Serine-Grafted Cu₂O Electrode Enabling Specific β-Hydroxybutyrate Detection by Surface Sensitization-Promoted...

As the global prevalence of diabetes continues to rise, the home health testing market has experienced rapid growth. Although blood glucose monitoring is widespread among diabetic patients, there remains a significant lack of testing methods for diabetic ketoacidosis. The present study developed a feasible electrochemical technique for ketoacid detection using serine-immobilized copper(I) oxide nanoparticles (Cu₂O NPs) as the primary electrode material. Given that the serine on the nanoparticle surface enables conjugation with β-hydroxybutyrate (β-HBA) through an esterification reaction between the hydroxyl group of serine and carboxylic acid of β-HBA and another intramolecular nucleophilic acyl substitution between amine and ester groups to form irreversible amide bonding, thus resulting in the β-HBA deposition on the surface of the Cu₂O NP-coated electrode. The quantification of β-HBA can be determined through current variations in amperometry measurement. The results showed a highly linear relationship between reductive current and β-HBA concentration at 0-20 mM, with a reasonable detection limit of 0.1 mM. Moreover, a reasonable mechanism involving the NP surface covering-mediated electrolysis enhancement was proposed. The present method reveals a promising direction in developing sensors for small molecule detection with high specificity and sensitivity.