Investigating Cellular Magnetic Bioeffects Using Two-Channel, Two-Photon Autofluorescence Lifetime Microscopy

Magnetic fields may modulate the cellular reduction-oxidation (redox) state and subsequent redox signaling pathways through quantum spin chemistry in biochemical radical pair reactions. This study applied two-channel, two-photon autofluorescence lifetime microscopy for non-invasive label-free measurements of the metabolic cofactors FAD and NAD(P)H and the redox state in live human non-small lung adenocarcinoma A549 cells. This custom microscope and technique were used to investigate the cellular effects induced by 30-minute exposure to redox modulating chemicals as well as 72-hour exposure to a range of static magnetic fields between 50 μT and 10 mT. The label-free methods showed little sensitivity to the acute chemical exposure in A549 cells, while longer-term magnetic field exposure showed a potential yet non-significant increase in an oxidative stress-linked long lifetime species. A standard H₂O₂ assay used to validate these responses showed significant sensitivity to chemical redox modulation reactions, and a weak response to effects caused by magnetic fields. Cellular H₂O₂ was observed to increase then gradually saturate as magnetic field exposure increased. These results demonstrate the potential of label-free microscopy for studying subtle magnetic bioeffects in individual living cells.