Size Of AuNPs Research Articles

Ion-Specific Stability of Gold Nanoparticle Suspensions.

This study addresses the aging of three AuNP suspensions after the addition of various sodium salts along the well-known Hofmeister series (NaF, NaCl, NaBr, NaI, NaSCN) at different salt concentrations between 10 mM and 100 mM. The AuNP types differ in size (5 nm vs 11 nm in diameter) and the capping type (physisorbed citrate vs covalently bound mercaptopropionic acid (MPA)). We monitor the aggregation of the AuNPs and the suspension stability optically (absorption spectroscopy and photography) and by electron microscopy. The large range of salt concentrations results in a large variety of colloidal stability, i.e., from stable suspensions to fast destabilization followed by sedimentation, due to the impact of the anions on the interaction between the negatively charged AuNPs. At intermediate and high salt concentrations, strong ion-specific effects emerge that are nonmonotonous with respect to the Hofmeister series. In particular, the chaotropic salts, NaI and NaSCN, strongly alter the absorption spectra very differently. NaI fuses AuNPs together, influencing the primary absorption, while NaSCN retains the AuNP structure during aggregation much stronger than the remaining sodium halides, resulting in a secondary absorption peak. Although decreasing the size of AuNPs leads to more stable suspensions, the ion-specific effects are even more pronounced due to the increase in the total available surface. Even the covalently bound MPA capping cannot stabilize AuNPs against particle fusion by NaI, although it delays the process. Despite the complex interplay between different effects of ions on the stability of colloidal dispersions, this study disentangles the different effects from electrostatic screening, via adsorption at the interface and bridging of AuNPs, to the competition between ions and the capping agent of the AuNPs. These findings are crucial for the fabrication of inorganic/organic composites by the targeted assembly of AuNPs in a preexisting matrix controlled by the presence of salt.

Citrus maxima extract-coated versatile gold nanoparticles display ROS-mediated inhibition of MDR-Pseudomonas aeruginosa and cancer cells.

The expanding prevalence of microbial resistance to conventional treatments has triggered a race to develop alternative/improved strategies to combat drug-resistant microorganisms in an efficient manner. Here, the lethal impact of the biosynthesized gold nanoparticles (AuNPs) against multi-drug resistant (MDR) bacteria has been elucidated. AuNPs, synthesized from the extracts of the fruit, leaf and peel of the Citrus maxima plant, were physicochemically characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS), electron microscopy and spectroscopic techniques not only confirmed the production of AuNPs of size below 100nm but also identified the phytochemicals adsorbed onto the surface of NPs. AuFeNP not only showed excellent antioxidant activity (∼95% at 1mg/mL) but also exhibited a commendable antimicrobial activity against MDR-Pseudomonas aeruginosa as assessed by the zone of inhibition (13.5mm) and microwell broth dilution assays (9.5μg/mL, MIC). Transmission electron microscopy (TEM) displayed bacterial cell membrane destruction post-AuNPs exposure. The killing mechanism of AuNPs elucidated the permeabilization of the cell membrane and generation of reactive oxygen species (ROS), ∼10-fold high depletion of GSH, and eventually leaching protein out of the cell. DNA damage, as a marker of apoptosis, was also noticed, which could be an implication of ROS accumulation in MDR-PA. AuNPs displayed significant toxicity at∼10μg/mL on various cancer cells (HT-1080, MRC-5, MDA-MB-231 and B16-F10) and relatively low toxicity on normal cells (MRC-5 and HaCaT). Scratch assay to identify the migration capability of breast cancer cells on treatment with AuNPs deciphered hampering of migration potential of breast cancer cells. Apoptotic topographies in B16-F10 cells were confirmed using AO/EtBr dual dye staining, DNA fragmentation, Caspase-3 assay and cell cycle analysis using flow cytometry. Hemolysis revealed minimal toxicity of AuNPs on human red blood cells. Nominal toxicity (∼70% survival at 500μg/mL of AuNPs) on mammalian cells was evaluated using Cell Titer-Glo cell viability assay. Overall results advocate the promising potential of biosynthetic AuFeNP against multi-drug-resistant pathogens and for further formulation into anticancer agents.

