Background: The human inner ear (IE) contains complex sensitive cellular structures. These structures inside the cochlea are vulnerable to e.g. toxic substances, aging, diseases and inflammatory processes. Sensorineural hearing loss can be induced by a wide range of molecular and cellular pathologic changes. These pathologic changes and disease specific biomarkers can be identified in low volume perilymph (PL) samples by performing ultrasensitive analytic methods like proteomics [1], metabolomics and multiplex protein array (MPA) [2].

Methods: By liquid biopsy, we are able to collect PL samples with a volume of 0.5-12µl by modified micro glass capillaries during IE surgeries like cochlear implantations. The proteomics and metabolomics approach is based on liquid or gas chromatography coupled to mass spectrometry (MS). A bead based Luminex multiplex technology for MPA enabled the identification of 48 inflammatory proteins like cytokines, chemokines, epithelial and endothelial markers in human PL samples.

Results: The collected PL samples show an average volume of 2µl (14% <1µl; 75% 1-3µl; 11% >4µl). The modified MPA requires only 0.5-2µl sample volume, each MS analysis 2µl. Depending on the sample volume, we could perform 2 or even 3 analytic methods in one PL sample.

Conclusion: Our developed PL sampling method and reducing the required volumes for the applied analytic methods enable a combination of different analytic methods. These multiple analyses enable the identification of hundreds of proteins and metabolites in the obtained low volume PL samples and present a new window of opportunity for understanding the pathologic processes in the IE.

[1] Schmitt et al. J. Proteome R. 2017

[2] Warnecke et al. Front. Neurol. 2019

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