Label-free liquid crystal-based optical detection of norfloxacin using an aptamer recognition probe in soil and lake water

Analyst. 2024 Jul 8;149(14):3828-3838. doi: 10.1039/d4an00236a.

Abstract

Norfloxacin (NOX), a broad spectrum fluoroquinolone (FQ) antibiotic, is commonly detected in environmental residues, potentially contributing to biological drug resistance. In this paper, an aptamer recognition probe has been used to develop a label-free liquid crystal-based biosensor for simple and robust optical detection of NOX in aqueous solutions. Stimuli-receptive liquid crystals (LCs) have been employed to report aptamer-target binding events at the LC-aqueous interface. The homeotropic alignment of LCs at the aqueous-LC interface is due to the self-assembly of the cationic surfactant cetyltrimethylammonium bromide (CTAB). In the presence of the negatively charged NOX aptamer, the ordering changes to planar/tilted. On addition of NOX, the aptamer-NOX binding causes redistribution of CTAB at the LC-aqueous interface and the homeotropic orientation is restored. This results in a bright-to-dark optical transition under a polarized optical microscope (POM). This optical transition serves as a visual indicator to mark the presence of NOX. The devised aptasensor demonstrates high specificity with a minimum detection limit of 5 nM (1.596 ppb). Moreover, the application of the developed aptasensor for the detection of NOX in freshwater and soil samples underscores its practical utility in environmental monitoring. This proposed LC-based method offers several advantages over conventional detection techniques for a rapid, feasible and convenient way to detect norfloxacin.

MeSH terms

  • Anti-Bacterial Agents / analysis
  • Anti-Bacterial Agents / chemistry
  • Aptamers, Nucleotide* / chemistry
  • Biosensing Techniques* / methods
  • Cetrimonium / chemistry
  • Lakes* / analysis
  • Lakes* / chemistry
  • Limit of Detection*
  • Liquid Crystals* / chemistry
  • Norfloxacin* / analysis
  • Norfloxacin* / chemistry
  • Soil / chemistry
  • Water Pollutants, Chemical / analysis
  • Water Pollutants, Chemical / chemistry

Substances

  • Norfloxacin
  • Aptamers, Nucleotide
  • Soil
  • Anti-Bacterial Agents
  • Water Pollutants, Chemical
  • Cetrimonium