Silver Nanoparticles Synthesized from Abies alba and Pinus sylvestris Bark Extracts: Characterization, Antioxidant, Cytotoxic, and Antibacterial Effects

In recent years, phytofunctionalized AgNPs have attracted great interest due to their remarkable biological activities. In the present study, AgNPs were synthesized using Abies alba and Pinus sylvestris bark extracts. The chemical profile of these bark extracts was analyzed by LC-HRMS/MS. As a first step, the synthesis parameters (pH, AgNO₃ concentration, ratio of bark extract and AgNO₃, temperature, and reaction time) were optimized. The synthesized AgNPs were characterized by ATR-FTIR spectroscopy, DLS, SEM, EDX, and TEM. Their antioxidant, cytotoxic, and antibacterial properties were evaluated by the DPPH, ABTS, MTT, and broth microdilution assays, respectively. Abies alba and Pinus sylvestris bark extract-derived AgNPs were well-dispersed, spherical, small (average particle size of 9.92 and 24.49 nm, respectively), stable (zeta potential values of -10.9 and -10.8 mV, respectively), and cytotoxic to A-375 human malignant melanoma cells (IC₅₀ = 2.40 ± 0.21 and 6.02 ± 0.61 μg/mL, respectively). The phytosynthesized AgNPs also showed antioxidant and antibacterial effects.

Synergetic Antimicrobial Effect of Silver Nanoparticles Conjugated with Iprodione against Valsa mali

Apple tree canker induced by Valsamali is a vital disease in apple production around the world, and it highlyimpacts the development of apple industry. It is of great significance to study the inhibition effect of common fungicides and develop new fungistats for comprehensive control of apple tree canker. In this experiment, the inhibition activity of five fungicides, including mancozeb, metalaxyl, iprodione, prochloraz, and difenoconazole along with biosynthesized nanosilver against V. mali, were measured with the mycelium growth rate and agar well diffusion methods. The results showed that iprodione exhibited the best inhibitory effect, the median inhibition concentration (IC₅₀) of iprodione and nanosilver was 0.62 μg.mL⁻¹ and 45.50 μg.mL⁻¹, the suppression rate achieved 67.93% at 200 μg.mL⁻¹ of nanosilver. Moreover, a remarkable additive and synergistic antimicrobial effect was verified when silver nanoparticles were conjugated with iprodione at 9:1, 8:2, 7:3, and 6:4 (v/v), and the toxicity ratio was 1.04, 1.13, 1.01, and 0.98, respectively. It is proven that biosynthesized silver nanoparticles could effectively inhibit Valsamali, and it is possible to develop and screen silver nanoparticle-based nano pesticides to manage plant diseases synthetically.

Biosynthesis of Silver Nanoparticles by Conyza canadensis and Their Antifungal Activity against Bipolaris maydis

Silver nanoparticles were biosynthesized from Conyzacanadensis leaf extract with the help of a microwave oven. The UV-vis spectrum showed the maximum absorption at 441 nm, corresponding to the surface plasmon resonance of silver nanoparticles. Transmission electron microscope and scanning electron microscope images showed that the synthesized silver nanoparticles were spherical or near-spherical with an average diameter of 43.9 nm. X-ray diffraction demonstrated nanoparticles with a single-phase cubic structure. As-synthesized silver nanoparticles displayed prominent antifungal activity against Bipolaris maydis. The colony inhibition rate reached 88.6% when the concentration of nanosilver colloid was 100 μL·mL−1 (v/v). At such a concentration, no colony formation was observed on the solid plate. The diameter of the inhibition zone was 13.20 ± 1.12 mm. These results lay the foundation for the comprehensive control of plant pathogens using an environmentally friendly approach.

A Review on Silver Nanoparticles: Classification, Various Methods of Synthesis, and Their Potential Roles in Biomedical Applications and Water Treatment

