Green synthesis and characterization of nontoxic L-methionine capped silver and gold nanoparticles

A combined experimental and DFT study of metal core/indocyanine green shell hybrid nanoparticles

Indocyanine green (ICG) is the FDA-approved fluorescent dye used for in vivo medical imaging, diagnostics, and photothermal therapy. However, this dye is easily degradable in the human vascular system, and therefore its stabilization is preferable. In this work, ICG molecules were stabilized by their adsorption on the surface of the L-methionine-capped Ag and Au nanoparticles (Ag and Au @LM NPs) in aqueous colloidal dispersions. The result is the formation of hybrid metal core/ICG shell NPs in colloidal dispersions. Additionally, colloidal dispersions were stabilized, indicating a double effect of ICG adsorption. The obtained hybrid NPs were studied experimentally (UV-Vis spectrophotometry, HRTEM, DLS, FTIR) and theoretically (DFT calculations). HRTEM revealed that the interplanar spacing between adjacent planes of NPs decreases after the dye adsorption. The results obtained from the DFT study confirmed the formation of a covalent bond between the oxygen from ICG dye SO3- group and metal NPs. Considering the characteristics of both components of the NPs/ICG hybrid system, the authors assume that this hybrid system can exhibit the synergistic effect that could lead to more successful theranostic treatment of cancer in nanomedicine.

α-Amino Acids as Reducing and Capping Agents in Gold Nanoparticles Synthesis Using the Turkevich Method

Amino acid-capped gold nanoparticles (AuNPs) are a promising tool for various applications, including therapeutics and diagnostics. Most often, amino acids are used to cap AuNPs synthesized with other reducing agents. However, only a few studies have been dedicated to using α-amino acids as reducing and capping agents in AuNPs synthesis. Hence, there are still several gaps in understanding their role in reducing gold salts. Here, we used 20 proteinogenic α-amino acids and one non-proteinogenic α-amino acid in analogy to sodium citrate as reducing and capping agents in synthesizing AuNPs using the Turkevich method. Only four of the twenty-one investigated amino acids have not yielded gold nanoparticles. The shape, size distribution, stability, and optical properties of synthesized nanoparticles were characterized by scanning electron microscopy, differential centrifugal sedimentation, the phase analysis light scattering technique, and UV-vis spectroscopy. The physicochemical characteristics of synthesized AuNPs varied with the amino acid used for the reduction. We proposed that in the initial stage of gold salts reduction most of the used α-amino acids behave similarly to citrate in the Turkevich method. However, their different physicochemical properties resulting from differences in their chemical structures significantly influence the outcomes of reactions.

Sedeveria pink ruby Extract-Mediated Synthesis of Gold and Silver Nanoparticles and Their Bioactivity against Livestock Pathogens and in Different Cell Lines

Biological synthesis of metal nanoparticles has a significant impact in developing sustainable technologies for human, animal, and environmental safety. In this study, we synthesized gold and silver nanoparticles (NPs) using Sedeveria pink ruby (SP) extract and characterized them using UV–visible spectrophotometry, FESEM-EDX, HR-TEM, XRD, and FT-IR spectroscopy. Furthermore, antimicrobial and antioxidant activities and cytotoxicity of the synthesized NPs were evaluated. UV–visible absorption spectra showed λmax at 531 and 410 nm, corresponding to the presence of SP gold NPs (SP-AuNPs) and SP silver NPs (SP-AgNPs). Most NPs were spherical and a few were triangular rods, measuring 5–30 and 10–40 nm, respectively. EDX elemental composition analysis revealed that SP-AuNPs and SP-AgNPs accounted for >60% and 30% of NPs, respectively. Additionally, some organic moieties were present, likely derived from various metabolites in the natural plant extract, which acted as stabilizing and reducing agents. Next, the antimicrobial activity of the NPs against pathogenic microbes was tested. SP-AgNPs showed potent antibacterial activity against Escherichia coli and Yersinia pseudotuberculosis. Moreover, at moderate and low concentrations, both NPs exhibited weak cytotoxicity in chicken fibroblasts (DF-1) and macrophages (HD11) as well as human intestinal cancer cells (HT-29). Meanwhile, at high concentrations, the NPs exhibited strong cytotoxicity in both chicken and human cell lines. Therefore, the synthesized SP-AuNPs and SP-AgNPs may act as promising materials to treat poultry diseases.

