Voltammetric bioassay of caffeine using sensor implant.

In this article, we examined the performance of the voltammetric assay of caffeine using DNA immobilized onto a carbon nanotube paste electrode (DPE) and compared it with that of an ordinary carbon nanotube paste electrode (PE). Under optimal conditions, the working ranges for caffeine were from 0.1 to 12 mg l(-1) (for DPE) and 30-230 mg l(-1) (for PE). Detection limits (DLs) of 0.068 mg l(-1) (3.50 x 10(-7) M) DPE and 9.94 mg l(-1) (5.12 x 10(-5) M) PE were obtained and the relative standard deviation at the caffeine concentration of 5.0 mg l(-1) was 0.064% (n = 15) DPE under optimum conditions. The sensor could be implanted in a leaf skin or animal brain cell, which can then be interfaced with an electrochemical workstation. It can be used in real-time in vivo caffeine analysis in a live cell or leaf skin.