A sensitive fluorescent sensor based on the photoinduced electron transfer mechanism for cefixime and ctDNA

Quantum dots based sensitive nanosensors for detection of antibiotics in natural products: A review

Residual antibiotics in food products originated from administration of the antibiotics to animals may be accumulated through food metabolism in the human body and endanger safety and health. Thus, developing a prompt and accurate way for detection of antibiotics is a crucial issue. The zero-dimensional fluorescent probes including metals based, carbon and graphene quantum dots (QDs), are highly sensitive materials to use for the detection of a wide range of antibiotics in natural products. These QDs demonstrate unique optical properties like tunable photoluminescence (PL) and excitation-wavelength dependent emission. This study investigates the trends related to carbon and metal based QDs preparation and modification, and their diverse detection application. We discuss the performance of QDs based sensors application in various detection systems such as photoluminescence, photoelectrochemical, chemiluminescence, electrochemiluminescence, colorimetric, as well as describing their working principles in several samples. The detecting mechanism of a QDs-based sensor is dependent on its properties and specific interactions with particular antibiotics. This review also tries to describe environmental application and future perspective of QDs for antibiotics detection.

Synthesis and Investigation of Derivatives of 1,8-Naphthalimide with a Red Emission via an Aromatic Nucleophilic Substitution Reaction

1,8-Napthalimides (NIs) have been widely used as fluorescent molecules in biological, chemical, and medical fields because NIs shows high stability and various fluorescence properties under different conditions. However, NIs typically display a fluorescence emission wavelength in the range of 350 - 550 nm which can be notably interfered with by autofluorescence in living cells, significantly limiting their bio-applications. Moreover, low solubility in aqueous media is another major limitation for NIs. In this project, four derivatives of NIs (1-4) have been synthesized via an aromatic nucleophilic substitution reaction and their photophysical properties have been investigated in various media (water, MeOH, MeCN, DMSO, EtOAc, and THF). All of these derivatives (1-4) show a long emission wavelength around 600 nm and high solubility in polar solvents. Particularly molecules (1-4) show the longest emission (624-629 nm) in water and the fluorescence intensity is not significantly varied in the range of pH 4-11. These unique features, long emission wavelength, high solubility, and high stability in difference pH media, will allow these derivative (1-4) to be used as excellent labeling reagents in the biological system.

A novel SERS sensor for the ultrasensitive detection of kanamycin based on a Zn-doped carbon quantum dot catalytic switch controlled by nucleic acid aptamer and size-controlled gold nanorods

In this study, a novel surface enhanced Raman spectroscopy (SERS) sensor was developed for the ultrasensitive determination of kanamycin in foods. The sensor used two distinct signal amplification strategies, namely the surface plasmon resonance of gold nanorods and a Zn-doped carbon quantum dots catalytic cascade oxidation-reduction reaction switch controlled by a nucleic acid aptamer. Under optimized experimental conditions, the SERS sensor demonstrated a linear range of 10^-12 to 10^-5 g mL^-1 for the detection of kanamycin, with a limit of detection of 3.03 × 10^-13 g mL^-1. Experiments with antibiotics structurally similar to kanamycin and interferrants revealed that the sensor had excellent selectivity. Milkpowder and honey samples spiked with kanamycin were assayed, with recoveries ranging from 84.1% to 107.2% and a relative standard deviation of 0.74% to 2.81% being obtained. Quantification of kanamycin in milk samples revealed no significant difference between the results obtained with the sensor and by HPLC.

Fluorescent reversible regulation of cysteamine-capped ZnSe quantum dots successively induced by photoinduced electron transfer of herring sperm DNA and intercalation binding of ethidium bromide

A fluorescent reversible regulation was studied by fluorescence spectra, ultraviolet-visible spectra in the combination of molecular docking, which based on the photoinduced electron transfer(PET) from hsDNA (herring sperm DNA) to CA (cysteamine)-capped ZnSe QDs (quantum dots) and intercalation of ethidium bromide (EB) into hsDNA. It was proven that the QDs bound with the adding hsDNA by electrostatic force and formed 1:1 hsDNA-QDs complexes, leading to the PET from hsDNA to QDs, and consequently the fluorescence quenching of the QDs; with EB being added in the complex solution, it bound with hsDNA by intercalation interaction and caused hsDNA releasing from hsDNA-QDs complex with forming 2.5:1 EB-hsDNA complex, leading to the recovery of fluorescence, based on the greater binding constant (1.74 × 106 L·mol-1) of hsDNA with the embedded EB comparing to that of QDs with the captured hsDNA (4.25 × 104 L·mol-1). A good linear relationship existed between the fluorescence recovery yield and the EB concentrations under the range of 1.0-12.0 × 10-6 mol·L-1 with bare interference of related substances. This work provided some useful insights into the study of binding mechanism between DNAs with their intercalators and fluorescence bi-direction regulation, and showed great potential for the determination of trace EB.