A novel terbium (III) and aptamer-based probe for label-free detection of three fluoroquinolones in honey and water samples

Fluoroquinolones, a family of synthetic broad-spectrum antibiotics, are widely used in clinical medicine, farm animals and aquaculture. Residues of fluoroquinolones in samples have attracted much attention because of growing food safety and public health concerns. Here, a novel Tb³⁺ ion-enrofloxacin aptamer coordination probe was prepared to develop a sensitive and rapid label-free fluorescence assay for specific detection three fluoroquinolones. In presence of the target, Tb³⁺ ion- enrofloxacin aptamer probe specifically bound with enrofloxacin, norfloxacin and ciprofloxacin, leading to a sharp increase in fluorescence emission of the probe. Under the optimized conditions, fluorescence increased linearly in the 1.0-100.0 ng/mL range for the three fluoroquinolones, with 0.053 ng/mL limit of detection for ciprofloxacin, 0.020 ng/mL limit of detection for norfloxacin and 0.061 ng/mL limit of detection for enrofloxacin. Satisfactory recovery (80.10-102.48%) in spiked honey and water samples were obtained for the three fluoroquinolones with relative standard deviations between 0.21% and 5.44% (n = 3).

Quinolone Complexes with Lanthanide Ions: An Insight into their Analytical Applications and Biological Activity

Quinolones comprise a series of synthetic bactericidal agents with a broad spectrum of activity and good bioavailability. An important feature of these molecules is their capacity to bind metal ions in complexes with relevant biological and analytical applications. Interestingly, lanthanide ions possess extremely attractive properties that result from the behavior of the internal 4f electrons, behavior which is not lost upon ionization, nor after coordination. Subsequently, a more detailed discussion about metal complexes of quinolones with lanthanide ions in terms of chemical and biological properties is made. These complexes present a series of characteristics, such as narrow and highly structured emission bands; large gaps between absorption and emission wavelengths (Stokes shifts); and long excited-state lifetimes, which render them suitable for highly sensitive and selective analytical methods of quantitation. Moreover, quinolones have been widely prescribed in both human and animal treatments, which has led to an increase in their impact on the environment, and therefore to a growing interest in the development of new methods for their quantitative determination. Therefore, analytical applications for the quantitative determination of quinolones, lanthanide and miscellaneous ions and nucleic acids, along with other applications, are reviewed here.

Ribonucleic acid (RNA) condensation by thermal cycling with metal cations: yield of nanoparticles and their applicability for transfection

To the present, different efficient but expensive, multistage, and time-consuming technologies have been developed to deliver ribonucleic acids (RNA) into eukaryotic cells. Here, we report a simple and feasible solution to design RNA nanocarriers based on nucleic acid condensation by bi- and trivalent metal ions during thermal cycling. Efficient RNA conversion to nanoparticles with small size (10-50 nm) suitable for transfection was achieved using cations Ni²⁺, Co²⁺ or Cu²⁺ alone or in combination with Ca²⁺ at the specially selected concentrations (2.0 mM-3.5 mM), low ionic strength, and narrow pH range (8.0-8.5). Other ions - Mn²⁺, Zn²⁺, Tb³⁺, or Gd³⁺ - caused RNA-cleaving effect that was abolished in the presence of Ni²⁺, Co²⁺, Zn²⁺, or Cu²⁺. Naked RNA-metal ion nanoparticles were extremely unstable in phosphate buffer and sensitive to serum ribonucleases (RNases), and this problem was solved by treatment with polyarginines-16 and 8. Polyarginine-stabilized nanoparticles, containing malachite green (MG) aptamer RNA and metal cations, crossed the cell membrane, dissociated in the cytoplasm, and preserved the functionality of transported RNA, as judged from efficient transfection of human embryonic kidney 293 cells. The technology, involving RNA condensation by metal cations, can be used as a cheap alternative to produce nanoscale carriers to deliver various RNAs into cells in vitro and in vivo.Communicated by Ramaswamy H. Sarma.