Gold Nanoparticles as a Platform for Delivery of Immunogenic Peptides to THP-1 Derived Macrophages: Insights into Nanotoxicity

Background: Peptide-based nanovaccines have emerged as a promising strategy for combating infectious diseases, as they overcome the low immunogenicity that is inherent to short epitope-containing synthetic peptides. Gold nanoparticles (AuNPs) present several advantages as peptide nanocarriers, but a deeper understanding of the design criteria is paramount to accelerate the development of peptide-AuNPs nanoconjugates (p-AuNPs). Methods: Herein, we synthesized and characterized p-AuNPs of 23 nm (p-Au23) and 68 nm (p-Au68) with varying levels of peptide surface coverage and different peptide designs, investigating their effect on the cell viability (cell death and mitochondrial activity), cellular uptake, and cathepsin B activity in THP-1 macrophages. Results: p-Au23 proved no negative effect in the cell viability and high levels of nanoconjugate uptake, but p-Au68 induced strong toxicity to the cell line. The peptide sequences were successfully designed with spacer regions and a cell-penetrating peptide (pTAT) that enhanced cellular uptake and cathepsin B activity for p-Au23, while pTAT induced severe effects in the THP-1 viability (~40–60% cell death). Conclusions: These findings provide valuable insight into the design criteria of AuNPs and immunogenic peptides, along with nanotoxicity effects associated with AuNP size and surface charge in human monocyte-derived macrophages.

Impact of gold nanoparticle size and coating on radiosensitization and generation of reactive oxygen species in cancer therapy.

Radiation therapy is a common cancer treatment but often damages surrounding healthy tissues, leading to unwanted side effects. Despite technological advancements aimed at improving targeting, minimizing exposure to normal cells remains a major challenge. High-Z nanoparticles, such as gold nanoparticles (AuNPs), are being explored as nano-radiosensitizers to enhance cancer treatment through physical, biological, and chemical mechanisms. This study focuses on evaluating the chemical and biological radiosensitizing effects of AuNPs exposed to ionizing radiation (0-50 Gy), specifically their production of reactive oxygen species (ROS) and their impact on cancer cells. ROS generated by AuNPs of varying sizes and coatings were quantified using fluorescence probes for hydroxyl radicals (HO·) and singlet oxygen (1O2). The radiosensitizing effects on MDA-MB-231 cancer cells were assessed via clonogenic assays. Our results show a clear dependence of ROS production on AuNP size. Interestingly, PEG-capped AuNPs did not significantly enhance HO· production but greatly increased 1O2 production, suggesting that multiple reactive species contribute to the radiosensitization process. Clonogenic assays confirmed that PEG-capped AuNPs produced stronger radiosensitizing effects than citrate-capped AuNPs, with smaller AuNPs providing more pronounced biological effects. This study underscores the importance of conducting both chemical and biological evaluations to fully understand the radiosensitization efficacy of AuNPs.

The Effect of the Size of Gold Nanoparticle Contrast Agents on CT Imaging of the Gastrointestinal Tract and Inflammatory Bowel Disease.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD). CT imaging with contrast agents is commonly used for visualizing the gastrointestinal (GI) tract in UC patients. Contrast agents that provide enhanced imaging performance are highly valuable in this field. Recent studies have made significant progress in developing better contrast agents for imaging the gastrointestinal tract using nanoparticles. However, the impact of nanoparticle size on this application remains unexplored. Gold nanoparticles (AuNPs) serve as an ideal model to investigate the effect of nanoparticle size on imaging of the gastrointestinal tract due to their controllable synthesis across a broad size range. In this study, we synthesized AuNPs with core sizes ranging from 5 to 75 nm to examine the effect of the size in this setting. AuNPs were coated with poly(ethylene glycol) (PEG) to enhance stability and biocompatibility. In vitro tests show that gold nanoparticles are cytocompatible with macrophage cells (∼100% cell viability) and remain stable under acidic conditions, with no significant size changes over time. Phantom imaging studies using a clinical CT scanner indicated that there was no effect of nanoparticle size on CT contrast production, as previously demonstrated. In vivo imaging using a mouse model of acute colitis revealed a strong contrast generation throughout the GI tract for all agents tested. For the most part, in vivo contrast was independent of AuNP size, although AuNP outperformed iopamidol (a clinically approved control agent). In addition, differences in attenuation trends were observed between healthy and colitis mice. We also observed almost complete clearance at 24 h of all formulations tested (less than 0.7% ID/g was retained), supporting their value as a model platform for studying nanoparticle behavior in imaging. In conclusion, this study highlights the potential of nanoparticles as effective contrast agents for CT imaging of the gastrointestinal tract (GIT) in the UC. Further systemic research is needed to explore contrast agents that can specifically image disease processes in this disease setting.

