Size Of AuNPs Research Articles

Synthesis of gold nanoparticles with allicin to modify boron-doped diamond surface for oxygen sensor applications

Modification of surface of boron-doped diamond (BDD) film with gold nanoparticles (AuNPs) was carried out to increase its catalytic activity for an application as an oxygen sensor. Allicin was isolated from garlic by salting out extraction technique, and then used as the capping agent to synthesize AuNPs as it has a double bond structure that could be reacted to attach the BDD surface under UV light radiation. An average size of AuNPs at around 46,00 ± 9,06 nm was obtained, while the modification of the BDD surface by the synthesized AuNPs indicated that the surface of BDD could be covered by gold at around 0.6 % (w/w). Investigation of the AuNPs-modified BDD as a working electrode for the oxygen reduction by using cyclic voltammograms in 0.1 M phosphate buffer solution pH 7 observed a current peak at around -0.45 V (vs. Ag/AgCl). The current of this peak linearly increased proportionally to the dissolved oxygen concentrations (R2=0.9986). Moreover, a limit of detection of the dissolved oxygen of 0.12 ppm and limit of quantity 0.41 ppm could be achieved with excellent stability at 6.86% RSD with 6 repetitions and sensitivity at 19.086 μA/ppm indicated that the modified BDD is promising for applications as an oxygen sensor.

Optimization of Gold Nanoparticles Electrodeposition Duration on Screen Printed Electrode to Enhance Electrochemiluminescence of Nitrogen-doped Carbon Dots

In this work, the electrodeposition method was utilized to form gold nanoparticles on a carbon screen-printed electrode (SPE) using chronoamperometry at -0.4 V with various durations from 50 to 200 seconds. Scanning Electron Microscopy (SEM) images have proven that the electrodeposition method is capable of uniformly forming AuNPs on SPE (AuNPs- SPE). Apart from that, electrodeposition durations have increased the size of AuNPs by up to 66% based on average size measurements using ImageJ software. It can be observed that long electrodeposition durations permit the agglomeration of AuNPs on the electrode surface. The effect of electrodeposition duration on electrocatalytic performance in potassium ferricyanide and electrochemiluminescence (ECL) intensity of nitrogen-doped carbon dots (NCDs) was evaluated. Cyclic voltammetry (CV) of ferricyanide demonstrates that as the electrodeposition duration increases, AuNPs-SPE shows better electrochemical performance than bare SPE. ECL of NCDs displays that 100 s electrodeposition durations give the highest ECL intensity of 184% compared to bare SPE and have been chosen as the optimum parameter. The ECL mechanisms of bare SPE and AuNPs-SPE reveal that AuNPs- SPE has greater electrochemical and ECL performance than bare SPE, as evidenced by the CV of AuNPs-SPE having a faster reduction current, which rises to 87.2% ECL intensity and 510 mV faster ECL occurrence. These phenomena confirmed that the electrodeposition of AuNPs has improved the conductivity of SPE.

Hydrogen-assisted green synthesis of trimethyl chitosan gold nanoparticles

Gold nanoparticles (AuNPs) are arguably the most promising in terms of application among the noble metal nanoparticles. As such, researchers have dedicated a considerable amount of energy towards the synthesis of novel gold nanoparticles with different morphology and size, which in turn affect its potential application. This study synthesized novel spherical-shaped AuNPs via green reduction of gold ion in an aqueous solution of HAuCl4.3H2O in the presence of trimethyl chitosan as a stabilizing agent and pressurized H2 gas as a reducing agent on an ice water. The size, morphology, chemical composition, chemical environment and optical activities were examined by scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), x-ray photoelectron spectroscopy (XPS), and ultraviolet–visible spectroscopy (Uv–Visible), respectively. The average particle size of AuNPs is 37 nm while HR-TEM revealed a unique spherical morphology. The Tauc's plot calculation revealed a band gap of 5.0 eV. This unique morphology and optical local field enhancement in plasmonic nanocomposites could be suitable alternative for conducting devices and photocatalysis.

Single-Molecule X-ray Scattering Used to Visualize the Conformation Distribution of Biological Molecules via Single-Object Scattering Sampling.

