Fabrication and characterization of dexamethasone-releasing polylactic acid nanospheres for treatment of hearing loss

Worldwide, hearing loss affects about 1.57 billion people and is the third leading cause of disease in adults in 2019. Chronic inflammation in the inner ear is the main reason for hearing loss as it causes oxidative stress, activation of apoptosis, and dysfunction of the cell mitochondria. In general, corticosteroid drugs such as dexamethasone (DEX) reduce the number of inflammatory cells and prevent the spread of inflammation in hair cells, but for the treatment of hearing loss, there are limited treatment options available to doctors due to difficult access to the inner ear and its extreme vulnerability. In recent years, sustained drug delivery methods have emerged as a promising approach for the treatment of inner ear diseases. Delivering medicine to the ear based on particles results in a stable release of the medicine in the ear and reduces the side effects caused by high therapeutic doses of the medicine and increases the time the medicine stays in the middle ear. The goal of the present study was to prepare a nanoparticulate-based drug delivery system for the delivery of an anti-inflammatory drug into the inner ear. Accordingly, for the first time, dexamethasone loaded PLA nanospheres were fabricated by W/O/W double emulsion technique. Then, the prepared nanospheres were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and release studies. The SEM images showed the spherical shape of the prepared PLA nanoparticles. Also, it was observed that by reducing the PLA concentration, the mean size of the obtained nanospheres was decreased, which can be attributed to the change in the viscosity of the solution. The FTIR analysis revealed that dexamethasone has been successfully loaded into the nanoparticles and had no chemical interaction with the PLA polymer. Also, due to the observation of pure PLA DEX peaks and the absence of unrelated peaks, it shows that there is no other foreign substance in the system. This system showed a high encapsulation percentage of dexamethasone in nanoparticles, and according to the release studies on this system, in the first days of the experiment, it shows a good release profile, and as a result, we see the controlled release of dexamethasone from PLA particles. In conclusion, the findings of this study showed a promising potential of the prepared drug delivery system for enhancing the delivery of DEX, reducing the absorption of inflammatory factors by hair cells, controlling the inflammation of the inner ear and finally treatment of hearing loss.