BIOASSAY CHIP FOR EVALUATION OF MITOCHONDRIAL MEM- BRANE POTENTIAL WITH INTEGRATED ION-SELECTIVE MICROSENSORS

In this paper, we present the first on-chip tetraphenylphosphonium (TPP + ) ion selective electrode (ISE) microsensor and demonstrate the measurement of the mitochondrial membrane potential (ΔΨm) in a microfluidic environment. A continuous measurement of ΔΨm with isolated mitochondria (Heb7A) is performed with the fabricated devices. The concentration of isolated mitochondria used in the measurement was 0.3 ng/mL, four orders of magnitude smaller than the concentration used in conventional assays (3 mg/mL). The changes in ΔΨm and TPP ion concentration are measured in response to successive additions of substrates and inhibitors of the electron transport chain.