| Liquid crystal biosensor is a novel optical sensor to detect biomolecules usingcharacteristic birefringence properties of polarized light in liquid crystal. The targetbiomolecule which is imported to sensing interface leads to a change in the orientationof liquid crystal molecules and different response signals can be observed underpolarizing microscope, thus realizing the target detection. Although the research timeof liquid crystal biosensors is on the initial beginning stage, it still shows theadvantage of simple structure, easy miniaturization and array, and so on. So liquidcrystal biosensor as a novel optical sensor technology has received extensive attention.At present, the liquid crystal biosensors are mainly based on the direct coupling of theprotein, nucleic acid and other biological molecules directly on the sensor interface,thereby realizing qualitative or half quantitative detection of the biomolecules. Itsdetection sensitivity is difficult to meet the requirements of modern biological analysisand detection. Thus, the development of signal enhancement is improtant to furtherexpand the application field of the liquid crystal sensor. In this paper, we carried outthe following tasks through combination of the biological signal amplificationtechnology and the advantages of liquid crystal biological sensor.(1) Using K-ras gene mutation in codon12(GGTâ†'GTT) as a model, wedeveloped a novel liquid crystal DNA sensor combined with the rolling circleamplification. The feature is that rolling circle amplification can amplify the length oftarget sequence up to several ten thousand base pairs of single-stranded DNA, whichgreatly extending the length of target DNA and expanding the receptor molecular sizeand density on the liquid crystal biological sensing interface, and achieve theenhancement effect of polarized signal. The specific procer is as follows: First, a DNAsensor interface is constructed on the glass substrate, and then the extension product isobtained from rolling circle amplification and is captured by the capture probe fixed onthe glass substrate. The ordered arrangement of liquid crystal molecules is effectivelydisrupted through introducing long single-stranded DNA. Using the uniquebirefringent properties of liquid crystal molecules, the sensor can get an enhancedpolarization response signal, and achieve the seusitive detection of the target sequence.If it is the wild-type target sequences which presented single-base mutation, rollingcircle amplification can not be achieved and without extending DNA strand, so the ordered arrangement of liquid crystal molecular cannot be disturbed and there is nopolarizing response signal. The experimental results show that this method is a simple，practical and highly selective, high sensitive DNA detection technology.(Chapter2)(2) A new liquid crystal DNA sensor based on gold nanoparticle signalamplification is proposed for the dection of nucleic acid sequences in which two layersof DNA gold nanoparticles are used to enhance the liquid crystal sensing signal. In theexperiment, the typical three stage hybrid method is used, the capture probes, targetsequence and DNA-AuNPs complex are binded to a glass substrate surface in turn. Thenucleic acid sequence density on the basal surface is notably enhanced by introducingfunctionalized DNA gold nanoparticles, and the alignment of liquid crystal moleculesare disrupted and a great signal amplification effect is achieved and the experimentresult is satisfactory. The sensor can detect1fM of the target sequence, the signal isenhanced by3orders compared with that just using one layer of DNA-AuNPs. and itcan well distinguish the single base mismatches, showing good selective. This methodwas simple, rapid and highly sensitive and it fits for the detection of single-basemutation nucleic sequences.(Chapter3)(3) Based on the competitive immunoassay principle, we put forward a liquidcrystal immunosensor for the simple and fast detection of OTA using small molecularantigen OTA as a model. OTA is a kind of small molecule antigen which has littleeffect on the orientation of the liquid crystal molecules, however its antibody withlarge molecular weight has obvious influence on the alignment of liquid crystalmolecules. Therefore, in this paper, we used OTA antigen in the sample solution andBSA-OTA conjugates assembed on glass substrate surface to competitivly binding withthe OTA antibody. The orientation of liquid crystal molecule changes and with theincrease in the amount of the binding antibody on the sensing surface, resulting inpolarizing signal change. This method achieved a high sensitive detection for smallmolecular antigen OTA.(Chapter4)... |
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