Tese_Tânia Vieira.pdf - Ubi Thesis

Chapter III – Results and Discussion
When using chitosan of high molecular weight, several particles were formed for some
specific dextran/chitosan ratios like 1:6 and 1:3 for high molecular weight dextran (figure 7 A
and C) and 2:3 for both high and low molecular weight dextran (figure 7 E and F). In figures 7 E
and F are depicted the nanoparticles with a highly aggregated structure. Such assembly was
caused by a strong interaction between polyions that occur rapidly by random incorporation of
different polymeric chains into the particle structure (Sarmento et al. 2007). The finest particles
were obtained with high molecular weight dextran at 1:6 (v/v) ratio of dextran/chitosan (figure
7A). These particles were polydispersed and presented a spherical morphology with diameters
ranging from 150 nm to 300 nm. The use of polymers with high molecular weight to perform
nanoparticles can be an advantage for the posterior production of stabilized AgNPs. A study
reported by Shkilnyy and colleagues showed that increasing the molecular weight of the polymer
facilitates the formation of AgNPs, stabilizing therefore the colloids (Shkilnyy et al. 2009). A
summary of the chitosan/dextran ratios where the production of nanoparticles was achieved is
presented in the table 2.
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