One-Step Synthesis of Rox-DNA Functionalized CdZnTeS Quantum Dots for the Visual Detection of Hydrogen Peroxide and Blood Glucose.

As the blood glucose concentration is an important clinical parameter of diabetes, the rapid and effective detection of blood glucose is very significant for monitoring and managing diabetes. Here, a facile method to prepare Rox-DNA functionalized CdZnTeS quantum dots (QDs) was developed. The Rox-DNA functionalized CdZnTeS QDs were prepared by a one-pot hydrothermal method through phosphorothioate DNA bound to QDs, which were employed as a ratiometric fluorescent probe for the rapid and sensitive detection of H2O2 and glucose. Compared with the traditional multistep construction of ratiometric fluorescent probes, this presented approach is simpler and more effective without chemical modification and complicated separation. The CdZnTeS QDs with green fluorescence is specifically sensitive to H2O2, while the red fluorescence of Rox is invariable. H2O2 is the product from the oxidation of glucose catalyzed by glucose oxidase (GOx). Therefore, a facile method to detect H2O2 and glucose with a detection limit of 0.075 µM for H2O2 and 0.042 µM for glucose was developed. In addition, this proposed probe has been employed for the detection of glucose in human serum with a satisfactory result. Moreover, this probe has been used for visual detection, and the health and diabetics can be distinguished by the naked eye. Meanwhile, this nanoprobe is also generalizable and can be extended to the detection of many other H2O2-mediated analytes.

Group determination of 14-membered macrolide antibiotics and azithromycin using antibodies against common epitopes.

Erythromycin (ERY), clarithromycin (CLA), roxithromycin (ROX), and azithromycin (AZI) are macrolide antibiotics widely used in livestock and human medicine. Therefore, they are frequently found as pollutants in environmental water. A method based on indirect competitive enzyme-linked immunosorbent assay (ELISA) for group determination of these macrolides in foodstuffs, human biofluids, and water was developed. Carboxymethyloxime of clarithromycin (CMO-CLA) was synthesized and conjugated to bovine serum albumin (BSA) and gelatin to prepare immunogen and coating antigen with advantageous presentation of target epitopes, l-cladinose and d-desosamine, common for these analytes. Antibodies generated in rabbits were capable of recognizing ERY, CLA, and ROX as a group (100-150%), and AZI (12%) and did not cross-react with ERY degradants, which lack antibiotic activity. Assay displayed sensitivity of determination of 14-membered macrolides (IC50=0.13-0.2ng/ml) and low limit of detection (LOD) that was achieved at 0.02 to 0.03ng/ml. It allowed performing analysis of milk, muscle, eggs, bovine serum, water, human serum and urine, and avoiding matrix effect without special pretreatment using simple dilution with assay buffer. For 15-membered macrolide AZI, the corresponding characteristics were IC50=1.6ng/ml and LOD=0.14ng/ml. The recoveries of veterinary and human medicine macrolides from corresponding matrices were validated and found to be satisfactory.

Preparation and characterization of erythromycin molecularly imprinted polymers based on distillation-precipitation polymerization.

Erythromycin-imprinted polymers with excellent recognition properties were prepared by an innovative strategy called distillation-precipitation polymerization. The interaction between erythromycin and methacrylic acid was studied by ultraviolet absorption spectroscopy, and the as-prepared materials were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Moreover, their binding performances were evaluated in detail by static, kinetic and selective sorption tests. It was found that the molecularly imprinted polymers afforded good morphology, monodispersity, and high adsorption capacity when the fraction of the monomers was 7 vol% in the whole reaction system, and the adsorption data for imprinted polymers correlated well with the Langmuir model. The maximum capacity of the imprinted and the non-imprinted polymers for adsorbing erythromycin is 44.03 and 19.95 mg/g, respectively. The kinetic studies revealed that the adsorption process fitted a pseudo-second-order kinetic model. Furthermore, the imprinted polymers display higher affinity toward erythromycin, compared with its analogue roxithromycin.

Aptamer-free upconversion nanoparticle/silk biosensor system for low-cost and highly sensitive detection of antibiotic residues.

