Smaller AgNPs Research Articles

Fabrication of electrospun PA66 nanofibers loaded with biosynthesized silver nanoparticles: investigation of dye degradation and antibacterial activity.

In the current study, silver nanoparticles (AgNPs) incorporated Polyamide 66 (PA66) nanofiber mat as a photocatalyst which was prepared using electrospinning technique for degradation of methyl orange (MO). Considering the lack of reported studies on the influence of the ultrasonication on the size and stability of AgNPs, the purpose of the study was to produce a small size of AgNPs and compare it with the continuous stirring method. It is reasonable to report that the advantage of ultrasonication is to generate relatively smaller AgNPs (u-AgNPs) compared to fabrication by continuous stirring method (s-AgNPs). Helichrysum arenarium (HA) extract was used as a reducing agent as well as a capping agent in green synthesis of AgNPs. AgNPs were characterized by UV-visible spectrophotometry, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). PA66/u-AgNs nanofibers were then successfully electrospun and characterized by using scanning electron microscope (SEM), FT-IR, thermal gravimetric analysis (TGA), and water contact angle measurement (WCA). Fabricated PA66-based nanofiber mat with smooth surface and uniform diameters (330-340nm) was used as a catalyst in MO degradation. PA66/u-AgNP nanofibers were also evaluated for antibacterial performance and showed significant inhibition against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. According to these findings, it is expected that the fabricated novel PA66/u-AgNP nanofibers can be announced as a promising potent and applied to the wastewater applications.

Size- and Shape-Dependent Interactions of Lipid-Coated Silver Nanoparticles: An Improved Mechanistic Understanding through Model Cell Membranes and In Vivo Toxicity.

The widespread use of silver nanoparticles (AgNPs) in various applications and industries has brought to light the need for understanding the complex relationship between the physicochemical properties (shape, size, charge, and surface chemistry) of AgNPs that affect their ability to enter cells and cause toxicity. To evaluate their toxicological outcomes, this study systematically analyzed a series of homogeneous hybrid lipid-coated AgNPs spanning sizes from 5 to 100 nm with diverse shapes (spheres, triangles, and cubes). The hybrid lipid membrane comprises hydrogenated phosphatidylcholine (HPC), sodium oleate (SOA), and hexanethiol (HT), which shield the AgNP surface from surface oxidation and toxic Ag+ ion release to minimize its contribution to toxicity. To reduce any significant effects by surface chemistry, the HPC, SOA, and HT membrane composition ratio was kept constant, and the AgNPs were assessed using embryonic zebrafish (Danio rerio). While a direct comparison cannot be drawn due to the lack of complementary sizes below 40 nm for triangular plates and cubes due to synthetic challenges, significant mortality was observed for spherical AgNPs (AgNSs) of 5, 20, 40, and 60 nm at 120 h postfertilization at concentrations ≥6 mg Ag/L. In contrast, the 10, 80, and 100 nm AgNSs, 40, 70, and 100 nm triangular plate AgNPs (AgNPLs), and 55, 75, and 100 nm cubic AgNPs (AgNCs) showed no significant mortality at 5 days postfertilization following exposure to AgNPs at concentrations up to 12 mg Ag/L. With constant surface chemistry on the AgNPs, size is the dominant factor driving toxicological responses, with smaller nanoparticles (5 to 60 nm) being the most toxic. Larger AgNSs, AgNCs, and AgNPLs from 75 to 100 nm do not show any evidence of toxicity. However, when closely examining sizes between 40 and 60 nm for AgNSs, AgNCs, and AgNPLs, there is evidence that discriminates shape as a driver of toxicity since sublethal responses generally were observed to follow a pattern, suggesting toxicity is most significant for AgNSs followed by AgNPLs and then AgNCs, which is the least toxic. Sum frequency generation vibrational spectroscopy showed that irrespective of size or shape, all hybrid lipid-coated AgNPs interact with membrane surfaces and "snorkel" between phases into the lipid monolayer with minimal energetic cost. These findings decisively demonstrate that not only smaller AgNPs but also the shape of the AgNPs influences their biological compatibility.

