Independent Applications of Near-IR Broadband Light Source and Pulsed Electric Potential in the Suppression of Human Brain Cancer Metabolic Activity: An In-Vitro Study

Abstract

The roles of two different non-conventional techniques in suppressing the metabolic activity of a malignant human brain cancer (glioblastoma) cell line were explored through the application of (i) pulsed electric field, or (ii) independent application with a continuous wave broadband near infrared light channeled through a fiber-optic bundle exposing cancer cells within growth medium. Human glioblastomas were grown in T-75 flasks and were utilized when the cells were 50–70% confluent. The cells were either transferred into 96 well plates for exposures through a fiber bundle, or into 1.4 ml sterile eppendoff tubes for exposures to pulsed electric potential. The glioblastomas within wells were light exposed through a fiber bundle at an average intensity of 0.115 W/cm² from the underside of the well, with the light dose (fluence) values ranging from 0.115—50 J/cm². Glioblastomas exhibited a maximal decline in the metabolic activity (down 80%) relative to their respective sham exposed control counterparts between the fluence dose values of 5.0–10 J/cm². The cellular metabolic activities for various treatment doses were measured through the colorimetric MTS metabolic assay 3 days after the broadband near infrared light exposure. Interestingly, the metabolic activity was found to return back to the (sham exposed) control levels as the fluence of exposure was increased up to 50 J/cm². Glioblastomas in suspension within sterile eppendoff tubes were exposed to pulsed electrical potential fluctuations: rectangular pulse width = 250 ms with pulse amplitude = 100 V, with 8 square pulses per burst, 2 bursts per second. A time course study of treatment exposure revealed a complete obliteration of glioblastomas for in-vitro treatment duration beyond 7 min.