Below is an outline procedure for developing an ALT sensor on a ZP 501 carbon screen printed electrode.
Quick Concept Overview
Alanine aminotransferase (ALT) can be detected by coupling its activity to an electrochemical readout.
ALT catalyzes the reaction of alanine with α-ketoglutarate, producing pyruvate and glutamate.
The pyruvate is then converted by pyruvate oxidase (POx) into hydrogen peroxide (H₂O₂).
Hydrogen peroxide is easily detected amperometrically on a 501 carbon electrode — provided that the working electrode has first been modified with a Prussian Blue (PB) layer.
Note: Prussian Blue coatings are best prepared by the biosensor development team, rather than using pre-formulated PB sensors.
Electrodeposition of Prussian Blue by Cyclic Voltammetry
Deposition solution (example):
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3 mM K₃[Fe(CN)₆]
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3 mM FeCl₃
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0.1 M KCl
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(optional) 0.01–0.1 M HCl to slightly acidify
Procedure:
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Place 50 µL of the ferricyanide solution onto the ZP 501 carbon electrode.
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Run cyclic voltammetry (CV) between +0.6 V and −0.2 V vs Ag/AgCl for 5–15 cycles at 20–100 mV/s.
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A typical setup is 10 cycles at 50 mV/s.
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Watch for the development of characteristic peaks and a gradually increasing film — this indicates the Prussian Blue layer is forming.
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Rinse the electrode with Biosensor Rinse Solution.
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Add 50 µL of 0.1 M KCl (neutral) to the electrode surface and cycle CV between +0.4 V and −0.1 V for 5–10 cycles.
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This step stabilizes the Prussian Blue film.
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✅ At this point, your carbon electrode is modified with a stable Prussian Blue layer and is ready for sensitive hydrogen peroxide detection — and therefore for coupling into your ALT assay.
