Influence of Material Grade and Solvent Environment on Thermoresponsive Poloxamer-Based Injectable Hydrogels

Poloxamer 407-based hydrogels are widely used in injectable drug delivery because of their thermoreversible gelation, biocompatibility, and tunable rheological properties. Although commercially available under different trade names, including Kolliphor 407 and Pluronic F127, nominally identical poloxamers may exhibit formulation-dependent differences arising from manufacturing-related variability. Understanding these differences is important for pharmaceutical formulation development. This study compared poloxamer 407 hydrogels prepared from two commercial sources, Kolliphor 407 and Pluronic F127, at concentrations of 10–30% (w/w) in purified water and phosphate-buffered saline (PBS). Formulations were evaluated for gelation temperature, gelation time, and the effect of mixing on thermoresponsive behavior. Mechanical properties were assessed by spreadability and adhesion testing, while pH, in vitro hydrogel dissolution, and cytotoxicity assay using NIH/3T3 fibroblast cells were performed to evaluate material suitability as injectable drug delivery systems. The two commercial grades exhibited distinct formulation characteristics. Kolliphor 407 consistently showed lower gelation temperatures than Pluronic F127 at equivalent concentrations. PBS improved the mechanical properties of Kolliphor 407 formulations, whereas Pluronic F127 was less affected by solvent composition. Cytotoxicity studies demonstrated the superior biocompatibility of PBS-based hydrogels, with 18% formulations showing no significant cytotoxicity compared with controls. Among the tested systems, the 18% Kolliphor 407 hydrogel prepared in PBS demonstrated the most favorable combination of gelation near physiological temperature, appropriate mechanical properties, and excellent biocompatibility. These findings demonstrate that material grade and solvent environment significantly influence the performance of poloxamer 407 formulations despite their nominal chemical equivalence, emphasizing the importance of material selection during the design for potential injectable application.