Mechanism of Photochemical Sensitized Fluorescence of the Terbium-Lomefloxacin Complex

Lomefloxacin (LMFX) is one of the synthetic antibacterial fluoroquinolone agents of the third generation, which exhibits high activity against a broad spectrum of gram-negative and gram-positive bacteria. It has a good effect in clinical treatment. In consequence, it is of great importance to determine its contents in various biological fluids (blood,urine and tissues).     

Fabrication of polyvinyl alcohol/chitosan oligosaccharide hydrogel: physicochemical characterizations and in vitro drug release study

Abstract

Hydrogel composites from polyvinyl alcohol and chitosan have been developed by various researchers as a function of their composition for various medical applications. Although, the solubility of chitosan in acidic solvents may limit its wide bioengineering applications. In this article, we demonstrate that polyvinyl alcohol-chitosan oligosaccharide (water soluble) to develop cross-linked hydrogel network using chemical cross linker. X ray diffraction, Fourier transform infrared spectroscopy, and wettability study of these hydrogels were also performed. Lomefloxacin drug was loaded into the hydrogels and its release profile was studied.     

Preparation of Anti-Lomefloxacin Antibody and Development of an Indirect Competitive Enzyme-Linked Immunosorbent Assay for Detection of Lomefloxacin Residue in Milk

Lomefloxacin has been increasingly used in veterinary medicine to treat microbial infections. To avoid using a complicated instrumental method to detect lomefloxacin residue in food, a simple and convenient indirect competitive enzyme-linked immunosorbent assay method has been developed in this study. The antibody generated from immunogen of bovine serum albumin-lomefloxacin showed high sensitivity toward lomefloxacin with an IC₅₀ value of 0.35 ppb in PBS buffer and was suitable to be used as a screening assay to detect lomefloxacin residue in food products. The ELISA (Enzyme-Linked ImmunoSorbant Assay) developed in this study was compared with a commercial ELISA kit and significant improvement was achieved in terms of sensitivity and specificity. The antibody prepared showed excellent specificity with certain cross-reactivity with only two drugs including norfloxacin (17.5%) and fleroxacin (8.8%) among commonly used (fluoro)quinolones. The assay measured drug residue in defatted milk spiked with lomefloxacin with an inter-assay coefficient of variation <22.2% and an intra-assay coefficient of variation <18.2%. The average recovery rates at 0.1, 0.3, 0.6, 1.0, and 2.0 ppb were in the range of 120–85% for inter-assay and in the range of 113–90% for intra-assay.     

Determination of residual fluoroquinolones in honey by liquid chromatography using metal chelate affinity chromatography

A new analytical method for the simultaneous determination of seven fluoroquinolones, namely, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, orbifloxacin, sarafloxacin, and difloxacin, especially in dark-colored honey, has been developed. Fluoroquinolone antibiotics were extracted from samples with MacIlvaine buffer solution (pH 4.0) containing EDTA disodium salt dihydrate. The extracts were treated with both a polymeric cartridge and a metal chelate affinity column preloaded with ferric ion (Fe3+). LC separation with fluorescence detection was performed at 40 degrees C using an Inertsil ODS-4 analytical column (150 x 4.6 mm, 3 microm). The mobile phase was composed of 20 mM/L citrate buffer solution (pH 3.1)-acetonitrile mixture (70 + 30, v/v) containing 1 mM/L sodium dodecyl sulfate. Lomefloxacin was used as an internal standard. The developed method was validated according to the criteria of European Commission Decision 2002/657/EC. Decision limits and detection capabilities were below 2.9 and 4.4 microg/kg, respectively.     

Fluorometric study on the interaction between lomefloxacin and bovine lactoferrin.

The binding of lomefloxacin to bovine lactoferrin (BLf) in a dilute aqueous solution was studied using fluorescence spectra. The binding constant (K) and the number of binding sites (n) were obtained by a fluorescence quenching method. The binding distance (r) and energy-transfer efficiency (E) between lomefloxacin and bovine lactoferrin were also obtained according to the mechanism of Fo?rster-type dipole-dipole nonradiative energy-transfer. The effect of lomefloxacin on the conformation of bovine lactoferrin was also analyzed by synchronous fluorescence spectroscopy. The interaction between lomefloxacin and bovine lactoferrin is strong. Lomefloxacin can affect the conformation of bovine lactoferrin to some degree.     

