Size Of AuNPs Research Articles

One-pot generation of gold-polymer hybrid nanoparticles using a miniemulsion reactor system

We investigated one-pot synthesis of gold nanoparticles (AuNPs) and AuNPs-polymer hybrid nanoparticles in a water-in-oil (W/O) miniemulsion. Water nanodroplets were dispersed as a reactor in cyclohexane using dimethicone as a surfactant. First, we intended to generate AuNPs in water nanodroplets, which contained HAuCl4 with a mixture of 1-vinylpyrrolidone (VP) and N,N’-methylenebisacrylamide (MBAAm). Several AuNPs with the size of approximately 10–20 nm were generated in each nanodroplet via reduction of AuCl4- by dimethicone. On the other hand, AuNPs was scarcely generated in water nanodroplets containing HAuCl4 with 2-hydroxyethyl methacrylate (HEMA). Next, we carried out polymerization in water nanodroplets to encapsulate AuNPs into polymer nanoparticles. Several AuNPs were encapsulated within polymer particles by copolymerization of VP and MBAAm with an oil-soluble initiator (V-601), and some AuNPs were present in the oil phase. The encapsulation efficiency of AuNPs was 34%. The encapsulation efficiency of AuNPs was dramatically increased by increasing the concentration of the initiator. The same result was obtained by increasing the concentration of the crosslinker due to rapid gelation of nanodroplets. On the other hand, monodisperse particles could be obtained by polymerization of HEMA using a water-soluble initiator (V-65). After polymerization for 5 d at 65ºC, the color of the suspension changed from opaque blue to blue purple and the encapsulation efficiency of AuNPs (5–20 nm) increased to 99 wt%. The average number of AuNPs encapsulated in a PHEMA nanoparticle increased from 1.5 to 4.6 particle. Furthermore, the size of AuNPs could be tuned by increasing the HAuCl4 concentration, and the corresponding color of the suspensions such as blue, purple, and red could be observed. The number and location of AuNPs in polymer nanoparticles could also be tuned by additives such as L-histidine and polyvinylpyrrolidone. By drop-casting the obtained hybrid nanoparticles, we could obtain gold-polymer hybrid films where AuNPs were evenly distributed within a film. The films exhibited different colors corresponding to their LSPR of AuNPs.

Gold-nanoparticle-embedded hydrogel droplets with enhanced fluorescence for imaging and quantification of proteins in cells.

Conventional cellular protein detection techniques such as immunocytochemistry and flow cytometry require abundant cells, posing multiple challenges, including difficulty and cost for obtaining enough cells and the potential for clogging the instrument when using flow cytometry. Also, it is challenging to conduct cellular protein imaging and quantification simultaneously from a single experiment. We present a novel 3D platform, which integrates highly biocompatible cell-entrapped alginate hydrogel droplet array with gold-nanoparticle (AuNP)-based metal enhanced fluorescence (MEF), to achieve simultaneous imaging and quantification of proteins in intact cells in a sensitive manner. Compared to 2D immunocytochemistry, this 3D system allows for a higher cell loading capacity per unit area; together with the MEF-based signal enhancement from the embedded AuNPs, sensitive protein quantification was realized. Furthermore, compared to flow cytometry, this platform allows for protein imaging from individual cells. Taking the detection of EpCAM protein in ovarian cancer cells as a model, we optimized the AuNP size and concentration for optimal fluorescent signals. The 5nm AuNPs at 6.54 × 1013 particles/mL proved to be the most effective in signal enhancement, providing 2.4-fold higher signals compared to that without AuNPs and 6.4-fold higher signals than that of 2D immunocytochemistry. The number of cells required in our technology is 1-3 orders of magnitude smaller than that of conventional methods. This AuNP-embedded hydrogel platform combines the benefits of immunocytochemistry and flow cytometry, providing increased assay sensitivity while also allowing for qualitative analysis through imaging, suitable for protein determination in a variety of cells.

Effects of Au States in Thiol-Organosilica Nanoparticles on Enzyme-like Activity for X-ray Sensitizer Application: Focus on Reactive Oxygen Species Generation in Radiotherapy.

