FUNCTIONALIZED NANOBODIES AS DIAGNOSTIC REAGENTS FOR THE DETECTION OF TOXIC MICROALGAESandra Oloketuyi
, 2020, doctoral dissertation
Abstract: Early detection and monitoring of toxic microalgae remains a challenge that will be necessary to overcome for understanding harmful algal bloom events and their consequent ecological and environmental impacts. Although there are diagnostic techniques based on microscopy, fluorescence in situ hybridization (FISH), DNA microarrays, real-time PCR, sandwich hybridization assays employed for the detection of harmful algal species, such techniques are not suitable for field monitoring and especially for the quantification of Alexandrium minutum due to abundance of cryptic species that cannot be differentiated based on morphology or genomic traits. These approaches are also time-consuming and laborious, hence there is need for alternative simple, rapid and cost-effective methods. In this study, our aim was to develop different nanobody-based capture strategies for the detection of A. minutum. Nanobodies were successfully displayed on the surface of Escherichia coli to facilitate detection of A. minutum. The method is simple and cost effective as no antibody purification step is necessary. As an alternative, A. minutum was quantified by exploiting the peroxidase activity of a G-quadruplex DNAzyme covalently bound to nanobodies and by means of a label free electrochemical immunosensor which exploit nanobodies bound via an irreversible SpyTag-SpyCatcher system as the specific immunocapture element. Such immunosensor was prepared by immobilizing the SpyTagged anti-A. minutum nanobody (SpyTagged C1) by means of a selfassembled monolayer (SAMs) of L- cysteine (L-Cys) displayed onto a gold nanoparticle-modified glassy carbon electrode. Electrochemical Impedance Spectroscopy (EIS) was performed to measure the electrical response of the circuit as the function of A. minutum immunocaptured cells. The results of EIS studies confirmed that the sensing chip detected A. minutum selectively, exhibited a wide dynamic range spanning from 103 to 109 cell L-1 and a limit of detection of 3.1× 103 cell L-1. The immunosensor data can be recorded and then analyzed with a portable potentiostat. Such device can be interfaced with a smart phone, a condition suitable for the rapid A. minutum quantification in situ.
Keywords: Alexandrium minutum, nanobodies, bioreagents, immunosensor, toxic microalgae
Published in RUNG: 17.06.2020; Views: 3676; Downloads: 229
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