Synthesis, Characterization, and Antifungal Activity of Silver Nanoparticles Embedded in Pullulan Matrices

Steady developments made in nanotechnology-based products have facilitated new perspectives for combating drug-resistant fungi. Silver nanoparticles represent one of the most attractive nanomaterials in biomedicine due to their exclusive optical, electromagnetic, and catalytic properties and antifungal potency compared with other metal nanoparticles. Most studies show that the physicochemical parameters affecting the antifungal potential of AgNPs include the shape, size, surface charge, and concentration and colloidal state. For the present study, pullulan (P) and its oxidized counterpart (PO) have been selected as matrices for the silver nanoparticles’ generation and stabilization (AgNPs). The TEMPO (2,2,6,6-tetramethylpiperidin-1-yl radical)–sodium hypochlorite–sodium bromide system was used for the C6 selective oxidation of pullulan in order to introduce negatively charged carboxylic groups in its structure. The structure and morphology of the synthesized AgNPs were analyzed using FTIR and EDX. The main objective of this study was to elucidate the antifungal activity of AgNPs on the clinical yeasts isolates and compare the performance of AgNPs with the conventional antifungals. In this study, different concentrations of AgNPs were tested to examine antifungal activity on various clinical isolates.

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Phytochemical Constituents of Tulbaghia violacea Harv Extract and its Antifungal Potential Against Cryptococcus neoformans and Cryptococcus gattii

The Natural Products Journal ◽

10.2174/2210315509666181214154345 ◽

2019 ◽

Vol 9 (4) ◽

pp. 330-340

Author(s):

Mitradev Pattoo ◽

Vuyokazi Belewa ◽

Benesh Munilal Somai

Keyword(s):

Antifungal Activity ◽

Cryptococcus Neoformans ◽

Antifungal Therapy ◽

Developing World ◽

Chemical Constituents ◽

Cryptococcus Gattii ◽

Plant Part ◽

Aqueous Extracts ◽

Antifungal Activities ◽

Antifungal Potential

Background:In both the developed and developing world, the mortality rates of people afflicted with cryptococcosis are unacceptably high despite the availability of antifungal therapy. The disease is caused by Cryptococcus neoformans (predominantly in immunocompromised individuals) and by Cryptococcus gattii. Globally the disease is estimated to cause around 600,000 deaths annually. Antifungal therapy is available, but in the developing world, may be unaffordable to many people, there is an increasing threat of resistance to the available drugs and our repertoire of antifungal drugs is very limited. Consequently, more research has been focusing on the use of medicinal plants as therapeutic agents. The originality of the current study is that although Tulbaghia violacea is a well-documented medicinal plant, the chemical composition of aqueous extracts and their antifungal potential against pathogenic yeasts are unknown. This is the first study that evaluates the chemical constituents of aqueous T. violacea root, leaf, rhizome and tuber extracts and their corresponding antifungal activities against C. neoformans and C. gattii.Objectives:The study aimed to investigate the phytochemical composition and antifungal potential of Tulbaghia violacea root, leaf, rhizome and tuber extracts against Cryptococcus neoformans and Cryptococcus gattii.Methods:Roots, leaves, rhizomes and tubers were extracted with water only for 48 h at room temperature with continuous shaking. Extracts were filter sterilized, freeze-dried and, chemically analyzed for saponin, flavonol, phenolic and tannin content. Chemical constituents of each extract were also identified by GC-MS analysis. The Minimum Inhibitory Concentration (MIC) of suitably diluted extracts of each plant part were also performed against C. neoformans and C. gattii, yeast pathogens commonly associated with HIV/AIDS sufferers.Results:Phytochemical analysis showed different concentrations of saponins (between 1023 and 2896.73 µg/ml), phenolics (between 16.48 and 51.58 µg/ml) and tannins (between 122.30 and 543.07 µg/ml) present in the different extracts. No flavonols were detected. GC-MS analysis identified a complex mixture of phytochemicals composed predominantly of sulphide, pyran, furan and ketone containing compounds to be present in the different plant parts. All extracts were dominated by the presence of 4 H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl, a pyran known to have antifungal properties. Although the root, leaf, rhizome and tuber extracts exhibited antifungal activities against both fungi, the rhizome and tuber extract were found to possess the lowest MIC’s of 1.25 mg/ml and 2.5 mg/ml against Cryptococcus neoformans and Cryptococcus gattii respectively.Conclusion:T. violacea extracts have a complex constituent of phytochemicals and each plant part exhibited a strong antifungal activity against C. neoformans and C. gattii. The rhizome and tuber extracts showed the highest antifungal activity against C. neoformans and C. gattii respectively. Thus, T. violacea aqueous extracts are strong candidates for further development into an antifungal chemotherapeutic agent.

