Integration of glucose and lactate biosensors into human cartilage-on-a-chip models for long-term monitoring of metabolic shifts in osteoarthritis
Mario Rothbauer, Jonathan Strauss, Eva I. Reihs, Johannes Heidenberger, Juergen Alphonsus, Sally A. N. Gowers, Yu‐Chih Chen, James McLeod, Stefan Toegel, Peter Ertl, Reinhard Windhager, Martyn G. Boutelle, Danny O’Hare
Abstract
Microphysiological cartilage models provide excellent opportunities for modelling joint pathologies, including osteoarthritis. They are currently limited by their inability to facilitate real-time measurements of crucial disease progression markers. We integrated glucose and lactate biosensors in a human cartilage-on-a-chip system for in situ detection of disease-related shifts in chondrocyte metabolism during inflammation. We optimized glucose and lactate oxidase-based biosensors to ensure signal stability and wide dynamic range, validated their signal against commercial luminescence-based assays, confirmed signal selectivity, reversibility, and repeatability and excluded signal interference by cell culture media components. We measured target analyte levels in healthy cartilage organoids and those inflamed by treatment with IL-1β and TNF-α to mimic the osteoarthritic cartilage environment. The chip-integrated biosensors detected decreased glucose (2.2-fold signal decrease) and increased lactate (8.9-fold signal increase) levels in cell-laden organoids, compared to cell-free controls, demonstrating the feasibility of direct in situ metabolic monitoring with the proposed system. Long-term measurements indicated enhanced glucose-to-lactate metabolism in chemically inflamed compared to untreated cartilage-on-a-chip. This was confirmed by measuring 1.7-fold decreased glucose and 5.1-fold increased lactate content in cell culture supernatants after 2 weeks of culture and 1.5-fold glucose decrease and 1.9-fold lactate increase in cell culture supernatants from inflamed versus non-inflamed tissues. In conclusion, this study demonstrates a proof-of-concept of glucose and lactate biosensor integration in human cartilage models, enabling real-time monitoring of osteoarthritis-related metabolic shifts. Integration of biosensors in tissue-mimetic in vitro models will advance joint-on-a-chip technologies and contribute to gaining a clearer understanding of metabolic processes in degradative joint disease. • Establishment of interference-free glucose and lactate microneedles sensors for musculoskeletal biochip integration. • Broad dynamic range of microneedle sensors fit for in vitro organoid culture conditions. • Successful long-term monitoring of lactate and glucose levels inside healthy and osteoarthritic cartilage-on-a-chip.