Promising way for enhancing light absorption in silicon via silver nanoparticles: experimental and numerical study

Silver nanoparticles (Ag-Nps) were grown on the surface of a p-type crystalline silicon (C-Si) substrate using electroless metal deposition. It was found that the Ag-Nps distribution on C-Si was controlled by the silver nitrate (AgNO3) concentrations. Atomic force microscopy observations revealed the formation of a continuous layer at high concentration. In contrast, a distribution of Ag-Nps with a spherical shape was obtained at lower concentration. The samples were also examined by optical microscopy under dark field illumination. The light reflected from Ag-Nps was obtained with different colors. This difference indicates a slight change in particle size. It is demonstrated that a silicon substrate with deposited Ag-Nps shows a significant decrease in reflectance and an increase of the absorption in the region from 200 to 800 nm. Moreover, the behavior of small Ag-Nps while interacting with light (absorbed or scattered light) is theoretically described using the Mie theory based on the Drude model. The introduction of silver nanoparticles on silicon surface is used to improve the efficiency of solar cells by reducing reflection and increasing the light absorption.

Silver ion-imprinted magnetic adsorbent hyphenated to single particle-ICP-MS for separation and analysis of dissolved silver and silver nanoparticles in antibacterial gel extracts

BackgroundSilver nanoparticles (Ag NPs) are extensively used in various applications, but their reactivity leads to oxidative dissolution into Ag(I). When dealing with real samples involving Ag NPs, it is inevitable to encounter situations where both Ag NPs and Ag(I) coexist. Single particle-inductively coupled plasma mass spectrometry (SP-ICP-MS) is a valuable technique for nanoparticle size characterization. However, the presence of coexisting dissolved ions strongly interferes with the accuracy of particle size analysis using SP-ICP-MS. Therefore, it is crucial to develop a reliable separation analysis method to accurately measure both Ag NPs and Ag(I). ResultsIn this study, we synthesized a silver ion-imprinted magnetic adsorbent with high adsorption capacity (149 mg g−1) and rapid adsorption kinetics (30 min) at both μg L−1 and mg L−1 concentration. The adsorbent selectively adsorbs Ag(I) at pH 7 while hardly adsorbing Ag NPs. It is reusable for more than 5 cycles after regeneration. Using this magnetic adsorbent prior to SP-ICP-MS, we accurately determined the sizes of standard Ag NPs in agreement with the size determined by transmission electron microscopy. The detection limit of particle size and number concentrations of Ag NPs was 12.6 nm and 6.3 × 105 particles L−1. Moreover, we successfully applied the developed method to analyze Ag(I) and Ag NPs in antibacterial gel extracts and validated its accuracy through acid digestion-ICP-MS, TEM, and spiking experiments. Significance and noveltyDirect SP-ICP-MS analysis in the presence of Ag(I) led to a high baseline, obscuring signals from smaller Ag NPs. Our method of selectively removing Ag(I) substantially improves the accuracy of Ag NPs detection via SP-ICP-MS in the antibacterial gel extracts (e.g. from 48.26 to 35.67 nm). Compared to other approaches used in SP-ICP-MS, our method has a higher adsorption capacity, allowing for better tolerance of coexisting Ag(I).

Controlled release of Ag+ ions to human cancer cells selectively neutralized with silver nanoparticles of different sizes produced by a green synthesis method

We present a facile green method to synthesize silver nanoparticles (AgNPs) with different sizes and uniform size distributions using an extract of Rhododendron mucronulatum flowers. Here, AgNPs were utilized to modify the release of Ag+ ions and selectively annihilate human cancer cells. AgNPs were prepared at ambient temperature (RT-AgNPs) and in higher-temperature water baths at 60 °C (W60-AgNPs) and 70 °C (W70-AgNPs) to modify the diameter and uniformity of the AgNPs. The W60-AgNPs were further treated with acid to modify their size and surface state (named AW60-AgNPs). The water-bath technique enabled an alteration of the relative rates of initial nucleation and growth of nanoparticles in a homogeneous environment, promoting the creation of small AgNPs with a uniform diameter distribution. The acid treatment eroded the surface particles to reduce their diameter and simultaneously introduced functional groups. The Ag+-ion release efficiency of the prepared nanoparticles and the toxicity of Ag+ ions on cancer cells were examined. Among the prepared samples, the AW60-AgNPs released the greatest amount of Ag+ ions and produced the largest amount of reactive oxygen species (O2̇−, ˙OH, and H2O2). All of the AgNP samples were applied to tumor cells (K562 and HT1080) and healthy cells (LO2) in vitro. In the presence of K562 cells, AW60-AgNPs showed the most efficient dose- and time-dependent early and late apoptosis as well as reduced viability. A crystal violet assay showed that the synthesized particles preferentially attack HT1080 cancer cells rather than LO2 normal cells. We found that Ag+ ions release efficiency and selectivity varied with particle size, and that DNA damage in tumor cells was due to the formation of Ag+-coordinated complexes within DNA base pairs.

