Abstract
There is increasing demand for reconstruction of glottal insufficiency. Several injection materials have been examined for this purpose, but all had limitations, such as poor long-term durability, migration from the injection site, inflammation, granuloma formation, and interference with vocal fold vibration due to viscoelastic mismatch. Here, we developed a novel injection material, consisting of polycaprolactone (PCL) microspheres, which exhibits better viscoelasticity than conventional materials, and Pluronic F127 carrier, which decreases the migration of the injection materials. The material was injected into rabbits with glottal insufficiency and compared with the FDA-approved injection material, calcium hydroxylapatite (CaHA). Endoscopic and histological examinations indicated that PCL/Pluronic F127 remained at the injection site with no inflammatory response or granuloma formation, whereas CaHA leaked out and migrated from the injection site. Therefore, vocal fold augmentation was almost completely retained during the 12-month follow-up period in this study. Moreover, induced phonation and high-speed recording of vocal fold vibration showed decreased vocal fold gap area in the PCL/Pluronic F127 group. Our newly developed injection material, PCL/Pluronic F127, permits efficient augmentation of paralyzed vocal fold without complications, a concept that can be applied clinically, as demonstrated by the successful long-term follow-up.
Highlights
The main functions of the larynx are to protect the lower airways and to produce the voice, which are accomplished by contact and closure of the two vocal folds
PCL microparticles into spherical particles through the isolated particle-melting method. In this method, crushed PCL microparticles isolated in a Pluronic F127 gel matrix are melted by heating above the melting temperature of PCL, and the molten PCL microparticles are spontaneously constrained into spheres by interfacial forces in the gel matrix, to minimize their surface area [24]
F127 gel remained at the injection site (Fig. 3 upper row), whereas some Calcium hydroxylapatite (CaHA) leaked out (Fig. 3 lower row)
Summary
The main functions of the larynx are to protect the lower airways and to produce the voice, which are accomplished by contact and closure of the two vocal folds. [10] Each of these substances has demonstrated limitations such as poor long-term durability, migration from the injection site, inflammation, granuloma formation, and interference with vocal fold vibration due to viscoelastic mismatch [11,12,13]. [15] several studies have reported patients who had complications after CaHA injection, including severe inflammation, migration, granuloma formation, and decreased vocal fold vibration. [18] PCL is nontoxic and tissue-compatible, and can eventually be resorbed by the vital organs without abnormal responses. It exhibits better viscoelasticity or flexibility at room temperature and at 37uC than other conventionally used polymeric biomaterials in clinical practice, such as poly-L-lactide (PLLA) and polyglycolide (PGA). It exhibits better viscoelasticity or flexibility at room temperature and at 37uC than other conventionally used polymeric biomaterials in clinical practice, such as poly-L-lactide (PLLA) and polyglycolide (PGA). [19] This potentially avoids the problem of decreased vibration of the vocal fold when CaHA is injected in the superficial portion
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