Designing pullulan phosphates with tunable structure-property relationships via a multicomponent reaction system for...

Phosphorylated polysaccharides are emerging as biodegradable, biocompatible and hydrogel-forming materials with growing relevance in biomedical applications, yet controlled phosphorylation of pullulan and the resulting structure-property relationships remain insufficiently explored. Here, pullulan was phosphorylated in a multicomponent organic system containing tributyl phosphate, orthophosphoric acid, phosphorus pentoxide and chloroform, yielding water-soluble and hydrogel-forming derivatives with phosphorus contents from 1.2 to 19.9 wt%. FTIR, ¹H/¹³C/³¹P NMR, GPC, SEM, rheology and TGA/DSC showed that increasing phosphorylation enabled tuning of swelling capacity (1.6-370 g/g) and viscoelastic properties, with storage moduli up to 40 kPa, while shifting the onset of thermal degradation from ∼320 °C (native pullulan) to 180-240 °C and increasing the residual mass at 600 °C to 69%. Enzymatic degradation with pullulanase (pH 6.9, 37 °C) led to complete loss of low-phosphorus soluble derivatives within 3 days, whereas crosslinked hydrogels retained approximately 30% and 10% of their mass after 7 days, depending on network density. All derivatives induced <2% hemolysis and maintained ≥80% fibroblast viability at concentrations up to 2 mg/mL. Collectively, these findings demonstrate that multicomponent phosphorylation affords pullulan derivatives with tunable composition, mechanics, degradation behavior and in vitro biocompatibility, highlighting their potential for drug delivery, wound dressings and soft tissue engineering.