Confined growth of ultrasmall monodisperse gold nanoparticles in amino functionalized cellulose beads as effective catalysts for 4-nitrophenol reduction.

This study aims to prepare a monodisperse catalyst with a space-confined strategy, employing cellulose beads (CBs) as a carrier. Amino functionalized cellulose beads (ACBs) were prepared by grafting polyethyleneimine into the space of CBs via glutaraldehyde cross-linking. The in-situ reduction method was successfully employed to confine monodisperse ultrasmall gold nanoparticles (AuNPs) within the amino functionalized cellulose beads (AuNPs@ACBs) matrix. The AuCl4- ions were first immobilized on the amino substance (such as -NH3+/-NH2+, CN and CN) by chelation and electrostatic interaction. Then the Au(III) was reduced to Au(0) by electron transfer. The presence of amino groups in ACBs controls the size and dispersion of AuNPs. AuNPs@ACBs was used as a catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), it reveals excellent catalytic activity, which can be ascribed to the smaller particle size of AuNPs (TOF = 7.86 min-1). The spherical structure of AuNPs@ACBs permits straightforward recovery from the aqueous solution after the reaction is completed, thus improving the reusability and catalytic stability. The catalytic efficiency of AuNPs@ACBs can still reach 64.7 % after 10 cycles. After more than 3000 min, the column continues to run without detecting 4-NP in the eluent, which is still working.

Shape and Size Dependence of Pharmacokinetics, Biodistribution, and Toxicity of Gold Nanoparticles.

Gold nanoparticles (AuNPs) are extensively utilized in biomolecular sensing, photothermal therapy, drug delivery, and various imaging techniques like photoacoustic and fluorescent imaging. Despite their diverse applications, inconsistent findings from previous toxicity studies underscore the critical need for standardized methodologies. This study introduces ten distinct types of AuNPs─cubes, stars, rods, dumbbells, and bipyramids at sizes of 50 and 100 nm, to systematically assess their toxicity under controlled conditions both in vitro and in vivo. Our findings reveal a clear correlation between cytotoxicity and the morphology, size, incubation duration, and concentration of AuNPs. Anisotropically shaped nanoparticles, such as nanorods, nanodumbbells, and nanobipyramids, tend to exhibit higher cytotoxicity compared to more spherical forms like nanocubes and nanostars. Interestingly, while in vivo plasma biochemistry parameters show minimal variation, biodistribution, histopathological alterations, and pharmacokinetics are notably influenced by the shape and size of AuNPs. In most instances, smaller and anisotropic AuNPs that remain in the bloodstream for extended periods are observed. This research offers significant insights into the design of AuNPs with specific morphologies and sizes, particularly for their application in drug delivery systems via intravenous injection. These outcomes emphasize the nuanced toxicity profiles of AuNPs, necessitating tailored approaches in preclinical and clinical research.

Arsenic (III) and (V) complexes from solvent free condition and their kinetic factors leading to arsenic nanoparticles

A clear melt from catechol and sodium salts of arsenic (III and V) were obtained individually from the grinding mixing protocol (GMP). The as-obtained molten mass from exothermic reaction between catechol and arsenic salts motivated isothermal titration calorimetry (ITC) advocating the propensity of complex catecholate formation. Individual ITC results substantiated structurally two different mono-anionic complexes, one for arsenic (III) and the other for arsenic (V) ions, of catechol in water at room temperature. Then, the compositions of both the mono-anionic complexes with stoichiometry 1:2 and 1:3 (w∕w) were confirmed for arsenic (III) and (V), respectively. It was shown here for the 1st time that both the complexes supplemented two neat precursors for useful arsenic nanoparticle (As NP) preparation from pH control redox reactions. Again, galvanic replacement reaction (GRR) between As NP and HAuCl4 evolved Au NPs of comparable size as that of As NPs. Thus, thermodynamic results, binding constant (Kb) values, redox kinetic studies and ion associate formation of the two catecholates clearly differentiated the stability (labile and inert character) of As(III) and As(V) catecholates. Conclusively, electrochemistry, galvanic replacement reaction, DLS, thermal analysis, and diverse spectrometric results provided 1st hand support for the complex catecholates of arsenic, a p-block metalloid as labile and inert characters respectively in two different (III) and (V) oxidation states.

