Mixed hemimicelles solid-phase extraction of cephalosporins in biological samples with ionic liquid-coated magnetic graphene oxide nanoparticles coupled with high-performance liquid chromatographic analysis.

A novel mixed hemimicelles solid phase extraction based on magnetic graphene oxide (Fe3O4/GO) and ionic liquid (IL) was developed for the simultaneous extraction and determination of trace cephalosporins in spiked human urine. The high surface area and excellent adsorption capacity of the graphene oxide after modification with1-hexadecyl-3-methylmidazoliumbromide(C16mimBr) were utilized adequately in the solid phase extraction(SPE) process. A comprehensive study of the parameters affecting the extraction recovery, such as the zeta-potential of magnetic graphene oxide, amounts of magnetic graphene oxide and surfactant, pH of solution, ionic strength, extraction time, and desorption condition were optimized. A comparative study on the use of different surfacant-coated Fe3O4/GO NPs as sorbents was presented. Good linearity (R(2)>0.9987) for all calibration curves was obtained. The LODs were ranged between 0.6 and 1.9ng mL(-1) for the cephalosporins and the LOQs were 1.5 to 5.5, respectively. Satisfactory recoveries(84.3% to 101.7%)and low relative standard deviations from 1.7% to 6.3% in biological matrices were achieved. The mixed hemimicelles magnetic SPE (MSPE) method based on ILs and Fe3O4/GO NPs magnetic separation has ever been successfully used for pretreatment of complex biological samples.

[Fluorescence study on the interactions between carbon nanotubes and bovine serum albumin].

As a new family of nanomaterials, carbon nanotubes (CNTs) exhibit unique properties such as their capacity to penetrate into the cells and low immunogenicity, which have attracted increasing attention in biomedical field and make their application in drug and gene transfer systems being possible. So getting more information about the interaction of CNTs with biomacromolecules is crucial for further investigation of CNTs in therapeutic applications. The interaction between CNTs and BSA under physiological condition was investigated by fluorescence quenching, synchronous fluorescence and red edge excitation shift (REES)method. The results showed that CNTs could significantly decrease the fluorescence intensity of BSA. While the results of synchronous fluorescence and REES indicated that CNTs almost had no influence on the conformation of BSA. So the authors concluded that the mechanism of interaction between CNTs and BSA was non-specific adsorption.

[Fluorescence study on the interactions between G3.0 PAMAM dendrimers and bovine serum albumin].

The interaction between amine terminated G3.0 PAMAM dendrimers and bovine serum albumin (BSA) under physiological condition was studied by fluorescence spectroscopy. Our experiments demonstrated that the fluorescence intensity of BSA decreased after the addition of G3.0 PAMAM dendrimers and the quenching mechanism was suggested as static quenching according to the Stern-Volmer equation The binding constant of G3.0 PAMAM dendrimers with BSA was calculated to be 1.067 +/- 0.025 L x mmol(-1). At the same time, synchronous fluorescence and red edge excitation shift (REES) were adopted to review the conformational changes of BSA influenced by G3.0 PAMAM dendrimers, which provides important significance for clinical medication And the results indicated that G3.0 PAMAM dendrimers can change the conformation of BSA. Furthermore, this article also examined the influence of pH and ionic strength on the interactions, from which we can conclude that electrostatic interaction played major roles in the binding process. In conclusion, the fluorescence method is a highly sensitive and convenient way to study intermolecular interaction. Further investigation in this field will provide more important information for understanding the pharmacological effects and toxicities of drugs in human body.

[Fluorescence characteristic of terbium-ciprofloxacin complex and its application].

On binding to deoxyribonucleic acid, the complex of terbium-ciprofloxacin (Tb(3+)-CIP) increases its fluorescence quantum efficiency. Based on this, an easy, rapid and sensitive method for the determination of DNA was developed. Like ethidium bromide (EB), the complex can be intercalated into DNA bases, but it is non-poisonous. Determination can be made at pH 7.0, where the native structure of DNA is not disrupted. The maximum emission is at 545 nm with excitation at 325 nm. This method has good sensitivity (2.8 x 10(-9) mol x L(-1) of ctDNA), high selectivity and a wide linear range (4.3 x 10(-7)-3. 0 x 10(-5) mol x L(-1) of ctDNA). This complex was also employed for the clinical examination of DNA in whole blood of tumor patients. Ten tumor patients and 10 normal persons were enrolled in this study. It was showed that significant difference existed between control group and tumor group (p < 0.05).

[Study on the interaction of lomefloxacin terbium complex and bovine serum albumin by fluorescence spectra].

Using lomefloxacin-terbium as a fluorescent probe, the interaction of LFLX-Tb3+ and bovine serum albumin (BSA) was investigated by fluorescence spectra. The interaction of LFLX and BSA is quite strong. LFLX can affect the conformation of BSA to some degree. Meanwhile, the electrostatic binding of the BSA with Tb3+ in LFLX-Tb3+ complex could decease the nonradiative energy loss through O-H vibration of H2O molecule in Tb3+ complex. Under the optimum conditions, BSA can enhance the fluorescence intensity of the lomefloxacin-terbium complex at 545 nm, and the enhanced fluorescence intensity of Tb3+ is proportional to the concentration of BSA. Based on that, a new method is constructed for the determination of BSA. The linear ranges for BSA are 16.5-148.5 microg x mL(-1) with a detection limit of 68.8 ng x mL(-1) and relative standard deviations of 1.4%. This method is simple, practical and relatively free of interference from coexistent substances.