The ultra-sensitive detection of pathogens is crucial for early diagnosis and for the provision of preventive actions and/or treatments. A relevant pathogen which stirred the interest of researchers worldwide is the bacterium Xylella fastidiosa. X. fastidiosa is a gram-negative bacterium that causes disease in several crops and plants which are important not only for the ecosystems but also for the agricultural sector. Indeed, X. fastidiosa is one of the most dangerous plant bacteria worldwide, causing a variety of diseases, such as Pierce’s disease of grapevine, phony peach disease, plum leaf scald, citrus variegated chlorosis disease, and olive scorch disease. In this work, the Single Molecule with a Large Transistor (SiMoT) technology, based on an Electrolytegated Organic Field-effect transistor (EG-OFET), [1],[2] has been used to detect Xylella fastidiosa reaching a limit-of-quantification (LOQ) [3] of 2±1 bacteria in 0.1 mL (20 colony-forming-it/mL). The assay is carried out with a millimeter-wide gate, bio-functionalized with the Xylella-capturing antibodies, and it is directly performed in saps recovered from naturally infected plants. Furthermore, the selectivity of the SiMoT system has been proven against a non-binding bacterium, namely the Paraburkholderia phytofirmans. The Surface Plasmon Resonance (SPR) technique was used to independently evaluate the biofunctionalization protocol of the gold surfaces, eventually used as gate electrode, with the antibodies for the selective recognition of the target bacterium, and also to evaluate the capture efficiency of the antibodies.[4] Indeed, SPR holds the advantage of being a label-free detection method, enabling also the real-time monitoring of bio-affinity reactions. In addition, the bio-electronic platform has been benchmarked against the qPCR gold-standard,[3] whose LOQ turns out to be at least one order of magnitude higher than the bioelectronic assay. The proposed label-free, fast (30 minutes), and precise (false-negatives, false-positives below 1%) electronic assay, lays the ground for an ultra-high performing immunometric point-of-care platform potentially enabling large-scale screening of asymptomatic plant References 1. Bonnassieux Y, et al. Flexible and Printed Electronics, 6(2021) DOI 10.1088/2058-8585/abf986. 2. Torricelli F, et al.,. Nature reviews | methods primers, 1 (2021). DOI: 10.1038/s43586-021-00065-8 3. Harper S J, et al., Phytopathology, 100 (2010), 1282–1288. DOI: 10.1094/PHYTO-06-10-0168 4. M. J. Linman, et al.,, Analyst, 135 (2010), 2759. DOI: 10.1039/C0AN00466A
