHs were added to HAuCl4 solution and incubated for 24 h at 37 oC and 150 rpm. The formation of spherical AuNPs was monitored using a UV–vis spectrophotometer and verified by TEM. Our results showed that the formation of AuNPs occurred just for pH values between 7.0 -8.0. Measurement of the surface tension of the solution at different pH values was performed to find out the reason for this observation. Our results showed that the surface tension was also stable only between pH 7.0-8.0. This was inferred from precipitation of rhamnolipid at higher and lower pH values. The results of this work may help pharmacists to have a good prediction of behavior of rhamnolipid biosurfactants as a stabilizer for biomedical applications including tissue engineering and drug delivery.

Study of absorption of radio frequency field by gold nanoparticles and nanoclusters in biological medium

ABSTRACT Gold nanoparticles (AuNPs) and gold nanoclusters (AuNCs) are gaining interest in medical diagnosis and therapy as they are bio-compatible and are easy to functionalize. Their interaction with radiofrequency (RF) field for hyperthermia treatment is ambiguous and needs further investigation. A systematic study of the absorption of capacitive RF field by AuNPs and AuNCs dispersed in phosphate-buffered saline (PBS) is reported here in tissue mimicking phantom. The stability of AuNPs and AuNCs dispersed in PBS was confirmed for a range of pH and temperature expected during RF hyperthermia treatment. Colloidal gold solutions with AuNPs (10 nm) and AuNCs (2 nm), and control, i.e. PBS without nanogold, were loaded individually in 3 ml wells in a tissue phantom. Phantom heating was carried out using 27 MHz short-wave diathermy equipment at 200 and 400 W for control and colloidal gold solutions. Experiments were conducted for colloidal gold at varying gold concentrations (10–100 µg/ml). Temperature rise measured in the phantom wells did not show dependence on the concentration and size of the AuNPs. Furthermore, temperature rise recorded in the control was comparable with the measurements recorded in both nanogold suspensions (2, 10 nm). Dielectric property measurements of control and colloidal gold showed <3% difference in electrical conductivity between the control and colloidal gold for both nanoparticle sizes. From the measurements, it is concluded that AuNPs and AuNCs do not enhance the absorption of RF-capacitive field and power absorption observed in the biological medium is due to the ions present in the medium.

Environmentally benign rapid biosynthesis of extracellular gold nanoparticles using Aspergillus flavus and their cytotoxic and catalytic activities

In this study, the rapid biosynthesis of gold nanoparticles (AuNPs) by Aspergillus flavus culture supernatant was achieved by reducing 1 mM of chloroauric acid (HAuCl4) within 2 min at pH 7 and 30 °C. The biosynthesized nanoparticles exhibited maximum absorbance at 545 nm in UVvis spectroscopy. Transmission electron microscopy exhibited that AuNPs tend to take nearly spherical shapes with an average size of 12 nm. Fourier transform infrared analysis indicated that carboxyl, amine, and hydroxyl groups may participate in the biosynthesis and stabilization of AuNPs. Its zeta potential was found to be -33.01 mV. Energy dispersive X-rays showed a strong and typical beak of gold nanocrystallites with 80.84 % of analyzed sample. X-Ray diffraction spectrum displayed Bragg reflections identical to the gold nanocrystals. The results confirmed that biosynthesized AuNPs are a potent anticancer agent against A549, HepG2 and MCF7 cell lines with IC50 value 53.5, 60.7 and 100 μg/mL, respectively. Crystal violet assay confirmed the cytopathic effects of AuNPs on HepG2 and A549 cell lines. Annexin-V FITC assay and cell cycle confirmed the apoptotic effect and cell cycle arrest in G2/M phase, respectively for A549 cell line. Moreover, the results showed a degradation efficiency of AuNPs to 4-nitrophenol within 16 min.

Fabrication of paper-based SERS substrates by spraying silver and gold nanoparticles for SERS determination of malachite green, methylene blue, and crystal violet in fish.

