Concentration Of AuNPs Research Articles

Exploring In Vitro Antibiofilm Potential and In Vivo Toxicity Assessment of Gold Nanoparticles.

In this study, biogenically synthesized AuNPs were first characterized via UV visible spectroscopy, SEM, XRD, and FTIR followed by toxicity evaluation using mice model. UV-visible spectroscopy of biogenic AuNPs showed peaks at 540-549 nm, while FTIR spectrum showed various functional groups involving O-H, Amide I, Amide II, O-H, C-H groups, and so on. SEM showed the size variation from 30 to 60 nm. Antibacterial potential against pathogenic isolates showed bigger ZOI (31.0 mm) against Pseudomonas aeruginosa AuNPs. Antibiofilm activity showing up to 100% inhibition at 90 µg mL-1 concentration of AuNPs. Toxicity evaluation showed LD50 as 70 mg kg-1. Exposure to AuNPs caused significant changes in the levels of serum AST (p < 0.05) at 100-150 mg kg-1 of AuNPs exposure. Histopathology of male albino mice kidney and liver revealed that mice exposed to maximum concentration of AuNPs showed necrosis, cell distortion, and hepatocytes detachment. Present study showed that biologically synthesized AuNPs possess effective antimicrobial and biofilm inhibitory potential. AuNPs strong bactericidal effect even at lower concentration suggest that NPs could have excellent potential for combating pathogens. In conclusion, nanotechnology may revolutionize human life and medical industry by developing innovative drugs with the potential to treat diseases in shorter and noninvasive time period. Hence, in vitro biosafety and experimental observations followed by in vivo outcomes are crucial in shifting the novel therapeutics into medical practice thus leading further into their future development.

Easy reversible clustering of gold nanoparticles via pH-Induced assembly of PVP-b-PAA copolymer

The growing demand of novel hybrid organic/inorganic systems with exciting properties has contributed to an increasing need for simplifying production strategies. Here, we report a simple method to obtain controlled three-dimensional hybrid architectures, in particular hybrid supracolloids (hSC), formed by gold nanoparticles and a double hydrophilic block copolymer, specifically the poly(acrylic acid)-block-poly(N-vinyl-2-pyrrolidone) (PAA-b-PVP), directly in aqueous medium. The ubiquitous pH-sensitive poly(acrylic acid) (PAA) block initiates the assembly through pH changes, while the poly(N-vinyl-2-pyrrolidone) block assures the close affinity with the AuNPs. We demonstrate that the formation of hybrid supracolloids (hSC) is the result of the synergetic behavior of the two specific polymeric blocks. Additionally, the entire process shows spontaneous and fast switchability. The nanostructured copolymer behaves like a highly swollen hydrogel and displays a disordered internal structure. The driving force for the association of the copolymer chains is induced by the synergetic effects of the decrease in solubility of the poly(acrylic acid) block and the formation of inter and intra chains hydrogen bonds. These were demonstrated by using small angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation monitoring (QCM-D) and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX). In turn, the AuNPs are randomly spread all over the polymeric matrix, as demonstrated by field emission gun – scanning electron microscopy (FEG-SEM). A correlation analysis reveals the hSC density depends mostly on the initial concentration of AuNPs. These results can inspire the fabrication of more complex structures with multicomponent composition.

Enhanced Sensitivity and Homogeneity of SERS Signals on Plasmonic Substrate When Coupled to Paper Spray Ionization–Mass Spectrometry

