Liquid Crystal Mediated Bioassay for Protein Detection

Abstract

Detecting human serum albumin (HSA) in urine samples is a standard procedure for diagnosis of kidney problems and prognosis of patients with chronic kidney diseases (CKDs). This PhD work developed a HSA assay by incorporating a thin layer of liquid crystals (LCs) as a readout system such that the presence of HSA in urine samples can be detected as optical signals. In combination with dilution protocols, the assay can be used to estimate the concentration range of HSA simply by counting the number of bright spots. The results obtained show that the assay can detect HSA at lower concentrations and can thus provide a faster and simpler alternative for the technology currently in use of clinics. In addition, we further developed an immunoassay in which probe proteins are immobilized on the surface of liquid crystal (LC) droplets rather than on solid surfaces. The advantage of such a immunoassay is that the antibodies binding to the probe proteins can be transduced by the LC droplets directly. For example, for the LC droplets decorated with immunoglobulin G (IgG) in a solution containing anti-IgG (AlgG), their orientations are found changed from radial to bipolar configuration. In contrast, for the IgG-LC droplets in a solution containing anti-human serum albumin (AHSA), no changes in orientation can be observed. The change of orientational configuration indicates the formation of the antigen antibody immunocomplex on the surface of the LC droplets. Such technology can be used to detect antibody concentrations as low as 0.01 ug/mL for AlgG and 0.02 ug/mL for AHSA. The technology has the potential to be further developed as a portable and low-cost immunoassay.