Portable Smartphone-Based QDs for the Visual Onsite Monitoring of Fluoroquinolone Antibiotics in Actual Food and Environmental Samples

Abstract

Accurate onsite profiling of fluoroquinolone antibiotics (FQs) is of vital significance for ensuring food safety and estimating environmental pollution. Here, we propose a smartphone-based QD ratiometric fluorescence-sensing system to precisely report the level of FQs. As a proof of concept, we chose gatifloxacin (GFLX, a typical member of FQs) as the model for the analytical target, which could effectively trigger the fluorescence color variation of QDs from bright yellow-green (∼557 nm) to blue (∼448 nm) through the photoinduced electron-transfer (PET) process, thus yielding an evident ratiometric response. Based on this, the level of GFLX can be reported within a wide linear range from 0.85 nM to 3.6 μM. Moreover, this assay owns a high sensitivity with a low detection limit of 0.26 nM for GFLX and a quick sample-to-answer monitoring time of 5.0 min, manifesting that this platform could be fully qualified for onsite requirements. Interestingly, this portable device has successfully been applied for the onsite detection of GFLX in real food (i.e., milk and drinking water) and environmental (i.e., fish-farming water) samples with acceptable results. This developed platform offers a great promise for the point-of-care detection of FQ residues in practical application with the merits of being label-free, low-cost, and rapid, thus opening a new pathway for the onsite evaluation of food safety and environmental health.

A Ratiometric Fiber Optic Sensor Based on CdTe QDs Functionalized with Glutathione and Mercaptopropionic Acid for On-Site Monitoring of Antibiotic Ciprofloxacin in Aquaculture Water

“…The ratio of F 440 /F 710 changed distinctly only when the system was added into CIP, suggesting an anti-interference ability of GMPA@CdTe QDs towards CIP. The reason the ratio of F 440 /F 710 increased significantly after adding Cu 2+ is that the Cu 2+ can complex with GMPA@CdTe QDs, which weakens the fluorescent intensity of GMPA@CdTe QDs at a wavelength of 710 nm, resulting in a significant increase in F 440 /F 710 [ 51 ]. The high selectivity of GMPA@CdTe QDs towards CIP is attributed to the fact that the fluorescence emission wavelength of CIP is 430 nm, while the fluorescence wavelength of other analogues is about at 500 nm, thus a proportional fluorescence sensor was constructed to specifically detect CIP using the different fluorescence wavelengths of CIP and the principle of photoinduced electron transfer (PET) between CIP and GMPA@CdTe QDs.…”

“…The fluorescence quenching constants ( K SV ) were 0.01643 L·mol −1 at 293 K, 0.02001 L·mol −1 at 303 K, and 0.02351 L·mol −1 at 313 K by drawing the relationship between the fluorescence decay rate (F 0 /F) of GMPA@CdTe QDs at 710 nm and the CIP concentration. From the result, the positive correlation between KSV and incubation temperature can be observed ( Figure 7 a and Table 2 ) [ 51 ]. As the determination of fluorescence lifetime is the most authoritative method to differentiate the static and dynamic quenching processes, the fluorescence lifetime (τ) of the GMPA@CdTe QD before and after the interaction with CIP was also measured.…”

Advances in Antimicrobial Resistance Monitoring Using Sensors and Biosensors: A Review

“…Colorimetric sensors offer a number of advantages including: simple procedure, low cost, and the possibility of observing color changes with the naked eye or with simple instrumentation in the case of quantitative analysis [70,118]. The use of chemical species that changes color with respect to bacterial growth, such as Resazurin [19,119], or the use of enzymes, such as Horseradish Peroxidase (HRP), that modifies substrates according to the number of microbial cells, can help to measure susceptibility in real-time [70].…”

ASSURED Point-of-Need Food Safety Screening: A Critical Assessment of Portable Food Analyzers

“…It was found that individual RGB channels often produce optimal colorimetric performance, although other color spaces such as CieLAB or even novel artificial channel combinations of various color spaces combined may equally perform very well in certain assays [ 36 ]. The reviewed smartphone-based colorimetric detection strategies are based on the immunoassay test strips [ 37 , 38 ], nanoparticle aggregation [ 39 , 40 ], or enzyme inhibition assays [ 41 , 42 ]. Although the limits of detection of the colorimetric smartphone-based food analyzers reported in the literature are fit for screening methods based on the food safety regulations, they only provide qualitative or semi-quantitative results.…”