Study Of Liquid-crystal-based Biosensor For Cardiac Troponin ?

Cardiac troponin I(cTnI)is one of the most specific and sensitive biomarkers for the detection of myocardial cell injury.It can detect very minor myocardial injury and is considered as a major biochemical indicator for rapid diagnosis of acute myocardial infarction and acute coronary syndromes.Early detection methods of cardiac troponin I,such as colorimetry,electrochemical method,have good specificity for cTnI and play an important role in detecting cardiac biomarkers.However,these traditional methods have some obvious disadvantages,such as cumbersome labeling process,requiring precise and expensive instruments,long time consuming and complex detection steps.Therefore,it is of great importance to establish a rapid,sensitive,low-cost and label-free detection method for cardiac troponin I.In the meanwhile,liquid crystal(LC),as a kind of material with many excellent properties,has drawn the focus of many scholars.As a special material form between disordered liquid and solid crystal,it has the order and optical anisotropy of crystal molecule arrangement.The orientation of liquid crystal molecules is highly sensitive to surface molecular binding events,which provides the possibility for sensitive detection of biological molecules or chemical reactions.Liquid crystal biosensors use the birefringence of polarized light to monitor the biological target molecules.When the biological target molecules appear,the orientation of liquid crystal molecules will-change,resulting in the change of optical signal under polarized light microscope.As a label-free sensor,liquid crystal biosensor has the advantages of simple structure,convenient operation,no special light source and low cost Therefore,liquid crystal biosensors have great potential value in biomedical and chemical fields.To this end,this paper has done the following work in the construction of a new liquid crystal biosensor to realize the rapid and sensitive detection of cardiac troponin I:(1)A liquid crystal biosensor based on silanization N,N-dimethyl-N-octadecyl(3-aminopropyl)trimethoxysilyl chloride(DMOAP)/(3-aminopropyl)triethoxysilane(APTES)self-assembly membrane was prepared,and a kind of aldehyde,gludialdehyde(GA),was used as a coupling agent,which can be combined with the antibody to the glass substrate.The influence of the ratio of DMOAP/APTES and the concentration of GA on the liquid crystal molecular orientation was investigated,the optimal concentration was obtained through the experiment:1%APTES and 1%DMOAP,and the concentration of GA was determined to be 2%.The image of the polarized microscope was shown as a uniform black,which would not disturb the follow-up detection of the biological target molecule.(2)The LC cell one-sided biosensor based on the antigen-antibody specific immune response was constructed.the top slide was treated with only surfactant DMOAP,and the antibody can be combined with the GA from the bottom slide in the base chemical membrane When the antibody fixed on the surface is combined with the cTnI,the alignment of the liquid crystal molecules in the sensor will change,resulting in the change of optical signals under the polarization microscope.The experimental results show that the detection limit of biosensor for cTnI can be low to 0.01ng/ml.The sensor can detect low concentration of cTnI quickly and efficiently,and it requires no complex label process,and the detection is convenient and rapid(3)A double-sided sensing method based on antigen-antibody specific immune reaction was proposed,and the method of only a simple surfactant treatment on the top slide of the liquid crystal cell was improved.Effective use of double-sided simultaneous sensing of the liquid crystal cell will increase the sensitivity of the sensor and it can detect lower concentrations cTnI.The experimental results show that the improved double-sided sensing method can further lower the detection limit of cTnI to 1pg/ml,and has good selectivity.