Silver Nanoparticles Biosynthesized with Spruce Bark Extract-A Molecular Aggregate with Antifungal Activity against Candida Species

Eco-friendly synthesis of silver nanoparticles from peel and juice C. limon and their antiviral efficacy against HSV-1 and SARS-CoV-2

The growing threat of viral infections requires innovative therapeutic approaches to safeguard human health. Nanomaterials emerge as a promising solution to overcome the limitations associated with conventional therapies. The eco-friendly synthesis of silver nanoparticles (AgNPs) currently represents a method that guarantees antimicrobial efficacy, safety, and cost-effectiveness. This study explores the use of AgNPs derived from the peel (Lp-AgNPs) and juice (Lj-AgNPs) Citrus limon "Ovale di Sorrento", cultivars of the Campania region. The antiviral potential was tested against viruses belonging to the Coronaviridae and Herpesviridae. AgNPs were synthesized by reduction method using silver nitrate solution mixed with aqueous extract of C. limon peel and juice. The formation of Lp-AgNPs and Lj-AgNPs was assessed using a UV-Vis spectrophotometer. The size, ζ-potential, concentration, and morphology of AgNPs were evaluated by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and field emission-scanning electron microscopy (FE-SEM). Cytotoxicity was evaluated in a concentration range between 500 and 7.8 µg/mL on VERO-76 and HaCaT cells, with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium test bromide (MTT). Antiviral activity consisted of virus pre-treatment, co-treatment, cellular pre-treatment, and post-infection tests versus HSV-1 and SARS-CoV-2 at a multiplicity of infections (MOI) of 0.01. Plaque reduction assays and real-time PCR provided data on the antiviral potential of tested compounds. Lp-AgNPs and Lj-AgNPs exhibited spherical morphology with respective diameters of 60 and 92 nm with concentrations of 4.22 and 4.84 × 1010 particles/mL, respectively. The MTT data demonstrated minimal cytotoxicity, with 50 % cytotoxic concentrations (CC50) of Lp-AgNPs and Lj-AgNPs against VERO cells of 754.6 and 486.7 µg/mL. Similarly, CC50 values against HaCaT were 457.3 µg/mL for Lp-AgNPs and 339.6 µg/mL for Lj-AgNPs, respectively. In the virus pre-treatment assay, 90 % inhibitory concentrations of HSV-1 and SARS-CoV-2 were 8.54-135.04 µg/mL for Lp-AgNPs and 6.13-186.77 µg/mL for Lj-AgNPs, respectively. The molecular investigation confirmed the antiviral data, recording a reduction in the UL54 and UL27 genes for HSV-1 and in the Spike (S) gene for SARS-CoV-2, following AgNP exposure. The results of this study suggest that Lp-AgNPs and Lj-AgNPs derived from C. Limon could offer a valid ecological, natural, local and safe strategy against viral infections.

Possible Molecular Targeting of Biofilm-Associated Genes by Nano-Ag in Candida albicans

The treatment of candidiasis infections is hindered by the presence of biofilms. Here, we report the biofilm-associated genes as potential molecular targets by silver nanoparticles (nano-Ag) in Candida albicans. Nano-Ag was biosynthesized using Bacillus licheniformis, Bacillus cereus, and Fusarium oxysporum. The physicochemical properties of the microbial-synthesized of nano-Ag are widely characterized by visual observation, ultraviolet-visible spectroscopy, scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy. Characterization results revealed the formation of nano-Ag. Antiplanktonic cells and antibiofilm activities of nano-Ag were also demonstrated by minimum inhibition concentrations (MIC), minimum fungicidal concentration (MFC), MFC/MIC ratio, crystal violet staining, 2,3-bis (2-methoxy-4-nitro-5 sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT), and microscopic image analysis. We have analyzed the expressions of biofilm-associated genes in C. albicans treated with different concentrations of nano-Ag based on MIC. The expression profile of BCR1, ALS1, ALS3, HWP1, and ECE1 showed downregulated genes involved in these pathways by the treatment with nanoparticles. Negative regulators, TUP1, NRG1, and TOR1, were upregulated by the treatment of nano-Ag. Our study suggests that nano-Ag affects gene expression and may subsequently decrease the pathogenesis of C. albicans by inhibiting biofilm formation. Molecular targeting of biofilm-associated genes involved in biofilm formation by nano-Ag may be an effective treatment strategy for candidiasis infections.

