The Development Of Novel Surfactant-mediated Visual Biosensing Strategies

Surfactant is a class of molecules with surface activity.Because of its influence on interfacial property and low-cost,it has used in applications such as commodity synthesis,microbiology,biosensing,nanotechnology,and wastewater treatment.The term "visualization" first originated in computer science and refers to the conversion of digital information into intuitive and tangibles images on the screen based on computer graphics and image processing technology for researchers to observe and study.In recent years,"visualization" biosensors have received a lot of attention due to their ability to directly observe results from the naked eye,and have developed testing products that are close to people’s needs,such as immunological test strips,blood glucose testing instruments,air quality testing kits,etc.Surfactant-mediated visualization-based biosensors are less being developed for applications of biosensing technology despite their advantages such as easy observation and low cost.In this thesis,a series of surfactant-mediated visualization biosensors were carried out.Three specific works are included:(1)A liquid crystal droplet release based colorimetric sensor is designed and developed for the detection of aflatoxin.In situ encapsulation of horseradish peroxidase(HRP)by anionic surfactants assists in the preparation of liquid crystal-water microdroplet.While the cationic surfactant can release HRP by electrostatically perturbing the droplet equilibrium to trigger the color development reaction.If the target binds to the specific DNA probe modified on magnetic beads and triggers a nucleic acid rolling circle amplification,the nucleic acid binds to the cationic surfactant and inhibits the release of HRP,thus causes a change in the absorbance of the solution to achieve detection.(2)A surfactant-mediated high-throughput nanogold colorimetric assay is designed for adenosine detection.The free cationic surfactant binds to the nucleic acid through electrostatic interaction causing a change in its concentration.The concentration of free cationic surfactant affects the aggregation of nanogold particles,thus changing the color of its solution,and the quantification of adenosine can be achieved by measuring the change in absorbance.On this basis,the introduction to aptamer recognition triggers the rolling circle amplification reaction against magnetic beads to further improve the detection sensitivity.Meanwhile,a portable device combining a smartphone and a data processing program are developed to achieve high-throughput detection of adenosine by analyzing color parameters.(3)A paper-based sensor based on the detetion of lateral flow distance was designed and successfully applied to lipase detection.Using surfactant oleate as a medium,the lipase enzymatic reaction and the alginate gelation processes are combined,and the aqueous alginate solution is separated out the hydrogel and the upper aqueous solution through phase separated,and the change in viscosity of the upper solution can be determined by the lateral flow distance from pH paper,and thus the concentration of lipase is also determined.This method is the first paper-based distance sensor that based on phase separation to cause viscosity changes,extending the versatility and generality of hydrogel detection methods.Overall,this work develops surfactant-mediated colorimetric and distance-based biosensing methods that improve the sensitivity,specificity,and portability of visualization assays by combining them with enzyme amplification techniques and rolling circle amplification,and expands the research of new methods of visualization biosensing assays.