A crown-ether containing the iodo-triazole moiety for simultaneous cation-anion binding through Lewis-basic nitrogen atoms and C-II halogen-bond-donating iodine atoms was prepared. The complexation of the heteroditopic receptor was illustrated by X-ray and DFT analysis. The cooperative effect boosting the anion affinity was quantified by H/C NMR titration experiments.

Monitoring the successful removal of antibiotics in waste and surface waters is of high interest to overcome the occurrence of antibacterial resistance in the ecosystem. Among the newly developed analytical methods, the lab-on-a-chip surface-enhanced Raman spectroscopic (LoC-SERS) technique has gained the interest of the scientific community in the last few years. Ciprofloxacin, a second-generation fluoroquinolone, is widely used and administered to patients in dosages up to 1000 mg. In addition, more than 50 % of the antibiotic is excreted in urine as the parental drug. Thus, ciprofloxacin in environmental samples may exceed the minimum inhibitory concentration (MIC) values. The present study aims to assess the potential of the LoC-SERS technique to detect the target analyte in spiked river water samples at MIC concentrations. As sample clean-up procedure, a simple filtration is proposed, while as SERS, active substrates silver nanoparticles prepared at room temperature are employed. Ciprofloxacin was successfully quantified in the 0.7-10 μM concentration range with data that were measured on two different days. Furthermore, because of the low solubility of the antibiotic at the neutral pH range, insights into the effect of pH on the SERS signal of the target molecule are also presented. Graphical Abstract Ciprofloxacin detected at MIC values by LOC-SERS.

The prodrug pyrazinamide (PZA) is metabolized by the mycobacteria to pyrazinoic acid (POA), which is expelled into the extracellular environment. PZA resistance is highly associated to a lack of POA efflux. Thus, by detecting a reduction of the concentration of POA in the extracellular environment, by means of lab-on-a-chip (LoC)-SERS (surface-enhanced Raman spectroscopy), an alternative approach for the discrimination of PZA resistant mycobacteria is introduced. A droplet-based microfluidic SERS device has been employed to illustrate the potential of the LoC-SERS method for the discrimination of PZA resistant mycobacteria. The two analytes were detected discretely in aqueous solution with a limit of detection of 27 µm for PZA and 21 µm for POA. The simultaneous detection of PZA and POA in aqueous mixtures could be realized within a concentration range from 20 μm to 50 μm for PZA and from 50 μm to 80 μm for POA.