Insights into the anti-Candida albicans properties of natural phytochemicals: An in vitro and in vivo investigation

Invasive candidiasis, attributed to Candida albicans, has long been a formidable threat to human health. Despite the advent of effective therapeutics in recent decades, the mortality rate in affected patient populations remains discouraging. This is exacerbated by the emergence of multidrug resistance, significantly limiting the utility of conventional antifungals. Consequently, researchers are compelled to continuously explore novel solutions. Natural phytochemicals present a potential adjunct to the existing arsenal of agents. Previous studies have substantiated the efficacy of phytochemicals against C. albicans. Emerging evidence also underscores the promising application of phytochemicals in the realm of antifungal treatment. This review systematically delineates the inhibitory activity of phytochemicals, both in monotherapy and combination therapy, against C. albicans in both in vivo and in vitro settings. Moreover, it elucidates the mechanisms underpinning the antifungal properties, encompassing (i) cell wall and plasma membrane damage, (ii) inhibition of efflux pumps, (iii) induction of mitochondrial dysfunction, and (iv) inhibition of virulence factors. Subsequently, the review introduces the substantial potential of nanotechnology and photodynamic technology in enhancing the bioavailability of phytochemicals. Lastly, it discusses current limitations and outlines future research priorities, emphasizing the need for high-quality research to comprehensively establish the clinical efficacy and safety of phytochemicals in treating fungal infections. This review aims to inspire further contemplation and recommendations for the effective integration of natural phytochemicals in the development of new medicines for patients afflicted with C. albicans.

Is Silver Addition to Scaffolds Based on Polycaprolactone Blended with Calcium Phosphates Able to Inhibit Candida albicans and Candida auris Adhesion and Biofilm Formation?

Candida spp. periprosthetic joint infections are rare but difficult-to-treat events, with a slow onset, unspecific symptoms or signs, and a significant relapse risk. Treatment with antifungals meets with little success, whereas prosthesis removal improves the outcome. In fact, Candida spp. adhere to orthopedic devices and grow forming biofilms that contribute to the persistence of this infection and relapse, and there is insufficient evidence that the use of antifungals has additional benefits for anti-biofilm activity. To date, studies on the direct antifungal activity of silver against Candida spp. are still scanty. Additionally, polycaprolactone (PCL), either pure or blended with calcium phosphate, could be a good candidate for the design of 3D scaffolds as engineered bone graft substitutes. Thus, the present research aimed to assess the antifungal and anti-biofilm activity of PCL-based constructs by the addition of antimicrobials, for instance, silver, against C. albicans and C. auris. The appearance of an inhibition halo around silver-functionalized PCL scaffolds for both C. albicans and C. auris was revealed, and a significant decrease in both adherent and planktonic yeasts further demonstrated the release of Ag+ from the 3D constructs. Due to the combined antifungal, osteoproliferative, and biodegradable properties, PCL-based 3D scaffolds enriched with silver showed good potential for bone tissue engineering and offer a promising strategy as an ideal anti-adhesive and anti-biofilm tool for the reduction in prosthetic joints of infections caused by Candida spp. by using antimicrobial molecule-targeted delivery.

Development and evaluation of an anti-candida cream based on silver nanoparticles

The ineffectiveness of azole drugs in treating Vulvovaginal Candidiasis (VVC) and Recurrent Vulvovaginal Candidiasis (RVVC) due to antifungal resistance of non-albicans Candida has led to the investigation of inorganic nanoparticles with biological activity. Silver nanoparticles (AgNPs) are important in nanomedicine and have been used in various products and technologies. This study aimed to develop a vaginal cream and assess its in vitro antimicrobial activity against Candida parapsilosis strains, specifically focusing on the synergy between AgNPs and miconazole. AgNPs were synthesized using glucose as a reducing agent and sodium dodecyl sulfate (SDS) as a stabilizer in varying amounts (0.50, 0.25, and 0.10 g). The AgNPs were characterized using UV-Visible (UV-Vis) and Fourier-Transform Infrared (FT-IR) spectroscopies, X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDX). Fifty strains of Candida parapsilosis were used to evaluate the synergistic activity. AgNPs synthesized with 0.5 g SDS had an average size of 77.58 nm and a zeta potential of -49.2 mV, while AgNPs with 0.25 g showed 91.22 nm and -47.2 mV, respectively. AgNPs stabilized with 0.1 g of SDS were not effective. When combined with miconazole, AgNPs exhibited significant antifungal activity, resulting in an average increase of 80% in inhibition zones. The cream developed in this study, containing half the miconazole concentration of commercially available medication, demonstrated larger inhibition zones compared to the commercial samples.

Synergistic Antifungal Interaction between Pseudomonas aeruginosa LV Strain Metabolites and Biogenic Silver Nanoparticles against Candida auris

Candida auris has been found to be a persistent colonizer of human skin and a successful pathogen capable of causing potentially fatal infection, especially in immunocompromised individuals. This fungal species is usually resistant to most antifungal agents and has the ability to form biofilms on different surfaces, representing a significant therapeutic challenge. Herein, the effect of metabolites of Pseudomonas aeruginosa LV strain, alone and combined with biologically synthesized silver nanoparticles (bioAgNP), was evaluated in planktonic and sessile (biofilm) cells of C. auris. First, the minimal inhibitory and fungicidal concentration values of 3.12 and 6.25 μg/mL, respectively, were determined for F4a, a semi-purified bacterial fraction. Fluopsin C and indolin-3-one seem to be the active components of F4a. Like the semi-purified fraction, they showed a time- and dose-dependent fungicidal activity. F4a and bioAgNP caused severe changes in the morphology and ultrastructure of fungal cells. F4a and indolin-3-one combined with bioAgNP exhibited synergistic fungicidal activity against planktonic cells. F4a, alone or combined with bioAgNP, also caused a significant decrease in the number of viable cells within the biofilms. No cytotoxicity to mammalian cells was detected for bacterial metabolites combined with bioAgNP at synergistic concentrations that presented antifungal activity. These results indicate the potential of F4a combined with bioAgNP as a new strategy for controlling C. auris infections.

