Research Of Novel Liquid Crystal Microarray Biosensor And The Detection For Molecules

Liquid crystal（LC）is a ubiquitous state of matter that exists in a wide variety of molecules.LC sensor uses LC molecules as signal elements that can convert the chemical and physical signals of chemical-biological binding events at the liquid crystal interface into optical signals,which has been achieved label-free,high sensitive determinations for many biomolecules and ions.However,the LC sensing interfaces still face some problems,such as the high requirements for the preparation of LC substrate,the non-reusability and instability of LC senging interface（easily affected by the external environment,e.g.temperature and humidity）.In the same time,the LC optical images are difficult to achieve the precise quantification for targets.Inverse opal photonic crystals（IOPh Cs）are ordered porous materials with excellent optical properties,and the voids and medium material of IOPh Cs have specific periodic arrangement in space,which can effectively control the propagation of light.It shows unique properties in the fields of optical modulation,biological detection,catalysis and anti-counterfeiting,etc.When the refractive index in the IOPh Cs void is changed,the modulation of the IOPh Cs optical signal can be achieved.In this paper,using IOPh Cs as templates and LC molecules as response elements,the liquid crystal microarray（LCM）film was prepared as LC sensing substrate.And the regulation of nucleic acid molecules and surfactants on the optical signals of LCM films was explored.Futhermore,the new LCM sensing signal is developed,and the LCM sensors are built for the label-free,rapid and sensitive detection of various small molecules.The main research contents are as follows:In chapter 2:Combined with the ordered microporous structure of IOPh Cs and the birefringence of liquid crystal,LCM films were prepared and the LCM sensing platform was constructed.The preparation conditions and optical properties of the inverse opal liquid crystal polymer film（IO-LCP）were explored.Through the changes in optical images and reflection peaks,the changes in the optical properties of LCM films before and after the injection of liquid crystal molecules were systematically analyzed.At the same time,the optical signals of LCM films changed with the change of mass fractions（0.2 wt%-1 wt%）and particle sizes（200 nm,230 nm,250 nm,280nm and 320 nm）of Si O₂ templates.Through recording the optical signal by the optical fiber spectrometer,the micro-spectral LC sensing optical signal is developed,and the liquid crystal microarray sensing system is fabricated.In chapter 3:The regulation of nucleic acid molecules on the optical signal of LCM film is explored by fluorescence images,polarizing microscope images and surface potential of LCM film.Single stranded nucleic acid molecules are adsorbed on the LCM film through exposed base groups and induce the LC molecules in the film,resulting in the change of the orientation of LC molecules.By researching the recyclability of the response of nucleic acid molecules to LCM film and the reusability of LCM film,the complete cyclic response progress is successfully constructed.The LCM films show good responsiveness to Ac solution after they are stored at room temperature for 6 months and still have a good responsive property after 10 cyclic experiments.According to the induction effect of aptamer on LC molecules and the specific recognition effect between aptamer and target,LCM sensor achieve the detection of cocaine by the change of reflection peak intensity,and the minimum detection concentration is 100 p M.In chapter 4:Based on the induction of ss DNA to LC milecules,a signal-on LCM sensor is designed by micro-spectral optical sensing signal for the determination of AFB1.Depending on the specific binding of aptamer in the double-stranded DNA(ds DNA_AFB1)and AFB1,the ss DNA is released from ds DNA and adsorbed on the LCM films to interact with LC molecules（5CB）,which leads to the change of the orientation of LC molecules from disordered to ordered arrangement.Based on this responsive principle,the LCM biosensor achieves the detection of AFB1 in the range of 300 p M to 100 n M.The sensor not only has good selectivity for AFB1,but also can detect AFB1 in actual samples（corn flour and beer）,showing good anti-interference ability.More importantly,the response mechanism of LCM films is discovered,the Partial Response Mechanism（PSM）,through the verification of optical images of LCM films.This mechanism not only provides fresh approaches for exploring a deeper understanding of the interfacial response mechanism of LCM sensing system but also promotes well the innovative research and development of LCM sensing technology in more fields.In chapter 5:The self-assembly of surfactant（SDS,C_nTAB,C12E4）at the interface of LCM films and the influence on the optical properties of LCM films were studied for the first time.The changes of reflection peak intensity and shifts of LCM films are regulated by surfactant.The LCM film was induced by myristoylcholine chloride（Myr）with similar surfactant structure to regulate the optical signal of LCM film.After the hydrolysis of Myr catalyzed by acetylcholinesterase（ACh E）,the hydrophilicity of the hydrolysate（tetradecanoic acid）decreased and the ability to induce LC molecules in LCM films increased,resulting in the LC molecules gradually approaching the vertical orientation and approaching the normal direction,further causing the change of the reflection peak waveleghth of LCM films.In the presence of inhibitors,the activity of ACh E decreased,so the target malathion can be detected by the shifts of the reflection peak of LCM film.When 10 m M Myr-LCM films and10 U ACh E are used,the minimum detection concentration to malathion by the LCM sensor is 10 pg/m L.The change of LCM reflection shifts is firstly used to detect the target,which provides a new vision and direction for the development of LCM sensing system.