Ratiometric detection of doxycycline in pharmaceutical based on dual ligands-enhanced copper nanoclusters

A Ratio Fluorescence Method Based on Dual Emissive Copper Nanoclusters for the Detection of Vanillin

In this study, a novel double-emission fluorescence probe at 340 and 400 nm was synthesized by one-pot method using phenylalanine (Phe) and ascorbic acid (AA) as stabilizing and reducing agents. It was found that the fluorescence intensity of the probe at 400 nm could be controlled by controlling the temperature within a certain range, and the ratio of double-emission fluorescence probe could be further regulated. Under the optimal conditions, the fluorescence intensity at 340 nm decreased significantly, while it only showed a slight decrease at 400 nm, which constituted the ratio fluorescence probe. The synthesized fluorescence probe showed good linearity in the range of 0.2-32 μM, and its detection limit was 63.4 nM. Moreover, the method was successfully employed to determine VA in vanilla drink and perfumes, and corresponding results were consistent with those of HPLC.

Histidine-capped copper nanoclusters for in situ amplified fluorescence monitoring of doxycycline through inner filter effect

There is a significant need to accurately measure doxycycline concentrations in view of the adverse effects of an overdose on human health. A fluorescence (FL) detection method was adopted and copper nanoclusters (CuNCs) were synthesized using chemical reduction technology. Based on FL quenching with doxycycline, the prepared CuNCs were used to explore a fluorescent nanoprobe for doxycycline detection. In an optimal sensing environment, this FL nanosensor was sensitive and selective in doxycycline sensing and displayed a linear relationship in the range 0.5-200 μM with a detection limit of 0.092 μΜ. A characterization test demonstrated that CuNCs offered active functional groups for identifying doxycycline using electrostatic interaction and hydrogen bonds. Static quenching and the inner filter effect (IFE) resulted in weakness in the FL of His@CuNCs with doxycycline with great efficiency. This suggested nanosensor was revealed to be a functional model for simple and rapid detection of doxycycline in real samples with very pleasing accuracy.

A sensitive multicolor fluorescence sensing strategy for chlorotetracycline based on bovine serum albumin-stabilized copper nanocluster

Fluorescent probes with on-site visual detection function have received extensive attention in the detection of chlortetracycline (CTC), which was widely used in aquaculture and animal husbandry. Copper nanoclusters (Cu NCs) with excellent optical properties were prepared using bovine serum albumin (BSA) as a template, and a multicolor fluorescence strategy based on BSA-stabilized Cu NCs (BSA-Cu NCs) for detecting CTC was proposed. BSA-Cu NCs had a red emission at 640 nm. After the addition of CTC, the red emission of BSA-Cu NCs gradually decreased for internal filtering effect, while the green emission of CTC was significantly enhanced under the sensitization of BSA. This simple sensing process can be achieved in real time by directly mixing the target sample with BSA-Cu NCs, and the detection limit (LOD) of the system for CTC was 12.01 nM. Based on this sensing strategy, a fluorescence film sensing detection platform was constructed to achieve ultra-fast detection of CTC within 30 s. This work provided a fluorescent film sensor with the advantages of portability, ultra-fast and low cost, which provided a feasible alternative for on-site ultra-fast screening of CTC.

Characterization of Climbazole-Bovine serum albumin interaction by experimental and in silico approaches

Interactive association of an antifungal drug, climbazole (CBZ) with the carrier protein in bovine circulation, bovine serum albumin (BSA) was explored by fluorescence and absorption spectroscopy along with in silico techniques. The fluorescence and absorption spectral alterations of the protein upon addition of CBZ affirmed the complex foration between CBZ and BSA. The inverse temperature dependence behaviour of the K_SV values as well as the hyperchromic result of the protein's absorption signals characterized CBZ-triggered quenching of BSA fluorescence as the static quenching. A weak binding affinity (K_a = 3.12-1.90-× 10³ M^-1) was reported towards the CBZ-BSA association process. Interpretation of thermodynamic data (entropy change = +14.68 J mol^-1 K^-1 and enthalpy change = -15.07 kJ mol^-1) and in silico analyses anticipated that hydrophobic forces, van der Waals forces and hydrogen bonds were the key intermolecular forces in the complex stabilization. Inclusion of CBZ to BSA produced microenvironmental perturbations around Tyr and Trp residues, and also significantly defended temperature-induced destabilization of BSA. The binding locus of CBZ was detected in the proximity of Sudlow's sites I (subdomain IIA) and II (subdomain IIIA) of BSA, exhibiting greater preference towards site II, as revealed by competitive site-marker displacement investigations and in silico analysis. The stability of the CBZ-BSA complex was further validated by the molecular dynamics simulation assessments.