Bactericidal Activity of Silver Nanoparticles on Oral Biofilms Related to Patients with and without Periodontal Disease

Background and Objectives: Periodontal disease (PD) is a multifactorial oral disease regularly caused by bacterial biofilms. Silver nanoparticles (AgNP) have offered good antimicrobial activity; moreover, there is no available scientific information related to their antimicrobial effects in biofilms from patients with PD. This study reports the bactericidal activity of AgNP against oral biofilms related to PD. Materials and Methods: AgNP of two average particle sizes were prepared and characterized. Sixty biofilms were collected from patients with (30 subjects) and without PD (30 subjects). Minimal inhibitory concentrations of AgNP were calculated and the distribution of bacterial species was defined by polymerase chain reaction. Results: Well-dispersed sizes of AgNP were obtained (5.4 ± 1.3 and 17.5 ± 3.4 nm) with an adequate electrical stability (−38.2 ± 5.8 and −32.6 ± 5.4 mV, respectively). AgNP showed antimicrobial activities for all oral samples; however, the smaller AgNP had significantly the most increased bactericidal effects (71.7 ± 39.1 µg/mL). The most resistant bacteria were found in biofilms from PD subjects (p < 0.05). P. gingivalis, T. denticola, and T. forsythia were present in all PD biofilms (100%). Conclusions: The AgNP showed efficient bactericidal properties as an alternative therapy for the control or progression of PD.

Silver nanoparticles production mediated by natural tetraploid Trifolium pratense L.: Characterization and potential biological activity

Abstract This study was aimed to present the green synthesis of silver nanoparticles through natural tetraploid Trifolium pratense L. containing high amounts of phenolic compounds and glycosidic bioactive macromolecules. Combinatorial optimization of AgNPs was achieved thanks to the stabilizing and reducing properties of the natural tetraploid T. pratense L. flowering herb extract. The biologically synthesized AgNPs were visualized by color change in UV–Vis spectroscopy. UV–Vis spectroscopy proved to be a fast and simple method to determine the synthesis of AgNPs. In addition, TEM, XRD, and FTIR analyses were performed to confirm and characterize the formation of crystalline silver nanoparticles. It was shown by the TEM analysis that AgNPs changed their size and shape when biosynthesized in different conditions. It was determined that smaller AgNPs were spherical and larger AgNPs had a truncated octahedron shape. The XRD analysis proved the presence of Ag0 in nanoparticles and showed its crystal structure and faced cubic shapes for AgNPs. Interactions between the plant bioactive compounds and the AgNPs were distinctly visible in the FTIR spectra. The biosynthesized AgNPs showed strong antioxidant activity against DPPH and ABTS; furthermore, the total phenol content was also high.

Atomic structure and optical properties of color centers of silver in AgAu/glass irradiated by UV laser

A study of the structural states of silver in glass after Ag+↔Na+ ion-exchange and further irradiation with different numbers of UV laser pulses has been performed using Ag K-edge XANES combined with DFT simulations and the processing of Ag K-EXAFS. Theoretical Ag K-edge XANES, calculated for DFT-generated structural models, showed high sensitivity to the number of nearest oxygen neighbors of the absorbing Ag+ ion, to changes in the corresponding interatomic distances RAg-O (changes ≳ 0.05 Å) and bond angles (changes ≳ 10° at apical Ag in atomic chain O–Ag–O), and to the presence of Ag+ ions among the second neighbors of Ag. The effect of more distant O and Si neighbors can be considered negligible. The applied combination of complementary techniques for structural analysis of the color centers of silver in glass has revealed that, after ion-exchange, Ag+ ions are predominantly present in glass in the form of dimers, in which the two Ag+ ions are separated by an interatomic distance, RAg-Ag, of 3.4 Å. Other interatomic distances RAg-O in the dimers have also been obtained. It has been determined that, under laser irradiation with the number of pulses up to 1000, only a small proportion (up to 10%) of Ag+ ions in glass samples is reduced from the states of isolated ions and the revealed Ag dimers present after Ag+↔Na+ ion-exchange. The reduced Ag atoms form monometallic Ag NPs and are also deposited on the surface of Au NPs, forming bimetallic AgAu NPs with a solid solution structure. The processes of the formation, growth, and dissolution of monometallic Ag NPs and bimetallic AgAu NPs with increasing number of laser pulses are discussed. Analysis of the blue shifts of ca. 20 nm of localized surface plasmon resonances (LSPRs) of Ag NPs with increasing number of UV laser pulses up to 1000 revealed that these shifts occurred due to a decrease in the average size of optically visible Ag NPs caused by the growth of initially less visible small Ag NPs (≲5 nm) and partial dissolution of the largest particles.