A disposable surface-enhanced Raman scattering (SERS) substrate was prepared by successively spraying silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) onto commercial filter paper using an inexpensive consumer sprayer. The strong surface enhancement of AgNPs and chemical stability of AuNPs can be advantageously combined. The substrate exhibited excellent SERS activity for malachite green (MG), methylene blue (MB), and crystal violet (CV) under 785-nm excitation, with limits of detection (LODs) of 4.3 × 10-9, 2.0 × 10-8, and 8.1 × 10-8M, respectively. The substrate exhibited long-term stability, and it can be stored under ambient conditionsfor 4weeks with a relative standard deviation of less than 3% among peak intensities. The substrate also showed good reproducibility with a relative standard deviation of 7.1% among different substrate peak intensities. The substrates enable on-site determination of residual fishery drugs and distinguish MG, MB, and CV mixtures in spiked fish within 5min, and the average recoveries in fish scales and fish meat were better 90.1% and 76.9%, respectively. The method exhibited rapidity, simplicity, and high sensitivity and is expected to be used for thescreening ofadditives in food.

SYNTHESIS AND STABILITY OF RESVERATROL-GOLD NANOPARTICLE-POLYETHYLENE GLYCOL-FOLIC ACID CONJUGATES

Objective: Gold nanoparticles (AuNPs) can be used as targeted drug delivery systems, however, AuNPs have high surface energy and easily aggregate,thus negatively impacting nanoparticle stability. Therefore, it is necessary to add a stabilizing agent to AuNPs. To synthesize AuNPs stabilized bypolyethylene glycol conjugated to folic acid (FA), thus creating a model drug (resveratrol [RSV]) carrier that targets FA receptors on cancer cells.Methods: AuNPs were synthesized using the Turkevich method and stabilized by adding FA conjugated to polyethylene glycol (PEG). After RSV wasloaded, the conjugate was physically characterized and subjected to stability tests.Results: The RSV-AuNP had an average particle size of 51.97 nm (polydispersity index [PDI] 0.694, zeta potential – 24.6 mV). The RSV-AuNP-PEG-FAconjugate (RSV-AuNP-PEG-FA) had an average particle size of 195.6 nm (PDI=0.233, zeta potential=−21.1 mV). Stability tests showed that RSV-AuNPPEG-FA was more stable than RSV-AuNP. Furthermore, RSV-AuNP-PEG-FA and RSV-AuNP were more stable in buffer pH 7.4 and bovine serum albumin2% than in buffer pH 4, cysteine 1%, and NaCl 0.9% solutions.Conclusion: PEG-FA conjugates can improve the stability of RSV-loaded AuNP.

Effects of gold nanoparticle morphologies on interactions with proteins.

In biological milieu, nanoparticles tend to bind with a variety of biomolecules, particularly proteins, thereby forming an interfacial corona that endows them with a new biological identity. A thorough understanding of these protein coronas is likely to provide insights into nanoparticle biodistribution and nanoparticle-mediated cytotoxicity, leading to the expansion of potential applications and the further elucidation of the biological impacts of nanoparticles in biomedical applications. Herein, three differently shaped AuNPs were synthesized, namely nanospheres (AuNSPs), nanorods (AuNRs), and nanostars (AuNSs). The effects of the morphologies of AuNPs on the structures and functions of adsorbed fibrinogen (FIB) and trypsin (Try) were investigated via circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). Simultaneously, two different types of proteins were employed to investigate their influences on the stability and aggregation of AuNPs, using UV-vis absorption spectroscopy, transmission electron microscopy (TEM), microscale thermophoresis (MST), and dynamic light scattering (DLS). It was found that, compared to AuNSPs, the irregularly shaped AuNPs (e.g., AuNRs and AuNSs) had the capacity to induce greater changes in the secondary structures of the proteins. Furthermore, it appeared that the differently shaped AuNPs had obvious effects on the secondary structure of Try, and slight effects on the secondary structure of FIB. Consequently, these preliminary results indicated that the formation of protein corona, as well as the aggregation behaviors of the AuNPs was intimately related to the specific shapes of the AuNPs and the unique structures of the proteins.

Attaching DNA to Gold Nanoparticles With a Protein Corona.

