In Situ Swelling of Cartilage Explants for Osteoarthritis Through Graphene Strain Sensing

Osteoarthritis (OA) is a widespread disease which involves the degeneration of cartilage. Healthy cartilage derives its function from a combination of mechanical integrity of the collagen matrix and the physiochemical contributors of negatively charged aggrecan contained inside the matrix. While mechanical integrity via cartilage stiffness is a commonly used biomarker—primarily due to the wide availability of indentation tests—there are few approaches which focus on restoring the aggrecan content, which manifest as the swelling behavior of cartilage in response to different osmotic environments. The challenge is that cartilage explants—which have high physiological relevance—are too large for sensitive instruments and swelling changes are too little for simple visual or mass-based techniques. Here, we developed a platform which uses embedded graphene strain sensors to measure the swelling behavior of equine cartilage explants in real time. By simulating OA-like degradation through a series of enzymes, we were able to identify distinctive swelling profiles of explants undergoing proteoglycan digestion versus broad spectrum matrix damage. This parallel and scalable platform would enable new approaches to OA regeneration based on restoring proteoglycan content.