Diagnostic device for cow mastitis based on the detection of superoxide secreted from neutrophils

Subclinical mastitis is a common infectious disease of dairy cows. To develop an early diagnostic device for mastitis, we focused our attention to the increase in the number of neutrophils in raw milk of mastitic cows. Since neutrophils secrete superoxide anion (O₂^-), it can be a good indicator to estimate the number of neutrophils. Neutrophils were separated from fat globules using the difference in specific gravity and specific adhesion of neutrophils to P-selectin. Neutrophils trapped in a microchannel were subsequently concentrated in an array of micropillars of a working electrode modified with P-selectin and superoxide dismutase (SOD). The O₂^- secreted from the trapped neutrophils was electrochemically detected. A distinct difference was observed between milk samples containing neutrophils and normal milk samples.