Biological macromolecules, the fundamental building blocks of life, exhibit dynamic structures in their natural environment. Traditional structure determination techniques often oversimplify these multifarious conformational spectra by capturing only ensemble- and time-averaged molecular structures. Addressing this gap, in this work, we extend the application of the single-object scattering sampling (SOSS) method to diverse biological molecules, including RNAs and proteins. Our approach, referred to as "Bio-SOSS", leverages ultrashort X-ray pulses to capture instantaneous structures. In Bio-SOSS, we employ two gold nanoparticles (AuNPs) as labels, which provide strong contrast in the X-ray scattering signal, to ensure precise distance determinations between labeled sites. We generated hypothetical Bio-SOSS images for RNAs, proteins, and an RNA-protein complex, each labeled with two AuNPs at specified positions. Subsequently, to validate the accuracy of Bio-SOSS, we extracted distances between these nanoparticle labels from the images and compared them with the actual values used to generate the Bio-SOSS images. Specifically, for a representative RNA (1KXK), the standard deviation in distance discrepancies between molecular dynamics snapshots and Bio-SOSS retrievals was found to be optimally around 0.2 Å, typically within 1 Å under practical experimental conditions at state-of-the-art X-ray free-electron laser facilities. Furthermore, we conducted an in-depth analysis of how various experimental factors, such as AuNP size, X-ray properties, and detector geometry, influence the accuracy of Bio-SOSS. This comprehensive investigation highlights the practicality and potential of Bio-SOSS in accurately capturing the diverse conformation spectrum of biological macromolecules, paving the way for deeper insights into their dynamic natures.

In-vitro Safety Assessment of Ultrasmall Gold Nanoparticles for Preclinical Drug Delivery Applications

Background: The development of safe and biocompatible nanoparticles has always been a major concern in nanomedicine applications. Various studies on the size-dependent toxicity of na-noparticles have been reported but are still controversial. The potential of small-sized nanoparticles can be utilized for imaging and diagnostics. However, insufficient toxicity data on these nanoparti-cles prevents researchers from utilizing their potential in diagnostics. More studies are needed on the toxicity of small-sized nanoparticles to present unanimous report for safe systemic use. The pre-sent study aimed to investigate the toxicity concerns of very small-sized AuNPs (2 ± 0.5 nm, 5 ± 1 nm, and 10 ± 2 nm) and provide a platform for their safe in vivo use. Methods: The cellular interactions of these three small-sized AuNPs with regard to cytotoxicity were investigated on hepatocellular carcinoma (HepG2) and epithelial kidney (HEK-293) cell lines. The cytotoxicity investigation of both cell lines was done through MTT assays, PI & DAPI, and cy-tology. Cellular stress was investigated by Catalase, TBARS, GSH, SOD & ROS parameters. The AuNPs incubated cells were also assessed for immunogenicity by ELISA, protein interaction by BSA, and cellular internalization by TEM (Edax). Results: All three-sized AuNPs were not toxic on cell viability, apoptosis, necrosis, or cytology as-sessment. No oxidative stress was noted in both cell types in the presence of 2 and 5-nm-sized AuNPs, whereas 10 nm-sized AuNPs showed little oxidative stress. AuNPs of size 2 and 5 nm were immunologically inert, but 10 nm-sized AuNPs elicited interleukin (IL-4 and IL-10) and interferon IFN gamma response. AuNPs of sized 2 nm showed 4 times the adsorption of albumin protein as compared to AuNPs of sized 5 nm. The TEM micrographs and peak of gold in the Edax graph con-firmed the presence of AuNPs in cells. Conclusion: Our results are suggestive of utilizing the potential of these three-sized AuNPs safely in preclinical drug delivery applications.

Au-coated quartz fabric by plasma treatment as a flexible SERS substrate for rapid detection of harmful substances

Food safety remains a global concern and there is always demanded to advance methods to ensure that toxic substances and contamination do not pose safety concerns. This study discusses the development of a rapid, low-cost, portable, in situ method for the detection of harmful substances on the surface of fruits and vegetables to ensure safety for human consumption. Gold nanoparticles (Au NPs) are deposited onto quartz fabric by using a magnetron sputtering system. The argon flow rate and sputtering time are both controlled to produce Au NPs of different sizes on the quartz fabric with different gap distances. Scanning electron microscope images, X-ray diffraction spectra, and Raman intensity are used to evaluate the produced substrates. With an average grain size of about 32.35 nm, the Au particles with a thickness of 70 nm deposited onto the quartz fabric (i.e., Qt-70) provide the best surface-enhanced Raman scattering (SERS) performance of 65,639 counts towards a 10−3 M methylene blue (MB) solution. The results show that the Qt-70 SERS substrate is highly sensitive, reproducible, and stable, and demonstrates good reusability. Images of “hotspots” that form between two Au nanoparticles based on electric field distribution are simulated by using the finite-difference time-domain (FDTD) method to explain for the signal enhancement. In addition, Qt-70 can be used for the direct collection of pesticides, such as Rhodamine B (RhB), Rhodamine 6G (R6G), and Malachite green (MG), from food surfaces. This novel flexible SERS (FSERS) substrate has good potential for the rapid detection of harmful substances on food.

