In Vitro Assessment of Radiopharmaceutical Uptake in Brain Tumor Cells Using Focused Ultrasound Stimulation

Abstract

Malignant brain tumors remain a major therapeutic challenge due to poor intracellular delivery of therapeutics. Radiopharmaceuticals such as Technetium-99m (^^99mTc) are valuable for imaging and therapy but suffer from limited tumor uptake caused by cellular and membrane barriers. Focused ultrasound (FUS) offers a noninvasive strategy to transiently enhance membrane permeability through sonoporation. Unlike prior studies largely focused on blood–brain barrier disruption, this work specifically investigates direct tumor cell sonoporation as an independent uptake mechanism. This study evaluates FUS-mediated enhancement of ^^99mTc radiopharmaceutical uptake in brain tumor cells and determines optimal acoustic parameters balancing efficacy and safety. Human glioblastoma (U87-MG) and astrocytoma (A172) cells were cultured and exposed to FUS at intensities of 0.3, 0.5, and 0.7 W/cm² for 30–120 s. Radiopharmaceutical uptake was quantified using γ-scintillation counting. Membrane integrity was assessed by live/dead fluorescence microscopy and lactate dehydrogenase release, while cell viability was evaluated via medical training therapy (MTT) assays. U87-MG cells exhibited up to a 3.1-fold increase at 0.7 W/cm² for 120 s, with a 2.3-fold enhancement at the clinically relevant 0.5 W/cm² for 60 s while maintaining >92% viability. A172 cells showed similar trends with slightly lower magnitudes. Safety assays confirmed reversible membrane permeabilization at ≤0.5 W/cm². The temporal uptake kinetics aligned with established membrane pore resealing dynamics, supporting reversible sonoporation as the uptake mechanism. Importantly, while ^^99mTc complexes are primarily diagnostic, enhanced intracellular delivery achieved by optimized FUS may also support future theranostic strategies, including radionuclide therapy. These findings underscore the translational potential of FUS in neuro-oncology, where tumor heterogeneity necessitates parameter optimization to maximize radiopharmaceutical delivery, improve imaging contrast, and overcome therapeutic resistance.