Vocal Fold Augmentation with Beta Glucan Hydrogel Cross-Linked by gamma Irradiation for Enhanced Duration of Effect: In Vivo Animal Study

Abstract

This study explored a novel strategy to restore the vocal gap by using cross-linked beta-glucan hydrogel by gamma-irradiation. An aqueous solution of 5wt%beta-glucan was prepared and cross-linked using Co-60 gamma irradiation. Ten nude mice were injected with 0.8 mL of irradiated beta-glucan on the left back and the same volume of nonirradiated beta-glucan on the right back for comparison. The mice were sacrificed at 1 and 2 weeks after injection and histological evaluations were performed. Irradiated beta-glucan demonstrated a significantly larger volume than nonirradiated beta-glucan in the back of nude mice with less inflammatory reaction. After unilateral recurrent laryngeal nerve section in New Zealand White rabbits, irradiated and nonirradiated beta-glucan were injected into paralyzed vocal folds. Irradiated beta-glucan remained at the paralyzed vocal fold without definite inflammatory signs on endoscopy. Highspeed recordings of vocal fold vibration showed decreased vocal gap in irradiated group compared to nonirradiated group. Histologically, the laryngeal epithelium and lamina propria remained intact, without inflammatory cell infiltration. Our newly developed injection material, irradiated beta-glucan, showed excellent biocompatibility and remained longer than nonirradiated beta-glucan in vivo, suggesting irradiated hydrogels as a new therapeutic approach that may be useful for the long-term treatment of vocal fold palsy.