Gas Biosensor Arrays Based on Single-Stranded DNA-Functionalized Single-Walled Carbon Nanotubes for the Detection of Volatile Organic Compound Biomarkers Released by Huanglongbing Disease-Infected Citrus Trees

Abstract

Volatile organic compounds (VOCs) released by plants are closely associated with plant metabolism and can serve as biomarkers for disease diagnosis. Huanglongbing (HLB), also known as citrus greening or yellow shoot disease, is a lethal threat to the multi-billion-dollar citrus industry. Early detection of HLB is vital for removal of susceptible citrus trees and containment of the disease. Gas sensors are applied to monitor the air quality or toxic gases owing to their low-cost fabrication, smooth operation, and possible miniaturization. Here, we report on the development, characterization, and application of electrical biosensor arrays based on single-walled carbon nanotubes (SWNTs) decorated with single-stranded DNA (ssDNA) for the detection of four VOCs—ethylhexanol, linalool, tetradecene, and phenylacetaldehyde—that serve as secondary biomarkers for detection of infected citrus trees during the asymptomatic stage. SWNTs were noncovalently functionalized with ssDNA using π–π interaction between the nucleotide and sidewall of SWNTs. The resulting ssDNA-SWNT hybrid structure and device properties were investigated using Raman spectroscopy, ultraviolet (UV) spectroscopy, and electrical measurements. To monitor changes in the four VOCs, gas biosensor arrays consisting of bare SWNTs before and after being decorated with different ssDNA were employed to determine the different concentrations of the four VOCs. The data was processed using principal component analysis (PCA) and neural net fitting (NNF).

DNAzyme-Amplified Electrochemical Biosensor Coupled with pH Meter for Ca2+ Determination at Variable pH Environments

“…Neural network fitting (NNF) [ 33 ] is a non-parametric non-linear method that combines the advantages of neural networks and regression. The most important feature is that the mapping equation between the input and output does not need to be determined during learning.…”

Carbon-Based Nanomaterials for Sustainable Agriculture: Their Application as Light Converters, Nanosensors, and Delivery Tools

“…This overcomes the traditional Huanglong disease nucleic acid and other problems of low diagnostic accuracy [22]. Single-stranded DNA-functionalized SWC-NTs can also be used to detect volatile markers such as ethylhexanol, linalool, tetradecene, and phenylacetaldehyde of Huanglong disease, which is lethal to citrus, so as to realize the monitoring of the asymptomatic stage of the disease [23]. Moreover, 6-ssDNA modified SWCNTs can rapidly detect 4-ethylphenol, a major volatile organic compound released by Phytophthora cactorum-infected strawberries, within a few minutes via an electrostatic gating mechanism, with a wide concentration range, and high detection sensitivity and recovery [24].…”

Advances in Plant Disease Detection and Monitoring: From Traditional Assays to In-Field Diagnostics

“…Notably, a novel electrical biosensor array based on single-walled carbon nanotubes (SWNTs) functionalized with single-stranded DNA (ssDNA) was recently reported [ 73 ] for the detection of four VOCs (ethylhexanol, linalool, tetradecene, and phenylacetaldehyde) compounds, released by Huanglongbing-infected citrus trees, in the asymptomatic phase of the disease. Discrimination of VOCs species and contents was achieved using different mathematical models.…”