Mussel Inspired In Situ Preparation of Antibacterial Silver Nanoparticles by DOPA-Containing Silk Fibroin.

Silver nanoparticles (AgNPs) attract a great deal of attention for potent antibacterial capacity, but their use is challenged by limited stability. Inspired by the adhesive and redox properties of the mussel foot proteins containing L-3,4-dihydroxyphenylalanine (DOPA), a facile strategy for in situ synthesis of AgNPs using DOPA-containing fibroin is developed. Tyrosine residues in fibroin are transformed into DOPA via biomimetic synthesis method with content of 0.55mol%. In situ synthesis generates stable and small AgNPs through DOPA bound in fibroin as a reducing and stabilizing agent. Narrow size distribution with average diameter of 20nm and excellent monodispersity are obtained. Cross-linking with lysine increases the content of β-sheet to form hydrogel and achieves gradual release of silver. The material exhibits excellent antibacterial properties against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. It can be potentially applied in biological and medical fields to treat bacterial infections.

Green tubular micro/nano architecture constructed by in-situ planting of small AgNPs on Kapok fiber for oil spill recovery, smart oil–water separation and multifunctional applications

The ubiquitous existence of harmful contaminants in water is recognized as a major threat to aquatic ecosystems and human health, and renewable, economical, and superefficient new materials are needed to eliminate these dangers. Here, the ultrasmall silver nanoparticles (AgNPs) anchored Kapok fiber (KF) (KF/AgNPs) composite capable of efficiently separating various oil–water systems and eliminating other pollutants or bacteria was prepared by a green self-reducing reaction process using natural KF as the “microreactor” and water as the only solvent. The introduction of AgNPs endows KF/AgNPs with significantly improved liquid storage capacity, underwater superoleophobicity and underoil superhydrophobicity, so it shows excellent switchable oil–water separation capability. The oil–water separation efficiencies under gravity reached 99.90 % for the oil-in-water (O/W) emulsion (water flux: 1300 L·m−2·h−1), 99.91 % for the water-in-oil (W/O) emulsion (oil flux: 1500 L·m−2·h−1), and 99.80 % for the immiscible oil–water mixture (flux: 1900 L·m−2·h−1). In addition, KF/AgNPs composite can serve as absorbents to remove oil slicks from sewage (removal efficiency: 99.95 %; absorption capacity: 42.3 g/g) and adsorbents to rapidly remove microplastics in actual natural waters (concentration: 10 mg/L and can inhibit the growth of E. coli bacteria. After use, approximately 96.4 % of Ag was recovered from spent composite, and an excellent biochar adsorbent for the dye was obtained simultaneously.

Particle Size Modulates Silver Nanoparticle Toxicity during Embryogenesis of Urchins Arbacia lixula and Paracentrotus lividus.

Silver nanoparticles represent a threat to biota and have been shown to cause harm through a number of mechanisms, using a wide range of bioassay endpoints. While nanoparticle concentration has been primarily considered, comparison of studies that have used differently sized nanoparticles indicate that nanoparticle diameter may be an important factor that impacts negative outcomes. In considering this, the aim of the present study was to determine if different sizes of silver nanoparticles (AgNPs; 10, 20, 40, 60 and 100 nm) give rise to similar effects during embryogenesis of Mediterranean sea urchins Arbacia lixula and Paracentrotus lividus, or if nanoparticle size is a parameter that can modulate embryotoxicity and spermiotoxicity in these species. Fertilised embryos were exposed to a range of AgNP concentrations (1−1000 µg L−1) and after 48 h larvae were scored. Embryos exposed to 1 and 10 µg L−1 AgNPs (for all tested sizes) showed no negative effect in both sea urchins. The smaller AgNPs (size 10 and 20 nm) caused a decrease in the percentage of normally developed A. lixula larvae at concentrations ≥50 µg L−1 (EC50: 49 and 75 μg L−1, respectively) and at ≥100 µg L−1 (EC50: 67 and 91 μg L−1, respectively) for P. lividus. AgNPs of 40 nm diameter was less harmful in both species ((EC50: 322 and 486 μg L−1, for P. lividus and A. lixula, respectively)). The largest AgNPs (60 and 100 nm) showed a dose-dependent response, with little effect at lower concentrations, while more than 50% of larvae were developmentally delayed at the highest tested concentrations of 500 and 1000 µg L−1 (EC50(100 nm); 662 and 529 μg L−1, for P. lividus and A. lixula, respectively. While AgNPs showed no effect on the fertilisation success of treated sperm, an increase in offspring developmental defects and arrested development was observed in A. lixula larvae for 10 nm AgNPs at concentrations ≥50 μg L−1, and for 20 and 40 nm AgNPs at concentrations >100 μg L−1. Overall, toxicity was mostly ascribed to more rapid oxidative dissolution of smaller nanoparticles, although, in cases, Ag+ ion concentrations alone could not explain high toxicity, indicating a nanoparticle-size effect.

