Poster presentation given during AMiCI Action workshop in Ljubliana March'18

1. Agar/nanosilver composite coatings for prevention of biofilm formation
Slađana Davidović1*, Miona Miljković1, Suzana Dimitrijević1, Antonije Onjia1, Aleksandra Nešić2
1 University of Belgrade, Faculty of Technology and Metallurgy, Serbia
2 University of Belgrade, Vinča Institute of Nuclear Sciences, Serbia
INTRODUCTION
Bacterial contamination on various surfaces is very common and causes serious problems, particularly on hospital surfaces/furniture and medical devices
The formation of biofilms on such surfaces is recognized as the most critical biological contamination due to a difficult removal of microorganisms within
the biofilm and their high resistance to different antimicrobial agents. In an attempt to overcome these problems, various strategies have been employed to
develop methods that can effectively prevent biofilm formation. These methods usually include application of different antimicrobial coatings or biocides on
the surfaces which make them resistant to bacterial adhesion. Silver nanoparticles (AgNPs) have long been recognized as one of the most effective
antimicrobial agent with a broad spectrum of antimicrobial activity. However, surface coatings designed by use of nanosilver only, cannot provide both
strong antimicrobial effect and good biocompatibility. To overcome these disadvantages nanosilver can be incorporated into various polymeric materials. In
this study, we have prepared agar/AgNPs composite coatings using an environmentally-friendly method, i.e., reduction of AgNO3 in the presence of agar
solution.
MATERIAL AND METHODS
RESULTS
CONCLUSION
The agar/Ag nanocomposite films demonstrated antibacterial activity against both tested bacterial strains. The results show that
agar/Ag nanocomposite films could be applied as an eco-friendly surface coating to prevent bacterial contamination.
Acknowledgements
The authors gratefully acknowledge for the financial support given by Ministry of Science, Education and Technological
Development of the Republic of Serbia under the project TR 31035.
*sdavidovic@tmf.bg.ac.rs
1.5 wt % agar
pH 9
T = 60 °C
glycerol
AgNO3
NaCl
After 1h After drying
Figure 1. The UV-Vis absorption
spectra of the agar/Ag nanocomposite
films: (–) control, (–) sample 1, (–)
sample 2, (–) sample 3, (–) sample 4
Agar/Ag nanocomposite films
(samples 1 and 3) exhibited the
absorption maxima around 420
nm, which are attributed to the
plasmon resonance effect of the
AgNPs formed by reduction of
AgNO3. Generally, a typical
plasmon resonance band of AgNPs
has been observed in the range of
400 – 450 nm. The absence of
peaks in this region in samples 2
and 4 could be indication of AgCl
NPs formation.
Figure 2. Photograph of antimicrobial test result of agar/Ag film
against P. aeruginosa (left) and S. aureus (right)
Results of qualitative disc diffusion test (Fig. 2) showed that
agar/AgNPs composite films exhibit antimicrobial activity against
both tested pathogens. However, results of viable cell number
determination (Fig. 3) show that samples with 0.5 mM Ag inhibit
bacterial growth more efficiently.
Characterization
Sample
Composition
AgNO3,
mM
NaCl,
mM
Control 0 0
1 0.25 0
2 0.25 0.50
3 0.50 0
4 0.50 1.00
• UV/Vis spectra
• Antibacterial activity:
•Staphylococcus
aureus ATCC 25923
•Pseudomonas
aeruginosa ATCC
2739
Figure 4. Photograph of S. aureus
biofilm formed on uncoated Petri dish
(left) and the absence of biofilm on
Petri dish coated by agar/Ag
nanocomposite (right)
The antimicrobial properties of agar/AgNPs composite coatings were
assesed against two most common biofilm forming bacteria,
Staphilococcus aureus and Pseudomonas aeruginosa.
0
20
40
60
80
100
1
2
3
4Sample
%R
4h
24h
0
20
40
60
80
100
1
2
3
4Sample
%R
4h
24h
Figure 3a. The percentage of viable cell reduction obtained after 4h and 24 h
incubation of 106 CFU/mL of S. aureus with 10 mg agar/Ag film samples
Figure 3b. The percentage of viable cell reduction
obtained after 4h and 24 h incubation of 106 CFU/mL
of P. aeruginosa with 10 mg agar/Ag film samples