Sensitive polydopamine bi-functionalized SERS immunoassay for microalbuminuria detection

Albumin is a significant prognostic marker in diabetic nephropathy and cardiovascular disease. In this work, we developed a rapid, sensitive and inexpensive method for albumin detection based on the polydopamine (PDA) bi-functionalized glass chip and surface-enhanced Raman scattering (SERS) tag. Anti-albumin antibodies were encapsulated on the glass chip and SERS tag through dopamine self-polymerization in alkaline conditions and the immunoaffinity was highly maintained to form the sandwich structure with the addition of target microalbuminuria. Under the optimum experimental conditions, this SERS immunoassay showed the wide linear range of 10-300 mg/L with the limit of detection of 0.2 mg/L. High specificity and selectivity of this SERS method were demonstrated by performing with some common proteins include human hemoglobin protein (Hgb) and human immunoglobulin G (IgG) in urine. This method was also applied to detect albumin in urine samples from 17 patients and 5 healthy control and the results were highly consistent with those obtained from clinical standard immunoturbidimetric method. The volume requirement of urine samples is only 2 μL. Compared with traditional dipstick and immunoturbidimetric methods used in clinic, SERS-based method has higher accuracy, lower sensitivity and less sample consumption.