Sustainable-Green Synthesis of Silver Nanoparticles Using Aqueous Hyssopus officinalis and Calendula officinalis Extracts and Their Antioxidant and Antibacterial Activities.

Silver nanoparticles (AgNPs) biosynthesized using aqueous medical plant extracts as reducing and capping agents show multiple applicability for bacterial problems. The aim of this study was to expand the boundaries on AgNPs using a novel, low-toxicity, and cost-effective alternative and green approach to the biosynthesis of metallic NPs using Calendula officinalis (Calendula) and Hyssopus officinalis (Hyssopus) aqueous extracts. The formation of AgNPs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) techniques. The effectiveness of biosynthesized AgNPs in quenching free radicals and inhibiting the growth of Gram-positive and Gram-negative microorganisms was supported by in vitro antioxidant activity assay methods and using the Kirby-Bauer disk diffusion susceptibility test, respectively. The elucidated antimicrobial and antioxidative activities of medical plant extracts were compared with data from the engineered biosynthetic AgNPs. The antimicrobial effect of engineered AgNPs against selected test cultures was found to be substantially stronger than for plant extracts used for their synthesis. The analysis of AgNPs by TEM revealed the presence of spherical-shaped nano-objects. The size distribution of AgNPs was found to be plant-type-dependent. The smaller AgNPs were obtained with Hyssopus extract (with a size range of 16.8 ± 5.8 nm compared to 35.7 ± 4.8 nm from Calendula AgNPs). The AgNPs' presumably inherited biological functions of Hyssopus and Calendula medical plants can provide a platform to combat pathogenic bacteria in the era of multi-drug resistance.

Rational design of silver NPs-incorporated quaternized chitin nanomicelle with combinational antibacterial capability for infected wound healing

Bacterial and biofilm infections are prevalent, photothermal antibacterial therapy exploiting Ag NPs was an alternative. However, various matrix materials including polysaccharides used to stabilize Ag NPs are not efficiently utilized. In this study, catechol functionalized quaternized chitin (DQC) is first synthesized, then Ag+ is in situ reduced to small Ag NPs stabilized and well-dispersed by DQC to form Ag NPs-incorporated quaternized chitin (DQCA) nanomicelle in a green and simple way. The photothermal conversion efficiency of the DQCA was up to be 65 %, which was much higher than that of many reported systems. The rationally designed DQCA takes full advantage of each component, specifically, DQCA is endowed with bacterial targeting, sterilization effects of cationic groups and Ag NPs, and superior photothermal combinational bactericidal and antibiofilm activities. The in vitro antibacterial rate of DQCA with NIR laser irradiation was >95 % in 10 min (99.5 % for E. coli and 95.7 % for S. aureus, respectively), and the eradication efficiency against both of the E. coli and S. aureus biofilms reached up to 99.9 %. Moreover, full-thickness S. aureus biofilms-infected wound healing test in the mouse model demonstrates that the combinational effect of DQCA nanomicelle could significantly accelerate the wound healing, by simultaneously reducing inflammation, enhancing re-epithelialization and promoting collagen deposition. And the wound treated with DQCA plus NIR irradiation at day 15 possessed the smallest open wound (2.5 %). Collectively, these features indicate facilely fabricated DQCA nanomicelle gets the most use of each component, and could serve as an excellent alternative for bacterial infection therapy.

