A sensitive aptasensor based on rolling circle amplification and G-rich ssDNA/terbium (III) luminescence enhancement for ofloxacin detection in food

Ratiometric sensor based on Ag+-mediated luminescence of Tb-DNA complexes for visual detection of 4-aminophenol

Development of accurate, convenient and portable methods for monitoring 4-aminophenol (4-AP) is extremely important because of its strong toxicity. Here, a ratiometric fluorescence sensor based on Ag+-enhanced luminescence of Tb-DNA complexes has been presented for the detection of 4-AP. The luminescence of Tb-DNA complexes is enhanced about 30 times by Ag+, which can trigger energy transfer from DNA to Tb3+ more efficiently. In the presence of 4-AP, Ag+ can be reduced into Ag0 owing to its strong reducibility, inducing the decrease of Tb-DNA complexes at 545 nm remarkably. Besides, 4-AP exhibits intrinsic fluorescence at 375 nm under the same conditions. Therefore, ratiometric detection of 4-AP can be achieved using F375/F545 as readout with a detection limit of 0.4 μM. Real water samples have been tsted to evaluate this method in practical application and satisfactory results have been obtained. Furthermore, the addition of 4-AP into Tb-DNA-Ag+ system induces a visible color variation from green to bluish violet, enabling visual detection of 4-AP under the assistance of a smartphone.

Tb3+ assisted dithioerythritol stabilized copper nanocluster with AIE behavior for ratiometric fluorescent determination of fluoroquinolones

BACKGROUND

Fluoroquinolones (FQs) are widely used in livestock and poultry industry because of their satisfactory effects in preventing and treating bacterial infection. However, due to irrational use and poor biodegradability, FQs can easily remain in food animals and further enter the human body through the food chain. Therefore, accurate and sensitive detection of FQs residues in animal-origin food is significant. The traditional methods commonly used for FQs detection have some limitations. Ratiometric fluorescence detection technology has the advantages of fast, sensitive, self-correcting, and easy visualization. However, the reports on the use of ratiometric fluorescence probes for FQs detection are limited.

RESULTS

In this work, a novel probe was proposed for ratiometric fluorescent analysis of FQs. In this probe, the fluorescence of dithioerythritol stabilized copper nanoclusters (DTE-Cu NCs) was significantly enhanced due to the Tb3+ triggered aggregation-induced emission effect. FQs bound Tb3+ in Tb3+/DTE-Cu NCs through carboxyl and carbonyl groups, so that Tb3+ was effectively sensitized to emit green fluorescence. However, the red fluorescence of DTE-Cu NCs was not interfered. The fluorescence of the probe transformed from red to green with the increase of FQs concentration. Using norfloxacin (NOR), difloxacin (DIF), and enrofloxacin (ENR) as FQs simulants, this probe showed a sensitive linear response ranged from 0.025 to 22.5 μM, with the limits of detection of 9.6 nM, 9.3 nM, and 7.7 nM. The application potential for FQs detection was verified via a standard addition assay of egg samples with the recovery rate of 90.4 %-114.7 %.

SIGNIFICANT

The fluorescence probe based on Tb3+/DTE-Cu NCs is expected to realize the ratiometric fluorescence sensitive detection of FQs. The establishment of this simple, effective, and rapid detection platform opens up a new way for the detection of FQs residues in animal-origin foods, and also provides a new idea for the design of rapid detection platforms for other hazard factors.

A dual-mode fluorescence and colorimetric sensing platform for efficient detection of ofloxacin in aquatic products using iron alkoxide nanozyme

Trace detection of ofloxacin (OFL) with high sensitivity, reliability, and visual clarity is challenging. To address this, a novel dual-modal aptasensor with fluorescence-colorimetric capabilities was designed that exploit the target-induced release of 3,3',5,5'-tetramethylbenzidine (TMB) molecules from aptamer-gated mesoporous silica nanoparticles (MSNs), the oxidase-like activity of iron alkoxide (IA) nanozyme, and the fluorescence attributes of core-shell upconversion nanoparticles. Therefore, the study reports a dual mode detection, with a fluorescence detection range for OFL spanning from 0.1 μg/kg to 1000 μg/kg (and a detection limit of 0.048 μg/kg). Additionally, the colorimetric method offered a linear detection range of 0.3 μg/kg to 1000 μg/kg, with a detection limit of 0.165 μg/kg. The proposed biosensor had been successfully applied to the determination of OFL content in real samples with satisfactory recoveries (78.24-96.14 %).

