Design of a Redox-Responsive Dextran-Based Layer to Enhance the Colloidal Stability of CeO₂ Nanoparticles for Controlled Cargo Delivery Applications

The fabrication of thin macromolecular layers containing disulfide bonds, which can undergo reversible cleavage and reformation under redox conditions, holds great promise for advanced drug delivery applications. These layers enable rapid and reversible responses to specific biological stimuli. In this study, we introduce an approach utilizing a water-soluble, thiol-containing dextran as a polythiol grafted onto a thiol-functionalized flat substrate. Subsequently, a thiolated, dye-labeled dextran was immobilized onto the substrate via disulfide bonds under mild oxidative conditions, as verified by fluorescence imaging and quartz crystal microbalance analysis. The reversible release and reattachment of the dye in response to redox stimulation were successfully demonstrated. Furthermore, the designed redox-responsive dextran layer was applied to enhance the colloidal stability of cerium oxide (CeO2) nanoparticles, which inherently exhibit poor stability in aqueous media without a coating. This modification provided precise control over the particles stability in aqueous environments. Biocompatibility assessments using HEK293 cells confirmed that dextran-modified CeO2 nanoparticles maintained cell viability. These findings highlight the potential of redox-responsive coatings for tailoring colloidal stability and advancing nanotherapeutic applications, particularly in redox-sensitive microenvironments.