The detection of antibiotics is crucial for safeguarding the environment, ensuring food safety, and promoting human health. However, developing a rapid, convenient, low-cost, and sensitive method for antibiotic detection presents significant challenges. Herein, an aptamer-free biosensor was successfully constructed using upconversion nanoparticles (UCNPs) coated with silk fibroin (SF), based on Förster resonance energy transfer (FRET) and the charge-transfer effect, for detecting roxithromycin (RXM). A synergistic FRET efficiency was achieved by utilizing alizarin red and RXM complexes as energy acceptors, with UCNP as the energy donor, and immobilizing an ultrathin SF protein corona within 10 nm. The biosensor detects RXM in deionized water with high sensitivity primarily through monolayer adsorption, with a detection range of 1.0 nM-141.6 nM and a detection limit as low as 0.68 nM. The performance of this biosensor was compared with the ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for detecting antibiotics in river water separately and a strong correlation between the two methods was observed. The biosensor exhibited long-term stability in aqueous solutions (up to 60 d) with no attenuation of fluorescence intensity. Furthermore, the biosensor's applicability extended to the highly sensitive detection of other antibiotics, such as azithromycin. This study introduces a low-cost, eco-friendly, and highly sensitive method for antibiotic detection, with broad potential for future applications in environmental, healthcare, and food-related fields.

Effects of erythromycin and roxithromycin on river periphyton: Structure, functions and metabolic pathways.

Macrolides have been frequently detected in the surface waters worldwide, posing a threat to the aquatic microbes. Several studies have evaluated the ecotoxicological effects of macrolides on single algal and bacterial strains. However, without considering the species interaction in the aquatic microbial community, these results cannot be extrapolated to the field. Thus, the present study aimed to evaluate the effects of two macrolides (erythromycin and roxithromycin) on the structure, photosynthetic process, carbon utilization capacity, and the antibiotic metabolic pathways in river periphyton. The colonized periphyton was exposed to the graded concentration (0 µg/L (control), 0.5 µg/L (low), 5 µg/L (medium), 50 µg/L (high)) of ERY and ROX, respectively, for 7 days. Herein, high levels of ERY and ROX altered the community composition by reducing the relative abundance of Chlorophyta in the eukaryotic community. Also, the Shannon and Simpson diversity indexes of prokaryotes were reduced, although similar effects were seldomly detected in the low and medium groups. In contrast to the unchanged carbon utilization capacity, the PSII reaction center involved in the periphytic photosynthesis was significantly inhibited by macrolides at high levels. In addition, both antibiotics had been degraded by periphyton, with the removal rate of 51.63-66.87% and 41.85-48.27% for ERY and ROX, respectively, wherein the side chain and ring cleavage were the main degradation pathways. Overall, this study provides an insight into the structural and functional toxicity and degradation processes of macrolides in river periphyton.

Molecular dynamics in supercooled liquid and glassy states of antibiotics: azithromycin, clarithromycin and roxithromycin studied by dielectric spectroscopy. Advantages given by the amorphous state.

Antibiotics are chemical compounds of extremely important medical role. Their history can be traced back more than one hundred years. Despite the passing time and significant progress made in pharmacy and medicine, treatment of many bacterial infections without antibiotics would be completely impossible. This makes them particularly unique substances and explains the unflagging popularity of antibiotics within the medical community. Herein, using dielectric spectroscopy we have studied the molecular mobility in the supercooled liquid and glassy states of three well-known antibiotic agents: azithromycin, clarithromycin and roxithromycin. Dielectric studies revealed a number of relaxation processes of different molecular origin. Besides the primary α-relaxation, observed above the respective glass transition temperatures of antibiotics, two secondary relaxations in the glassy state were identified. Interestingly, the fragility index as well as activation energies of the secondary processes turned out to be practically the same for all three compounds, indicating probably much the same molecular dynamics. Long-term stability of amorphous antibiotics at room temperature was confirmed by X-ray diffraction technique, and calorimetric studies were performed to evaluate the basic thermodynamic parameters. Finally, we have also checked the experimental solubility advantages given by the amorphous form of the examined antibiotics.

