The effect of preparation processes on the physicochemical characteristics and antibacterial activity of chitooligosaccharides.

The bioactivities of chitooligosaccharides are markedly influenced by the degree of acetylation, degree of polymerization or molecular weight and pattern of acetylation. Thus, it is crucial to identify reproducible processes that will give rise to well-defined chitooligosaccharides and establish methods for their posterior physicochemical characterization in order to advance in the knowledge of their bioactivity. Chitooligosaccharides were prepared by two different processes. The first used chitosanase enzymatic hydrolysis and the second consisted of a two-step procedure based on chemical hydrolysis followed by chitosanase hydrolysis. Chitooligosaccharides produced in the second process were composed of 63 % of fully deacetylated sequences and inhibited the growth of Escherichia coli and Listeria monocytogenes. Better antibacterial activity was found for those obtained in the first process composed of 27 % of fully deacetylated sequences. Therefore, a low percentage of free amino groups and the presence of acetylated sequences are necessary in these molecules to exert good antibacterial capacity.

Poly-L-asparagine nanocapsules as anticancer drug delivery vehicles.

This work presents for the first time the development of novel poly-L-asparagine (PASN) nanocapsules and the in vitro evaluation of their potential as anticancer drug delivery systems. The design of PASN nanocapsules was inspired by the well-known avidity of cancer cells for the amino acid L-asparagine together with the expected ability of this hydrophilic polymer to escape to the mononuclear phagocytic system. Besides, these nanocapsules have an oily reservoir, which enables the efficient encapsulation of lipophilic drugs. PASN nanocapsules were obtained by an emulsification-polymer layer deposition process, which involves using a cationic surfactant as a bridge for the interaction of PASN with the lipid core. PASN nanocapsules showed sizes of around 170-200 nm and negative zeta potential values (around -20 mV to -40 mV). The model anticancer drug docetaxel was efficiently encapsulated (around 75%) and retained within the nanocapsule's structure upon dilution in a simulated physiological medium. Moreover, these nanocapsules exhibited the ability to interact with the NCI-H460 human cancer cells and to enhance the cellular toxicity of the anticancer drug. All these features together with their adequate stability profile render these nanocapsules a new attractive platform for anticancer intracellular drug delivery.