Low-cost colorimetric reader and label-free strategy for user-friendly detection of nucleic acid amplification products

Analyses of nucleic acid amplification products are generally performed by the complicated gel electrophoresis or costly florescence method. In this work, colorimetric detection of phosphate ions (Pis) generated in the amplification reaction was proposed for user-friendly and low-cost detection of nucleic acid products. To overcome the interference from nonspecific Pis, the effects of deoxyribonucleoside triphosphates (dNTPs) and Mg2+ concentrations, thermal cycle and initial template were investigated. The results showed that the yields of nonspecific Pis were constant, reproducible, and was the same at the presence/absence of target template, suggesting the potential to simply measure and subtract the interference. A colorimetric reader was developed to detect Pis in the amplification tube. It revealed that the unique structure of the tube would diverge, merge and reflect the transmitting light depending on the volume of solution, and could provide dependable results when the volume was higher than 160 mu L. Measurements of Staphylococcus aureus demonstrated detection limits of 10(4) copies mu L-1 for genomic DNA nuc and 2.2 x 10(1) CFU mL(-1) for milk cultured with 8 h. This method showed comparable sensitivity as the gel electrophoresis, avoided complicated operations and reduced the cost, demonstrating a promising potential to facilitate the detection of nucleic acid products.