Nano silver has antifungal properties on the skin Dermatophytes

Spherical silver nanoparticles (nano-Ag) were synthesized and their antifungal effects against skin pathogens were investigated. Nanosilver showed strong activity against clinical isolates and ATCC strains of Trichophyton mentagrophytes and Candida species (IC80, 1-7 µg/ml). The activity of nano-Ag was comparable to that of amphotericin B, but was superior to that of fluconazole (amphotericin B IC80, 1-5 µg/ml; fluconazole IC80, 10-30 µg/ml). In addition, we investigated their effect on Candida albicans dimorphism. The results showed that nano-Ag had an effect on mycelium. Therefore, the present study indicates that nanosilver may have significant antifungal activity, which deserves further investigation for clinical applications.

Nano silver to treat foot fungus

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Skin infections caused by fungi, such as Trichophyton and Candida species, have become more common in recent years [19]. In particular, fungal infections are more common in patients who are immunocompromised due to cancer chemotherapy, or infected with human or organ immunodeficiency virus [11]. This upward trend is worrisome, considering the limited number of antifungal drugs available because antifungal prophylaxis can lead to the emergence of resistant strains. Therefore, there is an urgent and unavoidable medical need for new antifungal drugs. Since ancient times, it has been known that silver and its compounds are effective antibacterial agents [6, 14, 15]. In particular, due to recent advances in metal nanoparticles research, nano-Ag has received special attention as a possible antimicrobial agent [1, 7, 9, 16]. Therefore, the preparation of uniform nano-sized silver particles with specific requirements on size, shape and physico-chemical properties is of great interest in new pharmaceutical formulations [3, 10]. . Many studies have shown their antibacterial effects, but the effect of nanosilver on pathogenic fungi on the skin is mostly unknown. In this study, nano-Ag was synthesized and its antifungal effect on clinical isolates and ATCC strains of Trichophyton mentagrophytes and Candida species were investigated.

Nano silver production

One hundred g of solid silver was dissolved in 100 ml of 100% nitric acid at 90°C, and then 1 l of distilled water was added. By adding sodium chloride to the silver solution, the Ag ions reduce and clump together to form single nanoparticles dispersed in the aqueous medium. Because the final concentration of colloidal silver was 60,000 ppm, this solution was diluted, and then samples of different concentrations were used to investigate the antifungal effect of nano-Ag. The size and morphology of nano-Ag were examined using a transmission electron microscope (H-7600; Hitachi, Ltd.). The results show that nano-Ag has a spherical shape and its average size is 3 nm (Figure 1).
Figure 1: TEM image of silver nano
Nano silver to treat foot fungus

Determination of susceptibility to fungi

A total of 44 strains of 6 fungal species were used in this study. Candida albicans (ATCC 90028), Candida glabrata (ATCC 90030), Candida parapsilosis (ATCC 22019) and Candida krusei (ATCC 6258) were obtained from the American Type Culture Collection (ATCC) (Manassas, VA, U.S.A.). Clinical isolates of Candida spp. were obtained from the Department of Laboratory Medicine, Chonnam National University School of Medicine (Gwangju, Korea), and clinical isolates of Trichophyton mentagrophytes were obtained from the Institute of Medical Mycology, Catholic Dermatology Clinic (Daegu, Korea). South Korea). Candida spp. and Trichophyton mentagrophytes were cultured in Sabraud dextrose agar (SDA) and potato dextrose agar (PDA) at 35°C, respectively. MIC kit for Candida spp. and T. mentagrophytes were determined using a broth dilution method based on the method of the National Committee for Clinical Laboratory Standards (NCCLS; now renamed the Clinical and Laboratory Standards Institute, CLSI) , 2000) are outlined in documents M-27A [12] and M-38P [13], respectively. RPMI 1640 medium buffered to pH 7.0 with 3 propanesulfonic acid (N-morpholino) (MOPS) was used as the culture and size medium for Candida spp. is 0.5 × 103 to 2.5 × 103 cells/ml and that of T. mentagrophytes is 0.4 × 104 to 5 × 104 cells/ml. Inoculated microbiological dilutions were incubated at 35°C, and turbidity of the growth control wells was observed every 24 h. The 80% inhibitory concentration (IC80) was determined to be the lowest concentration that inhibits 80% of growth as determined by comparison with growth in control wells. Growth was examined using a microplate reader (Bio-Tek Instruments, Winooski, VT, U.S.A.) by monitoring the absorption at 405 nm. In the present study, amphotericin B and fluconazole were used as an active control for the fungus; amphotericin B is a fungicide widely used in the treatment of serious systemic infections [4], and fluconazole is used in the treatment of superficial skin infections caused by dermatophytes and Candida species [2]. nanosilver, in the IC80 range from 1-7 µg/ml, showed significant antifungal activity against T. mentagrophytes and Candida species. For all fungal strains, nanosilver exhibited similar activity to amphotericin B, showing an IC80 value of 1-5 µg/ml. Nano silver showed itself to be more active than fluconazole, showing an IC80 value of 10-30 µg/ml. However, this compound exhibited less activity than amphotericin B, showing an IC80 value of 2-4 µg/ml for C. parapsilosis and C. krusei (Table 1)

The ability of silver nanoparticles to inhibit fungi

Effect of nanosilver on the Dimorphic . transition
C. albicans cells were maintained by periodic subculture in liquid yeast extract/peptone/dextrose (YPD) medium. The cultures of yeast cells (blastoconidia) were maintained in liquid YPD medium at 37°C. To induce mycelium formation, cultures were directly supplemented with 20% fetal bovine serum (FBS). The dimorphic conversion in C. albicans was investigated from cultures containing 2 mg/ml nano-Ag (at IC80), incubated for 48 h at 37°C [5, 17, 18]. The dimorphic to hyphae transition was detected by phase-contrast light microscopy (Nikon, Eclipsete300, Tokyo, Japan). The dimorphic conversion of C. albicans from yeast to hyphae is the causative agent of the disease, with mycelium being mainly found during invasion of host tissues. The mycelium can be induced by temperature, pH and serum [8]. As shown in Figure 2, the serum-induced mycelium was significantly inhibited from expansion and formation in the presence of nanosilver (Figure 2C), but the formed hyphae remained normal in the absence of nanosilver. -Ag (Figure 2B). These results suggest that nanosilver is a potential compound in the treatment of fungal infectious diseases. Many studies have shown the antibacterial effect of nanosilver [6, 14, 15], but the effect of nanosilver against skin fungal diseases including clinically isolated strains of T. mentagrophytes and Candida is almost not known. The main implication of this study is the observation that nano-Ag can inhibit the growth of dermatophytes, causing superficial fungal infections. To our knowledge, this is the first study to successfully apply nano silver to dermatology. Second, the fact that the nano-Ag preparation method described here is cost-effective is also important. Therefore, it can be expected that nano-Ag may have potential as an antitumor agent for human disease caused by dermatophytes.
Figure 2. Effect of nanosilver on the dimorphic transition in C. albicans. Yeast control without 20% FBS and nanosilver (A), without treated nanosilver (B), or with 2 µg/ml nanosilver (C).

Description: IC80 concentration of test solution inhibits 80% of fungi.

Reference: Antifungal effect of silver nanoparticles on dermatophytes

Kim, Keuk-Jun1, Woo Sang Sung1, Seok-Ki Moon2, Jong-Soo Choi2, Jong Guk Kim1,
and Dong Gun Lee1*