Preparation of polyclonal antibody and development of a biotin-streptavidin-based ELISA method for detecting kanamycin in milk and honey

A novel dual-model photoelectrochemical/electrochemical sensor based on Z-scheme TiO2 disks/methylene blue for kanamycin detection

Herein, a new dual-model photoelectrochemical (PEC)/electrochemical (EC) sensor based on Z-scheme titanium dioxide (TiO2) disk/methylene blue (MB) sensibilization for the detection of kanamycin (Kana) was developed. Metal-organic framework-derived porous TiO2 disks were synthesized and exhibited excellent anodic photocurrent under visible light excitation. Subsequently, amino-labeled double-stranded DNA (dsDNA) was introduced into the modified electrode. Photocurrent was enhanced with MB embedded in dsDNA to form Z-scheme TiO2/MB sensibilization. When the target, Kana, was present, it specifically bound to the aptamer in the dsDNA, leading to the disruption of the dsDNA structure and the release of MB. This release of MB and the increase in target spatial resistance resulted in a significant weakening of PEC signal and a decreased oxidation peak current of MB. The PEC sensor successfully detected Kana in the range of 2-1000 pM with an LOD of 0.17 pM. Meanwhile, the EC sensor for Kana detection showed a linear range of 5-500 pM with an LOD of 1.8 pM. Additionally, the sensor exhibited excellent selectivity, reproducibility, stability, and good recoveries when applied to milk and honey samples. As a result, this method has the potential for application in ensuring food safety through the rapid determination of antibiotics in food.

A fluorescent assay for sensitive detection of kanamycin by split aptamers and DNA-based copper/silver nanoclusters

Kanamycin was a group of essential antibiotics generally served in treating infections of animals which leached into the environment residual in food, causing health concerns. Thus, selective and sensitive monitoring of kanamycin was significant for food safety. In this work, split aptamers were used as templates to prepare fluorescent Cu/Ag NCs for detection of kanamycin. According to the impressive affinity of the aptamer to kanamycin, two different detection modes were designed using kanamycin aptamer as a recognition molecule, in which one was to combine split aptamer Apt-1 with Apt-2 to form an entangled DNA as a Cu/Ag NCs template, the other was to associate the normal aptamer after encirclement to form Cu/Ag NCs templates. After the addition of kanamycin, the fluorescence signals of the Cu/Ag NCs synthesized in the two modes were both enhanced, but the approach with split aptamer exhibited a superior observable sensitivity than that of the normal type. The detection range showed a well linear relationship between 80 nM and 10 μM when the emission wavelength was 560 nm, and the detection limit was 13.3 nM. In addition, when streptomycin, oxytetracycline, chloramphenicol and chlortetracycline were involved in the selective interference experiment under the same conditions, the fluorescence intensity of the system performed no significant changes. The results demonstrated that this method possessed favorable specificity and selectivity for the assay of kanamycin, proficiently achieving efficient, rapid and sensitive evaluation of kanamycin in the milk samples.

A label-free G-quadruplex aptamer fluorescent aptasensor for visual and real-time kanamycin detection in lake and human samples

Antibiotic abuse is considered a serious problem affecting human health, necessitating that great attention be paid to explore robust, simple and sensitive methods for rapid evaluation. In this paper, we developed a fluorescent aptasensor for visual and real-time kanamycin detection by taking advantage of the label-free strategy based on H-aggregate disassembly of a chiral cyanine dye induced by a G-quadruplex aptamer. The good sensitivity and selectivity enabled this aptasensor to have a detection limit as low as 43 nM and have high specificity for kanamycin recognition. Furthermore, this assay was successfully applied for the detection of kanamycin in lake water and urine with excellent recoveries.

Functionalized Persistent Luminescence Nanoparticle-Based Aptasensor for Autofluorescence-free Determination of Kanamycin in Food Samples

Selective and sensitive determination of trace kanamycin in complex food samples is of great importance for food safety because of its high toxicity. Here, we report a sensitive and autofluorescence-free persistent luminescence (PL) aptasensor for selective, sensitive, and autofluorescence-free determination of kanamycin in food samples. The aptamer for kanamycin was first conjugated onto the surface of magnetic nanoparticles Fe₃O₄ to serve as the recognition unit as well as the separation element, while the PL nanoparticles ZnGa₂O₄:Cr (PLNPs) were functionalized with the aptamer complementary DNA (cDNA) as the PL signal. The PL aptasensor consisted of the aptamer-conjugated MNPs (MNPs-apt) and cDNA-functionalized PLNPs (PLNPs-cDNA) and combined the merits of the long-lasting luminescence of PLNPs, the magnetic separation ability of MNPs as well as the selectivity of the aptamer, offering a promising approach for autofluorescence-free determination of kanamycin in food samples. The proposed aptasensor showed excellent linearity in the range from 1 pg mL^-1 to 5 ng mL^-1 with a limit of detection of 0.32 pg mL^-1. The precision for 11 replicate determinations of 100 pg mL^-1 kanamycin was 3.1% (relative standard deviation). The developed aptasensor was applied for the determination of kanamycin in milk and honey samples with the recoveries of 95.4-106.3%. The proposed aptasensor is easily extendable to other analytes by simply replacing the aptamer, showing great potential as a universal aptasensor platform for selective, sensitive, and autofluorescence-free detection of hazardous analytes in food samples.

High throughput detection of antibiotic residues in milk by time-resolved fluorescence immunochromatography based on QR code

Herein, we have successfully established a novel, rapid, and simple lateral-flow immunoassay based on time-resolved fluorescence and biotin-streptavidin to detect the residues of various antibiotics in milk. The fluorescence signal and sensitivity of immunochromatography were enhanced through biotinylated antibody coupled with streptavidin europium microspheres. Moreover, due to the use of a QR Code and fluorescent reader, quantitative detection and real-time data uploading can be achieved. Under the optimal conditions, the various antibiotic residues were detected in the milk samples. The results showed that the limits of detection of tylosin, lincomycin and doxycycline were 0.10, 0.06, and 0.27 ng/mL, respectively. The recoveries of the spiked milk samples were 88.9%~127%, with coefficients of variation less than 11%, and the test strip can be stored at room temperature for 12 months. This study shows that the proposed time-resolved fluorescence immunoassay is sensitive, rapid and reliable, and has the potential to be used for detection of veterinary antibiotic residues in food safety fields.

Colloidal Gold Immunochromatographic Strip Assay for the Detection of Azaperone in Pork and Pork Liver

In this study, a highly sensitive and specific monoclonal antibody (mAb) against azaperone was produced. The mAb belonged to the IgG2b subtype and its half maximal inhibitory concentration (IC₅₀) was 0.46 ng/mL. The limit of detection value was 0.081 ng/mL and the linear range (IC₂₀-IC₈₀) was 0.165-1.29 ng/mL. Based on this anti-azaperone mAb, a colloidal gold immunochromatographic strip assay method was established for the detection of azaperone in pork and pork liver samples. For pork samples, the cutoff value of the colloidal gold immunochromatographic strip assay was 10 ng/g, and the cutoff value was also 10 ng/g in pig liver samples. This colloidal gold immunochromatographic strip assay is a rapid, simple, and practical method for the detection of azaperone in pork and pork liver samples available in markets.