Study On Surface-enhanced Raman Scattering For Detection Of Tobramycin Based On Bilayer Magnetic-plasmonic Satellite Nanoassemblies

In recent years,the toxic side effects,allergic reactions and bacterial resistance caused by the abuse of antibiotics have attracted people’s attention,and the antibiotic residues in the field of food safety have also attracted high attention.Tobramycin（TOB）is a widely used an-ti-infective drug and feed additive.Long-term overuse leads to the accumulation of tobramy-cin in various animal-derived foods,disrupting the balance of microflora in humans,which in turn induces various infectious diseases and seriously endangers human health.In response to the growing problem of tobramycin residues,the establishment of a highly sensitive method for the detection of tobramycin is therefore a key issue that needs to be addressed.The detec-tion methods of biosensors based on specific biometric elements have been developed rapidly in the field of biological detection due to the characteristics of rapid and sensitive,among which Raman biosensors have the advantages of non-destructive detection,hyperspectral specificity,excellent photobleaching resistance and no spontaneous fluorescence,and have gradually become a research hotspot in this field.The study was a construction of a bilayer magnetic-plasmonic satellite nanoassemblies（BMPSNs）for the ultra-sensitive and specific detection of TOB based on surface-enhanced Raman scattering（SERS）technology.The re-search contents are as follows:（1）A functional single-layer magnetic plasma satellite nanomodule（Fe₃O₄@Au NP-DNA1/DNA2）was constructed.Fe₃O₄@Au NP showed a uniform spherical morphology.A spherical Au NP with a size of 20 nm was uniformly dispersed on the 200 nm Fe₃O₄ surface.Fe₃O₄@Au NP has the standard diffraction peaks of Fe₃O₄ and Au NP.At the same time,gold nanostars（Au NS@4-MBA-DNA3）modified with DNA and Raman tags were constructed.They have uniform star morphology with spiny projection,size of about 60nm,Zeta potential of–10.16 m V,and have the optical properties of Au NS and good colloidal stability.（2）The feasibility of BMPSNs for TOB detection was explored.Non-denatured poly-acrylamide gel electrophoresis was used to verify the design process of DNA strand assembly.The results showed that the designed DNA can be successfully assembled step by step.BMPSNs has a strong Raman enhancement effect,and the calculated EF value is as high as1.67×10¹¹.（3）The important conditions in the process of BMPSNs system were optimized.The op-timal complement number of TOB Apt and c DNA was 23 bp,the optimal concentration and time of 4-MBA incubation were 650μmol·L^-1 and 1 h,the optimal concentration of DNA1and DNA3 incubation were 5μmol·L^-1 and 10μmol·L^-1,the optimal dosage and action time of ExoⅢwere 40 U and 100 min,and the optimal volume of Au NS@4-MBA-DNA3 was200μL.（4）Due to excellent magnetic separation,exonuclease amplification and huge SERS en-hancement of various hot spots,the logarithm of TOB concentration and Raman signal inten-sity showed a good linear relationship（R²=0.991）within the concentration range of 1–10⁵fg·m L^-1,and the detection limit could reach 0.44 fg·m L^-1,which was more sensitive than the previously reported method.At the same time,BMPSNs were highly selective and stable,and could specifically detect TOB even in mixed samples,with little difference in detection sig-nals between batches,the Relative standard deviation（RSD）was 3.03%.In addition,the method was applied to the detection of TOB in milk and honey,the recovery rate was between95.17%and 106.00%,RSD were lower than 2.35%,showing good practical application abil-ity.The designed BMPSNs system was characterised by a wide detection range,low detec-tion limits,good interference immunity and high reproducibility,and has promising applica-tions in the trace detection of antibiotic residues.