Tese_Tânia Vieira.pdf - Ubi Thesis

Chapter II – Materials and Methods
Briefly, the dextran solution was added dropwise to chitosan solution under stirring. This process
was repeated with different ratios of dextran/chitosan (1:6, 1:3, 2:3 (v/v)) and for high and low
molecular weights of chitosan and dextran. The resulting nanoparticles were left to rest for 30
min and then, rinsed three times with destilled water and centrifugated at 17000 g, for 30 min.
A dried powder of particles was obtained by freeze-drying the particles overnight.
2.2.3. Preparation of the Chitosan/Dextran nanoparticles with silver
To the solution of chitosan/dextran nanoparticles already prepared was added to 50 µL of
0.01M of AgNO 3 solution. After 5 min of stirring, 50 µL of 0.01M of NaBH 4 were added dropwise
and left aged for 30 min. The same procedure was performed by replacing NaBH 4 for the same
concentration of C 6 H 8 O 6 . Then the particles were washed three times with destilled water and
centrifugated at 17000 g, during 30 min. A dried powder of particles was obtained by freezedrying
the particles overnight.
The formed AgNPs and chitosan/dextran nanoparticles were also produced by the dropwise
addition of 150 µL of AgNPs solution on the chitosan/dextran nanoparticles under stirring and left
aged for 30 min. Formerly, the particles were washed three times with destilled water and
centrifugated at 17000 g, during 30 min. A dried powder of particles was obtained by freezedrying
the particles overnight.
2.2.4. Nanoparticles Scanning Electron Microscopy Analysis
The morphology of the produced nanoparticles was analyzed by scanning electron
microscopy (SEM). First, the produced nanoparticles were resuspended in 100 µL of ultrapure
water and then, one drop was added to a 16 mm cover glasses and subsequently mounted in
aluminum board using a double-sided adhesive tape and covered with gold using an Emitech K550
(London, England) sputter coater. Then, the prepared samples were analyzed using a Hitachi S-
2700 (Tokyo, Japan) scanning electron microscope, operated at an accelerating voltage of 20 kV
with variable magnifications (Gaspar et al. 2011).
2.2.5. Nanoparticles Ultraviolet-Visible Spectroscopy Analysis
The produced AgNPs were analyzed by UV-Vis specroscopy. The UV-Vis spectra were
recorded using UV-1700 PharmaSpec from Shimadzu at 300 nm/min scanning rate, with a
wavelength range from 200 to 700 nm, and then analyzed with UVProbe Shimadzu 2.0 software.
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