Development of an ATP and hydrogen ion image sensor using a patterned apyrase-immobilized membrane

A bio-image sensor using a patterned apyrase-immobilized membrane was developed to visualize the activities of adenosine triphosphate (ATP) and H⁺ ion in real-time. An enzymatic membrane patterning technique was suggested to immobilize apyrase on a specific sensing area of a charge coupled device (CCD)-type image sensor. It was able to observe the spatiotemporal information of ATP and H⁺ ion. The smallest size of a patterned membrane is 250×250µm². The fabrication parameters of the patterned membrane, such as its thickness and the intensity of the incident light used for photolithography, were optimized experimentally. The sensing area under the patterned apyrase-immobilized membrane revealed a linear response up to 0.6mM of ATP concentration with a sensitivity of 37.8mV/mM. Meanwhile, another sensing area without the patterned membrane measured the diffused H⁺ ion from nearby membranes. This diffusion characteristics were analyzed to determine a measurement time that can minimize the undesirable impact of the diffused ions. In addition, the newly developed bio-image sensor successfully reconstructed ATP and H⁺ ion dynamics into sequential 2-dimensional images.