This work reports on the development of an analyte sampling strategy on a plasmonic substrate to amplify the detection capability of a dual analytical system, paper spray ionization–mass spectrometry (PSI-MS) and surface-enhanced Raman spectroscopy (SERS). While simply applying only an analyte solution to the plasmonic paper results in a limited degree of SERS enhancement, the introduction of plasmonic gold nanoparticles (AuNPs) greatly improves the SERS signals without sacrificing PSI-MS sensitivity. It is initially revealed that the concentration of AuNPs and the type of analytes highly influence the SERS signals and their variations due to the “coffee ring effect” flow mechanism induced during sampling and the degree of the interfacial interactions (e.g., van der Waals, electrostatic, covalent) between the plasmonic substrate and analyte. Subsequent PSI treatment at high voltage conditions further impacts the overall SERS responses, where the signal sensitivity and homogeneity significantly increase throughout the entire substrate, suggesting the ready migration of adsorbed analytes regardless of their interfacial attractive forces. The PSI-induced notable SERS enhancements are presumably associated with creating unique conditions for local aggregation of the AuNPs to induce effective plasmonic couplings and hot spots (i.e., electromagnetic effect) and for repositioning analytes in close proximity to a plasmonic surface to increase polarizability (i.e., chemical effect). The optimized sampling and PSI conditions are also applicable to multi-analyte analysis by SERS and MS, with greatly enhanced detection capability and signal uniformity.

Gold Nanoparticles Modulate Excimer and Exciplex Dynamics of PDDCP-Conjugated Polymers.

How plasmonic nanostructures modulate the behavior of exciplexes and excimers within materials remains unclear. Thus, advanced knowledge is essential to bridge this gap for the development of optoelectronic devices that leverage the interplay between plasmonic and conjugated polymer hybrid materials. Herein, this work aims to explore the role of gold nanoparticles (AuNPs) in modulating exciplex and excimer states within the conjugated polymer poly(2,5-di(3,7-dimethyloctyloxy) cyanoterephthalylidene) (PDDCP), known for its photoluminescent and semi-conductive properties, aiming to create innovative composite materials with tailored optical features. The spectral analysis was conducted to investigate the effects of AuNPs on the PDDCP, varying AuNP volume percentages to measure changes in the absorption profile, molar extinction coefficient (ε), absorption cross-section (σa), and optical bandgap (Eg). Fluorescence spectra of the mixture at different volume ratios were also examined to assess exciplex formation, while amplified spontaneous emission (ASE) profiles were analyzed to study the behavior and photochemical stability of the polymer-NP hybrid material. Increasing AuNP volume induced both blue and red shifts in the absorption profile of the PDDCP. Higher AuNPs concentrations correlated with decreased ε and σa, inversely impacting Eg. The emission spectra obtained at varied AuNP volume ratios indicated significantly enhanced exciplex and excimer formations. The ASE profiles remained consistent but showed reduced intensity with increasing AuNPs concentrations, indicating their influence on hybrid material behavior and stability. The findings suggest that AuNPs affect PDDCP's optical characteristics, altering the absorption profile, bandgap, and fluorescence spectra. Furthermore, the observed reduction in ASE intensity highlights their influence on the behavior and photochemical stability of the hybrid material. These results contribute to a better understanding of the versatile applications of plasmonic-conjugated hybrid polymers.

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.

Green Synthesis Gold Nanoparticles using Bioreductant Red Shoot Leaf Extract (Syzygium myrtifolium Walp.) and Activity as Antioxidant

Gold nanoparticles (AuNPs) are small-sized materials important in various commercial and industrial applications. Several methods have been developed to synthesise AuNPs. This study was conducted by synthesizing AuNPs using HAuCl4 as a precursor and red shoot leaf extract as a bioreductor. The concentrations of AuNPs used were 20, 10, 5, and 2.5 ppm. Characterization of gold nanoparticles at a concentration of 20 ppm was carried out using a UV-Vis spectrophotometer to measure the maximum wavelength and Transmission Electron Microscopy (TEM) to determine particle size. Antioxidant activity at 20, 10, 5, and 2.5 ppm was determined by measuring free radical capture activity using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. The results showed that gold nanoparticles had a maximum wavelength of 530 nm with a ruby red color and an average particle size of 14.907 nm. The synthesized AuNPs showed high antioxidant activity: 99.6% (20 ppm), 98.9% (10 ppm), 96.7% (5 ppm), and 91.0% (2.5 ppm), indicating that higher concentrations of AuNPs resulted in more significant free radical scavenging. This study successfully synthesized gold nanoparticles using red shoot leaf extract as an environmentally friendly bioreduction. The resulting nanoparticles have a nanometer particle size with very high antioxidant activity, especially at a concentration of 20 ppm. The method used in this study offers a more environmentally friendly alternative for synthesizing gold nanoparticles, which previously often used hazardous chemicals. The use of red shoot leaf extract as a bioreductor has not been widely reported in the literature, thus providing a new contribution to green nanotechnology. Further research is recommended to explore the potential applications of gold nanoparticles synthesized by this method in medical and other industrial fields. In addition, additional studies are needed to optimize the synthesis conditions and more in-depth characterization of the stability and toxicity of gold nanoparticles in practical applications.