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Synthesis and Biological Activity of 3-(substitutedphenyl)-6-(4-methoxyphenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine: Part II

Anti-Infective Agents ◽

10.2174/2211352518666200617144227 ◽

2020 ◽

Vol 18 ◽

Author(s):

Niranjan Kaushik ◽

Nitin Kumar ◽

Anoop Kumar ◽

Vikas Sharma

Keyword(s):

Antifungal Activity ◽

Opportunistic Infections ◽

Fungal Infections ◽

Mass Spectral Data ◽

Triazole Derivatives ◽

Mass Spectral ◽

Fungal Strains ◽

Antifungal Properties ◽

Antifungal Potential ◽

Spectral Data Analysis

Background: Fungal infections are opportunistic infections that become a serious problem to human health. Objective: Considering the antifungal potential of triazole nucleus, the study was carried out with the objective to synthesize some novel triazole derivatives with antifungal potential. Method: 1,2,4-triazole derivatives were synthesized via a two step reaction (reported earlier). The first step involves reaction of substituted benzoic acid with thiocarbohydrazide to form 4-amino-3-(substituted phenyl)-5-mercapto-1, 2, 4-triazole derivatives (1a-1k) while in second step, synthesized compounds (1a-1k) were then subsequently treated with substituted acetophenone to yield substituted (4-methoxyphenyl-7H-[1, 2, 4] triazolo [3, 4-b][1,3,4] thiadiazine derivatives (2a-2k). All synthesized compounds were characterized by IR, 1H NMR, and Mass spectral data analysis and were screened for their antifungal properties against different fungal strains i.e. Candida tropicalis (ATCC-13803, ATCC-20913), Candida albicans (ATCC-60193), Candida inconspicua (ATCC-16783) and Candida glabrata (ATCC-90030, ATCC-2001). Results: Compound 2d displayed better percentage inhibition (26.29%, 24.81%) than fluconazole (24.44%, 22.96%) against ATCC-16783, ATCC-2001 fungal strains respectively at 100µg/ml. Compound 2f also displayed better percentage inhibition (28.51%) against ATCC-90030 as compared to fluconazone (27.4%) at 200 µg/ml. Similarly, compounds 2e and 2j also exhibited better antifungal properties than fluconazole at 200µg/ml. Compound 2e was found most potent against ATCC13803 (30.37%) and ATCC-90030 (30.37%) fungal strains as compared to fluconazole (28.14%, 27.4%) at 200 µg/ml respectively whereas compound 2j exhibited better antifungal activity (28.51%) against ATCC-60193 than fluconazole (27.7%) at 200 µg/ml. Conclusion: The results were in accordance with our assertions for triazole derivatives, as all compounds displayed moderate to good antifungal activity.

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Single-Step Green Synthesis of Highly Concentrated and Stable Colloidal Dispersion of Core-Shell Silver Nanoparticles and Their Antimicrobial and Ultra-High Catalytic Properties

Nanomaterials ◽

10.3390/nano11041007 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1007

Author(s):

Azam Ali ◽

Mariyam Sattar ◽

Fiaz Hussain ◽

Muhammad Humble Khalid Tareen ◽

Jiri Militky ◽

...

Keyword(s):

