A novel metal-organic frameworks composite-based label-free point-of-care quartz crystal microbalance aptasensing platform for tetracycline detection

Deep eutectic solvent-assisted synthesis of La-Ce hybrid nanorods for the colorimetric determination of tetracycline in foods

Tetracycline (TC) as a broad-spectrum antibiotic, is widely used in the prevention and treatment of various bacterial diseases. However, its abuse in the livestock industry may lead to interference in human microecology, thereby causing various side effects. In this study, deep eutectic solvents (DESs) were synthesized using L-(-)-threonine (L-(-)-Thr) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and later lanthanum nitrate hexahydrate (La(NO3)3·6H2O) was doped to synthesize La-Ce hybrid nanorods. These nanorods can be used for the determination of TC with high sensitivity and selectivity by the colorimetric method. This approach has a linear response to TC between 0.05 μM and 10 μM, with a detection limit of 0.016 μM. In this system, good dispersion provides the substance with a distinct peroxidase activity, which is used to create a colorimetric sensor for detecting TC. Mechanism studies show that the superoxide radical generated by the La-Ce nanomembrane plays a key role in peroxidase catalysis. Finally, the practicality of the method was verified by the determination of TC in food products (milk, pork and honey), which demonstrated that a good recovery rate can be obtained (91.4-102%).

Quartz crystal microbalance-based aptasensor integrated with magnetic pre-concentration system for detection of Listeria monocytogenes in food samples

A fast and accurate identification of Listeria monocytogenes. A new quartz crystal microbalance (QCM) aptasensor was designed for the specific and rapid detection of L. monocytogenes. Before detection of the target bacterium from samples in the QCM aptasensor, a magnetic pre-enrichment system was used to eliminate any contaminant in the samples. The prepared magnetic system was characterized using ATR-FTIR, SEM, VSM, BET, and analytical methods. The saturation magnetization values of the Fe3O4, Fe3O4@PDA, and Fe3O4@PDA@DAPEG particles were 57.2, 40.8, and 36.4 emu/g, respectively. The same aptamer was also immobilized on the QCM crystal integrated into QCM flow cell and utilized to quantitatively detect L. monocytogenes cells from the samples. It was found that a specific aptamer-magnetic pre-concentration system efficiently captured L. monocytogenes cells in a short time (approximately 10 min). The Fe3O4@PDA@DA-PEG-Apt particles provided selective isolation of L. monocytogenes from the bacteria-spiked media up to 91.8%. The immobilized aptamer content of the magnetic particles was 5834 µg/g using 500 ng Apt/mL. The QCM aptasensor showed a very high range of analytical performance to the target bacterium from 1.0 × 102 and 1.0 × 107 CFU/mL. The limit of detection (LOD) and limit of quantitation (LOQ) were 148 and 448 CFU/mL, respectively, from the feeding of the QCM aptasensor flow cell with the eluent of the magnetic pre-concentration system. The reproducibility of the aptasensor was more than 95%. The aptasensor was very specific to L. monocytogenes compared to the other Listeria species (i.e., L. ivanovii, L. innocua, and L. seeligeri) or other tested bacteria such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. The QCM aptasensor was regenerated with NaOH solution, and the system was reused many times.

A Recent Advancement in Food Quality Assessment: Using MOF-Based Sensors: Challenges and Future Aspects

Monitoring food safety is crucial and significantly impacts the ecosystem and human health. To adequately address food safety problems, a collaborative effort needed from government, industry, and consumers. Modern sensing technologies with outstanding performance are needed to meet the growing demands for quick and accurate food safety monitoring. Recently, emerging sensors for regulating food safety have been extensively explored. Along with the development in sensing technology, the metal-organic frameworks (MOF)-based sensors gained more attention due to their excellent sensing, catalytic, and adsorption properties. This review summarizes the current advancements and applications of MOFs-based sensors, including colorimetric, electrochemical, luminescent, surface-enhanced Raman scattering, and electrochemiluminescent sensors. and also focused on the applications of MOF-based sensors for the monitoring of toxins such as heavy metals, pesticide residues, mycotoxins, pathogens, and illegal food additives from food samples. Future trends, as well as current developments in MOF-based materials.

A universal design of turn-on fluorescent aptasensor based on luminescent MOFs: Application for the detection of bisphenol A in water, milk and chicken samples

A universal design of turn-on fluorescent aptasensor based on aptamer functionalized gold nanoparticles (AuNPs) and luminescent metal-organic frameworks (LMOFs) complex (AuNPs-Apt/NH₂-MIL-125(Ti)) was realized for bisphenol A (BPA) detection. LMOF NH₂-MIL-125(Ti) was prepared using facial hydrothermal method. BPA aptamer functionalized AuNPs were prepared and adsorbed on the surface of NH₂-MIL-125(Ti) to obtain platform of the fluorescent aptasensor. The fabrication process, sensing performance and applicability of the proposed aptasensor were characterized and investigated carefully. Linear detection range of the constructed aptasensor was from 1 × 10^-9 mol L^-1 to 1 × 10^-4 mol L^-1 with good selectivity, repeatability, stability and reproducibility under optimal experimental conditions. Meanwhile, the fluorescent aptasensor was successfully utilized for BPA detection in real samples with the recoveries of 95.80%-103.12%. The proposed aptasensor based on AuNPs-Apt/NH₂-MIL-125(Ti) holds significant potential for BPA detection in environmental and food samples, promoting the construction and application of LMOFs-based aptasensor.

Formation of Gold Nanoclusters from Goldcarbonyl Chloride inside the Metal-Organic Framework HKUST-1

Gas-phase infiltration of the carbonylchloridogold(I), Au(CO)Cl precursor into the pores of HKUST-1 ([Cu3(BTC)2(H2O)2], Cu-BTC) SURMOFs (surface-mounted metal-organic frameworks; BTC = benzene-1,3,5-tricarboxylate) leads to Au(CO)Cl decomposition within the MOF through hydrolysis with the aqua ligands on Cu. Small Aux clusters with an average atom number of x ≈ 5 are formed in the medium-sized pores of the HKUST-1 matrix. These gold nanoclusters are homogeneously distributed and crystallographically ordered, which was supported by simulations of the powder X-ray diffractometric characterization. Aux@HKUST-1 was further characterized by scanning electron microscopy (SEM) and infrared reflection absorption (IRRA) as well as Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectroscopy (ICP-OES).

Collaboration of two-star nanomaterials: The applications of nanocellulose-based metal organic frameworks composites

Nanocellulose, as the star nanomaterial in carbohydrate polymers, has excellent mechanical properties, biodegradability, and easy chemical modification. However, further practical applications of nanocellulose are limited by their inadequate functionalization. Metal-organic frameworks (MOFs), as the star nanomaterial in functional polymers, have a large surface area, high porosity, and adjustable structure. The collaboration of nanocellulose and MOFs is a desirable strategy to make composites especially interesting for multifunctional and multi-field applications. What sparks will be produced by the collaboration of two-star nanomaterials? In this review article, we highlight an up-to-date overview of nanocellulose-based MOFs composites. The sewage treatment, gas separation, energy storage, and biomedical applications are mainly summarized. Finally, the challenges and research trends of nanocellulose-based MOFs composites are prospected. We hope this review may provide a valuable reference for the development and applications of carbohydrate polymer composites soon.