Architecture of a multi-channel and easy-to-make microfluidic paper-based colorimetric device (μPCD) towards selective and sensitive recognition of uric acid by AuNPs: an innovative portable tool for the rapid and low-cost identification of clinically relevant biomolecules.

Uric acid (UA) is the end product of purine metabolism. Uric acid is usually excreted in the urine, but its abnormal increase and toxic amount can lead to diseases such as gout, hyperuricemia, Lesch-Nyhan syndrome, and cardiovascular disease. On the other hand, UA reduction can lead to neurodegenerative diseases such as sarcoma, glioblastoma, Hodgkin, and etc. Therefore, rapid identification of UA is of great importance. In this work, a simple, portable, inexpensive, and fast microfluidic paper-based colorimetric sensor based on the color change in the presence of UA by using AuNPs was developed. The results can be easily identified with naked eye and further confirmed by UV-vis spectrophotometry. In this method, iron pattern and fiberglass paper were used to construct diagnostic areas and hydrophilic microfluidic channels. We greatly reduced the preparation time of this pattern using a magnet (about three minutes). In this work, four types of nanoparticles with different lower limit of quantification (LLOQ) were used. Linear range of 10 -6 to 10 -3 M and LLOQ of 10 -6 M were obtained for the determination of uric acid using AuNPs-CysA as optical probe. Also, by AuNPs as optical probe a linear range of 10 -4 to 10 -2 M and the obtained LLOQ was 10 -4 M. Finally, by AuNFs as optical probe linear range from 10 -6 to 10 -2 M and 5 × 10 -5 to 10 -2 M along with LLOQ of 10 -6 and 5 × 10 -5 M, respectively. The designed system successfully studied in human urine samples.