To assess a smartphone-based, gold nanoparticle (AuNP)-based colorimetric lateral flow immunoassay paper sensor for quantifying urine 8-hydroxy-2′-deoxyguanosine (8-OHdG) as a biomarker for diabetic retinopathy (DR) screening.
Paper strips incorporate AuNP-8-OHdG antibody conjugates which produce color changes that are proportional to urine 8-OHdG and discernible on a smartphone camera photograph. Paper strip accuracy, precision, and stability studies were performed with 8-OHdG solutions of varying concentrations. Urine was collected from 97 diabetic patients receiving DR screening examinations, including seven-field fundus photographs. DR was graded by standard methods: low risk (no or mild DR) and high risk (moderate or severe DR). Paper sensor assays were performed on urine samples from patients, and 8-OHdG values were correlated with DR grades. The differences in 8-OHdG values between the low- and high-risk groups were analyzed for outliers to identify the threshold 8-OHdG value that would minimize false-negative results.
Lateral flow immunoassay paper strips quantitatively measure 8-OHdG and were found to be accurate, precise and stable. Average urine 8-OHdG concentrations in study patients were 22 ± 10 ng/mg of creatinine in the low-risk group and 55 ± 11 ng/mg of creatinine in the high-risk group. Screening cutoff values of 8-OHdG > 50 ng/mg of creatinine or urine creatinine >1.5 mg minimized screen failures, with 91% sensitivity and 81% specificity.
Urinary 8-OHdG is a useful biomarker to screen DR. Quantitative 8-OHdG detection with the lateral flow immunoassay paper sensor and smartphone camera demonstrates its potential in DR screening.

Copyright © 2020. Published by Elsevier Inc.