Thermosensitive Sprayable Lidocaine-Allantoin Hydrogel: Optimization and In Vitro Evaluation for Wound Healing

Background/Objectives: Wound healing requires simultaneous pain control, inflammation management, infection prevention, and tissue regeneration. This study aimed to develop and evaluate in vitro a non-contact thermosensitive spray hydrogel combining lidocaine for rapid analgesia and allantoin for tissue repair. Methods: The effects of chitosan and Poloxamer 407 on viscosity, spray diameter, and bioadhesion ability of hydrogels were optimized using response surface methodology. Lead formulations (S1 and S2) were selected via a desirability function within the software. The pH, gelation temperature (T_G), rheological behavior, sprayability, bioadhesion, and lidocaine release using the dialysis bag method were assessed. The in vitro cytotoxicity, anti-inflammatory activity (TNF-α), and cell migration (scratch assay) of the formulations were investigated. Results: The viscosity values (42.7-58.7 mPa·s) indicated suitability for spraying at room temperature. T_G was 28.7 ± 0.6 °C (S1) and 29.3 ± 0.3 °C (S2), enabling rapid sol-gel transition at skin temperature. The lidocaine release reached 95-100% within 120 min. S2 exhibited lower viscosity and wider spray diameter, improving applicability on larger wound areas. In vitro cytotoxicity, scratch assay, and inflammatory marker analyses demonstrated that the optimized sprayable hydrogels exhibited a biocompatible and cell-healing profile. Conclusions: The developed thermosensitive spray hydrogel enables the combined delivery of lidocaine and allantoin, rapid gelation at body temperature, and touch-free administration. Its suitable viscosity and sprayability, and fast lidocaine release profile indicate high patient compliance and a significant advantage over conventional cream/ointment formulations, particularly regarding painless application, reduced contamination risk, enhanced therapeutic potential, and confirmed in vitro biocompatibility with supportive effects on keratinocyte behavior.