In radiotherapy, the use of Au nanoparticles (Au NPs) has been proposed to enhance cell damage by X-ray irradiation. Although the role of Au in radiotherapy is not fully understood, the catalytic activity of Au has been actively studied in the industrial field. Moreover, owing to their enzyme-like activity and high biocompatibility in vitro and in vivo, Au NPs present significant potential for biological applications. In this study, we incorporated different Au states both on the surface and embedded in thiol-organosilica (thiol-OS/Au series) to investigate the efficiency of anticancer cell activity of Au in radiotherapy. The thiol-OS/Au series comprised different Au(I)/Au(0) ratios and Au NPs, and different sizes of Au NPs were embedded in thiol-OS/Au. These thiol-OS/Au series samples were evaluated for enzyme-like activities in reactive oxygen species (ROS) generation by X-ray irradiation. Thiol-OS/Au embedded with small Au NPs (AC600/thiol-OS/Au) exhibited peroxidase (POD)-like activity under acidic conditions. This POD-like activity improved ROS generation and cytotoxicity under X-ray irradiation. Furthermore, AC600/thiol-OS/Au exhibited catalase (CAT)-like activity under basic conditions and showed no cytotoxicity toward nonirradiated cells. These results revealed the efficiency of functionalizing with small Au NPs that possess pH-controlled POD- and CAT-like activity as a radiosensitizer. We compared the suitability of using Au with different states to obtain the thiol-OS/Au series samples for application as radiosensitizers. The findings of this study will aid the design of efficacious strategies for the Au nanostructure-based radiotherapy of cancer cells.

Synthesis and Characterization of a Multiporous SnO2 Nanofibers-Supported Au Nanoparticles-Based Amperometric Sensor for the Nonenzymatic Detection of H2O2

The challenges of a heme protein and enzyme-based H2O2 sensor was subdued by developing a highly sensitive and practically functional amperometric gold nanoparticles (Au NPs)/SnO2 nanofibers (SnO2 NFs) composite sensor. The composite was prepared by mixing multiporous SnO2 NFs (diameter: 120–190 nm) with Au NPs (size: 3–5 nm). The synthesized Au NPs/SnO2 NFs composite was subsequently coated on a glassy carbon electrode (GCE) and displayed a well-defined reduction peak during a cyclic voltammetry (CV) analysis. The SnO2 NFs prevented the aggregation of Au NPs through its multiporous structure and enhanced the catalytic response by 1.6-fold. The SnO2 NFs-supported GCE/Au NPs/SnO2 NFs composite sensor demonstrated a very good catalytic activity during the reduction of hydrogen peroxide (H2O2) that displayed rapid amperometric behavior within 6.5 s. This sensor allowed for highly sensitive and selective detection. The sensitivity was 14.157 µA/mM, the linear detection range was from 49.98 µM to 3937.21 µM (R2 = 0.99577), and the lower limit of detection was 6.67 µM. Furthermore, the developed sensor exhibited acceptable reproducibility, repeatability, and stability over 41 days. In addition, the Au NPs/SnO2 NFs composite sensor was tested for its ability to detect H2O2 in tap water, apple juice, Lactobacillus plantarum, Bacillus subtilis, and Escherichia coli. Therefore, this sensor would be useful due to its accuracy and sensitivity in detecting contaminants (H2O2) in commercial products.

D2B-Functionalized Gold Nanoparticles: Promising Vehicles for Targeted Drug Delivery to Prostate Cancer.

Despite the multitude of therapeutic agents available to treat prostate cancer (PC), there are still no effective and safe measures to treat the tumor. It remains a challenge to develop a simple approach to target PC with specific antibodies. In our study, D2B monoclonal antibodies against a prostate-specific membrane antigen (PSMA) were used. We investigated the functionalization of gold nanoparticles (AuNPs) with D2B to generate favorable physicochemical and biological properties that mediate specific binding to PC. For this purpose, AuNPs with a size of about 25 nm were synthesized in water using sodium citrate as a reducing and stabilizing agent and then coated with D2B. Major physicochemical properties of naked and D2B-coated AuNPs were investigated by ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), and zeta potential measurements. The successful binding of D2B to AuNPs-citrate caused a 15 nm red shift in the UV-vis. This was assessed by DLS as an increase in zeta potential from ∼-45 to ∼-23 mV and in the size of AuNPs from ∼25 to ∼63 nm. Scanning electron microscopy confirmed the size shift of AuNPs, which was detected as an exterior organic layer of D2Bs surrounding each AuNP. Even at high exposure levels of the bioconjugates, PSMA-PC-3 cells exhibited minimal cytotoxicity. The specific and dose-dependent binding of AuNPs-D2B to PC-3-PSMA cells was validated by flow cytometry analysis. Our data provide effective drug delivery systems in PC theranostics.

