Development Of Rapid Detection Method For Malachite Green Using Polyester Fiber Based SERS Substrate

Malachite Green?MG?is a synthetic toxic triphenylmethane compound that is both a dye and a bactericidal and parasitic chemical.Because of its low price,high efficiency of sterilization,and the lack of effective drugs that can solve Saprolegniasis in a short time,it always been found in the aquaculture industry.At present,the main detection methods of MG includehighperformanceliquidchromatography,highperformanceliquid chromatography-massspectrometry,gaschromatography-massspectrometry,and enzyme-linked immunosorbent assay.The sensitivity and accuracy of chromatographic mass spectrometry are high,but complex sample preparation and professional operators are required.The detection time is long,and a large amount of organic waste liquid is polluted.The sensitivity of enzyme-linked immunosorbent assay is not high.These methods are unable to meet the growing on-site rapid screening needs of aquatic products.SERS technology is widely used in surface science,analytical science,biological science,environmental monitoring and drug explosives research because of its convenient operation,simple sample preparation and rapid detection.Flexible SERS substrates have excellent mechanical properties,are not easily damaged,low in cost,and are easy to transport and carry.They can be flexibly coated on complex irregular sample surfaces while maintaining the number of"hot spots"on the substrate.These advantages are of great help to the further application of SERS technology in various fields.In this study,a novel flexible SERS substrate was prepared by modifying gold nanoparticles on polyester fibers.And the polyester fiber substrate was functionalized with high specificity and affinity aptamer.MG is detected with high sensitivity and specificity,which is of great significance for strengthening the monitoring of aquatic products and ensuring the safety of aquatic products.The main research contents are as follows:First,a flexible SERS substrate was successfully prepared by depositing gold nanoparticles on the surface of polyester fibers.It was characterized and the preparation conditions were optimized.The flexible SERS substrate has good reproducibility?RSD=14.89%?,stability and high sensitivity.The intensity of the MG's Raman characteristic peak at1178 cm^-1is plotted on the ordinate,and the logarithm of the MG concentration is linearly fitted on the abscissa.In the linear range of 10^-99 mol/L¹0^-44 mol/L,y=3942.3x+39803?R²=0.9955?,the lowest detectable concentration is 10^-10mol/L.The cultured water samples were spiked and recovered,the recovery rate is 73.55%¹12.44%.Shrimp meat samples were tested by in-situ wiping samples with a minimum detectable concentration of 10^-9mol/L.It is proved that the polyester fiber based SERS substrate can detect MG quickly and with high sensitivity.Then,in order to improve the specificity of substrate detection and take advantage of on-site detection,the substrate was functionalized with an aptamer,and two detection methods were developed using a portable Raman spectrometer:?1?Single signal detection method:The complementary chain with a thiol group is linked to the gold nanoparticles on the surface of the polyester fiber based SERS substrate through a gold-sulfur bond.The Cy5-labeled aptamer then hybridizes to the complementary strand.When the MG is in the detection system,the MG competes with the complementary strand for binding to the aptamer.Due to the high affinity of the aptamer to the MG,separation of the aptamer linked to Cy5 with the complementary strand results in a decrease in the Cy5 Raman signal.The MG was specifically detected based on the relationship between the MG concentration and the Cy5 Raman signal intensity.The detection strategy has good specificity and sensitivity.The Raman characteristic peak intensity of Cy5 at 1360 cm^-1is plotted on the ordinate,and the logarithm of the MG solution concentration is linearly fitted to the abscissa.In the linear range of 10^-9mol/L¹0^-5mol/L,y=-430.17x-794.19?R²=0.9975?,the lowest detectable concentration is 10^-1010 mol/L.The cultured water samples were spiked and recovered,the recovery rate is 84.00%¹09.60%,which proved that the method can be applied to the quantitative detection of MG in actual samples.?2?Dual signal detection method:The MG aptamer with a thiol group is linked to the gold nanoparticles on the surface of the polyester fiber based SERS substrate by gold-sulfur bonds.The complementary strand with Cy5 tagged is then hybridized to the aptamer.When the MG is in the detection system,it competes with the complementary strand for binding to the aptamer.Due to the high affinity of the aptamer to the MG,the complementary strand of Cy5 is replaced and washed away,resulting in a decrease in the Cy5 Raman signal;at the same time,the Raman signal of the MG molecule bound to the aptamer appears.The MG was specifically detected based on the relationship between the MG concentration change and the change of the Cy5 Raman signal and the MG Raman signal.The detection strategy has good specificity.The spiked detection of cultured water samples,the double signal changes of MG and Cy5 are consistent with the standard solution,which proves that the method can be applied to the qualitative detection of MG in actual samples.