Tese_Tânia Vieira.pdf - Ubi Thesis

Chapter I - Introduction
biomedical and pharmaceutical applications (Carmen Rodríguez-Argüelles et al. 2011).
Furthermore, it also presents very important biological properties among which antimicrobial,
anti-inflammatory, and antioxidant (Carmen Rodríguez-Argüelles et al. 2011).
Figure 4 – Representation of the chitosan chemical structure(Kumirska et al. 2011).
In this work, the chitosan aqueous solution was added to dextran sulfate polyanion
aqueous solution. The formation of polycation–polyanion (polyelectrolyte) complex was mainly
driven by an electrostatic mechanism where charge neutralization and possible local bridging
(such as hydrogen bounding, Coulomb forces, van der Waals forces, and transfer forces) occurs
(Yu et al. 2005; Meng et al. 2010). The advantages of chitosan/dextran nanoparticles are
enhanced stability and increased mechanical strength compared with chitosan/tripolyphosphaste
microparticles, whose lower stability and mechanical strength limit their application for drug
delivery (Chen et al. 2007). It has also been reported that DNA and insulin structures are
protected when dextran is used in the formulation of polyethylenimine/dextran nanoparticles
(Chen et al. 2007). Dextran was also described as being capable of reducing the cationic chargerelated
cytotoxicity of PEI nanoparticles in vitro (Chen et al. 2007). Therefore, it is possible that
the combination of chitosan and dextran as matrix materials, in an optimal charge ratio, may act
synergistically to incorporate and protect proteins and drugs, in order to reduce the toxicity of
chitosan caused by its cationic charge (Kean et al. 2010).
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