The as-prepared 3-APBA SAM-modified gold substrate was placed in 1.0 mL of HbA1c solution prepared in 0.05 M phosphate buffer at pH 8 for 10 min. Once the interaction between HbA1c and 3-APBA SAM on gold substrate was completed, the excess HbA1c was removed by rinsing with 0.05 M phosphate buffer at pH 8