Physicochemical properties of amorphous roxithromycin prepared by quench cooling of the melt or desolvation of a chloroform solvate.

Roxithromycin is a poorly soluble antibacterial drug. The aim of this study was to prepare and characterize an amorphous form of roxithromycin. The amorphous form was prepared by desolvation of its chloroform solvate, and by quench cooling a melt of the crystalline monohydrated solid. The X-ray powder diffraction pattern of the desolvated chloroform solvate was indistinguishable from that of the glass prepared by melting, which indicated that it was amorphous. The roxithromycin glass was determined to be a fragile glass, but due to its high Kauzmann temperature (approximately 8°C), it should remain fairly stable upon refrigeration or even at room temperature. It was also determined that this glass remains stable in the presence of moisture with no indication of crystallization.

Taste masking of roxithromycin by spray drying technique.

The spray drying technique was used to obtain the roxithromycin containing microcapsules with high taste masking efficiency. Eudragit L30D-55 was chosen as a barrier coating. The taste was evaluated by an electronic tongue, and taste-masking effect in water lasted at least several dozen hours.

Validation of experimental charge densities: refinement of the macrolide antibiotic roxithromycin.

Multipole refinements of larger organic molecules have so far been limited to a few exceptional cases. We report an investigation of the detailed experimental electron-density distribution (EDD) of roxithromycin, a macrolide antibiotic consisting of 134 atoms. Although the experimental multipole refinement on high-resolution synchrotron data converged smoothly, validation of the electron density by calculation of an `experiment minus invariom' difference density revealed conformational disorder of the H atoms. Hydrogen disorder is shown to affect the EDD, the electrostatic potential and atomic properties as defined by Bader's quantum theory of atoms in molecules. A procedure to obtain the electron density distribution in the presence of disorder is proposed.

An alternative liquid chromatography-mass spectrometric method for the determination of azithromycin in human plasma and its application to pharmacokinetic study of patients with malaria.

A simple, sensitive, selective and reproducible method based on high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/MS) was developed for the determination of a macrolide antibiotic azithromycin in human plasma. The internal standard (roxithromycin) was separated from azithromycin on a Hypersil Gold C18 column, with retention times of 10.71 and 13.67 minutes, respectively. The mobile phase consisted of a mixture of 20 mM ammonium acetate buffer (pH 5.2), acetonitrile and methanol (50:40:10, v/ v/v), running through the column at a flow rate of 0.3 ml/minute. Chromatographic analysis was carried out at 25 degrees C. Sample preparation was by liquid-liquid extraction with a mixture of 7:3 (v/v) diethylether:dichloromethane. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 5% (% coefficient of variations: % CV). Good accuracy was observed for both intra-day and inter-day assays. The limit of quantification was acceptable at 0.5 ng using 200 microl plasma samples. The mean recoveries for azithromycin and the internal standard were greater than 85%. The method was applied successfully to the investigation of the pharmacokinetics of azithromycin when given in combination with fosmidomycin as oral doses of 750 mg twelve hourly for 3 days in 5 Thai male patients with acute uncomplicated falciparum malaria.

Characterization of two unknown impurities in roxithromycin by 2D LC-QTOF/MS/MS and NMR.

Two unknown impurities in roxithromycin were discovered and preliminarily characterized by two-dimensional liquid chromatography coupled with QTOF mass analyzer (2D LC-QTOF MS/MS). The column-switching technique of 2D LC made the chromatographic conditions in official standard of roxithromycin compatible with mass spectrometric detector. The complete MS/MS fragmentation patterns of the impurities were studied to obtain structural information of these impurities. Furthermore, these two impurities were separated and purified by preparative HPLC, and their structures were confirmed by 1D and 2D nuclear magnetic resonance (NMR). Structural elucidation of two impurities by 1H NMR, 13C NMR, the 1H-1H COSY, HSQC and HMBC NMR spectra has been discussed. Based on high resolution MS/MS and NMR data, the structures of these two impurities were elucidated respectively as 11-O-[(2-Methoxyethoxy) methyl] roxithromycin and de(N-methyl)-N-formyl roxithromycin. In addition, the mechanisms for formation of the impurities were also proposed.

