DEAE/Catechol-Chitosan Conjugates as Bioactive Polymers: Synthesis, Characterization, and Potential Applications

This work provides the first description of the synthesis and characterization of water-soluble chitosan (Cs) derivatives based on the conjugation of both diethylaminoethyl (DEAE) and catechol groups onto the Cs backbone (Cs-DC) in order to obtain a Cs derivative with antioxidant and antimicrobial properties. The degree of substitution [DS (%)] was 35.46% for DEAE and 2.53% for catechol, determined by spectroscopy. Changes in the molecular packing due to the incorporation of both pendant groups were described by X-ray diffraction and thermogravimetric analysis. For Cs, the crystallinity index was 59.46% and the maximum decomposition rate appeared at 309.3 degrees C, while for Cs-DC, the values corresponded to 16.98% and 236.4 degrees C, respectively. The incorporation of DEAE and catechol groups also increases the solubility of the polymer at pH > 7 without harming the antimicrobial activity displayed by the unmodified polymer. The catecholic derivatives increase the radical scavenging activity in terms of the half-maximum effective concentration (EC50). An EC50 of 1.20 mu g/mL was found for neat hydrocaffeic acid (HCA) solution, while for chitosan-catechol (Cs-Ca) and Cs-DC solutions, concentrations equivalent to free HCA of 0.33 and 0.41 mu g/mL were required, respectively. Cell culture results show that all Cs derivatives have low cytotoxicity, and Cs-DC showed the ability to reduce the activity of reactive oxygen species by 40% at concentrations as low as 4 mu g/mL. Polymeric nanoparticles of Cs derivatives with a hydrodynamic diameter (Dh) of around 200 nm, unimodal size distributions, and a negative zeta-potential were obtained by ionotropic gelation and coated with hyaluronic acid in aqueous suspension, providing the multifunctional nanoparticles with higher stability and a narrower size distribution.

Automated summary

This study synthesized water-soluble chitosan derivatives (Cs-DC) by conjugating diethylaminoethyl (DEAE) and catechol groups onto the chitosan backbone to obtain a Cs derivative with antioxidant and antimicrobial properties. The incorporation of DEAE and catechol groups increased the solubility of the polymer without affecting its antimicrobial activity. Moreover, the catecholic derivatives showed increased radical scavenging activity. Cs-DC also exhibited low cytotoxicity and the ability to reduce reactive oxygen species activity. Polymeric nanoparticles of Cs derivatives were obtained by ionotropic gelation and coated with hyaluronic acid, providing higher stability and a narrower size distribution.