Oxidative Stress Induction by Gold Nanoparticles in HCT-116 Colon Cancer Cells

Background: Gold nanoparticles (AuNPs), a new cancer treatment, have few side effects. Objectives: This study aimed to investigate the effect of AuNPs on oxidative stress in HCT-116 colon cancer cells. Methods: The viability of HCT-116 cells was evaluated using the 3-(4,5-dimethylthiazol-2,5-diphenyl) tetrazolium bromide (MTT) assay after 24 and 48 hours of incubation with different concentrations of AuNPs (0 - 50 μg/mL). The state of oxidative stress, total antioxidant capacity (TAC), total oxidative status (TOS), reactive oxygen species (ROS) levels, and the activity of antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT), were determined by colorimetric and fluorometric methods. Results: Oxidative stress parameters and ROS were significantly increased in cells treated with 25 and 50 μg/mL concentrations of AuNPs during 24 and 48 hours of incubation compared to control cells (P &lt; 0.001). In contrast, the level of TAC and the activity of antioxidant enzymes SOD, GPX, and CAT were significantly decreased in the treated groups compared to the untreated cells after 48 hours of incubation (P &lt; 0.05). Conclusions: This study showed that AuNPs affect HCT-116 cancer cells by increasing ROS and oxidative stress while reducing the activity of antioxidant enzymes.

NbOx RRAM performance enhancement by surface modification with Au nanoparticles

Resistive random-access memory (RRAM) has been widely studied because of its high information storage density and easy integration, and it has potential to replace traditional memory storage means. However, it is prone to random formations and fracture of conductive filaments, which limits its commercial applications. In this study, magnetron sputtering was used to deposit NbOx films on different substrates modified with different concentrations of Au-nanoparticles (NPs). The as developed Pt-Aumin/NbOx/W tip device with the lowest concentration of Au-NPs modified bottom electrode exhibited the best performance; the Vset distribution of the device was more concentrated, Vreset decreased significantly, the distribution range was narrow, and the resistance distribution of high and low resistance states (HRS and LRS, respectively) was more stable. Modification of the bottom electrode with Au-NPs did not change the ohmic conduction behavior of NbOx RRAM in LRS; however, it changed the resistance switching mechanism from SCLC to P–F effect modified SCLC. The Au-NPs modified bottom electrode acted like a tip, enhancing the local electric field and promoting the formation of conductive filaments near the NPs. This work explains the internal mechanism for improving RRAM properties using a local electric field and provides theoretical guidance for enabling the rapid commercialization of RRAM.

The influence of Au-based nanoparticles on some physiological, biochemical and molecular characteristics of wheat plants during low temperature hardening

One of the most significant problems of the 21st century is the anthropogenic strain on the environment. The development of nanotechnology makes it possible to produce a variety of nanomaterials widely used in people's daily lives. However, nanomaterials can accumulate in ecosystems and spread through food chains. The environmental risks of nanoparticle proliferation are unclear. At the same time, certain nanoparticles act as adaptogens, improving plant tolerance to unfavorable stress factors. It is quite realistic to choose such experimental conditions, under which the effect on plant stress tolerance will be obvious and the accumulation of nanoparticles in tissues will be minimal. In this case, the main relevant factors are the type of nanoparticles, their concentration and their way of penetration into plants. We chose to study gold nanoparticles (Au-NPs), widely used in biomedical research. The concentration of Au-NPs was 20 μg/mL, which is considered safe for living organisms. The influence of Au-NPs on some physiological, biochemical and molecular characteristics of wheat plants during low temperature hardening was examined. The study of the photosynthetic apparatus and antioxidant system was the primary focus. The stimulating effect of Au-NPs on cold tolerance of wheat plants was shown. The results expand our knowledge of the processes by which nanoparticles impact plants and the potential applications of nanoparticles as adaptogens in science and agriculture.

