abstract
The fast and specific detection of the commensal and pathogenic bacteria Escherichia coli (E. coli) is an essential challenge in the aquaculture industry. Herein, we developed and validated a liquid crystal-based optical biosensor that exhibited the capacity to detect whole-cell E. coli with a detection limit of 2.8 CFUs/mL. The inner surfaces of the device were treated so that the molecules of nematic liquid crystal 4-Cyano-4'-pentylbiphenyl were perfectly aligned along a direction normal to the confinement surfaces. Anti-E. coli-specific antibodies were immobilized on the inner surfaces of the device to function as biorecognition molecules. The size of the bacterial cells is over one thousand times higher than the size of the liquid crystal molecules, so when in contact, they efficiently distort the mean orientation of the liquid crystal molecules, which is the principle behind the detection method. Our wholecell biosensor presents several advantages; it is a low-cost device for simple optical reading and interpretation that relies on portable technology. This immunosensor presents a faster detection time and a lower limit of detection (LOD) than most LC-based sensors described to detect bacteria. This study is an important contribution to a fast diagnosis, which allows to address a specific threat, with immediate application to the aquaculture field, an increasingly important industry.
keywords
LINKED-IMMUNOSORBENT-ASSAY; BACTERIA; SENSORS
subject category
Engineering; Instruments & Instrumentation; Physics
authors
Soares, MS; Sobral, RG; Santos, N; Marques, C; Almeida, PL
our authors
Carlos Marques
Assistant Professoracknowledgements
This work was supported in part by the National Funds from Fundacao para a Ciencia e a Tecnologia (FCT), IP (FCT/the Portuguese Ministry of Science, Technology and Superior Education, "Ministerio da Ciencia Tecnologia e Ensino Superior" in Portuguese (MCTES)); in part by the Research Unit on Applied Molecular Biosciences-UCIBIO under Project UIDP/04378/2020; in part by the Associate Laboratory Institute for Health and Bioeconomy-i4HB under Project LA/P/0140/2020; in part by the Associate Laboratory Institute of Nanostructures, Nanomodeling and Nanofabrication-i3N under Project LA/P/0037/2020, Project UIDP/50025/2020, and Project UIDB/50025/2020; and in part by FCT/MCTES through Digitizing Aquaculture: from predictive analytics to intelligent photonics platform (DIGIAQUA) under Project PTDC/EEI-EEE/0415/2021. The work of Maria Simone Soares supported by FCT/MCTES, for the Ph.D. Fellowship under Grant UI/BD/153066/2022.