Melt electrohydrodynamic 3D printed poly (ε-caprolactone)/polyethylene glycol/roxithromycin scaffold as a potential anti-infective implant in bone repair.

Implanted scaffold or bone substitute is a common method to treat bone defects. However, the possible bone infection caused by orthopaedic surgery has created a challenging clinical problem and generally invalidate bone repair and regeneration. In this study, a poly (ε-caprolactone) (PCL)/polyethylene glycol (PEG)/roxithromycin (ROX) composite scaffold was prepared via melt electrohydrodynamic (EHD) 3D printing. Fourier transform infrared spectroscopy (FTIR) spectroscopy was performed to verify the existence of PEG and ROX in the scaffolds. By water contact angle measurement, the addition of both PEG and ROX was found to improve the hydrophilicity of the scaffolds. By in vitro drug release assay, the PCL/PEG/ROX scaffolds showed an initial burst drug release and subsequent long-term sustained release behaviour, which is favourable for the prevention and treatment of bone infections. The antibacterial assays against E. coli and S. aureus demonstrated that the composite scaffold with ROX possessed effective antibacterial activity, especially for S. aureus, the main cause of bone infection. The immunostaining and MTT assay with human osteoblast-like cells (MG63) indicated that cells showed good viability and growth on the scaffolds. Therefore, the melt EHD 3D printed PCL/PEG/ROX scaffold could be a promising anti-infective implant for bone tissue engineering.

Occurrence and ecological risk of pharmaceutical and personal care products in surface water of the Dongting Lake, China-during rainstorm period.

The pharmaceutical and personal care product (PPCP) residues in freshwater lakes are being highlighted around the world. The occurrence and ecological risk of 34 PPCPs classified as antibiotics, non-steroidal anti-inflammatory drugs (NSAID), cardiovascular drugs, psychotropic drugs, anti-inflammatory drugs, psychostimulants, and pesticides during rainstorm period in surface water of the Dongting Lake, China, were studied. Twenty-six out of thirty-four PPCPs were detected, and the total concentrations of antibiotics ranged from 0.15 to 214.75 ng L-1 in surface water. The highest average concentration was observed for diclofenac, followed by diethyltoluamide (DEET). The PPCP concentrations were much lower in Dongting Lake compared to other rivers and lakes due to the strong dilution effect of rainstorm, while the detection rate remains high. Caffeine and DEET were detected with 100% frequency in Dongting Lake, and the detection rates of diclofenac, mefenamic acid, and roxithromycin were above 90%. The pollution levels of antibiotics decreased in the order of East Dongting Lake > South Dongting Lake > West Dongting Lake, which may be related to the distribution of aquaculture plants, sewage treatment plants, and population density. The risk quotient (RQ) method was used to evaluate ecological environment risk under the worst case and the results suggested that clarithromycin, diclofenac, roxithromycin, and erythromycin might pose a significant risk to aquatic organisms in Dongting Lake, especially clarithromycin. This study can provide data support for further research on the dilutive effect and mechanism of rainwater runoff on PPCPs in lakes on a large scale.

New insight into the toxic effects of chloramphenicol and roxithromycin to algae using FTIR spectroscopy.

Antibiotics have been frequently detected in the aquatic environment, and they may affect aquatic organisms such as algae. Here we investigated toxicity of chloramphenicol (CAP) and roxithromycin (ROX) on four species of green algae (Pseudokirchneriella subcapitata, Scenedesmus quadricauda, Scenedesmus obliquus, and Scenedesmus acuminatus) at biochemical level by Fourier transform infrared spectroscopy (FTIR). The results revealed that both CAP and ROX had negative effects on algal growth and caused alterations of biochemical components. The toxic effects varied among the four algal species and S. acuminatus was found to be less sensitive than the other three species to the antibiotics. Even with similar mechanism of action, ROX displayed more adverse effects to algae than CAP. Both antibiotics could affect algae by inhibiting fatty acid synthesis and promoting protein and DNA aggregation, thus leading to accumulation of lipid peroxidation products, increment of the loose ß-sheet structure protein and transformation of B-DNA to Z-DNA. The findings from this study revealed the toxic mechanism of antibiotics to algae at the biochemical level.

