In vivo detection of L-tryptophan in tomatoes using multi-walled carbon nanotubes and poly (sulfosalicylic acid) film modified graphite rod electrode

Abstract

L-tryptophan (L-Trp) is an important precursor for the synthesis of auxin in plants, which can regulate plant growth via a series of life activities. The rapid quantitative detection of L-Trp is of great significance for the study of plant growth and development activities. The most-reported electrochemical methods for the determination of L-Trp are only limited to in vitro measurement due to the large dimension of the sensing electrode, which will inevitably damage the plants and hinder their growth. Here we report the method of constructing a miniature electrochemical sensor for the in vivo detection of L-Trp. A graphite rod electrode (GRE) modified with multi-walled carbon nanotubes (MWCNTs) and poly (sulfosalicylic acid) film (PSA) as sensing electrode could greatly reduce the oxidation potential and prevent the interference, resulting in the L-Trp sensor with the linear range of 10–110 μM and limit of detection (LOD) as low as 0.037–0.121 μM. The successful measurement of L-Trp in tomato juice/fruit reveals the applicability of the sensor in the in vivo detection of tryptophan. More importantly, the monitoring of the L-Trp level at different growth stages may be a great help to understand the growth process of tomatoes. We expect that the as-developed L-Trp sensor will exhibit significant potentials in intelligent agriculture.