Study Of Novel Liquid Crystal Sensor For Biomolecular Assay And Signal Amplification

Since the discovery of liquid crystal molecules, they have been widely applied to electronic display panels. At the same time, as special "sensing elements", liquid crystal molecules have recently also been introduced in sensor fields and especially they are used to build liquid crystal biosensor in life sciences, bursting on the scene edge. Liquid crystal biosensor is fast, simple, low cost, label-free, high sensitivity, low limit of determination and so on. Therefore, the new liquid crystal sensors are undoubtedly the developement of chemical and biological sensors with great potential. In this paper the development of new liquid crystal sensor has done as following:1. Based on the traditional method of liquid crystal alignment, a liquid crystal sensor has been constructed for the detection of alkaline phosphatase ALP. By rubbing the silane-modified membrane, the substrate for liquid crystal alignment is prepared. Alkaline phosphatase as biological macromolecules, assembled on the rubbed slide substrates, can effectively cover or landfill the orderly grooves and scratches, resulting in the change of nematic liquid crystal alignment direction and very different optical signals. A combination of silver deposition method based on the ALP catalyzation increase the impact of enzyme molecules to the alignment of liquid crystal, achieving an amplification of liquid crystal optical signal.2. DMOAP is introduced as a special chemical-sensing membrane. Combined with competitive immunoassay, a liquid crystal biosensor for the detection of clenbuterol has been developed successfully. Clenbuterol as a small biological molecules, has a minimal impact on the liquid crystal orientation, while the antibody molecules can impact on the liquid crystal orientation obviously due to its large molecular weight. Therefore, the clenbuterol in the solution can be detected through the competitive immune response. The results show that the sensor can be quickly and effectively to detect at low concentration levels of clenbuterol.3. A novel scheme for scanning electrochemical microscopy (SECM) assay of DNA based on hairpin probe and enzymatic amplification biosensor has been described. In this method, streptavidin-horseradish peroxidase(HRP) was captured by double-stranded DNA (ds-DNA) modified gold substrate via biotin-streptavidin interaction after hybridization of target DNA to the immobilized hairpin probe functioned with a biotin at its 3'end. In the presence of H2O2, hydroquinone (H2Q) was oxidized to benzoquinone (BQ) at the modified substrate surface through the HRP catalytic reaction, and the generated BQ corresponding to the amount of target DNA was reduced in solution by a SECM tip. The resulting reduction current allowed concentration detection of target DNA and SECM imaging of hybridization between the target DNA and the immobilized hairpin probe. The detection limit of this method was as low as 17 pM for complementary target DNA and it had good selectivity to discriminate between the complementary sequence and one containing base mismatches.