Chitosan: A versatile polyelectrolyte

Surface charge and wettability are prominent physical factors that affect a plethora of events, including protein adsorption, cell adhesion, and metal ions removal from waste.  Depending on the pH, many polysaccharides behave as polyelectrolytes. Chitosan (CHI) behaves as a polycation at pH lower than 6, making it interesting for layer-by-layer systems, scaffolds for cells, and as adsorbents, as follows.

A system for the control release of protein (BSA or lysozyme) was built by the alternated deposition of chitosan (positively charged) and heparin (negatively charged). The choice of positioning the same amount of protein within the bottom five layers or in the top five layers can result in clearly different release profiles, allowing tuning the protein delivery [1].

Physical properties of CHI scaffolds could be modulated by the incorporation of polydimethylsiloxane (PDMS) at 1% or 10% vol and vanillin (crosslinker). The addition of PDMS resulted in films with reduced swelling degree and increased gel content, contributing to the increased stiffness (elastic modulus increased from 60 kPa to 200 kPa). The presence of vanillin and PDMS increased the elastic modulus values from 200 kPa to 600 kPa. Cell viability assays indicated that CHI-PDMS based scaffolds can be applied for the attachment of myoblast cell line C2C12, whereas the presence of vanillin led to cytotoxicity [2].

Cryogels composed of chitosan (CHI) and sugarcane bagasse microparticles (SB) offered an efficient matrix for the treatment of a multi-metal waste sourced from laboratory settings, containing the mixture of Cr³⁺, Mn²⁺, Co²⁺, Fe³⁺, Ni²⁺, Cu²⁺, Zn²⁺, Sr²⁺, Hg²⁺, and Pb²⁺, at pH 1.0. The presence of SB increased the mechanical stability, opening the possibility to apply the adsorbents for large volume treatments in columns. The driving force for the adsorption between the metal ions and the positively charged surface of CHI was electrostatic interaction because most ions were present as coordination complexes with chloride ions [3].

[1] Delechiave, G. et al. Mater. Adv. 1 (2020) 2043-2056. DOI: 10.1039/d0ma00432d

[2] da Silva, R. L. C. G. et al. Int. J. Biol. Macromol. 286 (2025) 138445. DOI: 10.1016/j.ijbiomac.2024.138445

 [3] Braga, V. H.A. et al. J. Environ. Chem. Eng. 12 (2024) 113306. DOI:10.1016/j.jece.2024.113306

Acknowledgments:

FAPESP Grants 2018/13492-2 and 2020/05632-9, CNPq 30401/2021