Enhanced antidiabetic and antioxidant properties of gold nanoparticles green synthesized using blossom extract of Azadirachta indica: In vitro studies

This study describes the in situ biosynthesis of gold nanoparticles (AuNPs) using neem blossom (Azadirachta indica) extract with enhanced in vitro anti-diabetic and antioxidant properties. The formation of AuNPs was confirmed by the characteristic optical response through the surface plasmon resonance (SPR) band observed around 530 nm. The effect of phytochemical in the formation of AuNPs was investigated using Fourier-transform infrared spectroscopy (FTIR). The effect of reaction parameters such as temperature, pH and precursor concentration on the size and surface morphology of AuNPs was optimized using the SPR band. The metallic form of phytosynthesised AuNPs was confirmed by X-ray photoelectron spectra (XPS) results with a distinctive binding energy difference of 4f shells ΔE = 3.8 eV. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies confirmed the crystalline nature of the particles formed. The antioxidant property of AuNPs demonstrated the influence of phytochemical surfactants coated on the surface of AuNPs and the results revealed the higher antioxidant (90 %) efficiency compared to standard ascorbic acid. phytosynthesised AuNPs demonstrated 79 % enzyme inhibition efficiency in α-amylase assays. The antimicrobial evaluation results revealed the exceptional microbicidal efficacy of AuNPs against both gram-positive and gram-negative bacteria. Phytochemically activated AuNPs showed improved antioxidant, antimicrobial and antidiabetic properties and it could be a promising candidate for biological applications in medicine.

Polychaeta-mediated synthesis of gold nanoparticles: A potential antibacterial agent against Acute Hepatopancreatic Necrosis Disease (AHPND)–causing bacteria, Vibrio parahaemolyticus.

Gold nanoparticles (AuNPs) have emerged as a promising application in aquaculture. Their nano-sized dimensions, comparable to pathogens offer potential solutions for combating antibiotic resistance. In this study, AuNPs were synthesized by using polychaetes, Marphysa moribidii as the bio-reducing agent. Modifications were made to reduce agglomeration in green-synthesized AuNPs through ultrasonication. The antibacterial activities of AuNPs against V. parahaemolyticus were evaluated. The physicochemical characteristics of the green synthesized AuNPs were comprehensively investigated. The successful formation of AuNPs was confirmed by the appearance of a red ruby colour and the presence of surface Plasmon resonance (SPR) absorption peaks at 530 nm as observed from UV–vis spectroscopy. Scanning electron microscopy (SEM) revealed spherical-shaped AuNPs with some agglomerations. Transmission electron microscopy (TEM) showed particle size of AuNPs ranging from 10 nm to 60 nm, meanwhile dynamic light scattering (DLS) analysis indicated an average particle size of 24.36 nm. X-ray diffraction (XRD) analysis confirmed the high crystallinity of AuNPs, and no AuNPs were detected in the polychaetes extracts prior to synthesis. A brief ultrasonication significantly reduced the tendencies for AuNPs to coalesce. The green-synthesized AuNPs demonstrated a remarkable antibacterial efficacy against V. parahaemolyticus. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests revealed that a concentration of 0.3 g/ml of AuNPs effectively inhibited V. parahaemolyticus. These findings highlighted the potential of green-synthesized AuNPs as antibacterial agents for the prevention and management of AHPND in aquaculture.

Gold nanoparticles aggregation on graphene using Reactive force field: A molecular dynamic study.

