Enzymatic biosensor based on entrapment of d-amino acid oxidase on gold nanofilm/MWCNTs nanocomposite modified glassy carbon electrode by sol-gel network: Analytical applications for d-alanine in human serum.

•Novel enzymatic biosensor for determination of d-alanine was fabricated and developed in real samples.•DAAO electrostatically immobilized onto glassy carbon electrode surface by sol-gel film.•Characterization of enzyme biosensor was done by SEM, EDX and CV techniques and the response of proposed biosensor was investigated.•The modified biosensor showed good sensitivity, repeatability, stability and selectivity toward d-alanine oxidation.