The only sample treatment required was a proper dilution process with working buffer solution. The results obtained with the proposed biosensor were also validated by 3.5-dinitrosalicylic acid (DNS) method [32]. Spectrophotometric DNS method was performed
by addition of 0.5 ml DNS solution (0.04 M of 3,5-dinitrosalicylic acid, 1.0 M potassium sodium tartarate, and 0.4 M NaOH) to 0.5 ml of samples and allowed to stand in boiling water bath for 10 min. After that, the reaction was stopped by cooling it immediately. Distilled water (5.0 ml) was added to each test tube and the optical density
was measured at 546 nm against the blank. Maltose solutions ranging from 1.0 to 20.0 mM were used as standard solution. Furthermore, samples were also spiked with known amounts of standard maltose solution to test the sample matrix effect on the analysis.