Intracellular accumulation, dissolution, and distribution of AIEgen-coated silver nanoparticles in hemocyte subpopulations of oysters

Bivalve hemocytes act as the first line of defense against foreign particles and are composed of several subpopulations with different immune functions. In order to elucidate the processes of cellular internalization and transformation of AgNPs in bivalve hemocyte subpopulations, we employed two aggregated-induced emission (AIE) fluorogens AgNPs and Ag+ to study the intracellular behavior of AgNPs in oyster hemocyte subpopulations composed of agranulocytes, semigranulocytes, and granulocytes. Our study demonstrated that the accumulation ability of AIE-AgNPs differed by 4.2-fold, with an order of agranulocytes < semigranulocytes < granulocytes, whereas the dissolution ability differed by 2.4-fold, with an order of agranulocytes > semigranulocytes > granulocytes. Internalized AgNPs caused lysosomal alkalization, which then resulted in the inhibition of AgNP dissolution. Dissolution rate of AIE-AgNPs was 22.5% in the total oyster hemocytes combined, and the dissolved Ag+ was mainly located in lysosomes (71.8%) of granulocytes. During accumulation, 32% of AgNPs were distributed in lysosomes of granulocytes, but increased to 76.7% during the depuration period. Small AgNPs could rapidly enter and dissolve in lysosomes, while large aggregates of AgNPs were first phagocytosed to form phagosomes in the cytoplasm, then fused with lysosomes as time passed. Our results provided important information to understand the intracellular behavior of AgNPs in marine organisms.

Hybrid SERS platform by adapting both chemical mechanism and electromagnetic mechanism enhancements: SERS of 4-ATP and CV by the mixture with GQDs on hybrid PdAg NPs

Surface-enhanced Raman spectroscopy (SERS) is a versatile analytical technique widely adapted for the identification of target analytes even at an extremely low concentration. Herein, a unique hybrid SERS platform is demonstrated by utilizing the graphene quantum dots (GQDs) and hybrid PdAg NPs for the detection of 4-amino-thiophenol (4-ATP) and crystal violet (CV). GQDs offer the rich charge transfer to the LUMO and HOMO of 4-ATP and CV by the CM enhancement. A significant EM enhancement is achieved by the strong localized surface plasmon resonance (LSPR) of uniquely designed hybrid core-shell PdAg NP, possessing the narrow nano-gaps with the highly dense small Ag NPs and Pd core Ag shell configuration. As a result, orders of enhancement of originally weak 4-ATP and CV Raman signal is witnessed by the combination of electromagnetic mechanism (EM) and chemical mechanism (CM) enhancements on a single SERS substrate. The hybrid GQD/HNP SERS substrate demonstrates significantly improved hot spots and strongly localized electromagnetic fields as confirmed by the finite-difference time-domain (FDTD) simulations. A proper mixture ratio of GQDs and probe molecules presents largely enhanced SERS signals by a strong adsorption of probe molecules through π - π interaction and the enhancement factors vary by the mixture ratio depending on the adsorption kinetics and Raman cross-section of molecules.

Optimized Synthesis of Small and Stable Silver Nanoparticles Using Intracellular and Extracellular Components of Fungi: An Alternative for Bacterial Inhibition.

Silver nanoparticles (AgNPs) represent an excellent option to solve microbial resistance problems to traditionally used antibiotics. In this work, we report optimized protocols for the production of AgNPs using extracts and supernatants of Trichoderma harzianum and Ganoderma sessile. AgNPs were characterized using UV-Vis spectroscopy and transmission electron microscopy, and the hydrodynamic diameter and Z potential were also determined. The obtained AgNPs were slightly larger using the fungal extract, and in all cases, a quasi-spherical shape was obtained. The mean sizes of AgNPs were 9.6 and 19.1 nm for T. harzianum and 5.4 and 8.9 nm for G. sessile using supernatant and extract, respectively. The AgNPs were evaluated to determine their in vitro antibacterial effect against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The minimum inhibitory concentration (MIC) was determined, and in all cases the AgNPs showed an antimicrobial effect, with a MIC varying from 1.26–5.0 µg/mL, depending on the bacterial strain and type of nanoparticle used. Cytotoxicity analyses of AgNPs were carried out using macrophages and fibroblast cell lines. It was determined that the cell viability of fibroblasts exposed for 24 h to different concentrations of AgNPs was more than 50%, even at concentrations of up to 20 µg/mL of silver. However, macrophages were more susceptible to exposure at higher concentrations of AgNPs as their viability decreased at concentrations of 10 µg/mL. The results presented here demonstrate that small AgNPs are obtained using either supernatants or extracts of both fungal strains. A remarkable result is that very low concentrations of AgNPs were necessary for bacterial inhibition. Furthermore, AgNPs were stable for more than a year, preserving their antibacterial properties. Therefore, the reported optimized protocol using fungal supernatants or extracts may be used as a fast method for synthesizing small AgNPs with high potential to use in the clinic.

