Research On Liquid Crystal Sensor Of Heavy Metal Ions In Food Safety Detection

With the dramatic development of modern industrialization,which has caused a huge burden on our living environment,the caused food safety problems seriously threaten human health.Liquid crystal（LC）,as a unique optical material with both stimuli responsive and optical modulation characteristics,has been used to manufacture a variety of optical devices,and its application in sensing platforms has also been rapidly developed.The ordered long-range orientation of liquid crystal molecules provides a research foundation for the high efficiency,convenient operation and appropriate stability of the sensing platform.With the extensive application of biotechnology in disease diagnosis,food safety and environmental monitoring,the high sensitivity and excellent selectivity of liquid crystal biosensors can be used for unmarked,economical and real-time detection of multiple types of targets.In this paper,LC was used as the main sensing material,and the liquid crystal was combined with receptors such as protein and DNA to construct a liquid crystal sensing method for the detection heavy metal ions in food safety,and achieve signal amplification based on the small size effect of functional nanomaterials to improve the practicality of the sensor.Finally,a fast liquid crystal sensor device was designed to achieve high-precision,high-performance,cost-effective and rapid detection of heavy metal ions.The experiment focused on heavy metal ions that threaten food safety,and related LC sensors were designed and developed.The specific research includes the following aspects:1.Based on the interaction between bovine serum albumin（BSA）and metal ions,preliminary preliminary screening of heavy metal ions was conducted.The experiment optimized the BSA concentration and the parameters for constructing the sensing substrate,and found that the UV-modified DMOAP substrate surface could better immobilize the complex functional groups of BSA.When the BSA concentration was 5μg/ml,the substrate constructed by combining with ions was a uniform bright state,which could achieve kind optical effect.The sensor responds to heavy metal ions such as Cu²⁺,Pb²⁺and Cd²⁺,and the optical image appears bright.It does not respond to metal ions such as Na⁺,Ca²⁺and non-metal ions NH₄⁺,presenting a dark state,completed the feasibility and selectivity evaluation of the sensor.Taking Cu²⁺as an example for sensitivity experiments,it was proved that the sensor detection could reach theμM level.2.Based on the strong specificity and affinity of the aptamer and the corresponding target molecule,a label-free liquid crystal sensing method withÏ€-shaped DNA structure was constructed using heavy metal-cadmium（Cd）ions as a model,the substrate conditions were optimized,we found that the current substrate APTES/DMOAP was 1:1,the upper substrate DMOAP was 0.35%,and the GA content was 0.5%.By setting a concentration gradient experiment,it was verified that the detection limit of the Cd²⁺/LC sensor was 100 n M,and within the concentration range of 0.1-1000μM,the gray value exhibited a certain linear relationship with lg(Cd²⁺)fitting,achieving quantitative analysis within the detection range.Moreover,the sensor did not respond to reference ions such as Cu²⁺,Pb²⁺and Ca²⁺,completing the test of sensor sensitivity and specificity.In daily food safety experiments,the sensor responds to samples doped with Cd²⁺,which proves that the sensor has certain practical applicability.3.Gold nanoparticles（Au Nps）were introduced as the signal amplification medium to modify the substrate surface of the sensor to improve the detection limit of theÏ€-shaped DNA Cd²⁺sensor,we found that the detection limit of the LC sensor modified with Au Nps decreased by 2 orders of magnitude compared to the LC sensor without modifying nanomaterials,achieving signal amplification related to the Cd²⁺liquid crystal sensor.A three-dimensional model of the relevant detection kit was created,and on this basis,the kit was printed in 3D to verify the practical application and developability of the liquid crystal sensor.