Synthesis of Thermoresponsive PNIPAM-Grafted Cellulose Sulfates for Bioactive Multilayers via Layer-by-Layer Technique

The robust thermoresponsive and bioactive surfaces for tissue engineering by combining poly-N-isopropylacrylamide (PNIPAM) and cellulose sulfate (CS) remain highly in demand but not yet realized. Herein, PNIPAM-grafted cellulose sulfates (PCSs) with diverse degrees of substitution ascribed to sulfate groups (DSS) are synthesized for the first time. Higher sulfated PCS2 generally forms larger aggregates than lower sulfated PCS1 at their cloud point temperatures (TCP) of around 33 °C, whereas PCS1 leads to larger aggregates at body temperature (37 °C). Via the layer-by-layer (LbL) technique, biocompatible polyelectrolyte multilayers (PEMs) composed of PCSs as polyanions in combination with poly-l-lysine (PLL) or quaternized chitosan (QCHI) as polycations were fabricated. The resulting surfaces contained a more intermingled structure of polyanions with both polycations, while higher sulfated cellulose derivatives (CS2 and PCS2) displayed greater stability. Studies on toxicity and biocompatibility of PEM using 3T3 mouse fibroblasts showed a lower cytotoxicity of PEM with PCS2 and CS2 than PCS1 and CS1. Furthermore, the PEM using PCS2 particularly in combination with QCHI demonstrated excellent biocompatibility that is promising for new bioactive, thermoresponsive coatings on biomaterials and substrata for culturing adhesion-dependent cells.