氟喹诺酮类药物对大肠杆菌抑制作用量效关系的 热化学研究

用LKB-2277生物活性检测系统,测定了洛美沙星、诺氟沙星、培氟沙星三种氟喹诺酮类抗菌素在37℃时,对大肠杆菌的抑制作用过程的热效应变化。根据热动力学模型,拟合了药物的k～c,P~m~a~x～k,I%～c等关系,定量计算了药物的半抑制浓度Ic~5~0,从热动力学角度研究了氟喹诺酮类药物抗菌作用的量效关系,探讨了诺氟沙星和培氟沙星杀菌作用随着药物浓度增加呈双相变化的PE现象和作用机制。     

基于聚多巴胺磁性纳米微球的洛美沙星适配体筛选研究

基于纳米材料与单链核苷酸可能存在的氢键作用、π-π结合、电荷转移等非共价结合方式,可快速区分对目标靶分子有特异性结合的单链核酸适配体候选分子,从而缩短适配体筛选周期、提高筛选的成功率.本研究采用聚多巴胺磁性纳米微球(MNPs@PDAs)为分离载体,以洛美沙星(LMX)为靶标分子,利用磁分离技术建立了一种小分子的适配体筛选新方法.经过7轮筛选,获得了对洛美沙星分子具有高亲和性(KD=(17.57±0.5)nmol/L)的核酸适配体AF-3,且AF-3对于结构相似分子培氟沙星(PEFX)、氧氟沙星(OFLX)、诺氟沙星(NFLX)不具有亲和性.基于MNPs@PDAs的筛选方法有望于应用于其它重要靶分子的高效适配体探针获取.     

微芯片毛细管电泳快速测定盐酸洛美沙星

采用微芯片毛细管电泳非接触电导检测法快速测定了盐酸洛美沙星胶囊中盐酸洛美沙星的含量。探讨了缓冲液类型、浓度,添加剂种类、浓度及分离电压、进样时间等因素对分离检测的影响。实验采用5.0mmol/L HAc(pH=2.5)+5%乙醇为缓冲溶液,分离电压3.0 kV,在1 min内实现了盐酸洛美沙星的快速分离测定。优化条件下盐酸洛美沙星的线性范围为20.0～250.0μg/mL,检出限为10.0μg/mL(S/N=3),RSD=2.0%,加标回收率为98.6%～103%。     

Electrochemical adsorptive behavior of some fluoroquinolones at carbon paste electrode.

Cyclic voltammetry and differential pulse voltammetry were used to explore the adsorption behavior of three antibacterial agents at a carbon paste electrode. The drugs were accumulated on a carbon paste electrode, and a well-defined oxidation peak was obtained in acetate buffer (pH 5.0). The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH and accumulation time. A simple, precise, inexpensive and sensitive voltammetric method has been developed for the determination of the cited drugs (Lomefloxacin (LFX), Sparfloxacin hydrochloride (SFX), and Gatifloxacin (GFX)). A linear calibration was obtained from 2 x 10(-7) M to 4 x 10(-5) M for LFX, 2 x 10(-7) M to 6 x 10(-5) M for SFX, and GFX. The limits of detection (LOD) were 4.2 x 10(-7), 7 x 10(-7) and 6.6 x 10(-7) M, while the limits of quantification (LOQ) were 1.4 x 10(-6), 2.3 x 10(-6) and 2.2 x 10(-6) M for LFX, SFX, and GFX, respectively. The R. S. D. of five measurements at the 1 x 10(-6) M level were 0.4, 0.5 and 0.3 for LFX, SFX and GFX, respectively. The method was applied to the determination of LFX, SFX and GFX in dilute urine samples and dosage forms, and compared with the HPLC method.     

UV light induced photodegradation of liposome encapsulated fluoroquinolones: An MS study

Fluoroquinolone antibacterial agents are among the drugs most commonly causing phototoxic side effects. The phototoxicity may be originated in formation of reactive oxygen species upon ultraviolet exposure. Researches aiming the liposomal encapsulation of fluoroquinolones, expecting an increase in their therapeutic index, enhance the importance of studies on physicochemical properties and photostability of liposomal preparations. We studied the photodegradation of ciprofloxacin, ofloxacin and lomefloxacin by mass spectrometry upon various doses of UV irradiation. Lomefloxacin, the most phototoxic fluoroquinolone among them, was encapsulated into small unilamellar and multilamellar liposomes. Impact of vesicle structure and lipid composition – the presence of unsaturated fatty acid containing dioleoyl-phosphatidylcholine in dipalmitoyl-phosphatidylcholine liposomes – on the lomefloxacin photolysis was investigated; the structure of the main photoproducts was identified by mass spectrometry. It was found that the presence and type of lipids influence the ways of photodegradation process.     

