J. Microbiol. Biotechnol. (2008), 18(8), 1482–1484
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*
1Department of Microbiology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea
2Department of Dermatology, College of Medicine, Yeungnam University, Daegu 705-717, Korea
Received: February 1, 2008 / Accepted: April 16, 2008
Spherical silver nanoparticles (nano-Ag) were synthesized
and their antifungal effects on fungal pathogens of the
skin were investigated. Nano-Ag showed potent 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 superior to that of fluconazole
(amphotericin B IC80, 1-5 µg/ml; fluconazole IC80, 10-
30 µg/ml). Additionally, we investigated their effects on
the dimorphism of Candida albicans. The results showed
nano-Ag exerted activity on the mycelia. Thus, the present
study indicates nano-Ag may have considerable antifungal
activity, deserving further investigation for clinical
Keywords: Silver nanoparticles, antifungal effect, Trichophyton
mentagrophytes, Candida species
Skin infections caused by fungi, such as Trichophyton and
Candida species, have become more common in recent
years . In particular, fungal infections are more frequent
in patients who are immunocompromised because of cancer
chemotherapy, or organ or human immunodeficiency
virus infections . This upward trend is concerning,
considering the limited number of antifungal drugs available
because prophylaxis with antifungals may lead to the
emergence of resistant strains. Therefore, there is an
inevitable and urgent medical need for novel antifungals.
Since ancient times, it has been known that silver and its
compounds are effective antimicrobial agents [6, 14, 15].
In particular, because of the recent advances in research on
metal nanoparticles, nano-Ag has received special attention
as a possible antimicrobial agent [1, 7, 9, 16]. Therefore,
the preparation of uniform nanosized silver particles with
specific requirements in terms of size, shape, and physical
and chemical properties is of great interest in the formulation
of new pharmaceutical products [3, 10]. Many studies
have shown their antimicrobial effects, but the effects of
nano-Ag against fungal pathogens of the skin are mostly
unknown. In this study, nano-Ag was synthesized and its
antifungal effects on clinical isolates and ATCC strains of
Trichophyton mentagrophytes and Candida species were
Preparation of Nano-Ag
One-hundred g of solid silver was dissolved in 100 ml of
100% nitric acid at 90oC, and then 1 l of distilled water
was added. By adding sodium chloride to the silver
solution, Ag ions reduced and clustered together to form
monodispersed nanoparticles in the aqueous medium. Because
the final concentration of colloidal silver was 60,000 ppm,
this solution was diluted, and then samples of different
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Fig. 1. Transmission electron micrograph of the nano-Ag used
in this work.
ANTIFUNGAL ACTIVITY OF SILVER NANOPARTICLES
concentrations were used to investigate the antifungal effect
of nano-Ag. The sizes and morphology of nano-Ag were
examined by using a transmission electron microscope (H-
7600; Hitachi, Ltd.). The results showed that nano-Ag was
a spherical form and its average size was 3 nm (Fig. 1).
Determination of Antifungal Susceptibility
A total of 44 strains of 6 fungal species was 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 Medical School (Gwangju, Korea),
and clinical isolates of Trichophyton mentagrophytes were
obtained from the Institute of Medical Mycology, Catholic
Skin Clinic (Daegu, Korea). Candida spp. and Trichophyton
mentagrophytes were cultured in a Sabraud dextrose agar
(SDA) and a potato dextrose agar (PDA) at 35oC, respectively.