Capping agent-free aqueous gold nanoparticles generated by an environmentally friendly plasma-liquid method

This study investigates a simple approach for synthesizing gold nanoparticles (Au NPs) using atmospheric pressure plasma without the need for reducing agents, additives, or capping agents. The size, morphology, optical properties, and aggregation stability of the synthesized Au NPs were characterized using scanning electron microscopy, UV-vis spectroscopy, and zeta potential analysis. The UV-vis absorption spectra of the gold nanoparticles, obtained at various Au3+ concentrations and treatment durations with anode plasma discharge, were analyzed. The UV-vis spectra revealed a surface plasmon resonance absorption band between 530–600 nm, indicative of Au NP formation. Results demonstrated that the size of Au NPs can be tuned within the range of 30–75 nm by adjusting the gold salt precursor concentration from 0.3 to 2.5 mmol/L. It was found that plasma treatment for 3–10 minutes, at different Au3+ concentrations, resulted in the formation of Au NPs with varying sizes and morphologies. The study showed that particles with different shapes – spherical, hexagonal, and triangular – were formed depending on the initial concentration of Au3+. The plasma-chemically synthesized nanoparticles at an Au3+ concentration of 0.06 mmol/L were predominantly spherical and exhibited the highest stability (lasting 12–24 hours), with a zeta potential of –20 to –22 mV, compared to samples with Au3+ concentrations ranging from 0.3 to 2.5 mmol/L.

Quantification of the Surface Coverage of Gold Nanoparticles with Mercaptosulfonates Using Isothermal Titration Calorimetry (ITC).

This manuscript presents a comprehensive study on the quantification of modifier molecules adsorbed on gold nanoparticles (AuNPs) using two complementary techniques Ellman's method (UV-vis spectroscopy) and isothermal titration calorimetry (ITC). In this paper, we compare the feasibility of using the ITC technique and Ellman's method to study the interactions of mercaptosulfonate compounds (sodium mercaptoethanesulfonate, MES, and sodium mercaptoundecanesulfonate, MUS) with the surface of AuNPs of various sizes. The thermodynamic functions of the attachment of mercaptosulfonates to AuNPs were determined, revealing a linear relationship between the number of adsorbed molecules and the surface area of the nanoparticles. The amount of MES and MUS determined by Ellman's method (7 and 11 molecules per square nm, respectively) is more than twice that measured by the ITC technique (3 and 4 molecules per square nm, respectively). The slight differences in the adsorption of MES and MUS on the gold surface are due to differences in the carbon chain length of the ligand molecules. In the case of MES, the formation of the Au-S bond is the dominant stage of the adsorption process, whereas for MUS, the ordering process and self-assembly of molecules on the gold surface are dominant.

Rapid Size Determination of Quasispherical Gold Nanoparticles by Electrocatalysis Efficiency-Regulated Electrochemiluminescence.

The size of gold nanoparticles (AuNPs) largely decides their properties and applications, making the rapid screening of AuNP size important. Despite the fact that AuNP-amplified electrochemiluminescence (ECL) is widely used in various ECL sensing applications, the mechanism of ECL enhancement remains elusive, especially the quantitative relationship between the enhanced ECL intensity and the size of AuNPs. In this work, taking quasispherical and citrate-stabilized AuNPs as model nanoparticles, we have reported that the ECL intensity of the S2O82--O2 system enhanced significantly with the increasing AuNP size. AuNPs acted as bielectrocatalysts for reducing the S2O82- and O2. The further study of enhancement mechanism demonstrates that AuNPs with increasing size facilitate the electron transfer and promote the generation of radicals required for the ECL emission, which produces more emitters-singlet oxygen. Meanwhile, the high surface density of citrate on small AuNPs suppresses the ECL signal by forming an electrostatic barrier. On the basis of the above phenomena, an ECL-based rapid AuNP size screening approach has been established. The accuracy of this platform is verified by the consistent results in comparison to transmission electron microscopy (TEM) measurements. This work not only provides deep insight into the correlation between the AuNP size and the ECL enhancement but also contributes an alternative to the TEM technique for the rapid AuNP size screening. Additionally, this study also extends the exploration of ECL-based structure analysis techniques toward nanomaterials through clarifying the structure-electrocatalytic activity correlation.