Comparative evaluation of the antifungal efficacy of sodium hypochlorite, chlorhexidine, and silver nanoparticles against Candida albicans

Candida albicans is a microorganism that causes root canal infections. However, it cannot be eliminated with conventional irrigation solutions. Recently, silver nanoparticles (AgNPs) have become popular for their superior antimicrobial effects. The purpose of this study was to evaluate the antifungal effect of AgNPs to C. albicans comparing with 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX). Silver nanoparticles were synthesized by chemical reduction method. Minimum inhibitory concentration and minimum fungicidal concentration of AgNPs against C. albicans strain were determined according to microdilution method reported by Clinical Laboratory Standards Institute. C. albicans biofilm layer was formed on the dentin blocks for 10 days. The biofilm structure was observed by scanning electron microscopy. Statistical analysis was performed with one way analysis of variance analysis and group comparisons were performed with Tukey test. AgNPs showed the highest antifungal effect among the groups. 5.25% NaOCl showed the lowest antifungal effect among the groups. While the 2% CHX solution had a statistically lower antifungal effect than AgNPs, it was found to have a higher effect than NaOCl (p < .016). Nanoparticles present a wide research field as an alternative irrigation solution in root canal treatment. The antifungal effect of AgNPs against C. albicans was confirmed in this study. Further in vivo studies should evaluate the conditions of use and long-term prognosis of AgNPs.

Green Synthesis of Silver Nanoparticles (AgNPs) of Angelica Gigas Fabricated by Hot-Melt Extrusion Technology for Enhanced Antifungal Effects

Green synthesis for synthesizing silver nanoparticles (AgNPs) has been suggested as an environmentally friendly alternative to conventional physical/chemical methods. In this study, we report the green synthesis of AgNPs using a hot-melt extrusion-processed Angelica gigas Nakai (AGN) (HME-AGN) extract as a reducing agent to increase the water solubility of the active ingredient compared to the existing AGN. The mixture of the AGN extract and AgNO₃ at about 420 nm could not confirm the formation of AgNPs. The synthesis of AgNPs was found to be most advantageous at 60 °C when the mixing ratio of the HME-AGN extract was 9:1 (AgNO₃-extract, v/v) using 3 mM AgNO₃. The physicochemical properties of the optimized AgNPs were characterized by UV-Vis spectrophotometer, dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffractometer (XRD). DLS showed the particle size average of 102.3 ± 1.35 nm and polydispersity index (PDI) value of 0.314 ± 0.01. The particle surface charge was -35 ± 0.79 mV, confirming the stability of the particles. The particle shape was spherical, as shown through TEM analysis, and the presence of silver ions was confirmed through the EDS results. FT-IR data showed functional groups of biomolecules of the extract involved in the synthesis of AgNPs. The face-centered cubic (FCC) lattice of AgNPs was confirmed in the XRD pattern. The AgNPs had an effective antifungal activity against Candida albicans (C. albicans) that was better than that of the HME-AGN extract. In conclusion, this study suggests that the synthesis of AgNPs was improved by using the HME-AGN extract with increased water solubility through HME. In addition, it was suggested that the synthesized AgNPs can be used as an improved antifungal agent compared with the HME-AGN extract with antifungal activity.

Activity of Fusarium oxysporum-Based Silver Nanoparticles on Candida spp. Oral Isolates

Candida spp. resistant to commercially available antifungals are often isolated from patients with oral candidiasis, a situation that points to the need for the development of new therapies. Thus, we evaluated the activity of Fusarium oxysporum-based silver nanoparticles (AgNPs) on Candida spp. isolated from denture stomatitis lesions. Candida isolates were molecularly identified and submitted to susceptibility assays using AgNPs and commercial fungicides. The interference on biofilm formation and the mechanisms of action of AgNPs on Candida spp. were also investigated. Scanning electron microscopy was used to evaluate the morphology of AgNP-treated Candida. Candida albicans was the most frequent species isolated from denture stomatitis cases. All Candida spp. were susceptible to AgNPs at low concentrations, except Candida parapsilosis. AgNPs caused surface damage, cell disruption, and biofilm formation inhibition. The ergosterol supplementation protected C. albicans against the AgNP action. AgNPs are effective against Candida spp. and can be faced as a promising new therapeutic agent against oral candidiasis.