A HPTLC-Fluorescent Densitometry Assay for Simultaneous Detection of Enrofloxacin and Ciprofloxacin in Broiler Chicken Tissues

Comparison of oriented and non-oriented antibody conjugation with AIE fluorescence microsphere for the immunochromatographic detection of enrofloxacin

Antibodies and labels were typically non-oriented conjugated in conventional immunochromatographic assays (ICAs). In this work, a C-terminal cysteine-tagged recombinant protein A (rPA) was conjugated in an oriented manner onto aggregation-induced emission fluorescence microsphere (AIEFM). The Fc fragment of anti-enrofloxacin monoclonal antibody (anti-ENR mAb) was then conjugated onto the rPA. The resulting oriented mAb-AIEFM probe was used in an ENR-ICA for the rapid detection of ENR, a widely abused animal drug. The ENR-ICA with the oriented probe saved 66.7% of anti-ENR mAb and 25% of ENR-bovine serum albumin, and had a limit of detection of 0.035 ng/mL, compared with 0.079 ng/mL for the non-oriented probe. The corresponding linear ranges of the ENR-ICA based on the oriented and non-oriented probes were 0.25-10 ng/mL and 0.1-2.5 ng/mL, respectively. This novel ICA based on the oriented probe has the potential to be used for sensitive and rapid detection in food safety.

CdSSe Nano-Flowers for Ultrasensitive Raman Detection of Antibiotics

Surface-enhanced Raman scattering (SERS) technique is widely used for the highly sensitive detection of trace residues due to its unparalleled signal amplification ability and plays an important role in food safety, environmental monitoring, etc. Herein, CdSSe nano-flowers (CdSSe NFs) are synthesized via the chemical vapor deposition (CVD) method. CdSSe NFs thin film is used as a SERS substrate with an ultralow limit of detection (LOD, 10−14 M), high apparent enhancement factor (EF, 3.62 × 109), and excellent SERS stability (relative standard deviation, RSD = 3.05%) for probe molecules of Rh6G. Further, CdSSe NFs substrate is successfully applied in the sensitive, quantitative, and label-free analysis of ciprofloxacin (CIP) and enrofloxacin (ENR) antibiotics, which exhibit LODs of below 0.5 ppb. This excellent SERS platform may be widely utilized for sensitive life science and environmental sensing.

High performance thin layer chromatography-densitometry method based on picosecond laser-induced fluorescence for the analysis of thioridazine and its photoproducts

A densitometry method based on steady-state and time-resolved fluorescence assessments for thioridazine and its photoproducts applied on HPTLC plates has been developed. The excitation source was a picosecond diode laser emitting at 375 nm. This method was used for the analysis of the photoproducts resulted from thioridazine irradiation with 266 nm nanosecond-pulsed laser. The validation of the developed method was performed for thioridazine in terms of linearity, precision, limits of detection and quantification. Furthermore, analysis of the photoproducts of irradiated thioridazine was performed by steady-state and time-resolved fluorescence. The fluorescence spectra and fluorescence lifetime of each photoproduct were obtained and the horizontal chromatograms of fluorescence maxima were generated.

A novel electrochemiluminescence immunosensing strategy fabricated by Co(OH)2 two-dimensional nanosheets and Ru@SiO2-Au NPs for the highly sensitive detection of enrofloxacin

In this work, a novel sensitive electrochemiluminescence immunosensor based on Ru@SiO₂-Au NPs and Co(OH)₂ two-dimensional nanosheets (2D Co(OH)₂) is constructed for the detection of enrofloxacin (ENR). Ruthenium bipyridine silica spheres and modified gold nanoparticles were synthesized as immune probe materials, which were combined with ENR antibodies (Abs) to form the immune probe part. 2D Co(OH)₂ with a large specific surface area and good catalytic effect was firstly used as an immune substrate material, and at the same time, it was conjugated with the coating antigen (Ae) of ENR to form an immune substrate. Based on the principle of competitive immunity, ENR and ENR coated antigen could jointly compete for the specific binding sites on the ENR antibody, so as to achieve efficient detection of ENR. Under optimal conditions, the prepared immunosensor exhibited high sensitivity with a wide linear range from 0.0001 to 1000 ng mL^-1 and a low detection limit (LOD) of 0.063 pg mL^-1. The proposed immunosensor has been successfully applied to the detection of ENR residues in poultry, aquatic products and lake water.

Bipyridine- and Copper-Functionalized N-doped Carbon Dots for Fluorescence Turn Off-On Detection of Ciprofloxacin

Herein, a fluorescence turn off-on nanosensor has been successfully developed using functionalized N-doped carbon dots (N-CDs) as the label-free sensing probe for the ultrasensitive detection of Cu²⁺ ions first and then ciprofloxacin (CIP), one of the most commonly used antibiotics for disease control, in the presence of bipyridine. The homogeneous and narrowly distributed N-CDs with a mean size of 5.7 nm and a high quantum yield of 84% are fabricated via the hydrothermal method in the presence of citric acid and ethylenediamine as the carbon and nitrogen sources, respectively. The Cu²⁺ ions serve as both analyte and fluorescence quenchers in the sensing platform of N-CDs, and a good linear response to Cu²⁺ in the range of 0.01-0.35 μM with a limit of detection (LOD) of 0.076 nM is observed. Then, 0.35 μM Cu²⁺ is used as the fluorescence quencher of N-CDs to build up the fluorescence turn off-on sensing probe for the detection of CIP using bipyridine (bipy) as the linker for CIP and Cu²⁺ ions. The addition of CIP to the bipy-Cu@N-CD composites triggers the formation of CIP-bipy-Cu conjugate as well as the release of N-CDs, resulting in the recovery of fluorescence intensity after 6 min of incubation. The sensing probe exhibits a two-phase linear response to CIP in the concentration range of 0.05-1 and 1-50 μM with a LOD of 0.4 nM. In addition, the bipy-Cu@N-CD probe shows high sensitivity toward CIP over the 19 other interferences. Good recovery of 96-110% is also observed when 0.1-0.9 μM CIP is spiked into the real samples. Results obtained in this study clearly demonstrate a newly developed sensing platform with rapid detection of metal ions and antibiotics, which can open an avenue to develop highly efficient and robust sensing probes for the detection of metal ions, organic metabolites, and biomarkers in biological applications.

A ratiometric fluorometric ciprofloxacin assay based on the use of riboflavin and carbon dots

Carbon dots (CDs) were hydrothermally synthesized from selenious yeast. They were further coupled with riboflavin to form a dually emitting probe for ciprofloxacin (CIP). Under 370 nm excitation, the probe displays dual (blue and green) emissions with peaks at 443 and 510 nm. When CIP is added, the blue fluorescence of the CDs is enhanced while the green fluorescence remains unaffected. The ratio of the relative fluorescence intensities at 443 and 510 nm increases linearly in the 0.5-200 μM CIP concentration range. The fluorescent probe is selective and has a 0.13 μM detection limit. Satisfactory recoveries (97.9-101.1%) were received when the probe was used to quantify CIP in spiked water and human serum samples. Graphical abstractBlue-emissive carbon dots were prepared from selenious yeast via a hydrothermal method, and then coupled with riboflavin as a ratiometric fluorometric probe for ciprofloxacin determination.

Sensitive detection of enrofloxacin using an electrochemiluminescence immunosensor based on gold-functionalized C60 and Au@BSA nanoflowers

A novel competitive electrochemiluminescence (ECL) immunosensor based on CdSe quantum dots was developed for the detection of enrofloxacin (Enro).