Development of a microporous annealed particle hydrogel for long-term vocal fold augmentation

Abstract

Objectives/hypothesis: The purpose of this study was to develop and provide evidence of a novel permanent injectable biomaterial for vocal fold augmentation with the potential to treat glottic incompetence by evaluating its performance in two animal models.

Study design: Animal model.

Methods: Microporous annealed particle (MAP) hydrogel was fabricated using a water-in-oil emulsion method and synthetically tuned to match the stiffness modulus of native vocalis muscle. Thirty-two New Zealand White rabbits were administered unilateral injections of MAP (n = 16), saline (n = 8), and the clinical standard hyaluronic acid (Restylane-L) (n = 8), and evaluated at day 0, and 6-week, 4-month, and 6-month endpoints. Induced vocal fold vibration was recorded with a high-speed camera prior to euthanization, with glottic closure and mucosal wave characteristics assessed both quantitatively and qualitatively by an experienced voice clinician. Histologic analysis was performed to assess scaffold permanence, immunogenicity, and vascularization within the scaffold.

Results: Histologic analysis confirmed the MAP gel treatment group maintained its volume without migration for 6 months postimplantation. Immune staining showed minimal to nonexistent immunogenicity over the course of the implant lifetime. Extensive tissue integration and vascularization was observed histologically within the MAP gel group by immunofluorescence staining. Mucosal wave was not impaired by any of the injected materials, including the MAP gel augmentation.

Conclusions: MAP gel is a nonresorbable biostimulatory injectable implant that provides superior tissue integration, stiffness matching, and permanence compared to current injectable implants, with retained biomechanical function, suggesting its potential as a new therapeutic for glottic incompetence.

Level of evidence: NA Laryngoscope, 130:2432-2441, 2020.

Keywords: Biomaterial; glottic incompetence; injectable implant; vocal fold augmentation; vocal fold paralysis.