Thiol-End-Group Dendrons Decorated with Gold Nanoparticles Immobilized on Amino-Functionalized Graphene Oxide for SERS Detection

Surface-enhanced Raman scattering (SERS) has abundant chemical fingerprint information to analyze complex analytes under aqueous conditions. However, SERS requires uniform metal particles to generate a hotspot effect and improve sensitivity and enhancement by localized surface plasmon resonance. Therefore, in this study, SERS detection chips have been developed using uniform gold nanoparticle (AuNP) arrays embedded on thiol-end-group dendritic polymers immobilized on amino-functionalized graphene oxide (AGO) thin films of transmission electron microscopy (TEM) grids. The graphene oxide (GO) thin film was fabricated by low-damage plasma with mixed gas (O2/H2) and then further functionalized by diethylenetriamine to form AGO substrates. Based on the efficient building block of dual-functional 4-isocyanato-4′-(3,3-dimethyl-2,4-dioxo-azetidino)-diphenylmethane (IDD), the 0.5 and 1.5 generations of thiol-end-functionalized poly(urea/malonamide) dendrons (DG0.5-SH and DG1.5-SH) were precisely synthesized and grafted onto AGO substrates. The interparticle gap of AuNPs could be well controlled and decorated on these thiol-end-group dendrons to achieve the optimal SERS enhancement effect by manipulating the sizes of AuNPs and generating dendrons. The results indicate that 31 nm AuNPs immobilized on the DG0.5-SH@AGO substrate exhibited reproducible and strong SERS enhancement compared with free AuNPs. Graphene-based SERS substrates provide rapid and stable SERS detection in solutions, which offers great potential for practical applications in detecting biomolecules and environmental pollutants.

Cytotoxicity Study of Gold Nanoparticle Synthesis Using Aloe vera, Honey, and Gymnema sylvestre Leaf Extract.

Gold nanoparticles (AuNPs) have gained importance in the field of biomedical research and diagnostics due to their unique physicochemical properties. This study aimed to synthesize AuNPs using Aloe vera extract, honey, and Gymnema sylvestre leaf extract. Physicochemical parameters for the optimal synthesis of AuNPs were determined using 0.5, 1, 2, and 3 mM of gold salt at varying temperatures from 20 to 50 °C. X-ray diffraction was used to evaluate the crystal structure of AuNPs, which came out to be a face-centered cubic structure. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis confirmed the size and shape of AuNPs between 20 and 50 nm from the Aloe vera, honey, and Gymnema sylvestre, as well as large-sized nanocubes in the case of honey, with 21-34 wt % of gold content. Furthermore, Fourier transform infrared spectroscopy confirmed the presence of a broadband of amine (N-H) and alcohol groups (O-H) on the surface of the synthesized AuNPs that prevents them from agglomeration and provides stability. Broad and weak bands of aliphatic ether (C-O), alkane (C-H), and other functional groups were also found on these AuNPs. DPPH antioxidant activity assay showed a high free radical scavenging potential. The most suited source was selected for further conjugation with three anticancer drugs including 4-hydroxy Tamoxifen, HIF1 alpha inhibitor, and the soluble Guanylyl Cyclase Inhibitor 1 H-[1,2,4] oxadiazolo [4,3-alpha]quinoxalin-1-one (ODQ). Evidence of the pegylated drug conjugation with AuNPs was reinforced by ultraviolet/visible spectroscopy. These drug-conjugated nanoparticles were further checked on MCF7 and MDA-MB-231 cells for their cytotoxicity. These AuNP-conjugated drugs can be a good candidate for breast cancer treatment that will lead toward safe, economical, biocompatible, and targeted drug delivery systems.

