In the present study, a thin-film based on a Ag modified DNA aptamer immobilized on cellulose nanofibers was investigated for the determination of prostate specific Antigen (PSA) in biological samples. Reaction of amino-modified anti PSA aptamer with the Ag modified oxidized cellulose nanofibers was performed according to the procedure described by Khayamian et al. [1] with some changes. Following this, digital picture of the thin film was analyzed by investigating its Red-Green-Blue (RGB) components [2]. The results show that the RGB intensities of the thin film are proportionate to the PSA concentration in the sample solution. Under optimized conditions, the relative standard deviation is 3.2% (n=7). The calibration curve covers the 9–310 ngmL−1 range with reasonable linearity (r2>0.9969). Limit of detections were between 4.9 and 5.7 ngmL-1 and relative standard deviations were less than 6.1% under the optimized condition. Relative recoveries were found to be between 87.3 and 93.8%. Furthermore, the urine samples were analyzed with a standard PSA immunoassay. The comparison of the results shows no significant difference in analyte concentration obtained by the proposed method as an alternative method for the analysis of PSA in urine samples. Based on our knowledge, for the first time in this work, the specific and effective biochemically modified cellulose nanofibers were combined with the simplicity, speed, and inexpensiveness of smartphone detection. In addition, the proposed method has a wide dynamic range with a compatible limit of quantitation in comparison with the reported methods.
