Sustained delivery of triamcinolone acetonide from a thermosensitive microemulsion gel system for the treatment of sensorineural hearing loss

Abstract

Intratympanic administration for the delivery of steroids has been extensively studied but limited because of low permeability of the drug through the row window membrane. Here, to effectively deliver poorly soluble triamcinolone acetonide (TA), microemulsions (ME) were prepared from Capmul MCM (oil), Cremophor RH40 (surfactant), and tetraglycol (cosurfactant) based on solubility studies, emulsifying ability test, and pseudoternary phase diagrams. Microemulsion gel (MEG) was prepared by mixing TA-ME with a poloxamer hydrogel base. The physicochemical properties of ME and MEG formulations were characterized, and the toxicity and oto-protective effectiveness were evaluated in vitro and in vivo. The ME-3 formulation showed a small droplet size (16.5 ± 0.2 nm), narrow PDI (0.067 ± 0.041), and enhanced TA solubility (2619.7 ± 57.6 μg/g). The optimized MEG demonstrated temperature-dependent gelation with a gelation time of 208 ± 10 sec at 37 °C. Slow degradation of the gel matrix sustained release of TA from MEG compared to the ME formulation. Both TA-ME and TA-MEG were found to be nontoxic to NIH3T3 cells at the test concentrations (0 to 5 µg/mL), and biocompatible after intratympanic administration to mice. The incorporation of ME into thermosensitive hydrogels prolonged retention of TA at the site of administration until 6 days. As a consequence, the enhanced drug absorption into the cochlea in TA-MEG group (approximately 2 times higher than other groups) protected hair cells, spiral ganglion neurons, and stria vascular cells from cisplatin-induced damage. Therefore, this injectable TA-loaded MEG is an effective and safe vehicle for the sustained delivery of triamcinolone acetonide into the inner ear.

Graphical Abstract

Keywords:

• Intratympanic delivery
• thermosensitive microemulsion gel
• triamcinolone acetonide

Author contributions

Thu Nhan Nguyen: Conceptualization, Methodology, Formal Analysis, Investigation, Writing-Original Draft, Writing – Review & Editing. So-Yeol Yoo: Methodology, Formal Analysis, Investigation. Warisraporn Tangchang: Methodology, Formal Analysis, Investigation. Jae-Young Lee: Formal Analysis, Investigation, Data Curation, Visualization. Hwa-Young Son: Formal Analysis, Investigation, Data Curation, Writing-Original Draft, Visualization. Jeong-Sook Park: Conceptualization, Writing – Review & Editing, Supervision, Project administration, Funding acquisition.

Disclosure statement

No potential conflict of interest was reported by the authors.

Date availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) [NRF-2021R1A2C1011176].