Stir flat sheet membrane liquid phase microextraction for the selective chemiluminescence determination of ofloxacin and fleroxacin in human urine

Micelle-mediated chemiluminescence of 6-aza-2-thiothymine-protected gold nanoclusters for carbazochrome sodium sulfonate detection

Chemiluminescence (CL) intensity of luminol-H2O2 system was dramatically enhanced by cetyltrimethylammonium bromide (CTAB) micelle-mediated 6-aza-2-thiothymine-protected gold nanoclusters (ATT-AuNCs). It is proved that spherical micelles of CTAB in aqueous solution improved the dispersity of ATT-AuNCs, thus enhancing their catalytic activity, which brought in the increased CL intensity of luminol-H2O2 system. Carbazochrome sodium sulfonate (CSS) with a hemostatic containing tetrahydroindole structure broke the spherical micelles and notably quenched the CL intensity of luminol-H2O2-CTAB-ATT AuNCs system. Based on these results, a simple, fast, and sensitive CL method has been developed for the detection of CSS with a linear range of 0.25-25 μM and a detection limit of 0.11 μM. The method has also been successfully applied to the determination of CSS in serum with satisfied recoveries in the range of 89.6 % to 103.7 %. This study not only provides an effective approach for CSS detection but also paves the way for AuNCs-based CL applications.

A direct electrochemical sensor based on covalent organic frameworks/platinum nanoparticles for the detection of ofloxacin in water

A direct electrochemical sensor based on covalent organic frameworks (COFs)/platinum nanoparticles (PtNPs) composite was fabricated for the detection of ofloxacin (OFX) in water. Firstly, the COF material was synthesized via the condensation reaction of 1,3,5-tris(4-aminophenyl)benzene (TAPB) with terephthalaldehyde (TPA) and integrated with PtNPs by in situ reduction. Then, TAPB-TPA-COFs/PtNPs composite was loaded onto the surface of the glassy carbon electrode (GCE) by drip coating to construct the working electrode (TAPB-TPA-COFs/PtNPs/GCE). The electrochemical performance of TAPB-TPA-COFs/PtNPs/GCE showed a significant improvement compared with that of TAPB-TPA-COFs/GCE, leading to a 3.2-fold increase in the electrochemical signal for 0.01 mM OFX. Under optimal conditions, the TAPB-TPA-COFs/PtNPs/GCE exhibited a wide linear range of 9.901 × 10-3-1.406 µM and 2.024-15.19 µM with a detection limit of 2.184 × 10-3 µM. The TAPB-TPA-COFs/PtNPs/GCE-based electrochemical sensor with excellent performance provides great potential for the rapid and trace detection of residual OFX.

Aptamer-Based Functionalized SERS Biosensor for Rapid and Ultrasensitive Detection of Gastric Cancer-Related Biomarkers

Background

Gastric cancer (GC) as is the second deadliest malignancy still lacks rapid, simple and economical detection and early clinical screening techniques. Surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique based on the surface plasmon resonance of precious metal nanoparticles, which can effectively detect low-abundance tumor markers. Combining SERS technology with sensors has high potential in the diagnosis and screening of GC.

Methods

A novel Au/Si nano-umbrella array (Au/SiNUA) was prepared as a SERS substrate and the substrate was functionalized using the corresponding tumor marker aptamers for the detection of clinical biological samples using a one-step recognition release mechanism. Optimization of aptamer and complementary chain concentrations and detection time for optimal sensor preparation.

Results

Au/SiNUA were tested to have good SERS enhancement activity. The proposed aptamer biosensor has good specificity and stability, with a low detection time of 18 min and a limit of detection (LOD) at the fM level, which is superior to most of the methods reported so far; and the accuracy of the clinical assay is comparable to that of the ELISA method. The expression levels of PDGF-B and thrombin in the serum of GC patients and healthy individuals can be effectively detected and differentiated.

Conclusion

The ultrasensitive and specific aptamer biosensor is highly feasible for the diagnosis and screening of GC and has good application prospects.

Construction of graphene quantum dots ratiometric fluorescent probe by intermolecular electron transfer effect for intelligent and real-time visual detection of ofloxacin and its L-isomer in daily drink

The design of intelligent and real-time sensing devices is significant in the medical drug monitoring field, but it is still highly challenging. Here, ratiometric fluorescent detections of ofloxacin (OFL) and its L-isomer levofloxacin (LEV) constructed from tri-doped graphene quantum dots (T-GQDs) are reported, and the detection limits reach as low as 46/67 nM toward OFL/LEV due to the intermolecular electron transfer (intermolecular ET) effect. After adding OFL/LEV, the generation of electrostatic bond provides a channel for the intermolecular ET from the edge of T-GQDs to OFL/LEV, resulting in the fluorescence quenching at 414 nm and the fluorescence promoting at 498 nm. Furthermore, a smartphone can be used for the visual and quantitative detection of OFL and LEV by identifying the RGB values of test paper and drink samples. This work not only reveals the physics mechanism of ratiometric detection, but also develops a convenient smartphone diagnostic for OFL and LEV.

Cu/Au nanoclusters with peroxidase-like activity for chemiluminescence detection of α-amylase

Herein, a novel chemiluminescence method was developed for efficient and sensitive detection of α-amylase activity. α-Amylase is closely related to our life, and α-amylase concentration is a marker for the diagnosis of acute pancreatitis. In this paper, Cu/Au nanoclusters with peroxidase-like activity were prepared using starch as a stabilizer. Cu/Au nanoclusters can catalyze H₂O₂ to generate reactive oxygen species and increase the CL signal. The addition of α-amylase makes the starch decompose and causes the nanoclusters to aggregate. The aggregation of the nanoclusters caused them to increase in size and decrease in the peroxidase-like activity, resulting in a decrease in the CL signal. α-Amylase was detected by the CL method of signal changes caused by dispersion-aggregation in the range of 0.05-8 U mL^-1 with a low detection limit of 0.006 U mL^-1. The chemiluminescence scheme based on the luminol-H₂O₂-Cu/Au NC system is of great significance for the sensitive and selective determination of α-amylase in real samples, and the detection time is short. This work provides new ideas for the detection of α-amylase based on the chemiluminescence method and the signal lasts for a long time, which can realize timely detection.

Green microfluidic liquid-phase microextraction of polar and non-polar acids from urine

In this work, hippuric acid (log P = 0.5), anthranilic acid (log P = 1.3), ketoprofen (log P = 3.6), and naproxen (log P = 3.0) were simultaneously extracted by a green microfluidic device based on the principles of liquid-phase microextraction (LPME). Different deep eutectic solvents (DESs) were investigated as supported liquid membrane (SLM), and a mixture of camphor and menthol as eutectic solvents in the molar ratio 1:1 was found to be highly efficient for the simultaneous extraction of non-polar and polar acidic drugs. LPME was conducted for 6 min per sample. Urine sample was delivered to the system at 1 μL min^-1, and target analytes were extracted exhaustively (75-100% recovery) across the DES SLM, and into pure aqueous phosphate buffer pH 11.0 delivered as acceptor at 1 μL min^-1. The acceptor was analyzed with liquid chromatography-UV detection. Interestingly, the DES enabled extraction of both the polar and non-polar model analytes at the same time; all chemicals were green and non-hazardous, and the chemical waste was less than 1 mg per sample.