Developing a biosensing prototype utilising a 7CB liquid crystal for human insulin detection

Abstract

This paper presents a novel prototype for human insulin detection using a 4-heptyl-4-biphenylcarbonitrile liquid crystal (7CB-LC). Human insulin is essential for regulating blood glucose levels and facilitating the metabolism of carbohydrates, lipids, and proteins. Insufficient insulin can lead to hyperglycemia, where cells cannot utilise glucose effectively for energy production. Prolonged hyperglycemia can affect the nervous and cardiovascular systems. Our work investigates the scope of using 7CB-LC as a prototype for the label-free detection of human insulin. Both temperature and time-dependent studies conducted using a polarising optical microscope (POM) on human insulin in the concentration range from 25 μM to 500 μM showed that human insulin interacting with 7CB-LC produces radial, twisted-radial, pre-radial and bipolar textures. A detection limit of 25 μM was observed since no distinguishable textures were observed below this concentration. An RGB (red, green, and blue) and grey index study showed a positive correlation graph with an R² value of 0.97279, proving the selectivity of the proposed biosensor. Molecular docking and Raman spectroscopy studies were conducted to learn more about the interaction between insulin and 7CB-LC at the molecular level. Docking studies revealed how the position of the 7CB core and tail ends interacted with amino acid residues of insulin. Raman spectroscopy studies investigated the segmental mobility of different parts of LC and changes occurring in the core and terminal regions due to insulin interactions. Vibrational studies conducted using Raman spectroscopy analysed the change in 7CB-LC parameters such as the peak position (PP), line width (LW) and integrated intensity (II) on interacting with human insulin. This unique prototype technique shows how 7CB-LC can potentially be employed in biosensing to detect human insulin since it provides better visualisation in a label-free detection method.