An integrative round window membrane/cochlear microphysiological system with sensing components for the study of real-time drug response†

Most hearing loss often results from permanent damage to cochlear hair cells, and effective treatments remain limited. A reliable, scalable, and physiologically relevant ear model can accelerate the development of hearing-loss protection therapeutics for injury prevention and hearing restoration. The challenge remains on screening delivery systems for regenerative compounds, and no in vitro screening systems exist that capture the complexity of inner ear properties. Here, we present a high-throughput, microphysiological system (MPS) featuring a round window membrane (RWM) model co-cultured with murine auditory hair cells. It is integrated with a transepithelial electrical resistance (TEER) sensor module to monitor epithelial barrier function development in continuous measurements, without sacrificing a sample and thus allowing “real-time” monitoring of the RWM construct progress. The MPS integrates a syringe pump, tissue compartment, multi-channel fluid distributor, and sensors into a microfluidic continuous-flow system, allowing for on-demand sample collections of analytes triggered by the cellular response to the introduced compounds. Drug screening was conducted with protective antibiotic, antioxidant, and anti-inflammatory compounds. RWM cell and hair cell viability, TD₅₀ values, and membrane integrity were measured. In addition, we also designed a graphene field-effect transistor (GFET)-based cytokine sensor to study proinflammatory cytokine release from cells during damaging exposure. The system was employed to assess drug diffusion efficiency, cell viability, and the drug's TD₅₀ and compared to published data from animal studies. Cell membrane integrity was also analyzed, and proinflammatory cytokine release was measured using a GFET sensor. We evaluated and monitored the real-time structural integrity of the RWM epithelial barrier using the integrated TEER sensor in the MPS. The sensor's ability to measure TEER and cytokine levels was validated by comparing its readings to those obtained from commercial TEER signal processing equipment and standard cytokine concentration measurements. This ear-on-a-chip design enables high-throughput screening of investigational new drugs, reducing the need for animal models in complex studies of inner ear damage and regeneration. It allows for the real-time study of drug responses. It facilitates the development and identifying novel agents that protect against hearing loss and the design of delivery methods for hearing regeneration compounds.