Synthesis of 99m Tc-roxithromycin: A novel diagnostic agent to discriminate between septic and aseptic inflammation.

Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the current study, roxithromycin (ROX) was successfully labeled with technetium-99m for early diagnosis of bacterial infection and discrimination between septic and aseptic inflammation. The highest radiochemical purity of ≥95% was achieved by investigating different labeling parameters such as pH, ligand/reducing agent concentration, temperature, and amount of stabilizing agent. For this purpose, 0.3-0.5 mg ligand, 2-6 µg SnCl2 ·2H2 O as a reducing agent at basic pH (8-10 pH) and 2 mg mannitol used as a stabilizing agent, in the end, 370 MBq 99m Tc added into the reaction vials and incubated for a wide range of temperature (-4 to 65°C). The percent radiochemical purity of 99m Tc-roxithromycin was assessed with the help of the radio-thin-layer chromatography technique. The characterization studies were carried out using electrophoresis and Radio-HPLC techniques as well as saline stability and serum stability studies were also performed. Furthermore, biodistribution study was also performed in an inflamed animal model to discriminate between septic (heat-killed Staphylococcus aureus) and aseptic (turpentine oil) inflammatory lesions. The results were elaborated that 99m Tc-roxithromycin (99m Tc-ROX) was clearly bounded at the septic inflammation site (T/NT ratio of 7.08 ± 1.14) at 30 min postadministration, and maximum accumulation was seen in heart, lungs, liver, stomach, kidneys, and intestine. The results were suggested that 99m Tc-ROX might be used to discriminate between septic and aseptic inflammatory lesions at an early stage.

Degradation of typical macrolide antibiotic roxithromycin by hydroxyl radical: kinetics, products, and toxicity assessment.

The degradation of roxithromycin (ROX) by hydroxyl radical (·OH) generated by UV/H2O2 was systematically investigated in terms of degradation kinetics, effects of water chemistry parameters, oxidation products, as well as toxicity evaluation. The degradation of ROX by UV/H2O2 with varying light irradiation intensity, initial ROX concentration, and H2O2 concentration in pure water and wastewater all followed pseudo-first-order kinetics. The second-order rate constant for reaction between ROX and ·OH is 5.68 ± 0.34 × 109/M/s. The degradation rate of ROX increased with the pH; for instance, the apparent degradation rates were 0.0162 and 0.0309/min for pH 4 and pH 9, respectively. The presence of natural organic matter (NOM) at its concentrations up to 10 mg C/L did not significantly affect the removal of ROX. NO3- and NO2- anions inhibited the degradation of ROX due to the consumption of ·OH in reactions with these ions. Fe3+, Cu2+, and Mg2+ cations inhibited the degradation of ROX, probably because of the formation of ROX-metal chelates. A total of ten degradation products were tentatively identified by HPLC/LTQ-Orbitrap XL MS, which mainly derived from the attack on the oxygen linking the lactone ring and the cladinose moiety, tertiary amine and oxime side chain moiety by ·OH. The toxicity evaluation revealed that UV/H2O2 treatment of ROX induced the toxicity to bioluminescent bacteria increased.

A new insight into solid-state conformation of macrolide antibiotics.

Quantitative analysis of the molecular conformations of the 14-membered macrolide antibiotics erythromycin A and B, clarithromycin, and roxithromycin in the solid state was performed. While the erythronolide macrocycle adopts a very similar folded-out conformation in all the macrolides studied, the proximity of the monosaccharide moieties, L-cladinose and D-desosamine, to each other is demonstrated to be the distinctive feature of their molecular conformations, based on atom-atom interaction energy analysis. More surprisingly, the common features in the relative orientation of the monosaccharide moieties (in terms of non-bonded atom-atom interactions) were revealed between the 14- and 15-membered (azithromycin) macrolide antibiotics. Herein we report on the details of the spatial arrangement of the monosaccharide moieties in these structurally related drug molecules and their influence on the biopharmaceutical properties of erythromycin derivatives.

