Cerium oxide particles: coating with charged polysaccharides for limiting the aggregation state in biological media and potential application for antibiotic delivery†

Bacterial resistance to antibiotics has emerged as a major health issue. Developing new antibacterial systems is crucial. We propose to exploit cerium oxide particles which present interesting physicochemical and biological properties. We demonstrated by zeta potential measurement that according to the pH, cerium oxide particles present either negatively or positively charged surfaces (isoelectric point determined around 8). We then take advantage of this property for modifying the particle surfaces with charged polysaccharides (dextran derivative to limit aggregation in aqueous media). The surface modification of particles has been examined by FT-IR, DRX and TGA measurements. The physicochemical properties of the resulting dispersion have been investigated as the size, dispersity and potential zeta value in physiological media. A fluorescent probe (Nile red) has then been loaded as a model of hydrophobic cargo, and then a hydrophobic antibiotic has been loaded (e.g. ciprofloxacin). Finally, the inhibitory effect on bacterial growth of the resulting antibiotic-loaded particles has been evaluated against antibiotic-resistant bacteria, namely spectinomycin-resistant Escherichia coli. These findings demonstrated the potential of the particles to be employed as an antimicrobial material, more specifically those resistant to antibiotic therapy.