Aminosilane assisted deposition of gold nanoparticles on Zn(OH)2 nanosheets and their application in electrochemical sensor

A facile and efficient method for systematical deposition of gold nanoparticles (AuNPs) on Zn(OH)2 nanosheets (NS) with different Zn and Au ratios was established in the presence of N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TPDT silane), without adding any external reducing agents, at room temperature. Here, TPDT silane behaves as both a stabilizing and reducing agent. UV–vis absorption spectroscopy, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the formation of AuNPs on Zn(OH)2 NS. As the concentration of AuNPs increased, a proportional increase in both the number and size of deposited AuNPs on Zn(OH)2 NS was observed. To understand how the variation in the number and size of AuNPs affects their catalytic activity, the electrocatalytic activity of different composition ratios of Zn(OH)2-Au NS toward nitrite ions was studied using cyclic voltammetry and amperometric technique. The TPDT-stabilized Zn(OH)2-Au NS showed high electrocatalytic activity, attributed to the effective electron transfer from Zn(OH)2 NS to AuNPs, creating a synergistic effect that enhances the overall activity. The optimal Zn(OH)2-Au NS modified electrode showed an amperometric sensitivity of 5.72 nA/µM and a limit of detection of 1.2 µM for nitrite ions in water sample well below the guideline value of WHO. This demonstrates the practical applicability of this method for real-world water analysis.

Impact of Surface Functionality on Biodistribution of Gold Nanoparticles in Silkworms

To date, animal models are still indispensable for studying biodistribution and elimination of nanomaterials. However, the use of mammals for in vivo experiments faces various challenges including increasing regulatory hurdles and costs. This study aims to validate larvae of the domestic silkworm Bombyx mori as an alternative invertebrate model for preliminary in vivo research. Organ distribution and elimination of gold nanoparticles (AuNPs) are compared with four different surface functionalities in silkworms after systemic administration: AuNPs coated with poly(ethylene glycol) (PEG), with polyglycidols (PGs) that are slightly hydrophobic (PG(alkyl)), positively charged (PG(+)), or negatively charged (PG(−)). Subsequent inductive coupled plasma mass spectrometry 6 or 24 h after AuNPs administration reveals the biodistribution in silkworm hemolymph, midgut, epidermis, and excrements. Even after 24 h incubation, hemolymph contains the highest AuNPs concentrations, independent of surface functionalization indicating a prolonged circulation time and slow distribution into different silkworm organs and tissues. Positively charged PG(+)AuNPs show three times higher concentrations in the midgut and are excreted at the fastest rate when compared to other AuNPs. In the findings, a surface‐dependent biodistribution and elimination of AuNPs are indicated in silkworms, and the feasibility of using this inexpensive animal model for time‐ and cost‐effective, preliminary in vivo studies of NPs is confirmed.

Synthesis and characterization of gold/nickel oxide nanoalloy via green laser irradiation

In the present study, a gold/nickel oxide (Au/NiO) nanoalloy was generated by irradiating two nano-metallic material solutions using a green laser. The produced Au/NiO nanocomposites were characterized by UV–Vis–NIR spectroscopy, an X-ray diffraction pattern, TEM and SEM imaging, and photoluminescence and DLS tests. Depending on the concentration of Au NPs in the suspension medium, the final characteristics of Au/NiO nanocomposites vary significantly. Au NPs exhibit an extremely high plasmonic absorption peak at approximately 530 nm. They melted by absorbing the energy of the second harmonic of the laser beam, forming an Au/NiO nanocomposite. Additionally, our results demonstrated that after irradiation with a green laser, the bandgap energy of samples was reduced to 5, 4.3, and 4 eV as the number of Au NPs in nanocomposite structures increased, indicating that the addition of gold to nickel oxide NPs improves their conductivity and reduces the bandgap energy of samples. Moreover, due to composition formation, the number and size of Au NPs dropped following green laser irradiation, while NiO NPs grew in size. This work created an AuNiO nanocomposite by laser ablation, which is a highly effective approach for fabricating nanostructures.

