Nanosensor Detection of Synthetic Auxins In Planta using Corona Phase Molecular Recognition

Abstract

Synthetic auxins such as 1-naphthalene acetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) have been extensively used in plant tissue cultures and as herbicides because they are chemically more stable and potent than most endogenous auxins. A tool for rapid in planta detection of these compounds will enhance our knowledge about hormone distribution and signaling and facilitate more efficient usage of synthetic auxins in agriculture. In this work, we show the development of real-time and nondestructive in planta NAA and 2,4-D nanosensors based on the concept of corona phase molecular recognition (CoPhMoRe), to replace the current state-of-the-art sensing methods that are destructive and laborious. By designing a library of cationic polymers wrapped around single-walled carbon nanotubes with general affinity for chemical moieties displayed on auxins and its derivatives, we developed selective sensors for these synthetic auxins, with a particularly large quenching response to NAA (46%) and a turn-on response to 2,4-D (51%). The NAA and 2,4-D nanosensors are demonstrated in planta across several plant species including spinach, Arabidopsis thaliana (A. thaliana), Brassica rapa subsp. chinensis (pak choi), and Oryza sativa (rice) grown in various media, including soil, hydroponic, and plant tissue culture media. After 5 h of 2,4-D supplementation to the hydroponic medium, 2,4-D is seen to accumulate in susceptible dicotyledon pak choi leaves, while no uptake is observed in tolerant monocotyledon rice leaves. As such, the 2,4-D nanosensor had demonstrated its capability for rapid testing of herbicide susceptibility and could help elucidate the mechanisms of 2,4-D transport and the basis for herbicide resistance in crops. The success of the CoPhMoRe technique for measuring these challenging plant hormones holds tremendous potential to advance the plant biology study.

Non-destructive Technologies for Plant Health Diagnosis

“… (A) Paper-based electro-analytical device used in detection of H 2 O 2 in circular plant samples punched out of the tomato leaves (Sun et al, 2020 ); (B) Miniaturized electrochemical sensor inserted into tomato fruits for detection of auxin precursor, Tryp (Yang et al, 2021 ); (C) in situ ABA electrochemical sensor assembled onto a microneedle array for detection in fruits (Wang et al, 2021 ); (D) Current-time curves generated when the ABA microneedle sensor is inserted into cucumber where ABA concentrations is linearly correlated with the step current observed (Wang et al, 2021 ); (E) in situ SA electrochemical sensor arranged in an IDME array for insertion into cucumber leaves (Liu et al, 2021 ); (F) Response current (top) and derived SA concentration (bottom) obtained from the IDME array sensor in 5 different live cucumber leaves (Liu et al, 2021 ); (G) Brightfield (left) and corresponding false-colored images (right) of a spinach leaf infiltrated with H 2 O 2 (red arrow) and reference (blue arrow) nanosensors on both sides of the leaf mid-vein. False-colored images shows the transient H 2 O 2 wave upon mechanical wounding of the leaf at t = 0 min (Lew et al, 2020b ); (H) H 2 O 2 nanosensor response to different types of stress applied to the plant, including mechanical wounding (red), flg22 treatment (green), high light (orange) and high heat (blue) stresses (Lew et al, 2020b ); (I) Real-time sensing of 2,4-D uptake in hydroponically grown pak choi and rice leaves using nanosensors which illustrated a turn-on response observed in pak choi but not in rice over a time-period of 5 h (Ang et al, 2021 ); (J) Arsenite nanobionic sensor infiltrated into hyperaccumulator plant Pteris creticas fern, showing intensity changes corresponding to arsenic accumulation detected over 7-day time period upon arsenite exposure (Lew et al, 2021 ); (K) Schematic of standoff detection of nitroaromatic compound, picric acid, using nanosensors with real-time information relayed from the nanosensor-infiltrated plant to a portable Raspberry Pi-based electronic device (Wong et al, 2017 ). …”

“…It complements popular agricultural techniques used by farmers to maximize yield including crop rotation, intercropping and genetic modification (Uzogara, 2000 ; Wang et al, 2014 ; Yang et al, 2020 ). It also allows the precise calibration of optimal dosage and application of agrichemicals such as pesticides, herbicides or plant growth regulators (Ang et al, 2021 ; Roper et al, 2021 ). However, current chromatography-based analytical techniques are limiting the potential of plant health monitoring in influencing farm management decisions on a day-to-day basis (Pan et al, 2010 ; Balcke et al, 2012 ).…”

In vivo imaging of fluorescent single-walled carbon nanotubes within C. elegans nematodes in the near-infrared window

“…Despite being highly hydrophobic nanostructures, SWCNTs can be easily suspended in aqueous solution using noncovalent functionalization by polymers, DNA, RNA, dendrons, proteins, peptides, or specific recognition elements like antibodies or aptamers [ [50] , [51] , [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] , [60] , [61] , [62] , [63] , [64] , [65] , [66] , [67] ]. Only functionalized, suspended SWCNTs reveal a fluorescence signal.…”

“…Only functionalized, suspended SWCNTs reveal a fluorescence signal. Several studies demonstrated the feasibility of SWCNTs as fluorescence sensors or markers in vivo [ [46] , [47] , [48] , 51 , 59 , [68] , [69] , [70] , [71] , [72] , [73] , [74] , [75] , [76] ]. For example, single nanoparticle tracking of SWCNTs in the extracellular space of live brains could locally resolve its dimensions and viscosity [ 77 , 78 ].…”

Detektion und Visualisierung der Pflanzen‐Pathogen‐Response durch Nah‐Infrarot‐fluoreszente Polyphenolsensoren

“…[17][18][19] Diese Te chnik wurde angewendet, unter anderem zur Detektion von genetischem Material, [20] Proteinen, [21,22] Lipiden, [23] bakteriellen Motiven [24] oder kleinen Signalmolekülen wie Neurotransmitter, [19,25] reaktiven Sauerstoffspezies (ROS) [26][27][28] oder Stickstoffmonoxid (NO). [29] In jüngerer Zeit ermçglichte ihre Verwendung als nicht genetisch kodierte Sensoren die Visualisierung von ROS-Mustern, [27,30,31] Auxinen [32] oder der Schwermetallaufnahme [33] in Pflanzen. [34] Um die SWCNT-Sensoreigenschaften maßzuschneidern, wurden verschiedene chemische Designstrategien fürd ie Oberflächenfunktionalisierung entwickelt.…”