Planar Electrodes Modified by Nanodiamonds and Biocomposite Silica-Choline Oxidase Film For Choline Determination

Nanodiamonds obtained by detonation synthesis (dND) and modified with carboxylic groups were electrodeposited onto the surface of Au screen printed electrode (AuSPE). Modified electrode demonstrated electrocatalytic activity to H
₂
O
₂
molecules. The layer of silica sol-gel film with encapsulated choline oxidase (SiO
₂
-ChOx) was formed onto the surface of AuSPE-dND using method of electroassisted deposition. Choline oxidase immobilized inside silica film on the surface of AuSPE possessed high catalytic activity to choline. The electrode modified with biocomposite film AuSPE-dND-SiO
₂
-ChOx demonstrated stable analytical signal to a product of enzymatic reaction of choline oxidation. The developed biosensor was successfully applied for the determination of choline in food and biological tissues and demonstrated good reproducibility of the results. The influence of ascorbic acid was removed by passing the analyzed solution through the column with anion-exchange resin.