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications.

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.

Gold nanoparticles spectral CT imaging and limit of detectability in a new materials contrast-detail phantom

This study involves the synthesis, characterization, and spectral photon counting CT (SPCCT) imaging of gold nanoparticles tailored for enhancing the contrast of small cancer lesions. We used the modified Turkevich method to produce thiol-capped gold nanoparticles (AuNPs) at different concentrations (20, 15, 10, 5, 2.5, 1.25, 0.6 mg/ml). We thoroughly characterized the AuNPs using Transmission Electron Microscopy (TEM), X-ray diffraction spectroscopy (XRD), Dynamic Light Scattering (DLS), and UV–visible absorption spectroscopy. To assess the AuNPs contrast enhancing performance, we designed and built a new material contrast detail phantom for CT imaging and determined the minimum detectable concentrations of AuNPs in simulated lesions of small diameters (1, 2, 3, and 5 mm). The synthesized AuNPs are spherical with an average size of approximately 20 ± 4 nm, with maximum UV absorption occurring at 527 nm wavelength, and exhibit a face-centered cubic structure of gold according to XRD analysis. The synthesized gold nanoparticles demonstrated high contrast in SPCCT, suggesting their potential as contrast agents for imaging cancer tissues. The AuNPs image contrast was directly proportional to the AuNPs concentration. We are the first to determine that the lowest visually distinguishable contrast was achieved at a gold concentration of 5 mg/ml for a 2 mm simulated lesion. For 1 mm size lesion the smallest visible concentration was 10 mg/ml. This newly developed phantom can be used for determining the minimal concentration required for various high-Z nanoparticles to produce detectable contrast in X-ray imaging for small-size simulated lesions.

Localize surface plasmon resonance of gold nanoparticles and their effect on the polyethylene oxide nanocomposite films

Colloidal Gold nanoparticles (AuNPs) with sodium citrate coating were successfully synthesized using a chemical reduction method with an average spherical size of about 20 nm dispersed in the water with high stability. The localized surface plasmon resonance (LSPR) peak was studied by experimental measurement and Mie theory. The absorbance spectrum of AuNPs exhibits a fingerprint peak in the 500–600 nm range, corresponding to the LSPR of AuNPs. Moreover, PEO/AuNPs nanocomposite films with different concentrations of AuNPs were also prepared to evaluate the effect of LSPR of AuNPs on the electrical conductivity and photoconductivity of nanocomposite films. The degree of crystallinity (Xcrys) and melting enthalpy (ΔHm) increase as the AuNPs content in the polymer matrix increases up to 0.5 wt% due to the enhanced nucleation points. The electrical conductivity of pure PEO film is 1.93×10−6 S.cm−1. Increasing the AuNPs concentration to 0.5 wt% in the PEO matrix leads to an increase in the electrical conductivity to 2.28×10−3 S.cm−1 as AuNPs.

Low Concentrations of Gold Nanoparticles as Electric Charge Carriers in Piezoelectric Cement-Based Materials.