Voltammetric behavior and analytical applications of lomefloxacin, an antibacterial fluorquinolone.

Lomefloxacin was reduced on a dropping mercury electrode, producing one or more peaks, depending on the pH of the aqueous medium. Coulometric measurements gave an experimental value of 1 electron for the main peak. Electrolysis was followed by UV spectrophotometry and liquid chromatography (LC), showing that a new band at 413 nm appeared for the electrolysis product in an acidic medium. Furthermore, by using UV spectrophotometry, an apparent pKa value of 6.75 +/- 0.05 was obtained for lomefloxacin corresponding to the carboxyl moiety in the 3-position. For analytical studies, the differential pulse polarographic mode in 0.1 N HCl was selected. The repeatability and reproducibility of the method were adequate (coefficient of variation [CV], 0.51%). The calibration curve method was used for the lomefloxacin concentration range of 7.0 x 10(-6) to 7.0 x 10(-5)M. The detection and quantitation limits were 1.0 x 10(-6) and 6.9 x 10(-6)M, respectively. For purposes of comparison, both UV spectrophotometric and LC (with UV and fluorimetric detection) methods were developed. The polarographic method showed good selectivity with respect to both excipients and degradation products. The recovery study showed a CV of <2% and an average recovery of 99.5% and it was not necessary to treat the sample before analysis. The method was applied to the determination of the uniformity content of lomefloxacin commercial tablets. The polarographic method was also successfully applied to the quantitation of lomefloxacin in urine, and the renal excretion profile was also determined.     

Simultaneous determination of fluoroquinolone and tetracycline antibacterials in sewage sludge using ultrasonic-assisted extraction and HPLC-MS/MS

A reliable method was proposed for the simultaneous determination of five fluoroquinolones (FQs) and two tetracyclines (TCs) in sewage sludge using ultrasonic-assisted extraction (USE) followed by SPE cleanup and high-performance liquid chromatography-mass spectrometry (HPLC-MS)/MS analysis with electrospray ionisation (ESI) in a positive mode. The USE conditions (e.g. extraction solvent, pH, and extraction cycles) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) parameters were optimised. Quantification was performed by internal standard calibration in multiple reaction monitoring mode. Recoveries of the antibacterials ranged from 41 to 123%, with relative standard deviations within 17%. The sample-based limits of quantification were 10–63?ng?g^?1 dry weight (dw) for FQs (ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin) and 250–500?ng?g^?1 dw for TCs (tetracycline and oxytetracycline). The method was applied to determine the antibacterials in sewage sludge and sediment samples were collected from the Pearl River Delta, China. Ciprofloxacin, norfloxacin, and ofloxacin were frequently detected, ranging from 1052 to 17740?ng?g^?1 dw in dewatered sludge samples, 585–3545?ng?g^?1 dw in untreated solids, and 98–258?ng?g^?1 dw in an urban stream sediment sample, respectively. Lomefloxacin and enrofloxacin were also occasionally detected.     

Photochemical decomposition of lomefloxacin in vitro and in vivo

To obtain an idea of the photostability of Lomefloxacin (Lom) under in vivo conditions the compound was exposed to UV-A (310-360 nm) in PBS buffer pH 7.4. Exposure of 10 microg/ml of Lom in PBS pH 7.4 led to more than 50% decomposition within 10 min. Loss of the fluorine atom at C-8 and partial breakdown of the piperazine ring occurred. The only two photoproducts formed under these conditions were AEA, 1-ethyl-6-fluoro-1,4-dihydro-7-(2-aminoethyl-amino)-4-oxo-3-quinolinecarboxylic acid, and APA, 1-ethyl-6-fluoro-1,4-dihydro-7-(2-aminopropyl-amino)-4-oxo-3-quinolinecarboxylic acid. When Lom was exposed in whole blood in vitro, the same photochemical decomposition was observed in the plasma as in PBS buffer: APA and AEA were the only products. During UV-A exposure, Lom was shown to be taken up by the leukocytes. This process appeared to be less rapid during UV-A exposure than in the dark. As soon as UV-A exposure commenced, AEA and APA were found. As in the plasma, the total amount of Lom and the two photoproducts in the leukocytes was not significantly different from the amount of Lom found in unexposed cells at the same time point. The erythrocytes did not take up Lom, but exposure of whole blood to Lom and UV-A under the above conditions led to more than 7% haemolysis. Treatment of rats with a combination of Lom and UV-A demonstrated photodecomposition of Lom in vivo. In urine produced during exposure and by the irradiated rats during the twilight period after exposure, a considerable amount of AEA and APA was found. The blood plasma from rats exposed simultaneously to UV-A and Lom proved to contain AEA and APA and, in the leukocytes, APA. This was not the case with animals kept in twilight.     