Effect of gold-nanoparticle size on microfiber saturable absorber for mode-locked erbium-doped fiber lasers

The optical performance of passively mode-locked erbium-doped fiber laser incorporating gold-nanoparticles (Au-NPs) of different sizes as saturable absorbers (SAs) was compared. A composite of Au-NPs with polydimethylsiloxane was spin coated on the surface of a microfiber waveguide. The fabricated Au-NP-based SA was deployed in a ring cavity erbium-doped fiber laser and its lasing performance was evaluated by comparing SA characteristics as well as pulse qualities among the different Au-NP sizes. The optimum pulse performance was realized when the SA was fabricated with 20 and 40 nm Au-NP size. For the former, time-bandwidth product of 0.34 was demonstrated which was the closest to its bandwidth-limited pulse. As for the latter, the fabricated SA exhibited 4.0% modulation depth and an average pulse duration of 886.7 fs. The research work has demonstrated the functionality of Au-NPs as a saturable absorption material for ultrashort pulses generation. In addition, the influence of nanomaterial size towards the characteristics of saturable absorbers, ergo the quality of laser pulse, was verified. This finding is also valuable in customizing ultrashort pulse output that can effectively suit system performance need.

Gold Nanoparticles Induced Size Dependent Cytotoxicity on Human Alveolar Adenocarcinoma Cells by Inhibiting the Ubiquitin Proteasome System.

Gold nanoparticles (AuNPs) are widely used in biomedicine due to their remarkable therapeutic applications. However, little is known about their cytotoxic effects on the ubiquitin proteasome system (UPS). Herein, the cytotoxicity of different sizes of AuNPs (5, 10, and 80 nm) on the UPS was investigated with a particular focus on deubiquitinating enzymes (DUBs) such as ubiquitin-specific proteases (USP) and ubiquitin carboxyl-terminal hydrolases (UCHL-1) in human alveolar epithelial adenocarcinoma (A549). It was found that all sizes of AuNPs reduced the percentage of viable A549 cells and increased lactate dehydrogenase (LDH) release, measured using the MTT and LDH assays, respectively. Furthermore, the 5 nm AuNPs were found to exhibit greater cytotoxicity than the 10 and 80 nm AuNPs. In addition, apoptosis and necrosis were activated through reactive oxygen species (ROS) generation due to AuNPs exposure. The internalisation of AuNPs in A549 cells increased with increasing particle size (80 > 10 > 5 nm). Interestingly, the expression of USP7, USP8, USP10, and UCHL-1 was significantly (p < 0.001) downregulated upon treatment with 5-30 µg/mL of all the AuNPs sizes compared to control cells. Moreover, the inhibition of these proteins triggered mitochondrial-related apoptosis through the upregulation of poly (ADP-ribose) polymerase (PARP), caspase-3, and caspase-9. Collectively, these results indicate that AuNPs suppress the proliferation of A549 cells and can potentially be used as novel inhibitors of the proteasome.

Occupational Exposure to Metal Engineered Nanoparticles: A Human Biomonitoring Pilot Study Involving Italian Nanomaterial Workers

Advances in nanotechnology have led to an increased use of engineered nanoparticles (ENPs) and the likelihood for occupational exposures. However, how to assess such exposure remains a challenge. In this study, a methodology for human biomonitoring, based on Single Particle Inductively Coupled Plasma Mass Spectrometry (SP-ICP-MS), was developed as a tool to assess the ENPs exposure of workers involved in nanomaterial activities in two Italian Companies. The method was validated for size and number concentration determination of Ag, Au, In2O3, Ir, Pd, Pt, and TiO2 NPs in urine and blood samples. The results showed the presence of In2O3 NPs in blood of exposed workers (mean, 38 nm and 10,371 particles/mL), but not in blood of controls. Silver, Au, and TiO2 NPs were found in urine (mean, Ag 29 nm and 16,568 particles/mL) or blood (mean, Au 15 nm and 126,635 particles/mL; TiO2 84 nm and 27,705 particles/mL) of workers, though these NPs were found also in controls. The presence of ENPs in both workers and controls suggested that the extra-professional exposure is a source of ENPs that cannot be disregarded. Iridium, Pd, and Pt NPs were not detected neither in blood nor in urine. Overall, the findings provided a rational basis to evaluate the exposure assessment to ENPs in cohorts of workers as part of risk assessment and risk management processes in workplaces.

