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

Abstract

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 °C, while for Cs−DC, the values corresponded to 16.98% and 236.4 °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 (EC 50 ). An EC 50 of 1.20 μg/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 μg/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 μg/mL. Polymeric nanoparticles of Cs derivatives with a hydrodynamic diameter (D h ) of around 200 nm, unimodal size distributions, and a negative ζ-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.

Self-Cross-Linkable Chitosan–Alginate Complexes Inspired by Mussel Glue Chemistry

“…This cross-linking reaction mediated by catechol oxidation and subsequent catechol–amine interactions can potentially be triggered through various approaches including pH regulation, the addition of oxidants, and UV light. , Apart from this cross-linking effect, the presence of catechol groups can yield additional advantages dependent on the intended applications. Examples include the selective separation of impurities when employed as a membrane or the enhancement of mucoadhesive properties of a drug carrier through catechol–mucus interactions. , …”

Chitosan and Its Derivatives: Preparation and Antibacterial Properties

“…Indeed, if chitosan is treated with an alkylating reagent, for example, diethylaminoethyl chloride, then under conventional conditions, the substitution occurs at both nucleophilic centers, with a significant predominance of N -substitution [ 110 , 111 , 112 ]. There are certain strategies for controlling this synthetic process that allow for the preparation of chitosan derivatives selectively at the desired reaction center with the desired degree of substitution.…”

“…These well-established methodologies within chitosan chemistry are succinctly illustrated in Scheme 3. Indeed, if chitosan is treated with an alkylating reagent, for example, diethylaminoethyl chloride, then under conventional conditions, the substitution occurs at both nucleophilic centers, with a significant predominance of N-substitution [110][111][112]. There are certain strategies for controlling this synthetic process that allow for the preparation of Examples of chemical structures of substituents of antibacterial chitosan Nderivatives [92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109].…”