Resolving overlapped spectra with curve fitting

A novel method of curve fitting based on Gaussian function, which is used to resolve the overlapped peaks, is presented in this paper. The resolution of several kinds of overlapped peaks with noise simulated by computer has been performed and discussed in details. This method has been used for resolving of the UV-vis overlapped spectrum. The results indicate that the proposed algorithm can been used to resolve overlapped spectra effectively and satisfactorily.     

The Spectrophotometric Determination of Sc in Eriochrome Canine R(Chrome azurol s)- Phosphatidl Choline System

Abstract

Eriochrome cyanine R(chrome azurol S) is used as a color reagent to determine Sc in the presence of phosphatidyl choline, σ = 3.7 × 10⁴ (4.5 × 10⁴). This method has been connected to extraction separation to determine Sc in the presence of rare earth elements, and good results have been obtained.

Phosphatidyl choline(PC) is a biochemical reagent, which can be used as a surfactant. It has been reported that chrome azurol S(CAS) can be used to determine Be in the presence of PC¹ but it has not been reported that eriochrome cyanine R(ECR) and CAS can be used to determine Sc in the presence of PC. This paper has put forward a method by which Sc can be determined. ECR (CAB) has been used as a color reagent and PC as a surfactant. Conditional experiments have been made and this method has been connected to extraction separation. Tributyl phosphate (TBP) extracts Sc from rare earth elements to make a determination and good results have been obtained.     

Preparation and Property of the Water Absorbent Hybrid Resin

Water absorption material has been attracted much more attention for its wide use in soil and water conservation, agriculture, etc. But this material will actually apply in agriculture, soil and water conservation only when it is cheap enough. Pulp fiber and starch to prepare high absorbing-water resin is a good method for decreasing the cost [1,2]. However, it still has a long way to turn it into reality. Now the montmorillonite is widely used in preparing nanocomposites [3]. But used it in preparing absorbing-water resin has little report. In this article the water absorption hybrid resin has been prepared by one step intercalation polymerization method. In the process of intercalation the partly neutralization acrylic acid and urea have been used as intercalating reagent. Beside that, the urea also has been used as cross-linking agent.     

A study of structure-carcinogenicity relationship for 86 compounds from NTP data base using topological indices as descriptors

86 compounds from NTP carcinogenic potency data base have been used to derive neural network models. Compounds were described with topological indices. Carcinogenicity has been given as a binary quantity--a compound is carcinogenic or non carcinogenic. Several models have been tested with a recognition ability test and with the leave-one-out cross validation method. For the best model the ratio between correct and wrong classifications was 70/30. Furthermore, the model has been used to classify 17 compounds not used for setting of the models. The predicted carcinogenic classes and the neighbors in the neural network influencing the predictions have been discussed.     

Polystyrene degradation during combustion

A novel driven-rod, radiant pyrolysis technique has been used to study steady-state linear regression of vertically mounted polystyrene rods degrading under high-flux, nonflaming conditions that simulate those of combustion. With this technique a reliable, reproducible temperature-depth profile (identical for combustion and radiant pyrolysis) for polystyrene has been obtained and used to successfully calculate the observed mass loss rate. Residues and volatiles have been analyzed. Mechanistic treatment of these results indicates that degradation of polystyrene under these rapid-heating conditions is similar to that under more conventional slow-heating conditions in the absence of oxygen. Oxidation is unimportant in the condensed-phase degradation of polystyrene in this configuration. This radiant pyrolysis technique has also been used to obtain the heat of gasification of polystyrene.     

TRANSPORT STUDIES ON MACROMOLECULES USED AS DRUG CARRIERS

Abstract

Modecular transport of drugs through carier polymeric materds has been an active area of research. A number of soluble polymers have been used to deliver the drugs selectively to specific parts of the body. The literature in this area of research is extensive and diverse. An effort has been made to review the transport of drug molecules through physiological systems via polymeric materials. A brief introduction to the fundamentals and concepts which are frequently used in the drug-delivery area are covered in the following sections. Various aspects of the problems related to polymer-drug complexes, carrier molecules, and their degradability have been discussed. Both natural and synthetic biopolymers have been included in the discussion. Only representative references during the period 1977–1989 have been used in the discussion of results, and thus the reader is advised to look further into the original literature for greater information.