We examine the aggregation behavior of AuNPs of different sizes on graphene as function of temperature using molecular dynamic simulations with Reax Force Field. In addition, the consequences of such aggregation on the morphology of AuNPs and the charge transfer behavior of AuNP-Graphene hybrid structure are analyzed. The aggregation of AuNPs on graphene is confirmed from the center of mass distance calculation. The simulation results indicate that the size of AuNPs and temperature significantly affect the aggregation behavior of AuNPs on graphene. The strain calculation showed that shape of AuNPs changes due to the aggregation and the smaller size AuNPs on graphene exhibit more shape changes than larger AuNPs at all the temperatures studies in this work. The charge transfer calculation reveals that, the magnitude of charge transfer is higher for larger AuNPs-graphene composite when compared with smaller AuNPs-graphene composite. The charge transfer trend and the trends seen in the number of Au atoms directly in touch with graphene are identical. Hence, our results conclude that, quantity of Au atoms directly in contact with graphene during aggregation is primarily facilitates charge transfer between AuNPs and graphene. Our results on the size dependent strain and charge transfer characteristics of AuNPs will aid in the development of AuNPs-graphene composites for sensor applications.

Rotating disk diluter hyphenated with single particle ICP-MS as an online dilution and sampling platform for metallic nanoparticles characterization in ambient aerosol

The application of single particle inductively coupled plasma mass spectrometry (spICP-MS) for online metallic nanoparticles (NPs) characterization in ambient aerosol remains a challenge. In this study, a hyphenated setup consisting of a rotating disk diluter (RDD) with spICP-MS (RDD-spICP-MS) was used for online sampling and characterization NPs in ambient pressure aerosols. The elemental composition, particle size distribution, and particle number concentration (PNC) of metallic NPs in aerosols could be obtained simultaneously. The RDD allowed sampling of the aerosol at a constant flow rate, adjusting the optimal dilution ratio for characterizing NPs at different PNCs, and exchanging the gas matrix to achieve the requirement of spICP-MS for direct aerosol characterization. In this proof-of-concept study, the feasibility of this setup was tested with AuNPs of different sizes from the argon-based and air-based aerosol. The limit of detection for number concentration is below 30 #/L, which is lower than the regulated environmental level. Moreover, multi-modal samples, as well as the interference of ionic species, were accurately investigated. Finally, AuNPs were spiked with environmental PM10 and Road dust to evaluate the matrix effect as well as the capabilities of the setup to characterize environmental aerosol samples. These results indicate that RDD-spICP-MS has a great potential for online characterization of metallic NPs in the ambient aerosol.

Blue-emitting SiO2-coated Si-doped ZnSeS quantum dots conjugated aptamer-molecular beacon as an electrochemical and metal-enhanced fluorescence biosensor for SARS-CoV-2 spike protein

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which was first reported in early January 2020, continues to devastate the worlds public health system. Herein, we report on the development of a novel metal-enhanced fluorescence (MEF) and electrochemical biosensor for SARS-CoV-2 spike (S) protein. To develop the MEF biosensor, SiO2-coated Si-doped ZnSeS quantum dots (QDs) were newly synthesized and conjugated to an aptamer-molecular beacon (Apta-MB) probe. Thereafter, cationic AuNPs, used as a localised surface plasmon resonance (LSPR) signal amplifier, were self-assembled on the QDs-Apta-MB conjugate to form a QDs-Apta-MB-AuNP probe. To develop the electrochemical biosensor, the QDs-Apta-MB assay was carried out on a carbon nanofiber-modified screen-printed carbon electrode. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode surface whilst spectrophotometric, spectroscopic, fluorescence polarization and electron microscopic techniques were used to characterize the materials. Under optimal experimental conditions, the QDs binding to the Apta-MB, quenched the QDs’ fluorescence and with SARS-CoV-2 S protein binding to the Apta-MB, LSPR signal from cationic AuNPs of different sizes and shapes were used to tune the fluorescence signal to obtain enhanced sensitivity. On the other hand, using [Fe(CN)6]/K3−/4- buffered with NaAc-KAc-TrizmaAc-KSCN-Borax as the electrolyte solution, anodic peaks of the QDs from the CV and DPV plots were unravelled. Electrochemical detection of SARS-CoV-2 S protein was accomplished by a systematic increase in the QDs anodic peak current generated from the DPV plots. The limits of detection obtained for the SARS-CoV-2 S protein were 8.9 fg/mL for the QDs-Apta-MB-AuNP MEF probe and ∼0.5 pg/mL for the QDs-Apta-MB electrochemical probe. Detection of SARS-CoV-2 S protein in saliva was demonstrated using the QDs-Apta-MB-AuNP MEF probe.