DNA-functionalized gold nanoparticles (AuNPs) have been widely used in directed assembly of materials, biosensors, and drug delivery. This conjugate may encounter proteins in these applications and proteins may affect not only DNA adsorption but also the function of the attached DNA. Bovine serum albumin (BSA) with many cysteine residues can strongly adsorb on AuNPs and this conjugate showed high colloidal stability against salt, acid and base. Similar protection effects were also observed with a few other common proteins including catalase, hemoglobin, glucose oxidase, and horseradish peroxidase. DNA oligonucleotides without a thiol label can hardly displace adsorbed BSA, and BSA cannot displace pre-adsorbed DNA either, indicating a strongly kinetically controlled system. Thiolated DNA can be attached at a low density on the AuNPs with a BSA corona. The BSA corona did not facilitate the hybridization of the conjugated DNA, while a smaller peptide, glutathione allowed faster hybridization. Overall, proteins increase the colloidal stability of AuNPs, and they do not perturb the gold-thiol bond in the DNA conjugate, although a large protein corona may inhibit the hybridization function of DNA.

One step preparation of stable gold nanoparticle using red cabbage extracts under UV light and its catalytic activity

Herein, we have reported the synthesis, characterization and catalytic activity of highly stable gold nanoparticles (Au NPs) using red cabbage extract (RCE) under UV irradiation. The anthocyanin groups predominantly existing in RCE play an essential role for biosynthesis of stable Au NPs. The reasons for using anthocyanins: 1) they act as chelating agents for preferentially reacting with gold ions (Au3+) to form Au3+- anthocyanin complexes, 2) as light-active reductants for reduction of Au3+ to zero valent Au0 under UV irradiation and 3) as stabilizing agent for preventing Au NPs from aggregation in high salt concentration owing to their unique salt tolerance property. We also demonstrate that how reaction time, concentration of RCE, pH value of reaction solutions and using one more reducing agent affected formation of the Au NPs. The stability of RCE Au NPs was comparatively studied with commercial (citrate stabilized) Au NPs against 100 mM salt (NaCl) solution. The RCE-Au NP showed reduction ability for conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). UV–vis spectrometry, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential (ZT) methods were utilized to characterize the Au NPs. We demonstrated that how whole RCE (anthocyanins molecules are major component) can be used as photo-active reducing and stabilizing agents to form Au NPs in a short time under UV irradiation and strong reducing agent without additional agents.

Determination of adenosine triphosphate based on the use of fluorescent terbium(III) organic frameworks and aptamer modified gold nanoparticles.

A thiol-labeled adenosine triphosphate (ATP) binding aptamer is covalently linked on the surface of gold nanoparticles (AuNPs). This warrants protection of the red AuNPs from aggregation in high salt condition. The dispersed AuNPs can quench the fluorescence of the Tb(III)-MOFs at 547nm with the excitation wavelength of 290nm. This is ascribed to the combined action of inner filter effect, dynamic quenching and fluorescence resonance energy transfer. If the aptamer binds ATP to form folded structures, the AuNPs aggregate in high salt medium and the green fluorescence of the Tb(III)-MOFs is recovered. This method shows good sensitivity and selectivity for ATP, and the linear range is from 0.5 to 10μM of ATP with the detection limitat of 0.32μM. It was applied to the determination of ATP in (spiked) human plasma with satisfactory recoveries (from 93.2% to 106.3%). Oppositely, when the unlabeled aptamer is used instead of thiol-labeled aptamer in this process, the ATP-aptamer complexes rather than unlabeled aptamer provide greater protection for AuNPs against salt-induced aggregation. It is found that when the aptamer covalently binds to AuNPs, the steric hindrance is dominant for the stabilization of AuNPs; for unlabeled aptamer, the electrostatic repulsion is responsible for their stability, irrespective of whether ATP is present or not. These two different forces lead to the aggregation or dispersion of AuNPs with addition of target in salt solution. Graphical abstractThe impact of two repulsive forces (electrostatic repulsion and steric repulsion) on the stabilization of gold nanoparticles, and its application in fluorescent terbium metal-organic frameworks as a nanoprobe for adenosine triphosphate.