Piezoelectric cement-based composites could serve to monitor the strain state of structural elements or act as self-powered materials in structural health monitoring (SHM) applications. The incorporation of piezoelectric materials as an active phase within cement matrices has presented a highly attractive avenue until today. However, their application is challenged by the low electrical conductivity of the hydrated cement matrix. Gold nanoparticles (Au NPs) possess substantial potential for elevating the free electrical charge within the matrix, increasing its electrical conductivity between the Au NPs and the cement matrix, thereby enhancing the piezoelectric response of the composite. In this sense, the objective of this study is to investigate the effects of incorporating low concentrations of gold nanoparticles (Au NPs) (442 and 658 ppm) on the electrical and piezoelectric properties of cement-based composites. Additionally, this study considers the effects of such properties when the material is cured under a constant electric field. Electrical impedance spectroscopy was used to evaluate the polarization resistance and piezoresistive properties of the material. Additionally, open-circuit potential measurements were taken alongside the application of mechanical loads to assess the piezoelectric activity of the composites. The findings revealed a notable decrease in the composite's total electrical resistance, reaching a value of 1.5 ± 0.2 kΩ, almost four times lower than the reference specimens. In the realm of piezoelectricity, the piezoelectric voltage parameter g33 exhibited a remarkable advancement, improving by a factor of 57 when compared to reference specimens. This significant enhancement can be attributed to both the concentration of Au NPs and the electrical curing process. In summary, the outcomes of this study underscore the feasibility of creating a highly electrically conductive cement-based matrix, using low concentrations of gold nanoparticles as electric charge carries, and indicate the possible piezoelectric behavior of the studied compposite.

Green synthesis of gold nanoparticles from Coleus scutellarioides (L.) Benth leaves and assessment of anticancer and antioxidant properties

Gold nanoparticles (AuNPs) have gained significant attention in the field of biomedicine due to their versatile potential and diverse applications. In this study, AuNPs were biologically synthesized using the leaf extract of Coleus scutellarioides (L.) Benth to explore the in vitro anticancer and antioxidant properties. The synthesized AuNPs underwent thorough characterization through various analyses, the UV–Visible Spectroscopy (UV–Vis) of the AuNPs displayed a peak at 532 nm, indicating the occurrence of surface plasmon resonance. The crystalline structure of the AuNPs was confirmed by analyzing the X-ray Diffraction pattern (XRD). Moreover, Transmission Electron Microscopy (TEM) analysis revealed a spherical morphology for the AuNPs, with an average particle size of 40.10 nm, consistent with the measurements obtained from Dynamic light scattering (DLS). After that, the biological performance of those biomolecules functionalized AuNPs was studied. This study investigated the potential cytotoxic effects of synthesized AuNPs using the MTT assay. The assay was employed to evaluate the cell viability against the human breast cancer cell line (MDA-MB-231) compared to the human foreskin fibroblast cell line (Hs-27), with concentrations ranging from 7.5 to 60 µg/ml over 24 h. The study findings reveal a concentration-dependent impact of synthesized AuNPs on MDA-MB-231 cells. As the AuNPs concentration increases, there is a corresponding increase in the inhibition of MDA-MB-231 cells, reaching an IC50 value of 36.10 µg/ml within a 24-hour period. Contrarily, the synthesized AuNPs exhibited no apparent toxicity against the noncancerous normal Hs-27 cells. Furthermore, the antioxidant efficacy of AuNPs was evaluated through a free radical scavenging DPPH assay. These findings suggest the potential of Coleus scutellarioides (L.) Benth leaf extract as an effective bio-reductant for synthesizing stable AuNPs with anticancer activity and antioxidant properties.

Photoporation-mediated spatial intracellular delivery of stem cell-derived cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (iPSCCMs) are promising candidates for disease modeling and therapeutic purposes, however, non-viral intracellular delivery in these cells remains challenging. Gold nanoparticle (AuNP)-sensitized photoporation creates transient pores in the cell membrane by vapor nanobubble formation, allowing diffusion of extracellular biomolecules. This non-viral technique was employed to test and optimize its distinct physical mode of action in iPSCCMs. Photoporation optimization was aimed at achieving high delivery rates while minimizing cell death. Various AuNP concentrations, in conjunction with different laser fluences, were explored to facilitate the intracellular delivery of 10 kDa and 150 kDa FITC-labelled dextran as model macromolecules. Cardiomyocyte viability was assessed using the CellTiter-Glo® viability assay, while the delivery efficiency was quantified through flow cytometry. On 30 day-old cardiomyocytes, AuNP photoporation was able to yield ∼60 % delivery efficiency while maintaining a high cell viability (∼70 %). Overall, higher AuNP concentrations resulted in greater delivery efficiencies, albeit at the expense of lower cell viability. Finally, photoporation was capable of patterning a geometric shape, demonstrating its exceptional selective resolution in delivering molecules to spatially restricted regions of the cell culture. In conclusion, AuNP-photoporation exhibits considerable potential as an effective and gentle non-viral method for intracellular delivery in iPSCCMs.•AuNP-photoporation is a non-viral intracellular delivery method suitable for iPSCCMs with high efficiency and cell viability•This method is capable of spatially resolved intracellular delivery with excellent resolution