Multifunctional gold nanoparticles for cancer theranostics.

The diagnosis and treatment of cancer can often be challenging requiring more attractive options. Some types of cancers are more aggressive than others and symptoms for many cancers are subtle, especially in the early stages. Nanotechnology provides high sensitivity, specificity and multimodal capability for cancer detection, treatment and monitoring. In particular, metal nanoparticles (NPs) such as gold nanoparticles (AuNPs) are attractive nanosystems for researchers interested in bioimaging and therapy. The size, shape and surface of AuNPs can be modified for improving targeting and accumulation in cancer cells, for example through introduction of ligands and surface charge. The interactions of AuNPs with electromagnetic radiation (e.g., visible-near-infrared, X-rays) can be used for photothermal therapy and radiation therapy, through heat generated from light absorption and emission of Auger electrons, respectively. The subsequent expansion and high X-ray attenuation from AuNPs can be used for enhancing contrast for tumor detection (e.g., using photoacoustic, computed tomography imaging). Multi-functionality can be further extended through covalent/non-covalent functionalization, for loading additional imaging/therapeutic molecules for combination therapy and multimodal imaging. In order to cover the important aspects for designing and using AuNPs for cancer theranostics, this review focuses on the synthesis, functionalization and characterization methods that are important for AuNPs, and presents their unique properties and different applications in cancer theranostics.

A gold nanoparticle-enhanced dCas9-mediated fluorescence resonance energy transfer for nucleic acid detection

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated Cas proteins coupled with pre-amplification have shown great potential in molecular diagnoses. However, the current CRISPR-based methods require additional reporters and time-consuming process. Herein, a gold nanoparticle (AuNP)-enhanced CRISPR/dCas9-mediated fluorescence resonance energy transfer (FRET) termed Au-CFRET platform was proposed for rapid, sensitive, and specific detection of nucleic acid for the first time. In the Au-CFRET sensing platform, AuNP was functionalized with dCas9 and used as nanoprobe. Target DNA was amplified with FAM-labeled primers and then precisely bound with AuNP-dCas9. The formed complex rendered the distance between AuNP acceptor and FAM donor to be short enough for the occurrence of FRET, thus resulting in fluorescence quenching. Moreover, AuNPs were demonstrated to enhance binding efficiency of dCas9 to target DNA in Au-CFRET system. The key factors regarding the FRET efficiency were analyzed and characterized in detail, including the length of donor/acceptor and the size of AuNPs. Under the optimal conditions, Au-CFRET could determinate CaMV35S promoter of genetically modified rice as low as 21 copies μL−1. Moreover, Au-CFRET sensing system coupled with one-step extraction and recombinase polymerase amplification can identify the genuine plant seeds within 30 min from sampling to results at room/body temperature without expensive equipment or technical expertise, and requires no additional exogenous reporters. Therefore, the proposed sensing platform significantly simplified the system and shortened the assay time for nucleic acid diagnoses.

Efficient stabilizing agent-free synthesis of gold nanoparticles via square-wave pulse deposition for enhanced catalytic performance in ethanol electrooxidation

The pressing environmental concerns and the depletion of fossil fuel reserves necessitate a transition toward sustainable energy sources. Ethanol, a renewable biomass-derived fuel, is a promising alternative due to its availability and high energy density. This study investigates the synthesis of gold nanoparticles (Au NPs) via a square-wave pulse deposition technique, aiming to enhance catalytic activity for ethanol electrooxidation. By varying pulse durations, we were able to exert precise control over Au NP size and distribution without stabilizing agents. Characterization using field emission scanning electron microscopy and X-ray diffraction techniques confirmed the formation of clustered nanoparticles of metallic gold phase. Electrochemical characteristics analyses revealed that Au NPs synthesized with a 900 ms pulse duration exhibited the lowest charge transfer resistance and the highest electrochemically active surface area. The electrocatalytic performance test of these Au NPs demonstrated an anodic current density of 2.5 mA cm−2 and a Tafel slope of 78 mV dec−1, indicating superior catalytic performance and reaction kinetics. Additionally, the Au NPs showed high resistance to poisoning, as evidenced by a low jb/jf ratio of 0.28 and stable chronoamperometric response. These findings underscore the potential of this synthesis method for producing high-performance electrocatalysts utilized in exploiting ethanol's potential as an environmentally friendly energy carrier.