In English

Gold nanoparticles (Au NPs) have found a variety of applications in different areas, particularly in biomedical practices. The activity of Au NPs strongly depends on the size and association of particles in colloid, that in turn are greatly affected by experimental parameters of the reaction. The obtaining of Au NPs even via classical procedure of citrate method can be a challenge. In the present work we applied different experimental approaches to affect the process of Au NPs formation in the presence of sodium citrate. Au NPs were obtained using different experimental procedures and varying the ratio of reagents, their concentrations, temperature of reaction, duration of heating, the order of introduction of reagents into the reaction mixture, pH, and so on. Comparative analyses of UV-vis spectra with DLS data by number, volume and intensity basis allowed to trace the changes in Au NPs colloid, find optimal experimental conditions and predict prolonged stability of colloids. Applying size-dependent Hamaker constant to DLVO theory explains experimental results. The formation of Au NPs strongly depends on the ratio of the functional groups of the molecule involved simultaneously in the reduction of metal ions, the binding to the surface of Au NPs and the formation of a charge for stabilization due to electrostatic repulsion. The change in the ratio of components is not enough to get a different size of Au NPs. Big concentration of the reagents mostly affects the aggregation process and colloid aging. Temperature is a critical activation factor, that should be about 100 °C, but prolonged heating causes collision induced aggregation. The initial stage of particles growth (the mechanism) can be affected with the change of pH of the system due to formation of deprotonated carboxyl groups and gold hydroxocomplexes.

Gold Nanoparticle-Based Colorimetric Sensors: Properties and Application in Detection of Heavy Metals and Biological Molecules.

During the last decade, advances have been made in nanotechnology using nanomaterials, leading to improvements in their performance. Gold nanoparticles (AuNPs) have been widely used in the field of sensor analysis and are also combined with certain materials to obtain the desired characteristics. AuNPs are commonly used as colorimetric sensors in detection methods. In developing an ideal sensor, there are certain characteristics that must be met such as selectivity, sensitivity, accuracy, precision, and linearity, among others. Various methods for the synthesis of AuNPs and conjugation with other components have been carried out in order to obtain good characteristics for their application. AuNPs can be applied in the detection of both heavy metals and biological molecules. This review aimed at observing the role of AuNPs in its application. The synthesis of AuNPs for sensors will also be revealed, along with their characteristics suitable for this role. In the application method, the size and shape of the particles must be considered. AuNPs used in heavy metal detection have a particle size of around 15-50 nm; in the detection of biological molecules, the particle size of AuNPs used is 6-35 nm whereas in pharmaceutical compounds for cancer treatment and the detection of other drugs, the particle size used is 12-30 nm. The particle sizes did not correlate with the type of molecules regardless of whether it was a heavy metal, biological molecule, or pharmaceutical compound but depended on the properties of the molecule itself. In general, the best morphology for application in the detection process is a spherical shape to obtain good sensitivity and selectivity based on previous studies. Functionalization of AuNPs with conjugates/receptors can be carried out to increase the stability, sensitivity, selectivity, solubility, and plays a role in detecting biological compounds through conjugating AuNPs with biological molecules.

DNA-bridged double gold nanoparticles-based immunochromatography for dual-mode detection of ochratoxin A.

A novel immunochromatography strip (ICS) based on the DNA-bridged double gold nanoparticles was established and evaluated for the dual-mode detection of ochratoxin A (OTA). For this purpose, the streptavidin was coupled with the big size of gold nanoparticle (40nm, AuNP), the OTA monoclonal antibody and biotinylated DNA-SH were simultaneously immobilized on the small size of AuNP (20nm), and then the enhanced ICS was self-assembled and evaluated. The dual-mode detection of semi-quantification and quantification had been achieved and performed by the proposed ICS. The LOD for semi-quantification (semi-Q-LOD) was 0.06ng/mL by the directly naked eye (eightfold enhanced than conventional ICS). By the on-site reader, the LOD for quantification (Q-LOD) was 0.03ng/mL (threefold enhanced), with the detection range between 0.03 and 1.2ng/mL. The specificity, reliability, and practicability had been well represented. Furthermore, the OTA-positive results of the enhanced ICS method correlated well with those obtained by the referenced HPLC-MS/MS for the market samples. This study provided a new ICS pattern of semi-quantification and quantification for OTA contamination, which could be used as a valuable reference for improving the ICS technology and enhancing the sensitivity.

