Study On Nano-signal Amplification Technology In Detection Of Cecropin B By Liquid Crystal Sensor

Liquid crystal(LC)biosensor is an optical sensor.It based on the change of vertical alignment of liquid crystal molecules to achieve the purpose of detection.Compared with other detection methods,it has lower detection limit.However,when the liquid crystal biosensor was used detect some small molecules(such as amino acids),the sensitivity of the liquid crystal biosensor will be reduced due to the low degree of liquid crystal disturbance caused by the small volume of the substance to be measured,which will affect the low degree of liquid crystal disturbance.Nanomaterials have the advantages of good biocompatibility,large specific surface area and so on,and have larger size relative to biomolecules.Therefore,nanomaterials can be combined with biomolecules and applied liquid crystal biosensor,which can play a role of signal amplification.In this paper,AuNPs and AgNPs were used signal amplification substances.Then conjugated with cecropin B antibody(anti-CB)to prepare three different coupling complexes which were used in the liquid crystal biosensor for detecting cecropin B(CB)to reduced the detection limit.The specific research content is as follows:(1)We used self-assembly of the substrate using silanization reagent method.DMOAP/APTES/GA were used self-assemble the substrate.DMOAP as an organic silane long chain can induce the vertical alignment of liquid crystal molecules and APTES+GA as a functional group to fix biomolecules to the substrate surface.Finally,contact angle measurement and atomic force microscope was used to characterize the self-assembled film on the substrate surface,confirming that DMOAP/APTES/GA was successfully fixed to the substrate surface,that is,the liquid crystal biosensor substrate was successfully constructed.(2)AuNPs was used as signal amplifiers.AuNPs was coupled to anti-CB by physical adsorption,and CB was detected.The AuNPs-anti-CB coupling complex was immobilized on the substrate surface using GA.According to the specific binding of CB and anti-CB,moreover the amplification of AuNPs,the vertical alignment of liquid crystal molecules is greatly changed,which reduces the detection limit of CB.Finally,a linear fit was found for different concentrations of CB and their corresponding image gray values,when the concentration of CB is between 10-500 ng·mL-1,the linear relationship between the gray value and the concentration is y=0.05 1x+4.811,and the detection limit of CB is as low as 9.28 ng·mL-1.(3)AuNPs was used as signal amplifiers.AuNPs was coupled with anti-CB by the chemical coupling,and cecropin B was detected.Coupling by chemical reaction between anti-CB and AuNPs that after N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride(EDC)activated carboxy,to prepare AuNPs-anti-CB coupling complexes by chemical bonding.The amino group of the anti-CB in the reacts with the aldehyde group of the substrate GA and fixes the complex on the substrate surface.The specific binding of the antigen and antibody is used to fix the test object CB to the substrate surface.Since the volume of AuNPs is larger than that of CB,the topography of the substrate surface is greatly changed,causing the vertical sequence of liquid crystal molecules is greatly changed,and the detection limit of CB is reduced.Finally,finding that there is a linear relationship between the two things when the CB concentration is between 10-200 ng·mL-1.The linear relationship is y=0.068x+5.073 and the detection limit was found to be as low as 2.13 ng·mL-1.(4)AgNPs was used as signal amplifiers.AgNPs was coupled with anti-CB by chemical coupling,and CB was detected.Using GA to fix AuNPs-anti-CB coupling complex on the substrate,according to the specific binding of CB and anti-CB to fix the test object CB,the vertical alignment of liquid crystal molecules greatly disturbed by AgNPs signal amplification,playing the role of local optical signal amplification and achieve the purpose of detecting lower concentrations of CB.By linear fitting between the CB concentration and its corresponding image gray value,finding that there is a linear relationship between the two things when the CB concentration is between 10-100 ng·mL-1.The linear relationship is y=0.353x+3.33.The experimental results show that taking signal amplification of CB by AgNPs,the detection limit is as low as 1.02 ng·mL-1.