Thermo- and Photoresponsive Smart Nanomaterial Based on Poly(diethyl vinyl phosphonate)-Capped Gold Nanoparticles.

A new nanodevice based on gold nanoparticles (AuNPs) capped with poly(diethylvinylphosphonate) (PDEVP) has been synthesized, showing interesting photophysical and thermoresponsive properties. The synthesis involves a properly designed Yttriocene catalyst coordinating the vinyl-lutidine (VL) initiator active in diethyl vinyl phosphonate polymerization. The unsaturated PDEVP chain ending was thioacetylated, deacetylated, and reacted with tetrachloroauric acid and sodium borohydride to form PDEVP-VL-capped AuNPs. The NMR, UV-Vis, and ESI-MS characterization of the metal nanoparticles confirmed the formation of the synthetic intermediates and the expected colloidal systems. AuNPs of subnanometric size were determined by WAXD and UV-Vis analysis. UV-Vis and fluorescence analysis confirmed the effective anchoring of the thiolated PDEVP to AuNPs. The formation of 50-200 nm globular structures was assessed by SEM and AFM microscopy in solid state and confirmed by DLS in aqueous dispersion. Hydrodynamic radius studies showed colloidal contraction with temperature, demonstrating thermoresponsive behavior. These properties suggest potential biomedical applications for the photoablation of malignant cells or controlled drug delivery induced by light or heat for the novel PDEVP-capped AuNP systems.

AC-driven QLED based on far-field effect of Au NPs

As the pixel size continues to shrink, conventional display devices are unable to satisfy the increasing demand. Therefore, a novel light-emitting device has garnered significant attention. This device emitted light under an alternating current (AC) electric field and blocked the injection of external carriers by using the insulating layer. However, at the same time, this approach leads to a reduction in brightness. In this paper, we have realized the performance enhancement of AC-driven QLEDs by incorporating Au NPs of different sizes in PEDOT:PSS. Our investigation reveals that Au NPs of greater size exhibit a notable enhancement of the brightness, rising from 5512 cd/m2 to 7234 cd/m2, representing a substantial increase of approximately 31.2 %. It demonstrates the great potential of the "far-field" effect in AC-driven QLEDs.

Comparative evaluation of gold nanoparticles as contrast agent in multimodality diagnostic imaging

A contrast agent is clinically employed to aid the visualization of organs and structures when imaged by radiation based diagnostic imaging modalities. Iodinated contrast agents have been used for decades, but they carry a heightened risk of adverse allergy reactions and contrast-induced nephropathy. This study investigated the contrast enhancement characteristics of gold nanoparticles (AuNPs) through diverse cancer diagnostic imaging modalities as a potential alternative to the iodine-based contrasts. Solutions of 1.9 nm and 15 nm AuNPs, ranging from 3 to 20 mM concentrations, were prepared, alongside a low osmolar non-ionic iodine contrast agent as a control. All samples were scanned and imaged using x-ray computed tomography scanner (CT-Scan), digital mammography, digital radiography, and fluoroscopy modalities. The contrast-to-noise ratio (CNR) was measured to study the relationship between the size, the concentrations, and the influence of the tube voltage over the image contrast enhancement efficacy of the agents. A lower concentration of AuNPs produced lower CNR values. In addition, the 1.9 nm size of AuNPs caused lower CNR than the 15 nm AuNPs when tested with the highest concentration of 20 mM. High CT's HU values for both sizes of AuNPs indicated substantial contrast enhancement compare to iodine. Although the 15 nm AuNPs might set off higher CNR, a better quality of image contrast enhancement was also observed compared to the 1.9 nm AuNPs. The findings also suggested that the contrast enhancement by AuNPs is highly dependent on the modalities' type and x-rays energy. In conclusion, AuNPs could be applied as a contrast agent in various diagnostic imaging modalities representing promising approach in cancer detection particularly in cases of patients having adverse reactions towards the iodine based contrast agents.

