Investigation of a Biosensor Based on Phenylalanine Dehydrogenase Immobilized on a Polymer‐Blend Film for Phenylketonuria Diagnosis

We investigated a L‐phenylalanine (L‐phe) biosensor, functionalized through enzyme immobilization on a polymer‐blend film. The electron mediator 3,4‐dihydroxybenzaldehyde (3,4‐DHB) was employed at the electrode surface to improve direct oxidation of NADH to NAD+ and no additional reagents is required to be added to the sample solution. The bioactivated electrode was coated with a semi‐permeable cellulose acetate membrane in order to prevent dissolution of biofunctionalized polymer‐blend film. This constructed enzyme electrode is the first selective biosensor for phenylketonuria (PKU) detection. The sensitivity of the enzyme electrode was determined as 12.014 mA/M cm2. The Michaelis–Menten and current responses as well as sensitivity of the electrode showed improved values than those of previous works. This selective biosensor presented an excellent electroanalytical response for L‐phe, with a high steady‐state current being obtained after 20 s. The sensitivity of our biodevice is quite sufficient for the purpose of PKU detection because the reference range of clinical concern for L‐phenylalanine concentration is CL‐phe>0.5 mM. This surface‐bioactivated enzyme electrode retained more than 80 % of its electrocatalytic activity after 16 days.