Stepwise sweeping-frequency ELF MF exposure and MTT-derived signal in U251 glioblastoma cells

Extremely low-frequency magnetic fields (ELF MF) have been reported to elicit parameter-dependent cellular responses, although experimental outcomes remain variable across biological models and exposure conditions. In this exploratory study, we evaluated the utility of a precisely characterized stepwise sweeping-frequency ELF MF (3–26 Hz) exposure system as a systematic in vitro screening platform under well-controlled exposure conditions. U251 human glioblastoma cells were exposed for 24 h to defined MF amplitudes (6–24 µT), followed by a 24 h post-exposure incubation period. Normalized MTT-derived signal was quantified using a standard MTT assay and calculated relative to exposure-specific and sham controls ( n = 3 independent experiments). Direct comparisons between complementary ELF MF-exposed and sham-exposed samples, representing the primary biological comparison of the study, did not reveal statistically significant differences under the present experimental conditions. As secondary analyses, comparisons with the respective control groups showed differences in normalized MTT-derived signal of approximately 10–15% at several magnetic field amplitudes (6, 10, 13, and 24 µT). These observations were restricted to selected exposure conditions and did not follow a monotonic relationship across the investigated magnetic field amplitudes. Overall, the results demonstrate the utility of the present protocol as an exploratory in vitro screening platform for systematic evaluation of a broad range of exposure conditions and identification of conditions suitable for subsequent targeted mechanistic investigations.