Surface Plasmon Resonance Assay for Label-Free and Selective Detection of Xylella Fastidiosa

Xylella fastidiosa is among the most dangerous plant bacteria worldwide causinga variety of diseases, with huge economic impact on agriculture and environment. A surveillance tool, ensuring the highest possible sensitivity enabling theearly detection of X. fastidiosa outbreaks, would be of paramount importance. Sofar, a variety of plant pathogen biomarkers are studied by means of surfaceplasmon resonance (SPR). Herein, multiparameter SPR (MP-SPR) is usedfor the first time to develop a reliable and label-free detection method for X.fastidiosa. The real-time monitoring of the bioaffinity reactions is provided aswell. Selectivity is guaranteed by biofunctionalizing the gold transducing interfacewith polyclonal antibodies for X. fastidiosa and it is assessed by means of anegative control experiment involving the nonbinding Paraburkholderia phytofirmans bacterium strain PsJN. Limit of detection of 105 CFU mL1 is achieved bytransducing the direct interaction between the bacterium and its affinity antibody.Moreover, the binding affinity between polyclonal antibodies and X. fastidiosabacteria is also evaluated, returning an affinity constant of 3.5 107 m1,comparable with those given in the literature for bacteria detection againstaffinity antibodies.