Electrophoresis deposition of Au‐nanoparticles on FTO electrode for As(III) detection

AbstractGold nanoparticles (AuNPs) were synthesized via redox reaction, using EDTA as a protecting and reducing agent, with HAuCl4 as precursor and seed solution. The appropriate reaction condition was found out, with the ratio of EDTA:HAuCl4 = 10:1, 40 μL of seed solution and stirring time of 5 minutes. The UV‐Vis spectroscopy observed that the appearance of two absorption peaks were at 574 and 755.5 nm with the average size of AuNPs was 64.5 nm, the zeta potential was positive. The synthesized AuNPs were deposited on FTO electrode by electrophoresis deposition. The results of solid UV‐Vis and SEM images showed that the spherical AuNPs ranging from 40 to 60 nm were deposited onto FTO to fabricate the AuNPs/FTO electrodes. The electrochemical activity of AuNPs/FTO were investigated based on the redox reaction of hydroquinone; the CV results showed the electrode with applied potential at 20 V for 60 minutes has the superior performance. The analysis of As(III) were conducted by AS‐SWV technique. The results showed that AuNPs/FTO electrode enable to detect As(III) at the concentrations higher than 5 ppb that is suitable for the WHO standard of domestic water.

Effects of interleukin-4-modified gold nanozymes on the full-thickness skin defects in diabetic mice

Effects of interleukin-4-modified gold nanozymes on the full-thickness skin defects in diabetic mice

Non-Invasive, Reliable, and Fast Quantification of DNA Loading on Gold Nanoparticles by a One-Step Optical Measurement.

An exquisite, versatile, and reproducible quantification of DNA loading on gold nanoparticles (Au NPs) has long been pursued because this loading influences the analytical, therapeutic, and self-assembly behaviors of DNA-Au NPs. Nevertheless, the existing methods used thus far rely solely on the invasive detachment and subsequent spectroscopic quantification of DNA, which are error-prone and highly dependent on trained personnel. Here, we present a non-invasive optical framework that can determine the number of DNA strands on Au NPs by versatile one-step measurement of the visible absorption spectra of DNA-Au NP solutions without any invasive modifications or downstream processes. Using effective medium theory in conjunction with electromagnetic numerical calculation, the change in DNA loading density, resulting from varying the ion concentration, Au NP size, DNA strand length, and surrounding temperature, can be tracked in situ merely by the one-step measurement of visible absorption spectra, which is otherwise impossible to achieve. Moreover, the simplicity and robustness of this method promote reproducible DNA loading quantification regardless of experimental adeptness, which is in stark contrast with existing invasive and multistep methods. Overall, the optical framework outlined in this work can contribute to democratizing research on DNA-Au NPs and facilitating their rapid adoption in transformative applications.

3-Aminophenylboronic Acid Conjugation on Responsive Polymer and Gold Nanoparticles for Qualitative Bacterial Detection.

Because of their sensitive and selective responses to a wide variety of analytes, colorimetric sensors have gained widespread acceptance in recent years. Gold nanoparticles (AuNPs) are widely employed in visual sensor strategies due to their high stability and ease of use. Combining AuNPs with a responsive polymer can result in distinct surface plasmon resonance (SPR) changes that can be utilized as colorimetric biosensors. The purpose of this research is to develop a colorimetric-based sensor through the utilization of the optical properties of gold nanoparticles (AuNPs) crosslinked with pH-responsive polymers poly (acrylic acid) (PAA) conjugated to 3-aminophenyl boronic acid (APBA). The polymer (PAA) was synthesized via RAFT polymerization. The inversed Turkevic method was used to produce AuNPs, which were subsequently used in a self-assembly process using poly (acrylic acid)-aminophenyl boronic acid (PAA-APBA) to create the self-assembled AuNPs-APBA-PAA. The particle size, zeta potential, and reversibility of the polymer-modified gold nanoparticles were determined using a transmission electron microscope (TEM), a particle size analyzer (PSA), and an Ultraviolet-Visible spectrophotometer (UV-Vis spectrophotometer). Visual, UV-Vis spectrophotometer and TEM observations confirmed the system's ability to identify bacteria. Statistical analysis was performed using a one-way analysis of variance using Excel software. Using UV-Vis spectrophotometry, the particle size of AuNPs was determined to be 25.7 nm, and the maximum absorbance occurred at 530 nm. AuNPs PAA APBA colloid exhibited an absorbance maximum of 532 nm, a zeta potential of -41.53, and a pH transition point between 4 and 5. At E. coli concentrations of 4.5 x 107 CFU/mL, the color of the system sensors changed from red to blue after 15 hours of incubation, whereas at S. aureus concentrations of 1.2 x 109 CFU/mL, the color changed to purple immediately after mixing. The TEM confirmed that the detection mechanism is based on the boronate-polyol bonding of saccharides on the outer membranes of Escherichia coli and Staphylococcus aureus. The use of APBA in conjunction with pH-responsive PAA polymers containing AuNPs to detect E. coli and S. aureus bacteria induces a maximum wavelength transition, followed by a color change from red to blue. By the process of de-swelling of the responsive polymer, which induces the aggregation of the AuNPs, the established sensor system is able to alter the color. The conjugated polymer and gold nanoparticle-based sensor system demonstrated a promising method for bacterial detection.

