AN ELECTRONIC ASSAY OF CELL DEATH

Resistance to apoptosis (programmed cell death) is a hallmark of cancer. Release of cytochrome c (Cyt c) from mitochondria in response to cell-death signals is the checkpoint in the heavily regulated intrinsic apoptosis pathway, and a target of pharmacological manipulation. We present here an electronic sensing platform that can detect peptide (Bcl-2 family) induced release of Cyt c from vital, isolated mitochondria tethered directly to an optically transparent, atomically thin (graphene) electrode. We detect these events on minute quantitates of mitochondria (from as few as 100 ng of mitochondrial or 7000 cells), while simultaneously allowing for fluorescence characterization via existing libraries of fluorophores for a variety of assays. CCCP induced inner membrane potential collapse, and Bcl-2 family peptide induced Cyt c release from the outer membrane result in significant changes to the graphene electrode conductance due to its exquisite pH sensitivity. As designed and demonstrated, this electronic assay could be used to assess the effectiveness of various potential chemotherapies in vitro, as well as eventually as part of a process to predict patient specific outcomes for personalized medicine.