Silver Nanoparticles ◽

Green Synthesis ◽

Tannic Acid ◽

Rate Constant ◽

Catalytic Properties ◽

Colloidal Dispersion ◽

Alkaline Condition ◽

Core Shell ◽

Average Particle ◽

Ag Nps

The versatile one-pot green synthesis of a highly concentrated and stable colloidal dispersion of silver nanoparticles (Ag NPs) was carried out using the self-assembled tannic acid without using any other hazardous chemicals. Tannic acid (Plant-based polyphenol) was used as a reducing and stabilizing agent for silver nitrate in a mild alkaline condition. The synthesized Ag NPs were characterized for their concentration, capping, size distribution, and shape. The experimental results confirmed the successful synthesis of nearly spherical and highly concentrated (2281 ppm) Ag NPs, capped with poly-tannic acid (Ag NPs-PTA). The average particle size of Ag NPs-PTA was found to be 9.90 ± 1.60 nm. The colloidal dispersion of synthesized nanoparticles was observed to be stable for more than 15 months in the ambient environment (25 °C, 65% relative humidity). The synthesized AgNPs-PTA showed an effective antimicrobial activity against Staphylococcus Aureus (ZOI 3.0 mM) and Escherichia coli (ZOI 3.5 mM). Ag NPs-PTA also exhibited enhanced catalytic properties. It reduces 4-nitrophenol into 4-aminophenol in the presence of NaBH4 with a normalized rate constant (Knor = K/m) of 615.04 mL·s−1·mg−1. For comparison, bare Ag NPs show catalytic activity with a normalized rate constant of 139.78 mL·s−1·mg−1. Furthermore, AgNPs-PTA were stable for more than 15 months under ambient conditions. The ultra-high catalytic and good antimicrobial properties can be attributed to the fine size and good aqueous stability of Ag NPs-PTA. The unique core-shell structure and ease of synthesis render the synthesized nanoparticles superior to others, with potential for large-scale applications, especially in the field of catalysis and medical.

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Discovery of high antibacterial and catalytic activities of biosynthesized silver nanoparticles using C. fruticosus (CF-AgNPs) against multi-drug resistant clinical strains and hazardous pollutants

Environmental Technology & Innovation ◽

10.1016/j.eti.2021.101607 ◽

2021 ◽

pp. 101607

Author(s):

Mina Shirzadi-Ahodashti ◽

Zirar M. Mizwari ◽

Zahra Hashemi ◽

Saba Rajabalipour ◽

Seyedeh Masoumeh Ghoreishi ◽

...

Keyword(s):

Silver Nanoparticles ◽

Drug Resistant ◽

Clinical Strains ◽

Catalytic Activities ◽

Hazardous Pollutants

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Ecofriendly Synthesis of Silver Nanoparticles by Terrabacter humi sp. nov. and Their Antibacterial Application against Antibiotic-Resistant Pathogens

International Journal of Molecular Sciences ◽

10.3390/ijms21249746 ◽

2020 ◽

Vol 21 (24) ◽

pp. 9746

Author(s):

Shahina Akter ◽

Sun-Young Lee ◽

Muhammad Zubair Siddiqi ◽

Sri Renukadevi Balusamy ◽

Md. Ashrafudoulla ◽

...

Keyword(s):

Silver Nanoparticles ◽

Spherical Shape ◽

Optimal Growth ◽

Rrna Genes ◽

Rrna Gene ◽

Strictly Aerobic ◽

Drug Resistant ◽

Protein Coding ◽

A Genome ◽

The Fourier Transform

It is essential to develop and discover alternative eco-friendly antibacterial agents due to the emergence of multi-drug-resistant microorganisms. In this study, we isolated and characterized a novel bacterium named Terrabacter humi MAHUQ-38T, utilized for the eco-friendly synthesis of silver nanoparticles (AgNPs) and the synthesized AgNPs were used to control multi-drug-resistant microorganisms. The novel strain was Gram stain positive, strictly aerobic, milky white colored, rod shaped and non-motile. The optimal growth temperature, pH and NaCl concentration were 30 °C, 6.5 and 0%, respectively. Based on 16S rRNA gene sequence, strain MAHUQ-38T belongs to the genus Terrabacter and is most closely related to several Terrabacter type strains (98.2%–98.8%). Terrabacter humi MAHUQ-38T had a genome of 5,156,829 bp long (19 contigs) with 4555 protein-coding genes, 48 tRNA and 5 rRNA genes. The culture supernatant of strain MAHUQ-38T was used for the eco-friendly and facile synthesis of AgNPs. The transmission electron microscopy (TEM) image showed the spherical shape of AgNPs with a size of 6 to 24 nm, and the Fourier transform infrared (FTIR) analysis revealed the functional groups responsible for the synthesis of AgNPs. The synthesized AgNPs exhibited strong anti-bacterial activity against multi-drug-resistant pathogens, Escherichia coli and Pseudomonas aeruginosa. Minimal inhibitory/bactericidal concentrations against E. coli and P. aeruginosa were 6.25/50 and 12.5/50 μg/mL, respectively. The AgNPs altered the cell morphology and damaged the cell membrane of pathogens. This study encourages the use of Terrabacter humi for the ecofriendly synthesis of AgNPs to control multi-drug-resistant microorganisms.

