Development of an amperometric screen-printed galactose biosensor for serum analysis

The development of a disposable amperometric biosensor for the measurement of circulating galactose in serum is described. The biosensor comprises a screen-printed carbon electrode (SPCE), incorporating the electrocatalyst cobalt phthalocyanine (CoPC), which is covered by a permselective cellulose acetate (CA) membrane and a layer of immobilized galactose oxidase (GALOX). The optimal response of the biosensor, designated as GALOX-CA-CoPC-SPCE, was obtained by systematically examining the effects of enzyme loading, temperature, pH, and buffer strength. The optimal performance of the biosensor occurred with 2 U of GALOX, at 35 °C, using 50 mM phosphate buffer solution (pH 7.0). The sensitivity was 7.00 μA mM−1 cm−2 and the linear range from 0.1 to 25 mM with a calculated limit of detection (LOD) of 0.02 mM; this concentration range and LOD are appropriate to diagnose galactosemia, i.e., concentrations >1.1 mM in infants. When the biosensor was used in conjunction with amperometry in stirred solution for the analysis of serum, the precision values obtained on unspiked (endogenous level of 0.153 mM) and spiked serum (1 mM added) (n = 6) were 1.10% and 0.11%, respectively, with a calculated recovery of 99.9%.