Touchable Electrochemical Hydrogel Sensor for Detection of Reactive Oxygen Species-induced Cellular Senescence in Articular Chondrocytes

In this study, a reactive oxygen species (ROS)-responsive hydrogel sensor (PD/MnO2 hydrogel) is developed that can efficiently detect senescent cells. Using immature murine articular chondrocytes with serial passages, the sensor can identify small interfering RNA (siRNA) knockdown of peroxisome proliferator-activated receptor-alpha (PPAR alpha) based on the concentration of ROS in cells, simultaneously maintaining its balance via scavenging activity to prevent cartilage degradation in osteoarthritis (OA). The hydrogel sensor exhibits a change in electronic properties, with a distinct resistance from 201.9 k omega for P0 to 362.9 k omega for P3, and fluorescence off/on performance with an increase in passaging time. In vitro investigation using PPAR alpha-specific siRNA reveals a correlation between pressure sensitivity and senescent activity, wherein an elevation in observed signal occurred (41.5%). In vivo analysis reveals significant decrease in degradation of the cartilage of both young, 3 months old aged, 18 months old, and PPAR alpha(-/-) mice compared to PPAR alpha(+/+) mice based on safranin O stains. The expression level of interleukin-1 beta is reduced in the cartilage of aged PPAR alpha(-/-) mice after implantation with hydrogel, indicating the potential of PD/MnO2 hydrogel as a therapeutic modality against OA.