Recent developments in nanoscience have appreciably modified how diseases are prevented, diagnosed, and treated. Metal nanoparticles, specifically silver nanoparticles (AgNPs), are widely used in bioscience. From time to time, various synthetic methods for the synthesis of AgNPs are reported, i.e., physical, chemical, and photochemical ones. However, among these, most are expensive and not eco-friendly. The physicochemical parameters such as temperature, use of a dispersing agent, surfactant, and others greatly influence the quality and quantity of the synthesized NPs and ultimately affect the material’s properties. Scientists worldwide are trying to synthesize NPs and are devising methods that are easy to apply, eco-friendly, and economical. Among such strategies is the biogenic method, where plants are used as the source of reducing and capping agents. In this review, we intend to debate different strategies of AgNP synthesis. Although, different preparation strategies are in use to synthesize AgNPs such as electron irradiation, optical device ablation, chemical reduction, organic procedures, and photochemical methods. However, biogenic processes are preferably used, as they are environment-friendly and economical. The review covers a comprehensive discussion on the biological activities of AgNPs, such as antimicrobial, anticancer anti-inflammatory, and anti-angiogenic potentials of AgNPs. The use of AgNPs in water treatment and disinfection has also been discussed in detail.

Biosynthesis of Silver Nanoparticles by Aspergillus terreus: Characterization, Optimization, and Biological Activities

In this study, mycelial filtrate of Aspergillus terreus BA6 was used to reduce AgNO₃ to form silver nanoparticles (AgNPs). The effect of seven independent variables on the diameter of AgNPs was studied by applying design of experiments (DOE). At optimal conditions, the diameter of AgNPs was reduced by approximately 26.7% compared to the basal culture condition and AgNO₃ concentration was found to be the most significant factor affecting the diameter of AgNPs. A. terreus nano-Ag was characterized using UV-visible spectroscopy, transmission electron microscopy, energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Zeta potential. The maximum UV absorption was obtained at 420 nm and the microscopic results showed particles with narrow size distribution ranging from 7 to 23 nm. XRD pattern of AgNPs revealed four diffraction peaks of metallic silver and the EDX spectrum showed a strong signal attributed to Ag nano-crystals. AgNPs mycofabricated by A. terreus showed potent minimum inhibitory concentration (MIC) and broad minimum bactericidal/fungicidal concentration (MBC/MFC) against 12 reference microorganisms. The MIC and MBC/MFC values of AgNPs were 0.312 to 1.25 μg/ml and 0.625 to 10 μg/ml, respectively. Nevertheless, AgNPs did not demonstrate any antagonistic activity against Coxsackie B virus. The in vitro cytotoxicity of the mycosynthesized AgNPs showed significant antitumor activity against adenocarcinoma epithelial cells from human breast cancer (Mcf-7) cell line with an inhibitory concentration (IC₅₀) of 87.5 μg/ml.

Assessment of antibacterial and anticancer capability of silver nanoparticles extracellularly biosynthesized using Aspergillus terreus

The present study explores biosynthesis of silver nanoparticles (AgNPs) employing extracellular extract of Aspergillus terreus ITCC 9932.15. Modulation of various variables that dictate the biosynthesis of AgNPs, suggested of optimal AgNPs synthesis using AgNO3, 1 mM at pH 8 and temperature, 35 °C. The biosynthesis of AgNPs was observed to be time dependent with incremental particle synthesis till 24 h. Various studies were undertaken to authenticate formation and characterization of AgNPs for size, crystallinity and biomolecules involved. A sharp SPR peak observed at 420 nm in the UV–vis absorption spectra validated synthesis of nanoparticles. These particles exhibited spherical morphology with size ∼25 nm and −16 mV of zeta potential. Further, the existence of proteins and other biomolecules onto the surface of AgNPs was confirmed with FTIR studies. The SAED pattern investigated by employing TEM authenticated the crystallinity of AgNPs. The AgNPs also exhibited potential antibacterial activity against Gram-negative and Gram-positive bacteria (E. coli and P. aeruginosa). In addition, remarkable anticancer activity was obtained in breast cancer cell line (MCF-7).

Novel mycosynthesis of cobalt oxide nanoparticles using Aspergillus brasiliensis ATCC 16404-optimization, characterization and antimicrobial activity

AIMS

Investigate the capability of Aspergillus brasiliensis ATCC 16404 to mycosynthesize Co₃ O₄ -NPs.

