In vitro evaluation of reactive oxygen species sensor for in vivo monitoring of periprosthetic infection and inflammation

Introduction Differentiating wear-induced hip and knee implant failure, such as aseptic and septic loosening, is challenging and can result in unnecessary operations or untreated infections, worsening patient outcomes. These failure modes arise from overlapping biological pathways, but differ in local H₂O₂ levels, reaching up to 100 μM during infection versus 5 μM during inflammation. Continuous in vivo H₂O₂ monitoring could increase true positive diagnoses and reduce complications. This in vitro study evaluated an electrochemical H₂O₂ sensor under simulated healthy, inflamed, and infected joint conditions, to assess its ability to distinguish between these failure modes after protein adsorption. Methods Platinum sensors coated with Nafion- and m -phenylenediamine were exposed to phosphate-buffered saline, protein-rich fluid containing synovial fluid protein analogues, or blood serum for up to 16 h at 35 or 40 °C and 7.4 or 6.7 pH. Results Sensor sensitivity, noise, and limit of detection met the requirements for infection detection but were insufficient for reliably detecting inflammation, particularly after exposure to the protein-rich fluid. The linearity remained excellent across all conditions (>0.985). Noise levels were influenced by fabrication variability, decreasing the overall reproducibility. Conclusion The sensors were able to distinguish conditions seen in an infected joint from those seen in an inflamed or healthy joint across all testing conditions, suggesting potential clinical utility for continuous in vivo infection monitoring. They were unable to distinguish conditions seen in an inflamed joint from those seen in a healthy joint. Longer test durations and broader biological interactions should be researched before starting in vivo studies.