Activities against Lung Cancer of Biosynthesized Silver Nanoparticles: A Review

Nanomedicine is an interdisciplinary field where nanostructured objects are applied to treat or diagnose disease. Nanoparticles (NPs) are a special class of materials at nanometric scale that can be prepared from lipids, polymers, or noble metals through bottom-up approaches. Biological synthesis is a reliable, sustainable, and non-toxic bottom-up method that uses phytochemicals, microorganisms, and enzymes to induce the reduction of metal ions into NPs. Silver (Ag) NPs exhibit potent therapeutic properties that can be exploited to overcome the limitations of current treatment modalities for human health issues such as lung cancer (LC). Here, we review the preparation of AgNPs using biological synthesis and their application against LC using in vitro and in vivo models. An overview of the staging, diagnosis, genetic mutations, and treatment of LC, as well as its main subtypes, is presented. A summary of the reaction mechanisms of AgNPs using microbial cell cultures, plant extracts, phytochemicals, and amino acids is included. The use of capping agents in the biosynthesis of AgNPs with anticancer activity is also detailed. The history and biological activities of metal-based nanostructures synthesized with gold, copper, palladium, and platinum are considered. The possible anticancer mechanisms of AgNPs against LC models are covered. Our perspective about the future of AgNPs in LC treatment and nanomedicine is added.

Evaluation of biosynthesized silver nanoparticles effects on expression levels of virulence and biofilm-related genes of multidrug-resistant Klebsiella pneumoniae isolates

The emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae is associated with high morbidity and mortality due to limited treatment options. This study attempts to biologically synthesize silver nanoparticles (AgNPs) and investigate their effect on expression levels of virulence and biofilm-related genes in clinically isolated K. pneumoniae. In this study, biofilm formation ability, antibiotic resistance pattern, extended-spectrum β-lactamases (ESBLs), and carbapenemases production were investigated for 200 clinical isolates of K. pneumoniae using phenotypic methods. Polymerase chain reaction (PCR) was used to detect virulence and biofilm-related genes, ESBL-encoding genes, and carbapenem resistance genes. AgNPs were synthesized using the bio-reduction method. The antibacterial effects of AgNPs were investigated by microdilution broth. In addition, the cytotoxic effect of AgNPs on L929 fibroblast cell lines was determined. The effects of AgNPs on K. pneumoniae virulence and biofilm-related genes (fimH, rmpA, and mrkA) were determined using quantitative real-time PCR. Thirty percent of the isolates produced a strong biofilm. The highest and lowest levels of resistance were observed against amoxicillin/clavulanic acid (95.4%) and tigecycline (96%), respectively. About 31% of isolates were considered positive for carbapenemases, and 75% of the isolates produced an ESBLs enzyme. Different frequencies of mentioned genes were observed. The synthesized AgNPs had a spherical morphology and varied in size. AgNPs inhibited the growth of MDR K. pneumoniae at 128 µg/ml. In addition, AgNPs downregulated the expression of fimH, rmpA, and mrkA genes by 10, 7, and 14-fold, respectively (p < 0.05), also exerted no cytotoxic effect on L929 fibroblast cell lines. It was revealed that AgNPs lead to a decrease in expression levels of virulence and biofilm-related genes; therefore, it was concluded that AgNPs had an excellent antibacterial effect on MDR K. pneumoniae.

“Soft Protein Corona” as the Stabilizer of the Methionine-Coated Silver Nanoparticles in the Physiological Environment: Insights into the Mechanism of the Interaction

The study of the interactions between nanoparticles (NPs) and proteins has had a pivotal role in facilitating the understanding of biological effects and safe application of NPs after exposure to the physiological environment. Herein, for the first time, the interaction between L-methionine capped silver nanoparticles (AgMet), and bovine serum albumin (BSA) is investigated in order to predict the fate of AgMet after its contact with the most abundant blood transport protein. The detailed insights into the mechanism of interaction were achieved using different physicochemical techniques. The UV/Vis, TEM, and DLS were used for the characterization of the newly formed “entity”, while the kinetic and thermodynamic parameters were utilized to describe the adsorption process. Additionally, the fluorescence quenching and synchronous fluorescence studies enabled the prediction of the binding affinity and gave us insight into the influence of the adsorption on the conformation state of the BSA. According to the best of our knowledge, for the first time, we show that BSA can be used as an external stabilizer agent which is able to induce the peptization of previously agglomerated AgMet. We believe that the obtained results could contribute to further improvement of AgNPs’ performances as well as to the understanding of their in vivo behavior, which could contribute to their potential use in preclinical research studies.

Glucose oxidase converted into a general sugar-oxidase

Entrapment of glucose oxidase (GOx) within metallic gold converts this widely used enzyme into a general saccharide oxidase. The following sugar molecules were oxidized by the entrapped enzyme (in addition to D-glucose): fructose, xylose, L-glucose, glucose-6-phosphate, sucrose, lactose, methylglucoside, and the tri-saccharide raffinose. With the exception of raffinose, none of these sugars have a natural specific oxidase. The origin of this generalization of activity is attributed to the strong protein-gold 3D interactions and to the strong interactions of the co-entrapped CTAB with both the gold, and the protein. It is proposed that these interactions induce conformational changes in the channel leading to the active site, which is located at the interface between the two units of the dimeric GOx protein. The observations are compatible with affecting the specific conformation change of pulling apart and opening this gate-keeper, rendering the active site accessible to a variety of substrates. The entrapment methodology was also found to increase the thermal stability of GOx up to 100 °C and to allow its convenient reuse, two features of practical importance.

