Synthesis and application of phenol-grafted rhamnan sulfate for 3D bioprinting

Rhamnan sulfate (RS) is a sulfated polysaccharide extracted from the cell wall of the green alga Monostroma nitidum. Owing to its negative charge, RS interacts with a variety of proteins, enabling various biological activities, such as antiviral, anticoagulant, and antitumor effects. However, RS does not form a stable hydrogel under physiological conditions, which is required for its beneficial biological activities in tissue engineering. To address this limitation, we developed phenol-grafted rhamnan sulfate (RS-Ph), which allows hydrogelation via horseradish peroxidase (HRP)-mediated cross-linking reactions and can be used for 3D bioprinting. Specifically, we synthesized RS-Ph with three different -Ph content: RS-LPh (16.4 mmol/g), RS-MPh (21.3 mmol/g), and RS-HPh (31.7 mmol/g). Surface plasmon resonance measurements revealed that RS-Ph exhibited a maximum binding capacity of more than 8.3 times higher than that of sodium alginate as a negative control. Additionally, a 10% w/v RS-HPh solution formed a hydrogel within 8.2 ± 0.7 s in the presence of 10 U/mL HRP. Furthermore, high-fidelity 3D bioprinting was achieved using an RS-Ph/cellulose nanofiber composite bioink. Our results demonstrate the potential use of bioactive RS-Ph hydrogels in a wide range of tissue engineering fields, including not only bioprinting but also drug delivery systems and wound dressings.