METHODS AND RESULTS

Mycelial cell-free filtrate of A. brasiliensis ATCC 16404 was applied for mycosynthesis of Co₃ O₄ -NPs. The preliminary indication for the formation of Co₃ O₄ -NPs was the change in colour from yellow to reddish-brown. One-factor-at a time-optimization technique was applied to determine the optimum physicochemical conditions required for the mycosynthesis of Co₃ O₄ -NPs and they were found to be: 72 h for reaction time, pH 11, 30°C, 100 rev min^-1 for shaking speed in the darkness using 4 mmol l^-1 of CoSO_4. 7H₂ O and 5·5% of A. brasiliensis dry weight mycelium (w/v). The mycosynthesized Co₃ O₄ -NPs were characterized using various techniques: spectroscopy including UV/Vis spectrophotometry, dynamic light scattering (DLS), zeta potential measurement, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffraction; and vibrating sample magnetometry and microscopy including field emission scanning electron microscopy and high-resolution transmission electron microscopy. Spectroscopic techniques confirmed the formation of Co₃ O₄ -NPs and the microscopic ones confirmed the shape and size of the mycosynthesized Co₃ O₄ -NPs as quasi-spherical shaped, monodispersed nanoparticles with a nano size range of 20-27 nm. The mycosynthesized Co₃ O₄ -NPs have excellent magnetic properties and exhibited a good antimicrobial activity against some pathogenic micro-organisms.

CONCLUSION

Ferromagnetic Co₃ O₄ -NPs with considerable antimicrobial activity were for the first time mycosynthesized.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of fungi as potential bionanofactories for mycosynthesis of nanoparticles is relatively a recent field of research with considerable prospects.

Ionic liquid - A greener templating agent with Justicia adhatoda plant extract assisted green synthesis of morphologically improved Ag-Au/ZnO nanostructure and it's antibacterial and anticancer activities

Metal and metal oxide nanoparticles (NPs) possess significant properties that are promising materials for biological applications. In this research work, we prepared ionic liquid assisted Ag-Au/ZnO NPs, using J.adhatoda leaves extract by hydrothermal method. Ionic liquids performed as a stabilizing and templating agent to improve the surface morphology of the synthesized Ag and Au doped ZnO NPs. The prepared ZnO, Ag-doped ZnO, Au doped ZnO, and AgAu doped ZnO NPs exhibit the average crystalline size of 36, 34, 32, and 25 nm and their band gap energy values are 3.36, 3.29, 3.17, and 2.98 eV respectively. The XRD and UV-DRS result shows that after doping of Au and Ag the ZnO crystalline size and band gap energy was decreased, which leads to enhanced the biomedical (antibacterial and anticancer) properties of AgAu doped ZnO NPs. The Raman active mode of A₁ (LO) and A₁ (TO) showed that the formation of lattice defects due to the Ag and Au doping in the ZnO crystalline plane to improve the Ag-Au/ZnO properties. SEM and TEM images revealed that the prepared AgAu doped ZnO NPs exhibits nano stick shape with particle size range from 20 to 25 nm. The EDX spectrum and elemental mapping results confirmed that Ag and Au atoms are doped and spread over the ZnO NPs. The corresponding SAED pattern also confirms the crystallinity of Ag-Au/ZnO NPs. Furthermore, the synthesized Ag-Au/ZnO NPs has been explored for its antibacterial and anticancer activities. It shows good antibacterial activity against E.coli and S.aureus bacteria. Additionally, the Ag-Au/ZnO NPs show excellent anticancer activity against the HeLa cancer cells. The excellent antibacterial and anticancer results prove that the bi-metal (Ag and Au) doping can enhance the biomedical properties of ZnO NPs. It will be a promising material in the biomedical field.

Biosynthesis of AgNPs by B. maydis and its antifungal effect against Exserohilum turcicum

In the present study, Bipolaris maydis was used to synthesise silver nanoparticles (AgNPs). Several parameters that influence the synthesis of AgNPs such as fungus age, the concentration of Ag nitrate (AgNO₃), and incubation time were explored to find the optimum synthesis condition. Furthermore, the antifungal activity of AgNPs against Exserohilum turcicum was determined by measuring inhibition zone diameter, colony formation, and conidia germination. The optimal biosynthesis system included fungus age of 7 days, 8 mM AgNO₃, and an incubation time of 120 h. Under these conditions, synthesised NPs were near round, and the average particle size was about 21 nm. At the experiment, the diameter of the inhibition zone reached a maximum of 8 mM AgNO₃ and 72 h. In addition, the inhibition rate of colony and conidia reached 83.39 and 100%, respectively, with 200 μg/ml AgNPs. The results offer a novel pathway for phytopathogen control and make it likely to develop new eco-friendly antimicrobial.