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Biodirected Synthesis of Silver Nanoparticles Using Aqueous Honey Solutions and Evaluation of Their Antifungal Activity against Pathogenic Candida Spp.

International Journal of Molecular Sciences ◽

10.3390/ijms22147715 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7715

Author(s):

Grzegorz Czernel ◽

Dominika Bloch ◽

Arkadiusz Matwijczuk ◽

Jolanta Cieśla ◽

Monika Kędzierska-Matysek ◽

...

Keyword(s):

Silver Nanoparticles ◽

Antifungal Activity ◽

Fungal Pathogens ◽

Fungal Growth ◽

Disc Diffusion ◽

Candida Spp ◽

Antifungal Effect ◽

Synthesis Of Nanoparticles ◽

Honey Solution ◽

Diffusion Assay

Silver nanoparticles (AgNPs) were synthesized using aqueous honey solutions with a concentration of 2%, 10%, and 20%—AgNPs-H2, AgNPs-H10, and AgNPs-H20. The reaction was conducted at 35 °C and 70 °C. Additionally, nanoparticles obtained with the citrate method (AgNPs-C), while amphotericin B (AmB) and fluconazole were used as controls. The presence and physicochemical properties of AgNPs was affirmed by analyzing the sample with ultraviolet–visible (UV–Vis) and fluorescence spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). The 20% honey solution caused an inhibition of the synthesis of nanoparticles at 35 °C. The antifungal activity of the AgNPs was evaluated using opportunistic human fungal pathogens Candida albicans and Candida parapsilosis. The antifungal effect was determined by the minimum inhibitory concentration (MIC) and disc diffusion assay. The highest activity in the MIC tests was observed in the AgNPs-H2 variant. AgNPs-H10 and AgNPs-H20 showed no activity or even stimulated fungal growth. The results of the Kirby–Bauer disc diffusion susceptibility test for C. parapsilosis strains indicated stronger antifungal activity of AgNPs-H than fluconazole. The study demonstrated that the antifungal activity of AgNPs is closely related to the concentration of honey used for the synthesis thereof.

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Reactivity and Chemical Sintering of Carey Lea Silver Nanoparticles

Nanomaterials ◽

10.3390/nano9111525 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1525

Author(s):

Sergey Vorobyev ◽

Elena Vishnyakova ◽

Maxim Likhatski ◽

Alexander Romanchenko ◽

Ivan Nemtsev ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Silver Nanoparticles ◽

Flexible Electronics ◽

Photoelectron Spectroscopy ◽

Colloidal Solutions ◽

Ag Nps ◽

Wide Range ◽

Carboxylic Groups ◽

The Media ◽

Sulfide Ions

Carey Lea silver hydrosol is a rare example of very concentrated colloidal solutions produced with citrate as only protective ligands, and prospective for a wide range of applications, whose properties have been insufficiently studied up to now. Herein, the reactivity of the immobilized silver nanoparticles toward oxidation, sulfidation, and sintering upon their interaction with hydrogen peroxide, sulfide ions, and chlorocomplexes of Au(III), Pd(II), and Pt(IV) was investigated using SEM and X-ray photoelectron spectroscopy (XPS). The reactions decreased the number of carboxylic groups of the citrate-derived capping and promoted coalescence of 7 nm Ag NPs into about 40 nm ones, excluding the interaction with hydrogen peroxide. The increased nanoparticles form loose submicrometer aggregates in the case of sulfide treatment, raspberry-like micrometer porous particles in the media containing Pd(II) chloride, and densely sintered particles in the reaction with inert H2PtCl6 complexes, probably via the formation of surface Ag-Pt alloys. The exposure of Ag NPs to HAuCl4 solution produced compact Ag films along with nanocrystals of Au metal and minor Ag and AgCl. The results are promising for chemical ambient temperature sintering and rendering silver-based nanomaterials, for example, for flexible electronics, catalysis, and other applications.

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