Gold nanoparticle effect on dose and DNA damage enhancement in the vicinity of gold nanoparticles

This study uses Monte Carlo simulations to examine the dose enhancement effect of gold nanoparticles (AuNPs) in radiation therapy and its effects on DNA damage. Using the GATE- 9.0 and Geant4-DNA packages, Monte Carlo simulations were used to simulate a mathematical phantom and determine the energy deposition in the vicinity of AuNP. The simulations were conducted for various photon beam energies (50, 100, 250, and 6000 keV) with and without the presence of different-size AuNPs (10, 30, 50 and 100 nm). The dose enhancement factor (DER) was evaluated using Geant4-DNA to examine the effects AuNP sizes and photon beam energies on DNA damage. A multi-scale Monte Carlo simulation was conducted to evaluate enhanced DNA damage owing to nanoparticles in the proximity of cancer cells. The Monte Carlo simulations indicated that AuNPs boost the dose delivery, resulting in enhanced energy deposition and subsequent DNA damage. The DER analysis revealed a significant increase in the dose deposition within DNA, leading to single or double-strand breaks. Geant4-DNA simulations revealed information on the dosage enhancement factor for various AuNP sizes and photon beam intensities, enabling a deeper comprehension of the underlying mechanics. The outcomes of this study emphasize the potential of AuNPs as effective radiosensitizers in radiation therapy and contribute to the growing body of research on the use of nanotechnology in enhancing cancer treatment outcomes. Further investigations and experimental validations are necessary to optimize the usage of AuNPs for improved radiation therapy.

Enhanced SERS performance of gold nanoparticle assemblies on a cysteine-mutant Tobacco mosaic virus scaffold

The employment of biomolecular templates for the synthesizing nanohybrid constructs is expanding, driven by their prospective uses in biosensing and biomedical fields. Gold nanoparticles (AuNPs) and, in particular, their assemblies are especially preferred for Surface Enhanced Raman Spectroscopy (SERS) because of their ability to amplify Raman signals through localized surface plasmon resonances, thus enabling the detection of molecules at exceedingly low concentrations. Our investigative approach is dedicated to studing the role of cysteine mutants in the nucleation and assembly of AuNPs on Tobacco mosaic virus (TMV-C, carrying T158C mutation) scaffolds. Employing biomineralization and direct grafting methods, we synthesized these nanohybrids and examined them using conventional transmission electron microscopy (TEM), in situ liquid TEM, and fluorescence spectroscopy. We demonstrated that the syntheses obtained with TMV-C give denser plasmonic nanostructures, with is ideal for SERS applications. The SERS performances of these novel nanohybrids with various AuNPs sizes and densities were evaluated, revealing excellent enhancement factors for the nanosystems obtained by direct grafting that highlight their potential for the detection of biomolecules in solution.

Uncoated gold nanoparticles create fewer and less localized defects in model prokaryotic than in model eukaryotic lipid membranes

The rise of the populations of antibiotic resistant bacteria represents an increasing threat to human health. In addition to the synthesis of new antibiotics, which is an extremely expensive and time-consuming process, one of the ways to combat bacterial infections is the use of gold nanoparticles (Au NPs) as the vehicles for targeted delivery of therapeutic drugs. Since such a strategy requires the investigation of the effect of Au NPs (with and without drugs) on both bacterial and human cells, we investigated how the presence of coating-free Au NPs affects the physicochemical properties of lipid membranes that model prokaryotic (PRO) and eukaryotic (EU) cells. PRO/EU systems prepared as multilamellar liposomes (MLVs) and hybrid structures (HSs) from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol (DPPG)/1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS) in the absence (MLVs)/presence (HSs) of differently distributed Au NPs (sizes ∼20 nm) reported stabilization of the gel phase of PRO systems in comparison with EU one (DSC data of PRO/EU were Tm(MLVs) ≈ 41.8 °C/42.0 °C, Tm¯ (HSs) ≈ 43.1 °C/42.4 °C, whereas UV-Vis response Tm(MLVs) ≈ 41.5 °C/42.0 °C, Tm¯ (HSs) ≈ 42.9 °C/41.1 °C). Vibrational spectroscopic data unraveled a substantial impact of Au NPs on the non-polar part of lipid bilayers, emphasizing the increase of kink and gauche conformers of the hydrocarbon chain. By interpreting the latter as Au NPs-induced defects, which exert the greatest effect when Au NPs are found exclusively outside the lipid membrane, these findings suggested that Au NPs reduced the compactness of EU-based lipid bilayers much more than in analogous PRO systems. Since the uncoated Au NPs manifested adverse effects when applied as antimicrobials, the results obtained in this work contribute towards recognizing AuNP functionalization as a strategy in tuning and reversing this effect.