Modified polysaccharides as fast disintegrating excipients for orodispersible tablets of roxithromycin.

The purpose of this study was to develop a dosage form that was easy to administer and provides rapid release of the drug roxithromycin, using modified polysaccharides as rapidly disintegrating excipients. Modified polysaccharides co grinded treated agar (C-TAG) and co grinded treated guar gum (C-TGG) were prepared by subjecting pure polysaccharides namely agar and guar gum respectively to sequential processes of wetting, drying and co grinding with mannitol (1:1). The modified polysaccharides were characterized by Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy and evaluated for particle size distribution, derived properties, swelling index and biodegradability. Optimization studies based on 2(2) factorial designs, with friability and disintegration time as response parameters were used to formulate orodispersible tablets of roxithromycin and evaluated for wetting time, water absorption ratio and in vitro drug release at salivary pH 6.4 and physiological pH 7.4. Results indicated that lower levels of modified polysaccharides namely C-TAG in F(3) and C-TGG in F(7) and higher levels of microcrystalline cellulose, exhibited least disintegration times without friability concerns. In vitro release of optimized formulations F(3) and F(7,) both at salivary pH and physiological pH was found to be more than 90% within 30 min as compared to 27.82% at the same time point of conventional formulation. Stability studies carried out as per ICH Q1A guidelines suggested the formulations to be stable for a period of 6 months. Thus the approach of using modified polysaccharides as fast disintegrating excipient can be used to formulate a stable orodispersible formulation.

Stabilization Mechanism of Roxithromycin Tablets Under Gastric pH Conditions.

Macrolide antibiotics are widely used at clinical sites. Clarithromycin (CAM), a 14-membered macrolide antibiotic, was reported to gelate under acidic conditions. Gelation allows oral administration of acid-sensitive CAM without enteric coating by hindering the penetration of gastric fluid into CAM tablets. However, it is unknown whether this phenomenon occurs in other macrolide antibiotics. In this study, we examined the gelation ability of 3 widely used macrolide antibiotics, roxithromycin (RXM), erythromycin A, and azithromycin. The results indicated that not only CAM but also RXM gelated under acidic conditions. Erythromycin A and azithromycin did not gelate under the same conditions. Gelation of RXM delayed the disintegration of the tablet and release of RXM from the tablet. Disintegration and release were also delayed in commercial RXM tablets containing disintegrants. This study showed that 2 of the 4 macrolides gelated, which affects tablet disintegration and dissolution and suggests that this phenomenon might also occur in other macrolides.

Preparation, characterization and in vitro release study of drug-loaded sodium carboxy-methylcellulose/chitosan composite sponge.

A sodium carboxy-methylcellulose (CMC)/chitosan (CS) composite sponge as drug carrier was prepared, and its structure and functions were investigated. Samples with different CMC/chitosan ratios and under different pH conditions were synthesized via a freeze-drying method. The microstructure of the dried sponges was analyzed by Scanning Electron Microscope (SEM). Molecule interactions between polymers were confirmed by Fourier transform infrared (FTIR) spectra and Thermal gravimetric analyze (TGA). The swelling degree, weight loss, in vitro drug release behavior and antibacterial property of the sponges were determined as well. The results showed that the CMC/chitosan ratio and the pH value significantly affected the appearance of the blending solution and the microstructure of the final product, and also affected the sponge's degradation behavior, drug-loading capacity and the antibacterial activity. Gentamicin (GEN) as a hydrophilic model drug was remarkably superior to the other two hydrophobic drugs, ibuprofen (IBU) and roxithromycin (ROX), with respect to in vitro releasing. Moreover, higher CMC content and lower pH value of the sponge were confirmed to lead a larger loading for GEN. The bacteriostatic experiment showed a strong antimicrobial ability of GEN-loaded sponges on inhibiting Escherichia coli.