A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001–0.004 mg mL−1 for HbA1c with a detection limit of 0.0015 mg mL−1.