Facile Green Synthesis of Silver Nanoparticles Using Aqueous Leaf Extract of Origanum majorana with Potential Bioactivity against Multidrug Resistant Bacterial Strains

The high prevalence of nosocomial bacterial resistance contributes to significant mortality and morbidity around the world; thus, finding novel antibacterial agents is of vital concern. Accordingly, the present study attempted to synthesize silver nanoparticles (AgNPs) using a green approach. Aqueous leaf extract of Origanum majorana was used to synthesize AgNPs and the antibacterial efficiency against multidrug resistant bacterial strains was detected. Characterization of the biogenic AgNPs was performed using ultraviolet-visible spectrophotometry (UV-Vis), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis, and X-ray diffraction analysis (XRD). The disc diffusion method was used to detect the antibacterial activity of AgNPs against three nosocomial multidrug-resistant strains. Preliminary UV-Vis analysis revealed the biosynthesis of AgNPs due to peak formation at 374 nm, corresponding to the surface plasmon resonance (SPR) of biogenic AgNPs. TEM micrographs detected the synthesis of small AgNPs with an average particle size of 26.63 nm. EDX analysis revealed the presence of the following elements: oxygen (3.69%), carbon (2.93%), aluminum (1.29), silicon (2.83%), chloride (17.89%), and silver (71.37%). Furthermore, XRD analysis revealed the presence of diffraction peaks at 2 theta (θ) degrees of 38.18°, 44.36°, 64.35°, and 77.54°, assigned to the planes of silver crystals (111), (200), (220), and (311), respectively. Collectively, these findings affirm the synthesis of biogenic AgNPs with potential physicochemical characteristics. The antimicrobial efficiency of the biogenic AgNPs indicated that Klebsiella pneumoniae strain was the most susceptible strain at concentrations of 50 and 100 µg/disk, with inhibitory zones of 21.57 and 24.56 mm, respectively. The minimum inhibitory concentration (MIC) of AgNPs against Klebsiella pneumoniae strain was found to be 10 µg/mL, while the minimum bactericidal concentration (MBC) was found to be 20 µg/mL. In conclusion, aqueous leaf extract of O. majorana mediated synthesis of small sized AgNPs, with potential antimicrobial effectiveness against multidrug-resistant bacterial pathogens.

Biological Synthesis of Monodisperse Uniform-Size Silver Nanoparticles (AgNPs) by Fungal Cell-Free Extracts at Elevated Temperature and pH.

Fungi’s ability to convert organic materials into bioactive products offers environmentally friendly solutions for diverse industries. In the nanotechnology field, fungi metabolites have been explored for green nanoparticle synthesis. Silver nanoparticle (AgNP) research has grown rapidly over recent years mainly due to the enhanced optical, antimicrobial and anticancer properties of AgNPs, which make them extremely useful in the biomedicine and biotechnology field. However, the biological synthesis mechanism is still not fully established. Therefore, this study aimed to evaluate the combined effect of time, temperature and pH variation in AgNP synthesis using three different fungi phyla (Ascomycota, Basidiomycota and Zygomycota) represented by six different fungi species: Cladophialophora bantiana (C. bantiana), Penicillium antarcticum (P. antarcticum), Trametes versicolor (T. versicolor), Trichoderma martiale (T. martiale), Umbelopsis isabellina (U. isabellina) and Bjerkandera adusta (B. adusta). Ultraviolet–visible (UV-Vis) spectrophotometry and transmission electron microscopy (TEM) results demonstrated the synthesis of AgNPs of different sizes (3 to 17 nm) and dispersity percentages (25 to 95%, within the same size range) using fungi extracts by changing physicochemical reaction parameters. It was observed that higher temperatures (90 °C) associated with basic pH (9 and 12) favoured the synthesis of monodisperse small AgNPs. Previous studies demonstrated enhanced antibacterial and anticancer properties correlated with smaller nanoparticle sizes. Therefore, the biologically synthesised AgNPs shown in this study have potential as sustainable substitutes for chemically made antibacterial and anticancer products. It was also shown that not all fungi species (B. adusta) secrete metabolites capable of reducing silver nitrate (AgNO3) precursors into AgNPs, demonstrating the importance of fungal screening studies.

