Volatile organic compounds (VOCs) have been proven to be important biomarkers for predicting pathogen/pest-induced diseases in plants¹. Methyl salicylate (MeSA) has been identified as one such important biomarker for biotic stress in plants^2-4. Advanced detection of MeSA could help in early identification of plant diseases and has a profound significance for precision agriculture industry to maintain effective use for disease precautions. Previous research has demonstrated the development of biosensor consisting salicylate hydroxylase (SH) / tyrosinase (TYR) for salicylate detection. However, the method requires high temperature hydrolysis and pH neutralization steps before detection, rendering it more complex for device miniaturization⁵. In this project, we aim to eliminate these additional steps by developing a tri-enzyme detection platform consisting of esterase (ES), SH and TYR for direct MeSA detection without additional hydrolysis or pH neutralization steps. Two different immobilization strategies were used and compared using a lab-on-chip model and the sensitivity and specificity were determined to be 3.1 ± 0.2 µA·cm^-2·µM^-1 and 0.8 ± 0.2 µM respectively. An open source computer hardware and software Arduino was used for fabricating the computer-controlled automatic collection device for VOC collection. The prototype of a portable device for MeSA detection device was designed and fabricated, and the measurement was carried with the enzymatic biosensor strip.

Reference

(1) Laothawornkitkul, J., et al., Discrimination of plant volatile signatures by an electronic nose: a potential technology for plant pest and disease monitoring. Environmental Science & Technology, 2008. 42(22): p. 8433-8439.

(2) Buttery, R., et al., Characterization of some volatile constituents of bell peppers. Journal of Agricultural and Food Chemistry, 1969. 17(6): p. 1322-1327.

(3) Seskar, M., V. Shulaev, and I. Raskin, Endogenous methyl salicylate in pathogen-inoculated tobacco plants. Plant Physiology, 1998. 116(1): p. 387-392.

(4) Zhu, J. and K.-C. Park, Methyl salicylate, a soybean aphid-induced plant volatile attractive to the predator Coccinella septempunctata. Journal of chemical ecology, 2005. 31(8): p. 1733-1746.

(5) Fang, Y., et al., Detection of methyl salicylate using bi-enzyme electrochemical sensor consisting salicylate hydroxylase and tyrosinase. Biosensors and Bioelectronics, 2016. 85: p. 603-610.