Construction Of As³⁺ SERS Biosensor Based On Aptamers And Application In Food

With the development of industry and agriculture,arsenic pollution is becoming more and more serious,posing a very serious threat to food safety.Among several kinds of arsenides,trivalent arsenides exhibits highest toxic.Therefore,developing a sensitive and efficient method for trivalent arsenides detection is of great significance in the field of food safety.Biosensors have been widely used for the detection of metal ions due to their high sensitivity and good selectivity.Among various sensor component,aptamers-based sensor component exhibits realtive high selectivity and specificity.Therefore,it is often used as a sensor component of a biosensor.Compared with traditional analytical technology,surface-enhanced Raman spectroscopy(SERS)is a fast and sensitive analytical technique,which is easy to operate and can perform nondestructive testing.SERS has great potential in the rapid detection of contaminants,chemical components,and pathogens in food.In this thesis,a aptamers-based SERS biosensor for high specifical As³⁺detection was investigated.The content of this paper is shown as followed:1.Construction of As³⁺biosensor based on SERS and aptamers.The aptamers were modified on the surface of gold membrane,and combining with cationic polymer polydiallyldimethylammonium bromide(PDDA)via electrostatic interaction to form a double helix structure.Then,mercaptoundecanoic acid-modified gold nanoparticles(AuNPs)was modified on the aptamers to form an AuNPs-aptamers-Au structure.At the same time,4-mercaptobenzonitrile(4-MBN)was immobilized on the gold film as a Raman signal molecule.In the presence of As³⁺,As³⁺coordinate with the aptamers,resulting in the separation of aptamers are from PDDA and the double-stranded structure formed was destroyed.The aptamers is bent and folded,bringing AuNPs close to the gold film surface and forming a narrow gap.Due to the plasmon resonance on the surface of AuNPs,the Raman signal of 4-MBN is enhanced.Therefore,this sensor can be used to detect As³⁺sensitively and efficiently.The linear range of the sensor is 10-150?g/L(R²=0.9941),and the detection limit is1.5?g/L(S/N=3).2.Construction of SERS biosensor for detecting As³⁺based on gold nanoparticles-aptamer.Aptamers and PDDA are mixed together and form a double-helix structure in the buffer solution.Then 4-mercaptobenzonitrile(4-MBN)modified gold nanoparticles(AuNPs)were added,and the AuNPs were in a stable state of dispersion.At this time,the AuNPs modified with 4-MBN are in a stable state of dispersion.When As³⁺is added,As³⁺interacts with the bases of aptamers,causing aptamers to separate from PDDA.Because PDDA is a cationic polymer,after separation from aptamers,it can enhance the ionic strength in the solution.Then,AuNPs will aggregate and the 4-MBN Raman signal will be enhanced.Therefore,As³⁺can be quantitatively analyzed.The linear range of the sensor is15-120?g/L(R²=0.9936),and the detection limit is 1?g/L(S/N=3).