Green Ionic Liquid Albumin Glassy Carbon Biosensor (ILAGC) for On-line Binding Studies of Human Serum Albumin with Retinol

A new biosensor composed of 1-butyl-3-methylimidazolium hexafluorophosphates (BMIMPF6)-human serum albumin (HSA) film coated on glassy carbon electrode (GCE) was produced. In the current work, the conjugation of ionic liquid (IL) with HSA improved the stability and binding affinity of protein onto GCE. A rapid and reliable voltammetric method for the on-line protein binding studies of retinol with HSA was developed by hyphenating ionic liquid albumin glassy carbon (ILAGC) biosensor with differential pulse anodic stripping voltammetry under physiological conditions. Detection limit and quantitation limit of 4.5 and 15.0 nmol L-1 were achieved, respectively. This gave us the opportunity to study the high binding constant between retinol and HSA by their detection in nanomolars. The electrochemical behavior of retinol onto ILAGC biosensor was monitored by cyclic voltammetry. The surface coverage of retinol on the proposed biosensor was calculated by double potential-step chronocoulometry. The binding constant of retinol with HSA was estimated to be 1.30×105 L mol-1 giving acceptable precision (SD ≤ 0.02) and good agreement with literature values. The proposed electrochemical biosensor opened a new venue for cheap, green and rapid on-line binding studies of small molecules with protein. As well, our proposed method could use to study either high or low binding affinities.