Size and concentration effects of gold nanoparticles on the plasmonic sensing of Cr(VI)

It is very important to determine the presence of toxic Cr(VI) in aqueous environment. Detection of Cr(VI) using AuNPs has been carried out based on the oxidation or etching principle, which results in the change of localized surface plasmon resonance. In this work, the effects of size and concentration of colloidal AuNPs on the Cr(VI) sensing characteristics were studied by both simulation and experiment. In the simulation study using MNPBEM toolbox, the etching process was described as shrinking of AuNPs with total volume loss reflecting the concentration of Cr(VI) as oxidizing ions. The experiment was carried out by exposing colloidal AuNPs with different size and concentration to Cr(VI). The AuNPs were obtained from laser-induced photochemical process, in which aqueous solution of Au ions were subjected to femtosecond laser irradiation. The simulation results showed wider blue-shift of λLSPR per total volume loss when larger AuNPs were employed and higher intercept value of extinction decrease per total volume loss when more AuNPs were present in the system. Correspondingly, the experiment demonstrated more distinct color change and wider λLSPR per Cr(VI) concentration when larger AuNPs were used. More concentrated colloid showed still-red color after Cr(VI) etching, representing higher intercept value of extinction decrease per Cr(VI). Both simulation and experiment results show that, in etching-based Cr(VI) sensing, large AuNPs displayed wider LSPR wavelength shift compared to the small nanoparticles. On the other hand, concentration of AuNPs contributes to the intensity change and higher concentration of AuNPs offers higher Cr(VI) sensing range. This result provided an insight on how colorimetric sensor performance might be affected by the choice of nanoparticle size and concentration used in the system.

Low-cost and highly sensitive colorimetric and visual detection of amikacin in milk using melamine functionalized gold nanoparticles.

This study developed a rapid, low-cost and highly sensitive analytical method using melamine functionalized gold nanoparticles (MA-Au NPs) as a colorimetric sensor to detect amikacin in milk. The MA-Au NPs were synthesized using a self-assembly process and analyzed using absorption spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The MA-Au NPs exhibited a distinct surface plasmon resonance (SPR) absorption peak at 520 nm and demonstrated excellent spherical dispersion. The reaction parameters were optimized, with a Au NP concentration of 2.0 × 10-7 mol L-1, MA concentration of 1.0 × 10-6 mol L-1, pH of 4.0, and reaction time of 15 minutes. In the optimization experiment, the effects of unmodified Au NPs and MA-Au NPs as colorimetric sensors for amikacin determination were compared. As a specific amount of amikacin was added to the Au NP solution, the reaction solution showed a visible change from wine red to purple and then to blue gray; a red-shift in the absorption spectrum of the solutions was observed, which could also be analyzed using the A640/A520 value, and the color changes were recorded using smartphones for visual detection through RGB (red-green-blue) data image analysis, which made the detection easy and fast. As a result, two approaches were devised using visible absorption spectra and smartphones. A linear correlation was established between the A640/A520 value and the concentration of amikacin in the range of 4.0 to 16.0 × 10-8 mol L-1. The minimal limit of detection (LOD) for absorption spectrum analysis was 3.75 × 10-9 mol L-1, whereas for smartphone analysis, it was 6.0 × 10-8 mol L-1. The recoveries ranged from 103.09% to 104.51%, while the relative standard deviations (RSDs) ranged from 3.76% to 4.25%. The proposed method was used to detect actual milk samples. The results showed that the method is simple, selective, and practical.