A screen-printed microelectrode for detection of hydrogen peroxide in solid tumor in vivo

Hydrogen peroxide (H 2 O 2 ), a crucial redox signaling molecule and neuromodulator, is closely associated with pathological processes, including cancer progression and neurodegenerative disorders. Current methods for in vivo H 2 O 2 detection, such as fluorescence imaging and chemiluminescence, suffer from the limitation of spatial resolution and invasiveness, which makes it difficult to monitor oxidative stress gradients in deep-seated tumors. Therefore, this research developed an implantable triple-electrode biosensor fabricated via screen-printing technology based on carboxylated multi-walled carbon nanotubes (MWCNT) and Prussian blue (PB) nanocomposites. The biosensor presented dual linear detection ranges of 0.8–1126 μM (R 2 =0.9937) and 1286–3766 μM (R 2 =0.9939) with a 0.47 μM detection limit. It demonstrated a >95% specificity compared with other interfering substances and maintained 93.2% signal retention over 30 days. Particularly, in situ implantation in melanoma-bearing mice with one-week-growth-time solid tumors revealed the H 2 O 2 levels 12- to 18-fold higher than in normal tissues, consistent with cancer-associated oxidative stress mechanisms. This platform addresses challenges such as rapid enzymatic degradation and microenvironmental complexity, enabling invasive profiling of H 2 O 2 detection in solid tumors.