| Liquid crystal,a unique phase state of matter between liquid and crystalline,combined the fluidity of liquid with the optical anisotropy of crystal.We established a novel liquid crystal biosensor with prominent advantages based on the birefringence property of the liquid crystal.This novel liquid crystal biosensor permited a label-free,highly sensitive and specific,low-cost,simple and fast detection for analytes and could be potentially applied in bioanalysis.The aim of liquid crystal biosensor detection is to change the birefringence characteristics of liquid crystal molecules by changing the assembly of the sensor substrate so as to display different optical signals under polarizing microscope.This paper applied it to the detection of HBD-2 combining the advantages of liquid crystal biosensor and discussing how to reduce the detection limit of this method.The specific research contents and results are as follows:?1?Sensor substrates were prepared by self-assembly membrane method based on silanization reagents.The DMOAP/APTES?Dimethyl octadecyl[3-?trimethoxysilyl?propyl]ammonium chloride/?3-aminopropyl?trimethoxysilan?mixed self-assembled monolayers formed by both long and short alkyls could cause vertical alignment uniformly of liquid crystal,and then the assembled membrane was modified with GA?glutaraldehyde?for conjugation of biological molecules.AFM?Atomic force microscope?and contact angle measurement were used to characterize the substrate assembly.The images were obtained through polarizing microscope after the liquid crystal cells was made and the orientation of liquid crystal molecules was determined according to the brightness of images.The results showed that when the volume ratio of APTES to DMOAP is 3:1 and the GA content is 2%,the optical image is a uniform black pattern without background interference.?2?A label-free liquid crystal biosensor based on the orientation changes of LC was developed for the detection of HBD-2 through direct immunoassay.Anti-HBD-2 antibody was tethered onto the semassembled film surface on a glass slide via a cross-linker glutaradehyde.The specific binding of HBD-2 and anti-HBD-2 antibody induced the homeotropic-to-tilted transition of liquid crystal,making a visible optical change observed under the crossed polarized light and achieving the detection of HBD-2.The average gray-scale intensty of optical appearances has a good linear relationship with the concentration of HBD-2 when the concentration of HBD-2 is in the range of 5 ngˇmL-1 to 150ngˇmL-1 and the linear equation is,the linear correlation coefficient is 0.9989 and the limit of quantification is 4.95 ngˇmL-1for the HBD-2.This study offers a simple,highly sensitive and specific,label-free method for HBD-2 detection.?3?A label-free liquid crystal biosensor based on the orientation changes of LC was developed for the detection of HBD-2 through competitive immunoassay.HBD-2 was tethered onto the semassembled film surface on a glass slide via a cross-linker glutaradehyde.The specific binding of anti-HBD-2 antibody and HBD-2 induced the homeotropic-to-tilted transition of liquid crystal,making a visible optical change observed under the crossed polarized light and achieving the detection of HBD-2.The average gray-scale intensty of optical appearances has a good linear relationship with the concentration of HBD-2 when the concentration of HBD-2 is in the range of 1 ngˇmL-1 to 10 ngˇmL-1 and the linear equation is,the linear correlation coefficient is0.9956 and the limit of quantification is 0.53 ngˇmL-1 for the HBD-2.This study offers a simple,highly sensitive and specific,lable-free method for HBD-2detection.?4?Gold nanoparticles?AuNPs?--anti-HBD-2 antibody complex was preparated and the AuNPs sizes of 13 nm were prepared by sodium citrate reduction method.The AuNPs and AuNPs--anti-HBD-2 antibody complexes were characterized by UV-vis,TEM and granulometer.The results showed that the synthesized AuNPs were stable and homogeneous,and the properties of AuNPs--anti-HBD-2 antibody were stable,which lays a foundation for the subsequent preparation of a liquid crystal biosensor based on AuNPs signal amplification to detect HBD-2. |
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