The wide-spread usage of ciprofloxacin (CIP) resulted in its presence in different parts of the ecosystem. Thus, a simple, reliable, on-spot detection method for CIP is required in environmental context. Herein, a colorimetric assay is developed for the detection of CIP based on the branched polyethyleneimine (PEI) conjugated silver nanoparticles (PEI-AgNPs). AgNPs are prepared using PEI as stabilizing agent following a simple one-pot two-phase procedure. The prepared PEI-AgNPs are subsequently used for an efficient and selective detection of CIP. The characteristic yellow colour of PEI-AgNPs changed to colourless when CIP was added which was further confirmed by quenching in the intensity of the SPR (surface plasmon resonance) band (hypochromic shift). The proposed method is efficient for the quantitation of CIP in a linear dynamic range (LDR) of 0.1–200 µM with a limit of detection (LOD) of 0.038 µM, and limit of quantification (LOQ) of 0.12 µM. The developed method is selective, efficient, and sensitive to CIP in the presence of numerous interfering species and in real biological, environmental, and commercial pharmaceutical samples. Excellent performance of the proposed method compared to UV-Vis spectroscopy and UPLC in environmental, biological, and commercial pharmaceutical samples is demonstrated.

The emergence of multidrug-resistant (MDR) pathogens and the gradual depletion of available antibiotics have exacerbated the need for novel antimicrobial agents with minimal toxicity. Herein, we report functionally substituted pyridine carbohydrazide with remarkable antimicrobial effect on multi-drug resistant strains. In the series, compound 6 had potent activity against four MDR strains of Candida spp., with minimum inhibitory concentration (MIC) values being in the range of 16–24 µg/mL and percentage inhibition up to 92.57%, which was exceptional when compared to broad-spectrum antifungal drug fluconazole (MIC = 20 µg/mL, 81.88% inhibition). Substitution of the octyl chain in 6 with a shorter butyl chain resulted in a significant anti-bacterial effect of 4 against Pseudomonas aeruginosa (ATCC 27853), the MIC value being 2-fold superior to the standard combination of ampicillin/cloxacillin. Time-kill kinetics assays were used to discern the efficacy and pharmacodynamics of the potent compounds. Further, hemolysis tests confirmed that both compounds had better safety profiles than the standard drugs. Besides, molecular docking simulations were used to further explore their mode of interaction with target proteins. Overall results suggest that these compounds have the potential to become promising antimicrobial drugs against MDR strains.