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

• Published in: Analyst (London) Vol. 149; no. 14; pp. 3828 - 3838
• Main Authors: Das, Sayani, Sil, Soma, Pal, Santanu Kumar, Kula, Przemys aw, Sinha Roy, Susanta
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 08.07.2024
• Subjects: Anti-Bacterial Agents - analysis; Anti-Bacterial Agents - chemistry; Aptamers, Nucleotide - chemistry; Aqueous solutions; Binding; Biosensing Techniques - methods; Biosensors; Cetrimonium - chemistry; Cetyltrimethylammonium bromide; Environmental monitoring; Labels; Lakes - analysis; Lakes - chemistry; Limit of Detection; Liquid crystals; Liquid Crystals - chemistry; Norfloxacin; Norfloxacin - analysis; Norfloxacin - chemistry; Optical microscopes; Optical transition; Recognition; Self-assembly; Soil - chemistry; Soil water; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry
• ISSN: 0003-2654; 1364-5528; 1364-5528
• DOI: 10.1039/d4an00236a

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. A schematic representation of the liquid crystal-based aptasensor for the optical detection of norfloxacin in soil and lake water.