A label-free 5CB-based aptasensor for highly selective optical detection of amoxicillin residue in freshwater samples

ABSTRACT

A novel application of thermotropic liquid crystal (LC) 5CB in an optical aptasensor for the sensitive detection of amoxycillin (AMOX) antibiotic has been reported. In the studied system, the glass substrates were treated with dimethyloctadecyl [3–(trimethoxysilyl) propyl] ammonium chloride (DMOAP) and an aqueous solution of cationic surfactant cetyltrimethylammonium bromide (CTAB) was used to obtain a homeotropically aligned 5CB monolayer at the LC-aqueous interface resulting in a uniformly dark appearance. A highly specific amoxycillin aptamer (AMXA) was immobilised on the glass substrate as a target recognition probe for AMOX molecules. The specific binding of AMXA and AMOX molecules induces orientational changes in LC ordering resulting in a change in LC optical textures observed under a Polarized Optical Microscope (POM). A low limit of detection (LOD) of 10 nM for AMOX was obtained using this sensing system. Additionally, a high specificity for AMOX was also observed during comparative analysis. Finally, the developed biosensor was used to successfully detect AMOX in environments of potential application like tap water and lake water samples. Thus, the developed LC-based aptasensor can be a simple, sensitive and label‐free platform for monitoring real‐time levels of AMOX in freshwater environments.

GRAPHICAL ABSTRACT

KEYWORDS:

• Liquid crystals
• cyanobiphenyl
• biosensors
• amoxycillin
• aptamer
• aqueous interface

Acknowledgments

This work was carried out using the facilities of Shiv Nadar Institution of Eminence. The authors are thankful to Prof. Santanu Kumar Pal, Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India, for his valuable help and guidance. The authors also acknowledge the contribution of Prof. Malay Kumar Das, Department of Physics, University of North Bengal, Siliguri, India, for his consistent assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02678292.2023.2280616