Eucalyptus globulus and Salvia officinalis Extracts Mediated Green Synthesis of Silver Nanoparticles and Their Application as an Antioxidant and Antimicrobial Agent.

Silver nanoparticles (AgNPs) biosynthesized using plant extracts as reducing and capping agents show multiple possibilities for solving various biological problems. The aim of this study was to expand the boundaries of AgNPs using a novel low toxicity and production cost phytochemical method for the biosynthesis of nanoparticles from Eucalyptus globulus and Salvia officinalis aqueous leaf extracts. Biosynthesized AgNPs were characterized by various methods (ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared (FTIR) spectroscopy with horizontal attenuated total reflectance (HART), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS)). The determined antioxidative and antimicrobial activity of plant extracts was compared with the activity of the AgNPs. The UV-vis spectral analysis demonstrated the absorption peaks at 408 and 438 nm, which confirmed the synthesis of stable AgNPs from E. globulus and S. officinalis, respectively. FTIR-HART results suggested strong capping of phytochemicals on AgNPs. TEM results show mainly spherical-shaped AgNPs, whose size distribution depends on the plant leaf extract type; the smaller AgNPs were obtained with E. globulus extract (with size range of 17.5 ± 5.89 nm compared to 34.3 ± 7.76 nm from S. officinalis AgNPs). The in vitro antioxidant activity evaluated by radical scavenging assays and the reduction activity method clearly demonstrated that both the plant extracts and AgNPs showed prominent antioxidant properties. In addition, AgNPs show much stronger antimicrobial activity against broad spectrum of Gram-negative and Gram-positive bacteria strains than the plant extracts used for their synthesis.

Biogenic Synthesis of Antibacterial, Hemocompatible, and Antiplatelets Lysozyme Functionalized Silver Nanoparticles through the One-Step Process for Therapeutic Applications

To evaluate silver nanoparticles’ (AgNPs) therapeutic and clinical potentials, antibacterial action, blood compatibility, and antiplatelet activities are the main concerns for toxicity profiling. Heat-denatured lysozyme-mediated formulation stabilized the AgNPs, thereby providing more bactericidal activity and blood compatibility. The study of the synthesis of AgNPs suggests the rapid and cost-effective formulation of AgNPs by one-step reaction using a 10:1 ratio of silver nitrate and lysozyme by incubating at 60 °C for two hours. Characterization of AgNPs was analyzed by UV–Visible spectroscopy, DLS, TEM, EDX, XRD, AFM, and FTIR, followed by antibacterial, hemocompatibility, and platelet aggregation testing. The average size of synthesized AgNPs was found to be 94.10 nm with 0.45 mV zeta potential and 0.293 polydispersity index by DLS. The TEM and EXD results indicated homogeneously 28.08 nm spherical-shaped pure formations of AgNPs. The XRD peaks showed the synthesis of small AgNPs with a crystallite size of 22.88 nm, while the AFM confirmed the homogeneity and smoothness of the monodispersed AgNPs. The FTIR spectra specified the coating of the lysozyme-derived amide group on the AgNPs surface, which provides stability and functionality of nanoparticles. The antibacterial activity of AgNPs was remarkable against six pathogenic bacteria and three multidrug resistance (MDR) strains (i.e., Escherichia coli, Klebsiella aerogenes, and Pseudomonas aeruginosa), which exhibited inhibition zones with diameters ranging between 13.5 ± 0.2 mm to 19.0 ± 0.3 mm. The non-hemolytic nature of the AgNPs was calculated by percentage hemolysis with four concentrations. The negative result of platelet aggregation using platelet-rich plasma suggests the antiplatelet effect of AgNPs. Only minor hemolysis of 6.17% in human erythrocytes and mild platelet aggregation of 1.98% were induced, respectively, by the use of 1000 µL of 1 mM AgNPs, which contains approximately 107.8 μg silver. The results indicated that the antiplatelet potency and non-hemolytic nature with the antibacterial action of the lysozyme functionalized AgNPs have a good chance to be used to solve in-stent restenosis and thrombosis issues of the coronary stent and may also have a possibility to use in vaccination to resolve the blood clotting problem. So, the optimized biogenic formulation of AgNPs offers promising opportunities to be used as a therapeutic agent.