Preliminary Evaluation of an Injectable Therapeutic for Cisplatin Ototoxicity Using Neuronal SH-SY5Y Cells

Background/Objectives: Though ototoxic, cisplatin is a mainstay of chemotherapy for a variety of cancers. One suggested mechanism of cisplatin ototoxicity involves damage to the spiral ganglion afferent neurons in the inner ear. There is a need for a high-throughput model to screen medications for efficacy against cisplatin and to develop a local therapeutic to mitigate cisplatin’s debilitating side effects. Microparticles encapsulating a therapeutic medication are an injectable and tunable method of sustained drug delivery, and thus a promising treatment. Methods: SH-SY5y human neuroblastoma cells were used as a cell line model for the spiral ganglion neurons. The cells were dosed with cisplatin and four potential therapeutics (melatonin, metformin, cyclosporine, and N-acetylcysteine), with cell viability measured by CCK-8 assay. The most promising therapeutic, N-acetylcysteine (NAC), was then encapsulated into multiple poly(lactic-co-glycolic acid) (PLGA) microparticle subtypes of varied lactide–glycolide (L:G) ratios and NAC amounts. The elution profile of each microparticle subtype was determined over two months. Results: Of the therapeutics screened, only cells dosed with 1 or 10 mM NAC prior to cisplatin injury demonstrated an improvement in cell viability (73.8%, p < 1 × 10⁻⁸) when compared to cells dosed with cisplatin alone. The 75:25 L:G microparticles demonstrated an increase in the amount of NAC released compared to the 50:50 L:G microparticles. Conclusions: NAC is a potential therapeutic agent for cisplatin toxicity when tested in a neuronal cell line model. NAC was encapsulated into PLGA microparticles and eluted detectable concentrations of NAC for 6 days, which is a first step towards otoprotection for the weeks long duration of chemotherapy treatment. This work describes a method of screening potential therapeutics and a strategy to develop local drug eluting treatments to protect against cisplatin ototoxicity.