Microchip Based Determination of Bacteria by in-Chip Sandwich Immunoassay

Kasap, Esin Nagihan
Çoğun, Ferah
Yıldırım, Ender
Doğan, Üzeyir
Boyacı, İsmail Hakkı
Çetin, Demet
Suludere, Zekiye
Tamer, Uğur
Ertaş, Nusret
Bacteria detection is still a challenging issue and conventional bacterial detection methods are time consuming. In this study, a passive microchip design was used for fast and sensitive determination of Escherichia Coli (E. Coli) based on sandwich immunoassay. Gold coated magnetic nanoparticles (MNPs) and cadmium telluride (CdTe) quantum dots (QDs) were synthesized, surface modified and functionalized using E.coli specific antibody and they were used to form an in-chip sandwich immunoassay. The developed microchip consists of four micro-chambers connected to each other by microchannels, which act as capillary valves. First the magnetic separation and preconcentration of the E.coli from the sample solution in the vial was performed and then, the first chamber was filled with MNP-bacteria conjugate. The second microchamber was filled with QD-antibody conjugate, the third and fourth chambers were filled with washing buffer (phosphate buffered saline, pH=7.4). The MNP-bacteria conjugates were transferred from the first chamber through the microchannel using a magnet and being interacted with the QDs and then, washed in the third chamber in order to eliminate free QDs. Signal measurement was performed at the forth chamber using hand held spectrofluorometer equipped with a 295 nm LED source for excitation and fiber optic reflection probe. Amount of MNP and QDs injected to the microchambers were optimized. The calibration was linear in the range of 101 -105 cfu/mL with a correlation coefficient higher than 0.988. River water samples were analyzed with a recovery of 92 ± 10 %. The detection limit of the method in PBS was calculated as 1 cfu/mL. The proposed technique provides an inexpensive, rapid and sensitive method for the determination of E. coli.
Citation Formats
E. N. Kasap et al., “Microchip Based Determination of Bacteria by in-Chip Sandwich Immunoassay,” Çanakkale, Türkiye, 2016, p. 31, Accessed: 00, 2021. [Online]. Available: http://aacd2016.comu.edu.tr/announcements/abstract_book_of_aac.