Physiochemical properties of Trichoderma longibrachiatum DSMZ 16517-synthesized silver nanoparticles for the mitigation of halotolerant sulphate-reducing bacteria

AIMS

In order to efficiently control the corrosive sulphate-reducing bacteria (SRB), the main precursor of the microbial influenced corrosion (MIC) in oil industry, the ability of Trichoderma longibrachiatumDSMZ 16517 to synthesize silver nanoparticles (AgNPs) was investigated and their biocidal activity against halotolerant SRB was tested.

METHODS AND RESULTS

The mycelial cell-free filtrate (MCFF) bioreduced the silver ions (Ag⁺ ) to their metallic nanoparticle state (Ag⁰ ), which was presumptively indicated by the appearance of a dark brown suspension and confirmed by the characteristic absorbance of AgNPs at ʎ_422nm . One-factor-at-a-time technique was used to optimize the effect of temperature, time, pH, fungal biomass and silver nitrate concentrations, stirring rates and dark effect. The dynamic light scattering (DLS) analysis revealed average AgNPs size and zeta potential values of 17·75 nm and -26·8 mV, respectively, indicating the stability of the prepared AgNPs. The X-ray diffraction (XRD) pattern assured the crystallinity of the mycosynthesized AgNPs, with an average size of 61 nm. The field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM) showed nonagglomerated spherical, triangular and cuboid AgNPs ranging from 5 to 11 ± 0·5 nm. The Fourier transform infrared spectroscopy (FT-IR) analysis of the mycosynthesized AgNPs affirmed the role of MCFF as a reducing and capping agent. A preliminary suggested mechanism for mycosynthesis of AgNPs was elucidated. The mycosynthesized AgNPs expressed high biocidal activity against a halotolerant planktonic mixed culture of SRB. The HRTEM analysis showed a clear evidence of an alteration in cell morphology, a disruption of SRB cell membranes, a lysis in cell wall and a cytoplasmic extraction after treatment with AgNPs. This confirmed the bactericidal effect of the mycosynthesized AgNPs.

CONCLUSION

The biocidal activity of the mycosynthesized AgNPs against halotolerant planktonic SRB makes it an attractive option to control MIC in the petroleum industry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research provides a helpful insight into the development of a new mycosynthesized biocidal agent against the corrosive sulphate-reducing bacteria.

Characterization and antimicrobial activity of silver nanoparticles mycosynthesized by Aspergillus brasiliensis

AIMS

Since mycosynthesis of metal nanoparticles (NPs) is advertised as a promising and ecofriendly approach. Thus, this study aims to investigate the capability of Aspergillus brasiliensis ATCC 16404 for mycosynthesis of silver NPs (AgNPs).

METHODS AND RESULTS

One-factor-at-a-time-technique was used to study the effect of different physicochemical parameters: the reaction time, pH, temperature, different stirring rates, illumination, and finally, the different concentrations of silver nitrate and fungal biomass on the mycosynthesis of AgNPs. The visual observation showed the characteristic brown colour formation due to the bioreduction of Ag⁺ ions to Ag⁰ by the mycelial cell-free filtrate (MCFF). The UV/visible spectrophotometric technique displayed a characteristic sharp peak at ʎ₄₄₀ confirming the mycosynthesis of AgNPs. The zeta potential value -16·7 mV assured the long-term stability of AgNPs and the dynamic light scattering analysis revealed good dispersion and average particle size 77 nm. The energy dispersive X-ray spectroscopy displayed a maximum elemental distribution of silver elements. The X-ray diffraction spectroscopy demonstrated the crystallinity of the mycosynthesized AgNPs. The field emission scanning electron microscope and high-resolution transmission electron microscope revealed monodispersed spherical shaped AgNPs with average particle size of 6-21 nm. The FTIR analysis showed the major peaks of proteins providing the possible role of MCFF in the synthesis and stabilization of the AgNPs. The mycosynthesized AgNPs expressed good biocidal activity against different pathogenic micro-organisms causing some water-related diseases and health problems to local residents.

CONCLUSIONS

This study proved that A. brasiliensis ATCC 16404 MCFF has good potential for mycosynthesis of AgNPs, which exhibited good antimicrobial effect on different pathogenic micro-organisms; thus, it can be applied for water disinfection.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research provides a helpful insight into the development of a new mycosynthesized antimicrobial agent.