Green synthesis of reduced graphene oxide/chitosan/gold nanoparticles composites and their catalytic activity for reduction of 4-nitrophenol

Gold nanoparticles (AuNPs) have attracted extensive attention in the past few years due to their unique properties and great potential application in catalysis. However, the application of AuNPs remains a significant challenge due to the lack of high efficiency and stability caused by aggregation. Immobilization of AuNPs on appropriate support shows promising results in avoiding aggregation and improving catalytic activity. In this work, reduced graphene oxide/chitosan/gold nanoparticles (rGO/CHS/AuNPs) composites were prepared using chitosan with different molecular weights (MW) as a reducing agent and stabilizer, and characterized by FT-IR, XRD, XPS, SEM, FESEM, EDS, TEM, HRTEM, and TGA. The preparation conditions of rGO/CHS/AuNPs composites, including chitosan MW, CHS/GO mass ratio, reaction temperature and time, and HAuCl4 concentration were investigated in detail. The results indicated that reduction activity of chitosan for GO increased with the decrease of chitosan MW. The C/O ratio of rGO reduced by low molecular weight chitosan (LMWC) with viscosity-average molecular weight (Mv) of 21 kDa was 6.34. Small spherical AuNPs were uniformly immobilized on the rGO surface. The particle size of AuNPs increased from 9.29 to 13.03 nm as chitosan MW decreased from 465 to 21 kDa. The rGO/CHS/AuNPs showed good catalytic activity for the reduction of 4-NP in the presence of NaBH4. The catalytic activity of rGO/CHS/AuNPs was closely related to chitosan MW. rGO/CHS/AuNPs synthesized by LMWC with Mv of 21 kDa showed the highest kinetic rate constant of 0.2067 min−1. The results of this experimental study could be useful in the development of effective catalysts for the reduction of aromatic nitro compounds.

Direct Synthesis of Gold Nanoparticles in Polymer Matrix.

We report an original method for directly fabricating gold nanoparticles (Au NPs) in a polymer matrix using a thermal treatment technique and theoretically and experimentally investigate their plasmonic properties. The polymeric-metallic nanocomposite samples were first prepared by simply mixing SU-8 resist and Au salt with different concentrations. The Au NPs growth was triggered inside the polymer through a thermal process on a hot plate and in air environment. The Au NPs creation was confirmed by the color of the nanocomposite thin films and by absorption spectra measurements. The Au NPs sizes and distributions were confirmed by transmission electron microscope measurements. It was found that the concentrations of Au salt and the annealing temperatures and durations are all crucial for tuning the Au NPs sizes and distributions, and, thus, their optical properties. We also propose a simulation model for calculations of Au NPs plasmonic properties inside a polymer medium. We realized that Au NPs having large sizes (50 to 100 nm) play an important role in absorption spectra measurements, as compared to the contribution of small NPs (<20 nm), even if the relative amount of big Au NPs is small. This simple, low-cost, and highly reproducible technique allows us to obtain plasmonic NPs within polymer thin films on a large scale, which can be potentially applied to many fields.

One-Pot Synthesis and Characterization of Gold Nanoparticle-Embedded Natural Magnetic Particles/Chitosan Composite

This research synthesized natural magnetic particles/chitosan/gold nanoparticles composites (NMP/Chi/AuNPs) using a green method. AuNPs were synthesized using chitosan as a reducing agent and stabilizer in one step. The obtained AuNPs were characterized using UV-Vis spectrophotometer and TEM. Results showed that AuNPs were spherical with an average of 14.9 nm and absorbed at visible light (~530 nm). Then, AuNPs were impregnated on NMP/Chi at room temperature. The impregnation results were characterized using FTIR, XRD, and TEM. In the IR spectra of NMP/Chi and NMP/Chi/AuNPs, the NH bending vibrations of NH2 are shown at 1604 and 1631 cm-1. The NMP/Chi/AuNP showed a decrease in intensity and the peak shift to 1395 cm-1, stretching vibration of C-O from primary alcohol group. Fe-O vibrations of Fe3O4 in NMP/Chi and NMP/Chi/AuNPs are shown at 566 and 583 cm-1. The intensity peak shift and decrease indicate an interaction between AuNPs and NMP/Chi. The results of the XRD NMP/Chi/AuNPs characterization showed that the diffraction peak at 2Ө 35.44° decreased in intensity, resulting in a decrease in crystallinity caused by impregnated AuNPs and the destruction of hydrogen bonds. The new diffraction peak at 2Ө 38.24° indicates the presence of AuNPs. TEM analysis showed an amorphous layer around the NMP, and the average size of AuNP in the NMP/Chi/AuNP composite was 23.01 nm.

