A novel smartphone-based colorimetric aptasensor for on-site detection of Escherichia coli O157:H7 in milk

Abstract

Effective testing tools for Escherichia coli O157:H7 can prevent outbreaks of foodborne illness. In this paper, a smartphone-based colorimetric aptasensor was developed using functionalized gold nanoparticles (GNP) and multi-walled carbon nanotubes (MWCNT) for monitoring E. coli O157:H7 in milk. The maximum absorption peak of GNP bonded with aptamer (Apt) generated evident transformation from 518 to 524 nm. The excess GNP-Apt was removed by functionalized MWCNT magnetized with carbonyl iron powder (CIP) and hybridized with a DNA probe, whereas the GNP-Apt immobilized on E. coli O157:H7 remained in the system. In the presence of a high-salt solution, the GNP-Apt that captured E. coli O157:H7 remained red, but the free GNP-Apt aggregated and appeared blue. The chromogenic results were analyzed by a smartphone-based colorimetric device that was fabricated using acrylic plates, a light-emitting diode, and a mobile power pack. To our knowledge, this was the first attempt to use a smartphone-based colorimetric aptasensor employing the capture of GNP-Apt coupled with separation of MWCNT@ CIP probe to detect E. coli O157:H7. The aptasensor exhibited good reproducibility and no cross-reaction for other bacteria. A concentration of 8.43 × 10 3 cfu/mL of E. coli O157:H7 could be tested in pure culture, and 5.24 × 10 2 cfu/ mL of E. coli O157:H7 could be detected in artificially contaminated milk after 1 h of incubation. Therefore, the smartphone-based colorimetric aptasensor was an efficient tool for the detection of E. coli O157:H7 in milk.

Colorimetric Detection of Escherichia coli O157:H7 via the Peroxidase-Like Activity of Aptamer-Modified Potassium/Sodium Poly(heptazine imide) Nanoparticles

“…The biosensor was compared to previously reported nanomaterial-based biosensors for the colorimetric detection of E. coli O157. − Table S6 shows that the biosensor demonstrates a superior response time over other sensors. The LOD of the biosensor is advantageous over most of the biosensors.…”

Nanomaterial-based biosensors for the detection of foodborne bacteria: a review

“…41 Yang et al developed a smartphone-based colorimetric aptamer biosensor using functionalized AuNPs and multi-walled carbon nanotubes (MWCNT) for detecting E. coli O157:H7 in milk samples. 42 E. coli O157:H7 were captured by GNP-Apt, and the excess GNP–Apt was separated through the MWCNT@CIP probe. In the presence of a high salt solution, the GNP–Apt without binding bacteria produced aggregation, causing a visible color change to blue.…”

Ultrafast colorimetric detection of Cr(vi) using Fe3O4@polydopamine/Prussian blue composites as a highly efficient peroxidase mimic

“…Recently, smartphone-based colorimetric sensors have sprung up, showing great potential for in situ detection. 16,17 Prevalent colorimetric methods are proposed on the basis of the nanozyme-catalyzed chromogenic reaction between 3,3 ′ ,5,5 ′ -tetramethylbenzidine (TMB) and hydrogen peroxide (H 2 O 2 ). In the catalytic process, nanomaterials usually act as peroxidase mimics, catalyzing the decomposition of H 2 O 2 and generation of the hydroxyl radical ($OH).…”