Sensing purine nucleoside phosphorylase activity by using silver nanoparticles

In this paper, an electrochemical biosensor to assay purine nucleoside phosphorylase (PNP) activity is reported. Due to the facilitation of sliver nanoparticles, which are modified on an electrode surface, to the electron transfer reactivity of guanosine and guanine, the electrochemical response of these species can clearly reveal the activity of the enzyme PNP. This electrochemical biosensor for the assay of PNP activity may have a broad linear range of 4–20 unit/mL with a detection limit of 0.1 unit/mL, which is good enough for clinical applications. Meanwhile, on the basis of the finding that guanosine and guanine can induce silver nanoparticles to different agglomeration degrees, we have also developed a rapid UV–vis spectroscopy assay method for PNP activity. This work may show acceptable reliability and specificity for the assay of PNP activity, and may avoid the utilization of coupled enzymes or radiochemical reagents, which are required to the previous reports.