Fluorescence "turn-off/turn-on" biosensing of metal ions by gold nanoclusters, folic acid and reduced graphene oxide

Magnetic covalent organic frameworks for extraction and determination of endocrine-disrupting chemicals in beverage and water samples

BACKGROUND

Phenolic endocrine-disrupting chemicals (EDCs) are widespread and easily ingested through the food chain. They pose a serious threat to human health. Magnetic solid-phase extraction (MSPE) is an effective sample pre-treatment technology to determine traces of phenolic EDCs.

RESULTS

Magnetic covalent organic framework (COF) (Fe3 O4 @COF) nanospheres were prepared and characterized. The efficient and selective extraction of phenolic EDCs relies on a large specific surface and the inherent porosity of COFs and hydrogen bonding, π-π, and hydrophobic interactions between COF shells and phenolic EDCs. Under optimal conditions, the proposed magnetic solid-phase extraction-high-performance liquid chromatography-ultra violet (MSPE-HPLC-UV) based on the metallic covalent organic framework method for phenolic EDCs shows good linearities (0.002-6 μg mL-1 ), with R2 of 0.995 or higher, and low limits of detection (6-1.200 ng mL-1 ).

CONCLUSION

Magnetic covalent organic frameworks (Fe3 O4 @COFs) with good MSPE performance for phenolic EDCs were synthesized by the solvothermal method. The magnetic covalent organic framework-based MSPE-HPLC-UV method was applied successfully to determine phenolic EDCs in beverage and water samples with satisfactory recoveries (90.200%-123%) and relative standard deviations (2.100%-12.100%). © 2023 Society of Chemical Industry.

Aggregation-induced emission enhancement of gold nanoclusters triggered by sodium heparin and its application in the detection of sodium heparin and alkaline amino acids

This work first reported that sodium heparin could cause the aggregation-induced emission enhancement (AIEE) effect of GSH-AuNCs (Glutathione functionalized gold nanoclusters). While it was interestingly found that the addition of alkaline amino acids would greatly weaken this effect. Thus, fluorescent system was designed for the quantitative detection of sodium heparin and alkaline amino acids. Negatively charged sodium heparin would connect with GSH-AuNCs through electrostatic attraction, leading to a significant AIEE effect. Then alkaline amino acids would competitively bind with sodium heparin, causing this effect to almost disappear. The reasons were as follows: (I) The hydrogen bonding between sodium heparin and alkaline amino acids was much stronger than electrostatic force, causing GSH-AuNCs to be competitively replaced. (II) Alkaline amino acids and GSH-AuNCs were both positively charged and repelled each other. The presence of alkaline amino acids would hinder the AIEE effect. (III) AIEE effect was confirmed to have a close relationship with the pH value which could be greatly affected by alkaline amino acids. (Ⅳ) Not only the hydrogen bonding, the electrostatic force also existed between the alkaline amino acids and sodium heparin. All the above reasons worked together to weaken the AIEE effect of GSH-AuNCs triggered by sodium heparin. Finally, both sodium heparin and alkaline amino acids were accurately detected, showing good correlation coefficients of 0.99 with the LODs of 0.0100 mg/mL (sodium heparin), 1.05 μM (histidine), 3.38 μM (arginine) and 6.16 μM (lysine), respectively.

Fluorescence anisotropy cytosensing of folate receptor positive tumor cells using 3D polyurethane-GO-foams modified with folic acid: molecular dynamics and in vitro studies

Integrated polyurethane (PU)-based foams modified with PEGylated graphene oxide and folic acid (PU@GO-PEG-FA) were developed with the goal of capturing and detecting tumor cells with precision. The detection of the modified PU@GO-PEG surface through FA against folate receptor-overexpressed tumor cells is the basis for tumor cell capture. Molecular dynamics (MD) simulations were applied to study the strength of FA interactions with the folate receptor. Based on the obtained results, the folate receptor has intense interactions with FA, which leads to the reduction in the FA interactions with PEG, and so decreases the fluorescence intensity of the biosensor. The synergistic interactions offer the FA-modified foams a high efficiency for capturing the tumor cell. Using a turn-off fluorescence technique based on the complicated interaction of FA-folate receptor generated by target recognition, the enhanced capture tumor cells could be directly read out at excitation-emission wavelengths of 380-450 nm. The working range is between 1×10 ² to 2×10 ⁴ cells mL ^-1 with a detection limit of 25 cells mL ^-1 and good reproducibility with relative standard deviation of 2.35%. Overall, findings demonstrate that the fluorescence-based biosensor has a significant advantage for early tumor cell diagnosis.

Reduced graphene oxide: Biofabrication and environmental applications

Green synthesis of high-quality reduced graphene oxide (rGO) from agro-industrial waste resources remains attractive owing to its outstanding environmental benefits. The remarkable properties of rGO include excellent morphology, uniform particle size, good optical properties, high conductivity, nontoxicity, and extraordinary chemical stability. Traditional methods for the synthesis of rGO nanomaterials involve several chemical reactions including oxidation, carbonization, toxic solvent, and pyrolysis which produce harmful byproducts. Green preparation of rGO is an emerging area of research in graphene technology which is cost-effective and sustainable in the procedure. Owing to the uniform particle rGO particle size, these smart nanomaterials have wide applicability, including in metal ions and pollutant sensing and adsorption, photocatalysis, optoelectrical devices, medical diagnosis, and drug delivery. Here we review the physicochemical properties of rGO, the biowaste sources and green methods of rGO synthesis, and the diverse applications of rGO, including in water purification and the biomedical fields. With this review, covering more than 200 research articles published on rGO in the last eight years ending in 2022, we aim to provide a quick guide for researchers seeking up-to-date information on the properties, production, and applicability of rGO, with special attention to rGO applications in water purification and the biomedical fields.

Nanocluster-Based Drug Delivery and Theranostic Systems: Towards Cancer Therapy

Over the last decades, the global life expectancy of the population has increased, and so, consequently, has the risk of cancer development. Despite the improvement in cancer therapies (e.g., drug delivery systems (DDS) and theranostics), in many cases recurrence continues to be a challenging issue. In this matter, the development of nanotechnology has led to an array of possibilities for cancer treatment. One of the most promising therapies focuses on the assembly of hierarchical structures in the form of nanoclusters, as this approach involves preparing individual building blocks while avoiding handling toxic chemicals in the presence of biomolecules. This review aims at presenting an overview of the major advances made in developing nanoclusters based on polymeric nanoparticles (PNPs) and/or inorganic NPs. The preparation methods and the features of the NPs used in the construction of the nanoclusters were described. Afterwards, the design, fabrication and properties of the two main classes of nanoclusters, namely noble-metal nanoclusters and hybrid (i.e., hetero) nanoclusters and their mode of action in cancer therapy, were summarized.