A halloysite nanotubes-based hybrid fluorous monolith as the mixed-mode sorbent for hydrophilic and hydrophobic interactions and its application for analysis of antibiotics from milk powder and milk samples

Determining the hydrophilic and hydrophobic antibiotics in milk and related products poses significant challenges due to their polarity differences and trace levels. Herein, we proposed a halloysite nanotubes-based hybrid fluorous monolith (HNTs-PFOTS monolith) as a sorbent for spin-tip solid-phase extraction (SPE). Leveraging the perfluorooctyl groups of the HNTs-PFOTS monolith, antibiotics can be adsorbed through hydrophilic and hydrophobic interactions. An analytical method was developed by combining the HNTs-PFOTS monolith-based spin-tip SPE method with liquid chromatography-tandem mass spectrometry. Under optimized conditions, the method exhibited excellent purification capabilities, low detection limits (0.01-0.03 μg/kg), high recoveries (80.0-112.3 %), and satisfactory reproducibility (intra-day RSDs of 0.4-8.8 % and inter-day RSDs of 1.0-10.9 %) for hydrophilic and hydrophobic antibiotics in milk and milk product samples. This study offers a novel approach for developing sorbents targeting antibiotics and provides a new analytical method for determining hydrophilic and hydrophobic antibiotics in food products.

Photocatalytic degradation of a typical macrolide antibiotic roxithromycin using polypropylene fibre sheet supported N-TiO2/graphene oxide composite materials

The post-treatment of recycling the fine photocatalyst nanoparticles restricts their application. In this study, a new photocatalytic material was synthesized by immobilizing the N-doped TiO2 and graphene oxide (GO) composite on polypropylene (PP) (N-TiO2/GO/PP) fibre sheet, and characterized based on X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). The photocatalytic activity was evaluated using roxithromycin (ROX) as a typical antibiotic pollutant. XRD, Raman spectra and SEM images proved that N-TiO2/GO/PP fibre sheet was successfully synthesized. The photocatalytic degradation of 10 mg L-1 ROX can reach up to 90% and the degradation rate constant was 0.2299 h-1 in surface water with the application amount of TiO2/GO/PP fibre sheet of 24.6 cm × 2.7 cm and reaction time of 9 h under the irradiation of simulated sunlight. The application amount of TiO2/GO/PP fibre sheet, initial concentration of ROX and water matrix significantly affect the degradation of ROX. A low concentration of natural organic matter (NOM) slightly promoted the degradation of ROX, while a high concentration of NOM significantly inhibited the degradation of ROX. Alkaline condition (pH 8-9) is favourable for the photocatalytic degradation of ROX by TiO2/GO/PP fibre sheet. The photocatalytic reactivity of the TiO2/GO/PP fibre sheet showed no significant decrease after three runs. Two primary degradation products of ROX were identified and they showed lower ecotoxicity than ROX. The results demonstrate that the new synthesized TiO2/GO/PP fibre sheet shows promising application prospects in the treatment of antibiotics in wastewater and surface waters.

Correlated quantification using microbiological and electrochemical assays for roxithromycin determination in biological and pharmaceutical samples

Microbiological and electrochemical assays, applying the cylinder-plate and differential pulse voltammetry as techniques, are reported for the quantitative determination of roxithromycin in serum and solid pharmaceutical form. The microbiological assay is based upon the inhibitory effect of this drug on the strain Bacillus subtilis ATCC 9372 used as the test microorganism. Linearity of the calibration curve was observed over the concentration range of 8.37-83.70 μg mL^-1, with relative standard deviation values less than 5.0%. The electrochemical behavior of roxithromycin was studied at a graphite screen-printed electrode modified with graphene by using cyclic voltammetry and differential pulse voltammetry. The current value of the oxidative peak obtained for roxithromycin at 0.65 V vs. Ag/AgCl in 0.03 mol L^-1 phosphate buffer solution (pH 7.0) with a scan rate of 0.1 V^-1 is a linear function of the concentration in a range of 4.19-83.70 μg mL^-1 (5-100 μmol L^-1). A comparative study was carried out and both methods were applied for the determination of roxithromycin in solid dosage forms and spiked serum. The bioassay results of human serum samples were in accordance with the electrochemical ones (R² = 0.988, P < 0.001), and the Bland-Altman method also showed good agreement between the values obtained by both procedures. Moreover, the statistical comparison indicated that there was no significant difference between the proposed techniques regarding both accuracy and precision.

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.