The MICs for Candida spp. and T. mentagrophytes were
determined by a broth microdilution method based on the
National Committee for Clinical Laboratory Standards
(NCCLS; now renamed as Clinical and Laboratory Standards
Institute, CLSI, 2000) method outlined in documents M-
27A  and M-38P , respectively. An RPMI 1640
medium buffered to pH 7.0 with 3-(N-morpholino)
propanesulfonic acid (MOPS) was used as the culture
medium, and the inoculum size of Candida spp. was
0.5×103 to 2.5×103cells/ml, and that of T. mentagrophytes
was 0.4×104 to 5×104cells/ml. The microdilution plates
inoculated with fungi were incubated at 35oC, and the
turbidity of the growth control wells was observed every
24 h. The 80% inhibitory concentration (IC80) was defined
as the lowest concentration that inhibited 80% of the
growth as determined by a comparison with the growth
in the control wells. The growth was assayed with a
microplate reader (Bio-Tek Instruments, Winooski, VT,
U.S.A.) by monitoring absorption at 405 nm. In the current
study, amphotericin B and fluconazole were used as a
positive control toward fungi; amphotericin B is a fungicidal
agent widely used in treating serious systemic infections
, and fluconazole is used in the treatment of superficial
skin infections caused by dermatophytes and Candida species
. Nano-Ag, in an IC80 range of 1-7 µg/ml, showed
significant antifungal activity against T. mentagrophytes
and Candida species. Toward all fungal strains, nano-Ag
exhibited similar activity with amphotericin B, showing
IC80 values of 1-5 µg/ml, but more potent activity than
fluconazole, showing IC80 values of 10-30µg/ml. However,
this compound exhibited less potent activity than amphotericin
B, showing IC80 values of 2-4 µg/ml for C. parapsilosis
and C. krusei (Table 1).
Effect of Nano-Ag on the Dimorphic Transition
C. albicans cells were maintained by periodic subculturing
in a liquid yeast extract/peptone/dextrose (YPD) medium.
Cultures of yeast cells (blastoconidia) were maintained in a
liquid YPD medium at 37oC. To induce mycelial formation,
cultures were directly supplemented with 20% of a fetal
bovine serum (FBS). The dimorphic transition in C.
albicans was investigated from cultures containing 2 mg/
ml of nano-Ag (at the IC80), which were incubated for 48 h
at 37oC [5, 17, 18]. The dimorphic transition to mycelial
forms was detected by phase contrast light microscopy
(Nikon, Eclipsete300, Tokyo, Japan). The dimorphic
transition of C. albicans from yeast form to mycelial form
is responsible for pathogenicity, with mycelial shapes being
predominantly found during the invasion of host tissue. A
mycelial form can be induced by temperature, pH, and
serum . As shown in Fig. 2, the serum-induced mycelia
Table 1. Antifungal activity of nano-Ag.
(no. of strains)
Nano-Ag Amphotericin B Fluconazole
C. albicans (4)
C. tropicalis (2)
C. glabrata (4)
C. parapsilosis (3)
C. krusei (1)
T. mentagrophytes (30)
Fig. 2. The effect of nano-Ag on the dimorphic transition in C. albicans.
Yeast control without 20% FBS and nano-Ag (A), without treated nano-Ag (B), or with 2 µg/ml of nano-Ag (C).
1484 Kim et al. Download full-text
were significantly inhibited from extending and forming in
the presence of nano-Ag (Fig. 2C), but the mycelia formed
was normal in the absence of nano-Ag (Fig. 2B). These
results suggested that nano-Ag is a potential compound in
the treatment of fungal infectious diseases.
Many studies have shown the antimicrobial effects of nano-
Ag [6, 14, 15], but the effects of nano-Ag against fungal
pathogens of the skin including clinical isolates of T.
mentagrophytes and Candida species are mostly unknown.
The primary significance of this study is the observation
that nano-Ag could inhibit the growth of dermatophytes,
which cause superficial fungal infections. To our knowledge,
this is the first study to apply nano-Ag successfully to
dermatophytes. Secondly, the fact that preparation method
of nano-Ag described here is cost-effective is also of
importance. Therefore, it could be expected that nano-Ag
may have potential as an anti-infective agent for human
disease caused by dermatophytes.
K.-J. Kim and W.S. Sung contributed equally to this work
and should be considered co-first authors.
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