Dispersive solid phase extraction of noble metal nanoparticles from environmental samples on a thiol-functionalized Zirconium(IV) metal organic framework and determination with atomic absorption spectrometry

This work reports for the first time, the utility of a thiol-functionalized Zr-metal organic framework (MOF-SH) for the extraction of noble metal nanoparticles from environmental water samples. Due to the presence of a free thiol terminal group, extraction of metal nanoparticles is performed on the external surface area of the MOF, instead of its pores, thus significantly decreasing the extraction time. Both gold nanoparticles and gold ions, as model species, could be quantitatively extracted from aqueous samples using dispersive solid phase extraction and determined with atomic absorption spectrometry. The MOF-SH material could effectively retain AuNPs of variable sizes and coatings thus enabling the determination of the total concentration of AuNPs in the sample. Due to the strong affinity of gold species for the thiol group, the separation of AuNPs from gold ions could be achieved prior to extraction with ultracentrifugation, followed by the independent extraction and determination of each species. Under the optimum experimental conditions, the method could effectively extract and discriminate gold nanoparticles and gold ions from freshwater samples with detection limits for AuNPs as low as 650 femto-mol/L (by extracting 25 mL of water sample), recoveries between 73 and 132% and precision between 11.8 and −13.4%, which are comparable to other methods.

Green synthesis of gallic acid–capped gold nanoparticles as novel electro-catalyst for electro-oxidation of ethylene glycol in alkaline media

This study reports the synthesis of gallic acid–capped gold nanoparticles (GA-AuNPs) through a simple, inexpensive, and environmentally friendly chemical method and their applications in fuel cells. In the proposed method, gallic acid acts as the reducing agent and stabilizer. The studies showed that the size and distribution of AuNPs could be controlled by controlling the molar ratio of gallic acid to gold ions. The prepared GA-AuNPs were used as an electro-catalyst to oxidize ethylene glycol (EG) molecules on the glassy carbon electrode (GCE) surface in alkaline media. The results showed that the modified electrode using GA-AuNPs with a 1:1 M ratio has a higher electrochemical active surface area (ECSA); therefore, it has improved electro-catalytic activity, increased stability, and durability for EG oxidation compared to other ratios of GA/Au and even to the bare Au electrode.

In situ synthesis of gold nanoparticles on layered double hydroxide nanoparticles for multiplexing molecular imaging of single cells

Quasi-spherical gold nanoparticles (AuNPs) are the most widely used surface-enhanced Raman scattering (SERS) nanotags. However, their surface plasmon resonance properties are significantly restricted by their poor colloidal stability in biological media. Herein, we developed a new strategy for in situ synthesis of AuNPs on layered double hydroxide (LDH) nanoparticles to improve the colloidal stability of AuNPs for SERS imaging with multiplexing capability using single laser excitation. The hybridized LDH-AuNPs were constructed via in situ growth of AuNPs on lactic acid-LDH nanoparticles. The size of AuNPs was tuned by changing the concentration of LDH. The LDH-AuNPs were further functionalized with Raman reporter molecules (Ra) to obtain LDH-AuNPs-Ra as SERS nanotags, which were examined in terms of the colloidal stability and photostability in biological media as well as cellular uptake in J774A.1 macrophage cell culture by single cell mapping via confocal Raman microscopy. The cellular uptake of multiple LDH-AuNPs-Ra functionalized with different Raman reporter molecules were further investigated, where the multiplexing capability of SERS assay endows simultaneous detection of multiple LDH-AuNPs-Ra distribution after cellular uptake for cell imaging. In summary, the LDH-supported in situ synthesis of AuNPs have shown the merits of stabilizing AuNPs by using LDH for SERS imaging, as well as demonstrating the multiplexing molecular imaging of single cells. This work thus provides a promising strategy and a new bioimaging nanoplatform for various biomedical studies in the near future.

Molecular Surface Quantification of Multifunctionalized Gold Nanoparticles Using UV-Visible Absorption Spectroscopy Deconvolution.

