In Vivo Assessment of Acute Dermal Toxicity and Reparative Efficacy of Phytoconstituent-Loaded Hydrogel Scaffolds Incorporating Calendula officinalis in Full-Thickness Wound

Abstract

Chronic full-thickness wounds remain difficult to manage due to infection risk, prolonged inflammation, and impaired tissue regeneration. We developed phytoconstituent-loaded hydrogel scaffolds incorporating Calendula officinalis (CO) and assessed their acute dermal safety and reparative efficacy. CO flowers (authenticated at FRI, Dehradun) were Soxhlet-extracted (70% ethanol) and embedded into PVA/alginate/chitosan hydrogels prepared by a freeze–thaw method. Three formulations (F1–F3) underwent in-vitro screening; the optimized batch (F2) exhibited skin-compatible pH (6.12 ± 0.08), workable viscosity (18,450 ± 210 cP), high swelling (482.6 ± 5.4% at 8 h), sustained moisture retention (81.4 ± 1.9% at 24 h), and controlled release (85.6 ± 1.7% at 24 h; Higuchi R² = 0.984). Acute dermal toxicity was evaluated in Wistar rats per OECD-402 (limit test, 2000 mg/kg, 24-h semi-occluded exposure): no mortality or systemic toxicity occurred; Draize erythema/edema scores were 0.0 throughout; body/organ weights and gross necropsy were unremarkable; histopathology of skin and major organs showed no treatment-related lesions. Reparative efficacy was then tested in an excision model (500 mm², ~1.5 mm depth; n = 6/group): compared with control and blank hydrogel, CO-hydrogel significantly accelerated wound closure (Day-21 contraction: 94.8 ± 1.3% for high-dose vs 78.2 ± 2.1% control, p < 0.05), shortened epithelialization time (17.2 ± 0.4 vs 23.8 ± 0.8 days), and improved scar quality (score 0 vs 3). These data indicate that CO-loaded hydrogels are dermally safe and enhance full-thickness wound healing via a moist, bioactive, diffusion-controlled delivery platform, supporting their translational potential for advanced topical care.