Exopolysaccharides (EPSs) are emerging as sustainable polymers for biomedical hydrogels. Here, we report hydrogels from sulfated EPSs produced by Porphyridium cruentum and ionically crosslinked with Ca2+, Ce3+, or Cu2+ to generate tunable networks with bioactive potential. Rheological analysis showed viscoelastic behavior was primarily governed by cation nature and accessible binding site density, with diminishing gains above 2.5 wt% EPS and limited benefit beyond 10 wt% crosslinker. Ce3+ produced the most solid-like gel, Ca2+ yielded more thixotropic networks, and Cu2+ promoted rapid, heterogeneous crosslinking consistent with fast surface complexation. These network signatures showed distinct in vitro performances. Cation selection tuned antibacterial activity against Staphylococcus aureus and Escherichia coli, with Cu2+ achieving rapid bactericidal effects and Ce3+ enabling an 8-log reduction after 24 h. The ABTS assay showed that Ca2+- and Ce3+-crosslinked gels had antioxidant potential (≥40 µM Trolox eq.mg−1); however, antioxidant capacity was assay dependent. Conditioned-medium assays showed ≥75% viability at day 3 for Ca2+- and Ce3+-crosslinked gels against human dermal fibroblasts (HDFs), while only Ce3+-crosslinked gels were cytocompatible against human keratinocytes (HaCaTs). Cu2+-crosslinked gels were highly cytotoxic across all tested conditions. Macrophage cytokine readouts (TNF-α and IL-6) indicated formulation-dependent immunobiological response. This work establishes microalgal EPSs as versatile polymers and links crosslinking chemistry to rheological modulation and multifunctional biomedical performance, while direct wound-healing efficacy remains to be demonstrated in future in vivo or wound repair functional models.
Duarte et al. (Thu,) studied this question.