Advanced optical liquid crystal biosensor for real-time detection of protein–ligand interactions via non-covalent mechanisms

The present study focuses on the fabrication and development of a liquid crystal (LC) biosensor utilizing non-covalent protein–ligand interactions for the detection of target molecules. We synthesized avidin-conjugated silica nanoparticles (Avidin@Silica NP) and biotin-conjugated gold nanoparticles (Biotin@GNP), and characterized them using X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Visible), and field emission scanning electron microscopy (FESEM) to examine their structural, optical, and morphological properties. The liquid crystal sample cell was fabricated in a sandwich assembly by spacing two DMOAP-coated glass slides with a 20 µm Mylar spacer, sealing with Araldite gum, and functionalizing the bottom slide with Avidin@Silica NP and Biotin@GNP to form the sensing substrate. Nematic liquid crystal (NLC) was introduced into the LC cell via capillary action. LC biosensor cells were prepared with varying concentrations of Avidin@Silica NP, ranging from 0 µl to 30 µl, and examined under a polarizing optical microscope. Results showed that while Biotin@GNP alone did not disrupt the NLC alignment, increasing concentrations of Avidin@Silica NP (0.5 µl to 30 µl) induced a disruption in the homeotropic alignment, leading to birefringence in the optical images. These observations confirm that the LC-based biosensor, driven by non-covalent protein–ligand interactions, provides an effective alternative to traditional antibody-based detection methods. This biosensor platform holds promising potential for the diagnosis of various tumors and surface antigens through protein–ligand interactions.