The rapid emergence of multidrug-resistant (MDR) bacteria presents a significant global health challenge, necessitating the development of alternative antimicrobial strategies. In this context, antimicrobial polymers bearing cationic moieties, such as quaternary ammonium salts, have emerged as promising alternatives to conventional antibiotics due to their ability to disrupt bacterial cell membranes, leading to cell lysis and bacterial death.1-2 Recently we reported novel bio-based antimicrobial polymers bearing quaternary ammonium salts, derived from sustainable feedstocks such as maleic anhydride and furfurylamine.3 The synthesis involved a tandem Diels–Alder and lactamization reaction to generate functional tricyclic oxanorbornene lactam derivatives, followed by ring opening metathesis polymerization (ROMP) to produce well-defined polymers with controlled molar masses and low dispersity.4 The resulting quaternized bio-based polymers exhibited potent broad-spectrum antimicrobial activity against clinically isolated MDR bacterial strains, with significantly lower minimum inhibitory concentrations (MICs) compared to several conventional antibiotics, while demonstrating low hemolytic activity.3
Furthermore, we developed a photocrosslinkable casein-based hydrogel incorporating a cationic polymer for advanced wound care applications. UV-induced bi-tyrosine crosslinking facilitated rapid in situ gelation at the wound site, while the cationic polymer enhanced both mechanical strength and antibacterial efficacy. In vitro and in vivo studies confirmed excellent biocompatibility, biodegradability, and anti-inflammatory properties, leading to accelerated wound healing.
Overall, these bio-derived antimicrobial polymers offer sustainable and effective solutions for infection control and wound management.

In the field of plant tissue engineering, there is a pressing need for new materials to ensure increased cell viability and cell proliferation. For example, protoplasts - osmotically fragile plant cells without a cell wall - require scaffolds with specific material properties that can promote cell wall regeneration and can guide cell differentiation [1]. Three key features required for such scaffolds are: high stiffness, viscoelastoplasticity and cytocompatibility. Next to this, the encapsulation of protoplasts in scaffolds requires a gentle fabrication procedure since various factors, such as mechanical agitation, can influence the protoplast viability. Due to their tunable mechanical properties and inherent biocompatibility, hydrogels have been extensively investigated as possible scaffolds for mammalian cell culture, however for plant cell culture their use is still at its infancy [2]. In the frame of plant tissue engineering, double network hydrogels in which two interpenetrated polymer networks synergistically enhance the stiffness and toughness of the hydrogel show great potential [3]. In this project, the encapsulation of protoplasts in double network hydrogels with tunable mechanical properties is investigated by systematically varying the polymer concentration, the chemical composition and the crosslinking density. Furthermore, the compatibility of the hydrogels and their liquid precursors with protoplasts are studied. In this way, scaffolds that closely mimic the native environment of plant cells are developed in order to increase protoplast cell viability and regeneration.

For biodegradable and sustainable polymers to serve as viable alternatives, they must meet the nanomaterial and biomedical science requirements. This necessitates achieving the same level of topological complexity—such as graft, block, and star structures—as their synthetic counterparts. Advanced bioorthogonal and efficient techniques, like click chemistry reactions, provide valuable tools for constructing diverse polymeric topologies from natural biodegradable polymers.1 Polysaccharides (PS) are essential materials in sustainable chemistry, with wide-ranging applications in materials science, biomedicine, and cosmetics. Polysaccharide-synthetic hybrids, modified at hydroxyl (OH), carboxyl (CO₂H), or amine (NH₂) groups within their saccharide repeating units, have existed since the early days of polymer science (e.g., cellulose acetate).2 However, the challenge of modifying the polysaccharide reducing end has significantly limited the development of polysaccharide diblock, graft, and star copolymers, where PS is linked to a core polymer via its reducing end.3 We demonstrate how Oxime click chemistry, Thiol-Maleimide Michael addition, and Strain-Promoted [3 + 2] Azide−Alkyne Cycloaddition—or combinations thereof—enable the synthesis of graft, star, and diblock copolymers from polysaccharides (Figure 1).4,5 Our examples include PS graft copolymers that mimic natural biomacromolecules and “chimeric” structures, where two polysaccharides (e.g., heparin and dextran) are linked via their modified reducing ends. These copolymers have potential applications in bioactive molecule encapsulation, hydrogel formation for regenerative medicine, and as hybrid systems to combine or modulate the bioactivity of different polysaccharides.

Extrusion bioprinting uses cell-laden hydrogels based on biocompatible polymers to fabricate 3D biomaterial constructs (Fig.1-A).¹ Hyaluronic acid (HA) is a good candidate for bioprinting, as a biocompatible and bioactive polysaccharide that is ubiquitous in the human body.² To tailor the rheology of HA hydrogels for printing, one strategy is to use dynamic covalent bonds³. These bonds are strong, yet they continuously break and reform, making the hydrogel self-healable and injectable (Fig.1-B). Recently, a HA dynamic covalent hydrogel (HA-DCH) based on boronate-ester bonds between phenylboronic acid (PBA) and fructose (FRU) has been developed in our group (Fig.1-C).³ The present work aims at studying the potential of this hydrogel for bioprinting. We focus on how chemistry and physico-chemical characteristics of the gel affect its rheology, and, in turn, its printability and cell compatibility.
To this aim, HA-DCHs were prepared at varying degrees of substitution (DS), different concentrations, and with non-substituted (free) HA. Results showed that higher DS and/or concentration increased hydrogel stiffness and yield stress, requiring higher extrusion pressure which could lower cell viability. Conversely, when free HA was present, the hydrogel could be printed at lower pressure (Fig.1-D). The printability of these gels was further predicted by evaluating their flow profile in capillary tubes (thanks to fluorescent markers). Finally, cell viability studies have proven biocompatibility of these hydrogels and HA-methacrylate was included in selected formulations to enable photo-crosslinking post-extrusion, yielding improved long-term stability. Overall, this resulted in printable HA-DCHs, whose ability to protect cells during extrusion is under study.

Alginates are promising sustainable alternatives to petro-plastics; they have varying properties and are found naturally in seaweed. The property variation is due to the ratios and patterns of their constituent monomers (α-L-guluronate (G) and β-D-mannuronate (M)), and the cations present; sodium alginate (SA) is used as a thickener, calcium alginate (CA) forms a hydrogel. The mechanisms which translate these variances into different properties remain uncertain. This project aims to further this knowledge through both experimental and computational methods.

Gel strength was characterised using compression (see figure): higher load values represent higher gel strengths. The factors investigated were SA type (encompassing M:G ratio and pattern, and molecular weight), SA, calcium, and sodium concentrations, and pH. Increasing G content, chain length, and SA concentration significantly increased gel strength. Another significant contributor was sodium concentration; increased sodium concentration reduced gel strength. Calcium concentration is vital in gel formation but did not affect gel strength as significantly as sodium concentration.

Computational work (molecular dynamics simulations) supported the result that high G content creates a higher strength gel in CA systems by showing that G chains cluster more than M and the calcium ions are more regularly in close contact with G. The effects of sodium ions were also seen, in part, through less alginate clustering and weaker and fewer chain-ion interactions than in calcium systems. Future work will focus on the interplay of sodium and calcium ions with both ions present to better represent the experimental gels and investigate sodium ion’s gel weakening effects.