Fluorescent Biosensors For Detection Of Hg²⁺ In Food And Aquatic Environment Based On Aptamer-functionalized Magnetic Beads

Mercury is a global pollutant that harms human health and the environment.Due to the discharge of industrial wastewater,Hg²⁺is widely present in the aquatic environment.It is enriched in aquatic organisms through the food chain and remains in aquatic products,making it easy to enter the human body.The existing methods for detecting Hg²⁺required expensive equipment,professional technicians,and cumbersome operation steps.The study found that the T base can specifically bind to Hg²⁺to form a T-Hg²⁺-T mismatch structure,which can be used to specifically recognize Hg²⁺.In this case,The paper proposes a fluorescent biosensor based on aptamer-functionalized magnetic beads for detecting Hg²⁺in food and aquatic environment.The paper mainly includes the following two parts:?1?The T-rich nucleic acid aptamer is immobilized on the surface of Fe₃O₄magnetic beads by using specific binding between streptavidin and biotin to form aptamer-functionalized magnetic beads.The T-Hg²⁺-T mismatch structure can be formed in the presence of Hg²⁺between the T-base-rich nucleic acid aptamer and the signal transduction probe labeled with a fluorescent group FAM.The signal transduction probe is separated from the detection solution after magnetic separation,,which caused the system to exhibit a weaker fluorescent signal.When Hg²⁺is absent,the signal transduction probe is free in the solution and will not be separated from the detection system with magnetic separation.At this time,the fluorescence signal of the detection solution is significantly enhanced.According to the change of fluorescent signal,Hg²⁺can be quantitatively detected.The design is very simple and has good selectivity and sensitivity.Under optimal conditions,the linear range is1¹00 nM and the detection limit is 0.34 nM.The method was successfully applied to detect the actual sample fish and river water,and the results were good.?2?Studies have found that when Hg²⁺and fluorescent signal probes combine directly,a fluorescence quenching effect is produced,which affects the accuracy of Hg²⁺fluorescence biosensor detection to a certain extent.Therefore,this part is designed to avoid the direct bond of Hg²⁺and the fluorescence signal probes for eliminating the fluorescence quenching effects.The T-rich nucleic acid aptamer is immobilized on the surface of Fe₃O₄ magnetic beads by using specific binding between streptavidin and biotin to form aptamer-functionalized magnetic beads.When Hg²⁺is present,a T-Hg²⁺-T mismatch structure is formed between the T-base-rich nucleic acid aptamers and the help strands.After magnetic separation,the signal transduction probe is free in the detection solution,and the system exhibits a strong fluorescent signal.However,the nucleic acid aptamer and the signal transduction probe can be bound together by base complementary pairing in the absence of Hg²⁺,so that the signal transduction probe is separated from the detection solution along with the magnetic separation process.Quantitative detection of Hg²⁺can be performed based on the changes of the fluorescence signals.The biggest advantage of this design is to avoid the influence of fluorescence quenching effect on the detection accuracy of fluorescence biosensor.At the same time,the method has good selectivity and high sensitivity.Under the optimal conditions,the linear range is 2¹60 nM,and the detection limit is 0.2.nM.The method was successfully applied to the detection of actual sample fish and river water and the results were good.In this paper,two kinds of fluorescence sensors were designed to detect Hg²⁺based on aptamer-functionalized magnetic beads,and they were successfully applied to the detection of Hg²⁺in actual sample fish and river water.The second design scheme successfully avoids the direct combination of Hg²⁺and fluorescent signal probes,thereby eliminating the fluorescence quenching effect on the detection accuracy of the fluorescent biosensor.It has certain innovation and has certain application potential in the detection of actual samples.