Nanocarriers potentially reduce or prevent chemotherapy-induced side effects, facilitating the translation of nanocarrier formulation into the clinic. To date, organ-specific toxicity by nanocarriers remains to be clarified. Here, we studied the potential of polymeric micelle nanocarriers to prevent the ototoxicity, which is a common side effect of high-dose cisplatin (CDDP) therapy. In this study, we evaluated the ototoxicity of CDDP-incorporating polymeric micelles (NC-6004) in guinea pigs in comparison with that of cisplatin. Their auditory brainstem responses (ABRs) to 2, 6, 12, 20, and 30kHz sound stimulation were measured before and 5 days after the drug administration. Groups treated with NC-6004 showed no apparent ABR threshold shifts, whereas groups treated with CDDP showed dose-dependent threshold shifts particularly at the higher frequencies. Consistent with the ABR results, groups treated with NC-6004 showed excellent hair-cell preservation, whereas groups treated with CDDP exhibited significant hair-cell loss (P<0.05). Synchrotron radiation-induced X-ray fluorescence spectrometry imaging demonstrated that the platinum distribution and concentration in the organ of Corti were significantly reduced (P<0.01) in guinea pigs treated with NC-6004 compared with guinea pigs treated with CDDP. These findings indicate that micellization of CDDP reduces its ototoxicity by circumventing the vulnerable cells in the inner ear.
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