Label-Free Liquid Crystal-Based Dielectric Genosensor for Infectious Bacterial Detection

A dielectric liquid crystal (LC)-based genosensor was developed for the detection of the bacterium, Neisseria gonorrhoeae, a sexually transmitted pathogen. The LC-dielectric sensing platform was fabricated by biomolecular immobilization of an N. gonorrhoeae-specific oligonucleotide probe (ssDNAprobe) on premodified electrodes of the LC cell for the detection of genomic DNA of N. gonorrhoeae (DNAN.g) using a low-frequency dielectric transduction mechanism. The sensing mechanism is based on dielectric spectroscopic analysis at 100 Hz, revealing a significant increase in relative permittivity caused by the random orientation of 5CB LC molecules at the LC-electrode interface due to DNA hybridization (ssDNAprobe-ssDNAN.g) at the electrode surface. The LC-dielectric genosensor demonstrated a linear change in relative permittivity (Δε') response over a wide range of 1 pM to 100 nM DNAN.g, with a low detection limit (LOD) down to 0.5 pM and a sensitivity of Δε' = 9.38 per decade of DNAN.g. The dielectric sensing performance of the LC genosensor was compared to that of optical transduction observed under polarized optical microscopy and was found to be 20 times better for low-level detection than the optical LOD of 10 pM DNAN.g. Specificity studies were performed with potential interferents of non-N. gonorrhoeaeNeisseria species, such as Neisseria sicca, Neisseria mucosa, and Neisseria meningitidis, and other bacterial species like Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The observation of insignificant dielectric response with the potential interferents demonstrated the good selectivity of the LC genosensor for N. gonorrhoeae. The comparatively higher sensitivity of dielectric transduction over the optical one indicates the suitability of the LC-dielectric genosensor as a promising tool for the sensitive detection of N. gonorrhoeae for improved diagnostic capabilities and management.