A novel Zn/Eu-MOF for the highly sensitive, reversible and visualized sensing of ofloxacin residues in pork, beef and fish

The study investigates a bimetallic organic framework (Zn/Eu-MOF) based fluorescent probe for visual detection of ofloxacin (OFL) in pork, beef and fish. The developed sensing probe recognizes OFL through internal filtration and cation-π interaction between OFL and Zn/Eu-MOF, resulting in a distinct color change from orange-red to light green. The content of OFL can be determined through RGB analysis by a mobile-phone. The developed sensing probe offers several advantages such as broad linear range (0.1 ∼ 80 μM), rapid response time (30 s), low detection line (0.44 μM). The effectiveness of the sensing probe can last for five rounds with good recovery. Moreover, the application of the sensing probe on pork, beef and fish samples are reliable, with recoveries ranging from 93.4 to 112.1%, and the relative standard deviations (RSD) within 1.17% to 2.06%. These results suggest that the developed sensing probe could have significant potential for practical on-site test in food.

MWCNT modified Ni-Fe LDH/BiVO4 heterojunction: boosted visible-light-driven photoelectrochemical aptasensor for ofloxacin detection

Sensitivity and selectivity, which can be identified by the photosensitivity of materials and the identification of elements, are two important factors for a photoelectrochemical aptasensor (PEC aptasensor). Herein, a patent PEC aptasensor for specifically detecting ofloxacin (OFL) was exploited, and a visible-light-active MWCNT/LDH/BiVO4 heterostructure was introduced as a photoactive material and identification elements, respectively. The combination of LDH with BiVO4 enhanced the photocurrent response, and MWCNT provided higher electron conductivity, which are advantageous for structuring PEC sensors. Furthermore, the two-pot synthesis of MWCNT/LDH/BiVO4 has the advantage of possessing an environmentally friendly character. Under optimal conditions, the photocurrent response of MWCNT/LDH/BiVO4 presents a linear trend with OFL concentration from 0.1 to 16 000 nM, and the limit of detection (S/N = 3) is as low as 0.03 nM. This new PEC sensing device afforded an ultra-sensitive sensor which has high selectivity and stability for detecting OFL.

Translation of aptamers toward clinical diagnosis and commercialization

The dominance of antibodies in diagnostics has gradually changed following the discovery of aptamers in the early 1990s. Aptamers offer inherent advantages over traditional antibodies, including higher specificity, higher affinity, smaller size, greater stability, ease of manufacture, and low immunogenicity, rendering them the best candidates for point-of-care testing (POCT). In the past 20 years, the research community and pharmaceutical companies have made great efforts to promote the development of aptamer technology. Macugen® (pegaptanib) was the first aptamer drug approved by the US Food and Drug Administration (FDA), and various aptamer-based diagnostics show great promise in preclinical research and clinical trials. In this review, we introduce recent literature, ongoing clinical trials, commercial reagents of aptamer-based diagnostics, discuss the FDA regulatory mechanisms, and highlight the prospects and challenges in translating these studies into viable clinical diagnostic tools.

Electrochemical detection of T4 polynucleotide kinase activity based on magnetic Fe3O4@TiO2 nanoparticles triggered by a rolling circle amplification strategy

An ultrasensitive electrochemical detection of the activity and inhibition of T4 polynucleotide kinase (T4 PNK) was developed by using magnetic Fe₃O₄@TiO₂ core-shell nanoparticles, which was triggered by a rolling circle amplification strategy (Fe₃O₄@TiO₂-RCA). We used Fe₃O₄@TiO₂ as a substrate to anchor a DNA primer. DNA S1 with 5'-OH termini was phosphorylated in the presence of T4 PNK and ATP, which was adsorbed on the surface of Fe₃O₄@TiO₂ NPs and served as the primer for subsequent RCA reactions. After adding circular template DNA S2, RCA was initiated in the presence of phi29 DNA polymerase and dNTPs. Then, Fc-labeled DNA S3 (Fc-S3) was hybridized with RCA. The obtained Fe₃O₄@TiO₂-RCA was adsorbed on the surface of a magnetic gold electrode (MGE) by magnetic enrichment, resulting in an enhanced electrochemical signal. The T4 PNK activity can be monitored by measuring the electrochemical signal generated. This electrochemical assay is sensitive to the activity of T4 PNK with a dynamic linear range of 0.00001-20 U/mL and a low detection limit of 3.0 × 10^-6 U/mL. The proposed strategy can be used to screen the T4 PNK inhibitors, so it has great potential in the discovery of nucleotide kinase-target drug and early clinical diagnosis of cancer.