AMiCI (CA15114). Workshop for Early Career Investigators (ECIs) and Short Term Scientific Missions (STSM) Riga, Latvia, 7th of March 2019

1. Nr.1.1.1.2/VIAA/2/18/331
Development of novel antimicrobial coatings with sharp Z-scheme
photocatalytic nanoarchitectures for indoor applications
To develop antimicrobial coatings with “sharp” (aligned nanowire (NW) forests) Z-scheme photocatalytic nanoarchitectures. Hematite
(Fe2O3) as non-toxic narrow band gap semiconductor with broad absorption in the visible light, will be used as the main element in
coating, “sharp” structures offering a long optical path for efficient light harvesting, that will increase photocatalytic efficiency of
structures. Similar “sharp” structures proved it effectiveness in bacteria killing by piercing into the bacterial cell wall and as repelling
surfaces that resist bacteria attachment. In our further experiments the hematite NW will be decorated with p-type semiconductor
Ca2Fe2O5 or CaFe2O4 nanoparticles in order to provide Z-scheme charge transfer mechanism. In this work an antimicrobial activity of
Fe2O3 NP was studied in suspension, in dependence on a nanostructure – sphere- (Fig.1 A) and wire-likes (Fig.1 B)– in the dark and
visible light (LED 6000K, 30W).
HEMATITE SPHERE- AND WIRE-LIKE NANOPARTICLES IN THE VISIBLE-LIGHT ASSISTED PROCESS:
EFFECT OF EXPERIMENTAL CONDITIONS
Fe2O3 sphere-like (Fig.1A) NP were synthesized by
hydrothermal method. 0.1 M Fe(NO3)3·9H2O solution
was transferred into a 50-ml Teflon-lined stainless steel
autoclave and heated at 150 ͦC for 24 h.
To obtaine Fe2O3 nanowires (Fig.! B), goethite
nanowires were synthesized by precipitation method.
Using 0.1 M Fe(NO3)3·9H2O solution and 0.4 solution of
NaOH, mixed and heated for 72 h at 60 ͦC temperature,
prepared NP after washing were annealed at 820 ͦC.
For comparison were prepared 4.samples: sphere-like
and wire-like NP solutions without dialysis and dialyzed
in cellulose tube in distilled water for 72 h (D water was
changed every 24 h).
Comparing cell morphology in a thin
layer of the microscopy preparation
after incubation with and without NP,
in the visible light and dark, differences
in cell morphology have been
observed.
It was attributed to both, NP and
visible light impact.
Fig.2. Cells of S.cerevisiae 14 after 24h
incubation in YPG medium in presence of
NP (0.01 mg/mL), in the microscopy
preparation. L – visible light, D - darkness.
Fig.4. Colony forming ability of
S.cerevisiae 14 after 24 h incubation
on 2% agar on the layer of Sphere-
like NP and 48 h of incubation on the
nutrient agar.
Fig.5. Micrographs of Wire-like dialyzed NP layer (A, D) and
grown-up S.cerevisiae 14. colonies (B,C,E,F,) on Rose
Bengal Chloramphenicol agar. B, C – after 24 h of
incubation; E, F - after 48 h of incubation on the nutrient
agar.
Yeast Saccharomyces cervisiae 14 was used as a test culture. Testing of antimicrobial properties of surface NP coatings with photocatalytic activity have some
methodical limitations. In particular, when NP are tested in suspension, a relatively thin layer of a liquid phase should be ensured. Three alternative
methodological approaches have been approbated in our experiments. First, microscopy preparations with cover slips protected from evaporation, were used
(Fig.2). Second, yeast cultivation in the presence of NP was performed in microplates with 4mm liquid layer (Fig.3). Third, NP and yeast suspension was
applied on the agar without nutrients (Fig.4).
Fig.3. Nanoparticle impact (OD620)on S.cerevisiae 14 grown in YPG medium (with
100 mg/L tetracycline) in microplate, for 48 h at 23 C. Concentration of NP 0; 1;
10; 100 µg/mL. Culture volume 300 L.
Research aim:
Materials, Methods and Results:
Visible-light can negatively affect the
physiological state of yeast, it should
be taken into account in the study of
photocatalytic processes.
Sphere-like dialyzed NP (with concentration
in the range from 1 to 100 µg/mL) inhibited
the growth of yeast S. cerevisiae 14 culture
in YPG broth under tested conditions,
regardless of dark/light and NP
concentration.
Application of NP and yeast suspensions on the
agarized surface has demonstrated an alternative
methodical approach for testing of a microbial
physiological response towards NP-coated
surfaces in dynamics, thus, maintaining the
humidity for cell physiological processes.
Svetlana Vihodceva1, Viktors Vibornijs2, Olga Muter2, Andris Sutka1
1 Riga Technical University ,Research Laboratoty of Functional Materials Technologies
2 University of Latvia, Institute of Microbiology & Biotechnology
Yeast cells after a direct contact with
the NP layer on the agarized substrate
during 24h, afterwards have been
transferred to the nutrient agar. Yeast
cells showed the ability to form colonies
after 48 h incubation. In subsequent
experiments, it is planned to quantify
both micro- and macro-colonies, during
changing the experimental conditions.
Cultivation of S. cerevisiae 14
in a YPG medium in a
microplate showed the
inhibitory effect of both types
of NP on the culture growth
in the visible light.
In addition, the HemaS-D
with concentration in the
range from 1 to 100 µg / mL
reduced the OD620 culture
after 48 hours of cultivation
by ≈ 45% compared to
control.
Fig.1.A. Sphere-like Fe2O3 NP
Fig.1.B. Wire-like Fe2O3 NP
This work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid
Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing
in human resources and infrastructure” of the Operational Programme “Growth and Employment” (No.1.1.1.2/VIAA/2/18/331)
CONCLUSION:
1. 2. 3.