Temperature/pH Smart Nanofibers with Excellent Biocompatibility and Their Dual Interactions Stimulus-Responsive Mechanism

Novel nanosized biomass-based pH- and temperature-responsive cellulose nanofibers (TOCNF-HPEI-IBAm) were designed and prepared by grafting hyperbranched polyethylenimine (HPEI) modified with isobutyramide (IBAm) groups (HPEI-IBAm) onto carboxylated cellulose nanofibers (TOCNFs). The as-prepared TOCNF-HPEI-IBAm possessed excellent biocompatibility and pH- and temperature-responsive properties. TOCNF-HPEI-IBAm showed a rapid wettability conversion from hydrophilic (WCA = 41.1°, WCA = 70.7°) to hydrophobic (WCA = 147.3°, WCA = 142.2°) in response to changes in pH and temperature from acidic conditions to alkaline conditions and from lower to higher temperatures. In addition, it possesses strong antibacterial activity against Escherichia coli and Listeria (Eb ≥ 97%). The amount of DOX loaded in TOCNF-HPEI-IBAm was 642.52 mg/g, and the maximum amount of DOX released was 39.30% at pH = 3.0 within 9 h. Furthermore, the dual interactions stimulus-responsive mechanism was revealed to be attributed to the expansion and collapse of the molecular chains of TOCNF-HPEI-IBAm in response to temperature and pH through mutual promotion and inhibition.