SOD1 and metabolic dysfunction-associated steatotic liver disease: <h4>Objective</h4>To develop a superoxide dismutase (SOD) fluorescent detection probe based on Phycoerythrin (PE) from <i>Porphyridium cruentum</i> for real-time monitoring of SOD activity, a core biomarker of oxidative stress, in a nonalcoholic fatty liver disease (NAFLD) model, and to explore the regulatory effect of astaxanthin.<h4>Methods</h4>Phycoerythrin and SOD were covalently coupled using the heterobifunctional cross-linker N-Succinimidyl 3-(2-pyridyldithio) propionate (SPDP), and the probe concentration and incubation time were optimized.