Methionine-Controlled Impediment of Secondary Nucleation Leading to Nonclassical Growth within Self-Assembled De Novo Gold Nanoparticles

The conventional key steps for seed-mediated growth of noble metal nanostructures involve classical and nonclassical nucleation. Furthermore, the surface of the seed catalytically enhances the secondary nucleation involving Au⁺ to Au⁰ reduction, thus providing in-plane growth of the seed. In contrast to this well-established growth mechanism, herein, we report the unique case of a methionine (Met)-controlled seed-mediated growth reaction, which rather proceeds via impeding secondary nucleation in the presence of citrate-stabilized gold nanoparticles (AuNPs). The interaction between the freshly generated Au⁺ and the thioether group of Met in the medium restricts the secondary nucleation process of further seed-catalyzed Au⁺ reduction to Au⁰. This incomplete conversion of Au⁺, as confirmed by X-ray photoelectron spectroscopy, results in a significant enhancement of the zeta (ζ) potential even at low Met concentrations. Nucleation of in situ generated small-sized particles (nAuNPs) takes place on the parent seed surface followed by their segregation from the seed. The self-assembly process of these nAuNPs arises from the aurophilic interaction among the Au⁺. Furthermore, the time-dependent growth of smaller particles to larger-sized particles through assembly and merging within the same self-assembly validates the nonclassical growth. This strategy has been successfully extended toward the seed-mediated growth reaction of AuNPs in the presence of three bio-inspired decameric peptides having varying numbers of Met residues. The study confirms the nucleation strategy even in the presence of a single Met residue in the peptide and also the self-assembly of nucleated particles with increasing Met residues within the peptide.

Genotoxicity of Nanomaterials: Advanced In Vitro Models and High Throughput Methods for Human Hazard Assessment-A Review

Changes in the genetic material can lead to serious human health defects, as mutations in somatic cells may cause cancer and can contribute to other chronic diseases. Genotoxic events can appear at both the DNA, chromosomal or (during mitosis) whole genome level. The study of mechanisms leading to genotoxicity is crucially important, as well as the detection of potentially genotoxic compounds. We consider the current state of the art and describe here the main endpoints applied in standard human in vitro models as well as new advanced 3D models that are closer to the in vivo situation. We performed a literature review of in vitro studies published from 2000-2020 (August) dedicated to the genotoxicity of nanomaterials (NMs) in new models. Methods suitable for detection of genotoxicity of NMs will be presented with a focus on advances in miniaturization, organ-on-a-chip and high throughput methods.

Synthesis and Efficacy of the N-carbamoyl-methionine Copper on the Growth Performance, Tissue Mineralization, Immunity, and Enzymatic Antioxidant Capacity of Nile tilapia (Oreochromis niloticus)

Immunogenic, methionine copper-induced response had proven to be precedent in providing resistance against certain diseases in fish. This study allocates the fitness strategy for Oreochromis niloticus by introducing and incorporating the well-designed, stabilized, and biocompatible N-carbamoyl-methionine copper (NCM-Cu) as a Cu potent source in diet that enhances the bioavailability and fitness. The synchronized NCM-Cu complex was characterized by directing ultraviolet and visible spectrophotometry (UV-vis), Fourier-transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. Results revealed blue columnar crystalline, NCM-Cu complex with an empirical formula as C₁₂H₃₀CuN₄O₁₀S₂. Anonymously, the overall growth performance of the fish remained unaltered with NCM-Cu adjunct feed. NCM-Cu significantly raised the Cu accumulation in the fish muscles, liver, gill, and intestine in contrast to the basic Cu-rich feed. The serum antioxidant enzyme activity elevated up to (ceruloplasmin: 19.38 U/L) and the lowest liver malondialdehyde (MDA) content (8.81 nmol/mg prot.) and triglyceride content (0.39 nmol/g prot.) were observed in the NCM-Cu group as compared to the basic Cu and CuSO₄ groups, suggesting that NCM-Cu promoted antioxidative responses and alleviated lipid peroxidation of O. niloticus. Overweening, the synthesized complex, NCM-Cu significantly regulated the expression levels of lysozyme, immunoglobulin M, complement 4, and complement 3 up to 10.93 U/mL, 0.72, 0.77, and 1.18 mg/mL in serum, respectively. Thus, such endorsed results reveal the preeminence of NCM-Cu-supplemented diet for the fitness in O. niloticus.