Antimicrobial effect of silver and gold nanoparticles in combination with linezolid on Enterococcus biofilm.

In the past few years, application of new antimicrobial e.g. nanoparticles (NPs) to treat infection caused by drug-resistant bacteria has increased. This study aimed to determine antimicrobial property of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) in combination with linezolid on Enterococcus biofilm. A total of forty-eight isolates of Enterococcus spp. were collected and confirmed by PCR method. The synthesis of biocompatible AgNPs was performed, then analyzed by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy. We carried out minimum inhibitory concentration (MIC) and biofilm forming capacity of AgNPs and AuNPs with linezolid. Twenty-two E. faecium isolates and twentysix E. faecalis investigated in this study. Strong biofilm formation was seen in 12 (25%) of isolates, and others isolates (75%) formed moderate biofilm. AgNPs and Au-NPs size were 26 nm and 20 nm respectively. The MIC of AgNPs was 23.2 μg/ml, and AuNPs were 92.1 μg/ml and the lowest MIC was obtained 2 μg/ml in linezolid. Biofilm formation inhibitory activity by AuNPs + Linezolide and AgNPs + Linezolide 70 to 80 percent increased in average. The antibiofilm activity of AgNPs and AuNPs increased when both agents were used in combination with linezolid in comparison with each agent alone.

WO3 Nanopores Array Modified by Au Trisoctahedral NPs: Formation, Characterization and SERS Application

The WO3 nanopores array was obtained by an anodization method in aqueous solution with addition of F- ions. Several factors affecting the final morphology of the samples were tested such as potential, time, and F- concentrations. The morphology of the formed nanopores arrays was examined by SEM microscopy. It was found that the optimal time of anodization process is in the range of 0.5-1 h. The nanopores size increased with the increasing potential. The XPS measurements do not show any contamination by F- on the surface, which is common for WOx samples formed by an anodization method. Such a layer was successfully modified by anisotropic gold trisoctahedral NPs of various sizes. The Au NPs were obtained by seed-mediated growth method. The shape and size of Au NPs was analysed by TEM microscopy and optical properties by UV-VIS spectroscopy. It was found that the WO3-Au platform has excellent SERS activity. The R6G molecules could be detected even in the range of 10-9 M.

Intrinsic properties of chitosan on the characteristics of gold nanoparticles and its application as smart packaging device.

Storage temperature fluctuation is a major problem faced in food and pharmaceutical industry, apart from prevailing fraud in marketing frozen products as fresh. The present work aimed to study the effect of intrinsic properties of chitosan on synthesis and performance of gold nanoparticles as smart packaging devices. Different types of Chitosan from shrimp waste were used as reducing and capping agent in the synthesis of metal nanoparticle. Time is taken to reduce gold atom to gold nanoparticles varied with the type of reducing agent, between 6 min 40 s to 15 min 02 s. The maximum absorbance (λmax) for AuNPs was observed between 517 and 530 nm. An increase in the concentration of chitosan resulted in smaller and uniform size AuNPs with size ranging from 8.09 to 9.95 nm compared with 14.44 to 19.88 nm for lower concentration of chitosan. Visible ruby red colour of AuNPs synthesised using trisodium citrate (TSC) and lower concentration of chitosan (0.1%) changed to colourless and grey to blue, respectively upon exposure to frozen condition (-18 °C ± 1 °C). UV Visible spectra indicated distinctly different (broader) spectrum with reduced peak intensity. A visible change in colour from ruby red to bluish and colourless state indicates that irrespective of the properties of available chitosan, it can be used for synthesis of gold nanoparticles as smart packaging to distinguish packed fresh/chilled/refrigerated products from frozen ones.