ANTIBACTERIAL CHITOSAN PHYSICAL HYDROGELS
J.G. SILVA1*, E.M. DEL AGUILA1, E.G. AZERO2, V.M.F. PASCHOALIN1 AND
1Universidade Federal do Rio de Janeiro, Instituto de Química
2Universidade Federal do Estado do Rio de Janeiro, Instituto de Biociências
3Universidade Federal do Rio de Janeiro, Instituto de Macromoléculas
Chitosan consists of a biodegradable and biocompatible polymer, obtained by chitin deacetylation, the second most abundant biopolymer in nature. Chitosan hydrogels have attracted great interest mainly as alternative controlled delivery systems, with medical and pharmaceutical applications. Chemically crosslinked hydrogels are irreversible tridimensional networks, in which the aqueous component is sustained by covalent bonds. On the other hand, physically crosslinked hydrogels are stabilized by reversible interactions, such as hydrogen bonds and electrostatic interactions. In this work, physical hydrogels were prepared by ionotropic gelation of purified commercial chitosan (CH, Polymar, Fortaleza, Brazil) and sodium tripolyphosphate (TPP, Sigma-Aldrich, Saint Louis, MO, USA), with and without the addition of zinc oxide (ZnO), a safe inorganic antimicrobial agent. ZnO, prepared from zinc acetate dihydrate (Sigma-Aldrich), was characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), methods that revealed the formation of aggregated and nonaggregated micrometric particles. Hydrogels without ZnO were formed by mixing under stirring CH (at 20 g/L in 1% acetic acid) with TPP at various concentrations (10 to 100 g/L in water). The products were characterized by FTIR, XRD, optical microscopy (OM), and rheological measurements under oscillatory and steady shear conditions. In the FTIR spectra, the shift observed for the amide II band, from 1557 to 1537 cm-1, proved the ionic interaction between the +N-H and P-O– moities. A total loss of crystallinity and a spherical morphology were revealed by XRD and OM analyses. The observed elastic behavior corroborated network formation. To introduce ZnO into CH/TPP microparticles, a two stage process was carried out. The bactericidal activity of the CH/TPP/ZnO microparticles against Escherichia coli was investigated and, at a 4.0 mg/mL concentration, inhibited 100% of the bacteria cells. These new antibacterial materials can be incorporated into polymeric films to preserve shelf life and safety of food products.
Financial Support: FAPERJ, CAPES and CNPq; Area: Food Science
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