Multifunctional gold nanoparticles (AuNPs) are of great interest, owing to their vast potential for use in many areas including sensing, imaging, delivery, and medicine. A key factor in determining the biological activity of multifunctional AuNPs is the quantification of surface conjugated molecules. There has been a lack of accurate methods to determine this for multifunctionalized AuNPs. We address this limitation by using a new method based on the deconvolution and Levenberg-Marquardt algorithm fitting of UV-visible absorption spectrum to calculate the precise concentration and number of cytochrome C (Cyt C) and zinc porphyrin (Zn Porph) bound to each multifunctional AuNP. Dynamic light scattering (DLS) and zeta potential measurements were used to confirm the functionalization of AuNPs with Cyt C and Zn Porph. Transmission electron microscopy (TEM) was used in conjunction with UV-visible absorption spectroscopy and DLS to identify the AuNP size and confirm that no aggregation had taken place after functionalization. Despite the overlapping absorption bands of Cyt C and Zn Porph, this method was able to reveal a precise concentration and number of Cyt C and Zn Porph molecules attached per AuNP. Furthermore, using this method, we were able to identify unconjugated molecules, suggesting the need for further purification of the sample. This guide provides a simple and effective method to quickly quantify molecules bound to AuNPs, giving users valuable information, especially for applications in drug delivery and biosensors.

Silver and gold nanoparticles: Eco-friendly synthesis, antibiofilm, antiviral, and anticancer bioactivities

For the first time in this study, silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were green synthesized by the cost-effective and eco-friendly procedure using Cotton seed meal and Fodder yeast extracts. The biosynthesized NPs were characterized by UV–Vis spectroscopy, dynamic light scattering analysis (DLS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and fourier-transform infrared (FTIR) spectroscopy. Furthermore, the biosynthesized NPs were tested in vitro against biofilm formation by some pathogenic negative bacteria (Escherichia coli, Proteus mirabilis, Klebsiella sp., Salmonella sp., and Pseudomonas aeruginosa) and negative bacteria (staphylococcus aureus) as well as against human denovirus serotype 5 (HAdV-5) and anticancer activity using HepG2 hepatocarcinoma cells. UV–Vis absorption spectra of reaction mixture of AgNPs and AuNPs exhibited maximum absorbance at 440 nm and 540 nm, respectively. This finding was confirmed by DLS measurements that the highest intensity of the AgNPs and AuNPs were 84 nm and 73.9 nm, respectively. FTIR measurements identified some functional groups detected in Cotton seed meal and Fodder yeast extracts that could be responsible for reduction of silver and gold ions to metallic silver and gold. The morphologies and particle size of AgNPs and AuNPs were confirmed by the TEM and SAED pattern analysis. Biosynthesized AgNPs and AuNPs showed good inhibitory effects against biofilms produced by Escherichia coli, Proteus mirabilis, Klebsiella sp., Salmonella sp., Pseudomonas aeruginosa, and Staphylococcus aureus. In addition, they showed anticancer activities against hepatocellular carcinoma (HepG-2) and antiviral activity against human adenovirus serotype 5 infection in vitro. Finally, the results of this study is expected to be extremely helpful to nano-biotechnology, pharmaceutical, and food packing applications through developing antimicrobial and/or an anticancer drugs from ecofriendly and inexpensive nanoparticles with multi-potentiality.

Enhancing fibre optic sensor signals via gold nanoparticle-decorated agarose hydrogels

The main objective of this work was to create a novel sensing material using different sizes of gold nanoparticles (AuNPs) embedded in agarose hydrogel (AG) encapsulated fibre optic sensors. AuNPs (4 nm–40 nm) were synthesized using the chemical reduction method with a reducing agent of sodium borohydride (1% w/v) and trisodium citrate (40 mM). The core of the fibre optic was coated either using a single-layer (4 nm AuNPs, 15 nm AuNPs and AG) or two-layer coating (Au-AG) with the first layer being AG then followed by AuNPs (4 nm or 15 nm). The signal resulting from the AuNPs-AG coated fibre optic probe was tested using spectroscopy with a scanning range from 200 to 1000 nm to establish which sample generated the highest sensing signal. The result demonstrated that the smaller size of AuNPs provides a higher signal compared to a larger size, while the two-layered coating of 4 nm Au-AG significantly boosts the signal of the fibre optic sensor up to 47%. The overall performance of the 4 nm Au-AG coated fibre optic probe was highly promising, demonstrating a refractive index (RI) sensitivity of 3669.8 ± 5.232 RIU−1, with an R2 value of 0.9802. This optimized configuration of coating materials presents the sensor platform as an excellent candidate for further exploration in designing specific sensing applications, such as gas sensors or biosensors. Its remarkable ability to enhance sensor sensitivity holds great promise for advancing sensing technologies.