Synthesis of Copper Nanoclusters and Their Application for Environmental Pollutant Probes: A Review

Copper nanoclusters (CuNCs) as a new type of probe for environmental contaminants are gaining increasing attention because of its low cost, superior water dispersibility, wide availability and excellent optical properties. Compared with the other probes such as quantum dots and organic dyes, CuNCs show much more potential in practical application for their excellent photostability, large Stokes shift, low toxicity and other preponderance, especially in the fields of biosensing and environmental monitoring. Recently, the template-assisted synthesis of metal nanoclusters (MNCs) has been widely studied. A variety of templates such as proteins, small thiol molecules, polymers, and DNA with different spatial configuration have been used for the preparation of MNCs so far. This review primarily described recent advances in CuNCs in terms of the synthesis of CuNCs from different templates, the methods to improve the fluorescence (FL) properties of CuNCs, as well as the basic detection mechanisms based on the FL properties or catalytic properties. Finally, to promote the practical application of CuNCs probes, the challenges and prospects of CuNCs multifunctional probes are also discussed.

Ratiometric fluorescence and visual determination of tetracycline antibiotics based on Y3+ and copper nanoclusters-induced cascade signal amplification

A ratiometric fluorescence probe is proposed for sensitive and visual detection of tetracyclinee (TC) based on cascade fluorescence signal amplification induced by bovine serum albumin-stabilized copper nanoclusters (BSA-CuNCs) and yttrium ions (Y³⁺). TC can combine with Y³⁺ to form the complex (TC-Y³⁺) to enhance the fluorescence of TC at 515 nm. Then, positively charged TC-Y³⁺ and negatively charged BSA-CuNCs was bonded together by electrostatic interactions to achieve the fluorescence resonance energy transfer (FRET) process. With the increase of TC concentration, the fluorescence intensity of TC-Y³⁺ at 515 nm (F₅₁₅) gradually increased; meanwhile, the fluorescence intensity of BSA-CuNCs at 405 nm (F₄₀₅) decreased gradually. The ratio of F₅₁₅ and F₄₀₅ was used for the quantitative determination of TC. The linear range of the constructed fluorescent probe is 1.0 to 60.0 μM, and the limit of detection is 0.22 μM. The method was successfully applied to the determination of TC in spiked milk with recoveries ranging from 94.3 to 112%. Furthermore, the color of this platform can be observed from dark violet to bright green under the UV lamp. Since the response time of the reaction is less than 10 s, an intelligent sensing platform based on the use of the smartphone as image acquisition equipment was also established to realize rapid on-site and portable detection of TC through the colorimetric recognition application.

Construction of a copper nanocluster/MnO2 nanosheet-based fluorescent platform for butyrylcholinesterase activity detection and anti-Alzheimer's drug screening

An abnormal level of butyrylcholinesterase (BChE) activity is highly connected with hepatic damage and Alzheimer's disease. Herein, a facile and efficient method was proposed for BChE detection by incorporating polyethyleneimine-capped copper nanoclusters (PEI-CuNCs) with manganese dioxide (MnO₂) nanosheets. The emission of PEI-CuNCs can be significantly quenched by MnO₂ nanosheets via the inner filter effect. With the addition of BChE, the hydrolysis of butyrylthiocholine iodide produces thiocholine which can reduce MnO₂ nanosheets to Mn²⁺, thus resulting in the fluorescence recovery of PEI-CuNCs. Based on that, a fluorescence "turn-on" sensing platform for BChE activity determination was constructed with a detection limit of 2.26 U L^-1. This sensing method is able to detect BChE in human serum samples and identify the serums of normal persons and cirrhotic patients effectively, indicating its great potential in the clinical diagnosis of liver diseases. Furthermore, the approach can also be used to screen BChE inhibitors, which are promising medications to alleviate the symptoms of Alzheimer's disease.