Cu- Polysaccharide complexes: Physico-chemical characterization & antimicrobial activity

The cells of the red microalga Porphyridium sp. are encapsulated within a sulfated polysaccharide, the external part of which dissolves and accumulates in the medium. The polysaccharide is negatively charged due to the presence of glucuronic acid and half-ester sulfate groups and acts as an ion exchanger. Thus, it can be used as a platform for metal complexation (e.g. Cu, Zn, Ag). Metals incorporation to the polysaccharide can yield novel materials with the synergistic activity of the polysaccharide and the metals. In the current study, the use of Porphyridium sp. sulfated polysaccharide as a platform for copper incorporation Cu-PS were examined. The research goals are to study the Cu-PS complex physical characteristics and its antimicrobial activity. For that, we developed the process of complexation (CuSO₄ (Cu⁺²-PS) & Cu₂O (Cu⁺¹-PS)) and the characterization of the Cu-PS complex using chemical & rheological methods. In parallel, the antimicrobial (antibacterial and antifungal) activity of Cu-PS complexes and its mode of action will be studied. From the results obtained it seems that the highest viscosity and conductivity are of the Cu⁺¹-PS complex as compared with Cu⁺²-PS complexes and the PS alone. In addition, the Cu⁺¹ ions bind to the polysaccharide by covalent bonds as indicated by FTIR and the surface morphologies of the complexes exhibit needle-like structures as was showed AFM. The highest antimicrobial activity also sheens in the Cu⁺¹-PS as was tested by pathogens models such as Escherichia coli (Gram (-)), Bacillus subtilis (Gram (+)) & Candida albicans (fungal). We believe that the activities of the complex results from the combination of the PS and the Cu resulting probably a novel biomaterial with superior qualities mainly for the pharmaceutics industry.