Synthesis and characterization of gold nanoparticles using fruit extract of Crescentia cujete L

Nanoparticles play important role in biotechnology such as food and drug industries. Gold nanoporticles(Au-NPS) have been wdely used in any drug therapies like drug delivery system for cancer, tumor, and diabetes treatment. Recently, Au-NPS have been devoleped to increase drug selectivity between tumor and normal cells. In the present studies, we use the fresh fruit ekstract (FFE) of crescentia cujete L mediated blue green alga for the synthesis of Au-NPS. The characterization of Au-NPS was carried out by using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and Transmission Electron spectroscopy (TEM). UV-VIS spectrometry indicated formation of nanoparticles which produces an intense absorbance peak at 531 nm. FTIR reveales the functional group involved in reduction and stabilization of Au-NPS. TEM have shown the morphology of Au-NPS with mean size 10,11 nm. Keywords: Crescentia cujete; gold nanoparticles; green alga

Analysis of temporally evolved nanoparticle-protein corona highlighted the potential ability of gold nanoparticles to stably interact with proteins and influence the major biochemical pathways in Brassica juncea

Nanoparticles (NPs) are known to adsorb proteins from their surroundings, forming NP-protein corona, which determines their fate, distribution, and effects, yet no information of protein corona (PC) has been gathered in the plants so far. Here we report, the analysis of temporally evolved (2 h–36 h) AuNP-protein coronas formed with Brassica juncea leaf crude protein & nuclear-enriched fraction. Protein coronas were characterized by the techniques including SDS PAGE (Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis), spectrophotometry, dynamic light scattering, zeta potential measurements, and Nano LC-MS/MS. Data analysis revealed the formation of two regimes (Regime I from 2 to 8 h & regime II from 16 to 36 h). Interestingly, coated AuNPs had approx. 30% higher zeta potential than pristine AuNPs after 36 h of interactions. The increase in hydrodynamic radii and adsorbed protein concentrations were consistent with the evolution of zeta potential, indicating the probable role of proteins in providing the better stability of AuNPs. MS analysis identified 97 proteins from regime I (soft corona) and 181 proteins from regime II (hard corona) of crude PC. On the other hand, 282 and 308 proteins were identified from nuclear soft and hard corona respectively, indicating better affinity of nuclear proteins. Besides, the high-affinity proteins (fold change ≥5) were found to be rich in lysine residues showing their involvement in promoting the adsorption. Notably, 27% of regime II corona proteins of the crude protein fraction were from energy-yielding pathways highlighting the potential ability AuNPs to influence the yield in Brassica juncea.

Effect of Phosphate, Sulfate, Arsenate, and Pyrite on Surface Transformations and Chemical Retention of Gold Nanoparticles (Au-NPs) in Partially Saturated Soil Columns.

The understanding of engineered nanoparticle (ENP) fate and transport in soil-water environments is important for the evaluation of potential risks of ENPs to the ecosystem and human health. The effects of pyrite grains and three types of oxyanions-sulfate, phosphate, and arsenate-on the retention of citrate-coated gold nanoparticles (citrate-Au-NPs) were studied in partially saturated soil column experiments. The mobility of Au-NP was found to be in the order: Au-NP-sulfide (originating from pyrite) > Au-NP-sulfate > citrate-Au-NP > Au-NP-arsenate > Au-NP-phosphate. Chemical retention mechanisms, including hydrogen bonding and calcium bridging, are proposed and discussed. The retention of Au-NPs in soil columns increases with the increased ability of transformed Au-NP surfaces to create strong hydrogen bonding through adsorbed oxyanions with soil surfaces. Oxyanions were also found to reduce aggregation and aggregate size of Au-NPs upon interaction with Ca2+ solution. While the effects of cationic substances on ENP transport and stability have been studied frequently, the results here demonstrate that anionic substances have a substantial effect on Au-NP transport and stability. Furthermore, this study highlights the importance of examining ENPs under environmentally relevant condition, and the significant effect of ENP transformations on their mobility in soils.