BACKGROUND: Kanamycin (KAN) residues in animal-derived foods continuously enter the human body, which will pose serious threats to human health such as hearing loss, nephrotoxicity and other complications. Therefore, to sensitively detect KAN residues by a reliable technology is extremely urgent in food quality and safety. Compared with traditional methods being limited by cost and complexity, photoelectrochemical (PEC) biosensors benefit from some merits such as rapid response, excellent sensitivity and good stability. In this study, the construction of a highly efficient PEC platform to realize KAN residues detection is discussed.
RESULTS: Herein, a novel p-n heterojunction consisting of flower-like BiOI microspheres and graphite carbon nitride (g-C3N4) nanoflakes was developed to establish a PEC aptasensor for KAN detection at 0 V. The prepared g-C3N4/BiOI heterostructure showed not only significantly enhanced PEC activity due to the larger specific surface area but also greatly increased charge separation efficiency owing to the strong internal electric field. Meanwhile, using g-C3N4/BiOI as a highly efficient photoactive material for binding amine-functionalized aptamers to capture KAN, the photocurrent signals showed a \'turn off\' mode to achieve the sensitive detection of KAN. The proposed PEC aptasensor exhibited linear response for KAN from 5 × 10-9 to 3 × 10-7 mol L-1 with a low detection limit of 1.31 × 10-9 mol L-1, and satisfactory recoveries (97.44-107.38 %) were obtained in real food samples analysis.
CONCLUSIONS: This work presented a novel p-n heterojunction-based PEC aptasensor with strong selectivity and stability, rendering it allowed to detect KAN in animal-derived foods including milk, honey and pork. Additionally, the detection range satisfied the MRLs for KAN specified by the national standards, demonstrating the potential application for food analysis. The study provides a new insight into the development of efficient and practical biosensors for antibiotic residues detection.

This research developed a signal amplification strategy to construct a highly sensitive electrochemiluminescent (ECL) aptasensor by incorporating dysprosium metal-organic framework (Dy-MOF) as a co-reaction accelerator (CRA) in gadolinium (Gd) luminescent complex based ECL system. A new Gd(III) complex GdPc(acac) (Pc = phthalocyanine, acac = acetylacetonate) with semi-sandwich structure was rationally selected as ECL emitter, exhibiting excellent luminescence performance owing to the \"antenna effect\" from the conjugated macrocyclic ligand. For further improving the sensitivity of the ECL biosensor, Dy-MOF was introduced into the ECL system as CRA. The purposive design and configuration of the Dy-MOF structure accelerated the separation and transport of photogenerated charges, and the nanosheets formed by the composite material provided more active sites, which could not only greatly increased the luminophore loading, but also effectively shorten the transport distance of ions and co-reactants. The constructed biosensor showed superior performance to monitor kanamycin within 0.001 pg/mL-1000 ng/mL and a detection limit down to 0.3 fg/mL (S/N = 3). The current work opened up a skillful strategy to amplify ECL singnal, extending the application field of lanthanide complexes and providing valuable information for the future biosensor design.

By utilizing a target biorecognition reaction to induce the self-assembly of G-quadruplexes and the aggregation of gold nanoparticles (Au NPs), this work develops a novel colorimetric biosensing method for kanamycin (Kana) antibiotic detection. The compact G-quadruplex structure was assembled from its two half-split sequences which were designed in two hairpin substrates of the Mg2+-dependent DNAzyme (MNAzyme). Besides hybridizing with the aptamer strand, the MNAzyme sequence was also split into two half fragments to be designed in the two substrates. Upon the aptamer-recognition reaction toward Kana, the MNAzyme strand could be quantitatively released to cause the exposure of the split G-quadruplex-sequences on two hairpin substrate-modified Au NPs and simultaneous release of two half fragments of the MNAzyme-sequence. Thus, the K+-assisted self-folding of G-quadruplexes causes the cross-linking of the two Au NPs to realize the Au NP aggregation-based colorimetric signal output (measured at the largest absorption peak near 520 nm). Meanwhile, the self-assembled formation of the second MNAzyme drastically amplified the signal response. Under the optimal conditions, a wide linear range from 0.1 pg mL-1 to 10 ng mL-1 and an ultrahigh sensitivity with the detection limit of 76 fg mL-1 were obtained. The dose-recovery experiments in real samples showed satisfactory results with recoveries from 98.4 to 105.4% and relative errors compared with the ELISA method less than 4.1%. Due to the high selectivity, excellent repeatability and stability, and simple manipulation, this method indicates a promising potential for practical applications. A novel homogeneous biosensing method was developed for the convenient detection of the kanamycin antibiotic. The target biorecognition-induced and dual DNAzyme-catalytic assembly of G-quadruplexes enabled the amplified aggregation of gold nanoparticles for the simple, cheap, stable, and ultrasensitive colorimetric signal transduction of the method.

The abuse of kanamycin (Kana) in many fields has led to increasing antibiotic pollution problems and serious threats to public health. Therefore, determining how to develop methods to realize the convenient detection of antibiotics in complicated environmental matrices is highly desirable. In this study, we utilized a target biorecognition-triggered hybridization chain reaction (HCR) assembly of a G-quadruplex DNAzyme (G-DNAzyme)-decorated nanotree to develop a novel homogeneous colorimetric biosensing method for the convenient and ultrasensitive detection of Kana antibiotic residues in real samples. Through the designed aptamer-recognition reaction, an Mg2+-dependent DNAzyme (MNAzyme) strand can be liberated. Thus, its catalyzed cleavage of the hairpin substrates anchored at a DNA nanowire will cause the assembled formation of an HCR-initiator; this process can be greatly amplified by the exonuclease III-assisted target recycling and the MNAzyme-catalyzed release of another MNAzyme strand. Based on the DNA-nanowire-accelerated HCR assembly of many G-DNAzyme-decorated DNA duplexes on the two sides of the nanowire, a DNA nanotree decorated by numerous G-DNAzymes will form to realize the ultrasensitive colorimetric signal output. Under the optimal conditions, this method exhibited a wide five-order-of-magnitude linear range and a very low detection limit of 28 fg mL-1. In addition, excellent selectivity, repeatability, and reliability were also demonstrated for this homogeneous bioassay method. These unique features along with its automatic manipulation and low assay cost show promise for practical applications.

In this work, a sensitive photoelectrochemical aptasensor was developed for kanamycin detection using an enhanced photocurrent response strategy, which is based on the surface plasmon resonance effect of gold nanoparticles deposited on a 3D TiO2-MoS2 flower-like heterostructure. A significant aspect of this development lies in the photoelectrochemical and morphological features of the unique ternary composite, which have contributed to the excellent performance of the sensor. To develop an aptasensor, mercapto-group modified aptamers were immobilised on the photoactive composite as a recognition unit for kanamycin. The TiO2-MoS2-AuNP composite was demonstrated to accelerate the electron transfer, increase the loading of aptamers and improve the visible light excitation of the sensor. Under optimal conditions, the aptasensor exhibited a dynamic range from 0.2 nM to 450 nM of kanamycin with a detection limit of 0.05 nM. Overall, we have successfully synergised both the electrical and the optical merits from individual components to form a ternary composite, which was then demonstrated as an effective scaffold for the development of PEC biosensors.