Self-cleaning paper-based microfluidic biosensor employing DNAzyme and semiconducting single-walled carbon nanotube for copper ion detection.

Microfluidic paper-based analytical device (μPAD) offers a simple and efficient platform for point-of-care monitoring, which can be beneficial for copper determination in livestock feed and manure. However, common cellulose paper has excellent hydrophilicity, causing μPAD is accompanied by poor mechanical properties, short service life, and low sensitivity. Here, a self-cleaning paper-based microfluidic biosensor for Cu2+ determination was proposed to overcome the mentioned shortages in the application. Polymeric octadecyl trichlorosilane was synthesized and decorated on cellulose paper to form hydrophobic paper, which can improve the hydrophobicity, self-cleaning, and pollution ability. In addition, hydrophobic paper, semiconducting single-walled carbon nanotube, and DNAzyme through the chemical bond were employed to fabricate a self-cleaning paper-based microfluidic biosensor. The properties were investigated using scanning electron microscopy, Raman, and electrochemical methods. The detecting parameters were also optimized. It could measure the Cu2+ concentration from 1 nM to 100 μM, and the detection limit was 0.65 nM. The self-cleaning paper-based microfluidic biosensor was applied to detect Cu2+ concentration in livestock feed and manure that can meet the requirements for fast screening and detection.