Effects of reaction pH on self-crosslinked chitosan-carrageenan polyelectrolyte complex gels and sponges
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Al-Zebari, N., Best, S., & Cameron, R. (2019). Effects of reaction pH on self-crosslinked chitosan-carrageenan polyelectrolyte complex gels and sponges. JPhys Materials, 2 (1) https://doi.org/10.1088/2515-7639/aae9ab
Macromolecular biomaterials often require covalent crosslinking to achieve adequate stability for their given application. However, the use of auxiliary chemicals may be associated with long-term toxicity in the body. Oppositely-charged polyelectrolytes (PEs) have the advantage that they can self-crosslink electrostatically and those derived from marine organisms such as chitosan (CS) and carrageenan (CRG) are inexpensive non-toxic alternatives to glycosaminoglycans present in the extracellular matrix of human tissues. The aim of this study was to explore the properties of crosslinker-free PEC gels and freeze-dried PEC sponges based on CS and CRG precursors. We offer new insights into the optimisation of conditions and mechanisms involved in the process and offer a systematic study of property changes across a full range of pH values. Zeta potential measurements indicated that the PECs produced at pH 2-6 had a high strength of electrostatic interaction with the highest being at pH 4-5. This resulted in strong intra-crosslinking in the PEC gels which led to the formation of higher yield, viscosity, fibre content and lower moisture content. The weaker interaction between CS and CRG at pH 7-12 resulted in higher levels of CS incorporated into the complex and the formation of more inter-crosslinking through entanglements and secondary interactions between PEC units. This resulted in the production of stable PEC sponge materials compared with the PEC materials produced at pH 6 and below. From the range of samples tested, the PECs produced at pH 7.4 appeared to show the optimum combination of yield, stability and homogeneity.
The authors would like to thank the Cambridge Home Scholarship Scheme (CHSS) for providing financial support to NAZ and the ERC Advanced Grant 320598 3D-E for funding this project.
European Research Council (320598)
External DOI: https://doi.org/10.1088/2515-7639/aae9ab
This record's URL: https://www.repository.cam.ac.uk/handle/1810/288037
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/