In Situ Construction Of Fe₃O₄@PDA@Au As SERS Probes For The Detection Of Acute Neuteophils And Contaminants

Objective: In recent years,acute toxic substances,represented by drug and pesticide poisoning,have become more and more dangerous to people’s health.Therefore,the development of highly stable and sensitive clinical analysis methods for the rapid detection of acute poisoning substances can provide a strong guarantee for human life and health.Current methods for the detection of acute toxicants include gas chromatography and high-performance liquid chromatography.These methods have long detection periods,require large instruments and high detection costs,which cannot meet the real demand for rapid detection of acute toxicants and are not conducive to rapid clinical detection of drugs.Surface-Enhanced Raman Spectroscopy(SERS)detection technology not only has the advantages of high sensitivity and rapid detection,but also provides fingerprint information of the substances to be measured,and these features bring new opportunities for highly stable and rapid clinical detection of acute neutrophiles.Therefore,in this study,the Fe3O4@PDA@Au core-shell satellite nanomaterial SERS probe was synthesized by growing gold nanoparticles in situ on the surface of polydopamine(PDA)coated Fe3O4.It combines magnetic separation technique and multi-hot spot structure,and by adjusting the amount of HAu Cl4,the size and gap of gold nanoparticles on the surface of the SERS probe can be adjusted to form a three-dimensional multi-hot spot structure.The good dispersion and superparamagnetic properties of this SERS probe not only allow it to fully contact the target molecules in solution,but also facilitate the separation and enrichment of the sample.This process increases the molecular density and the number of SERS hotspots,thus improving the detection sensitivity while also achieving rapid detection of acute toxicants benzodiazepines as well as contaminants,providing a basis for real-time detection of acute toxicants in the field.Method: First,Fe3O4 nanoparticles(NPs)were synthesized by hydrothermal method,Fe3O4@PDA(FP)Nps were synthesized by coating iron tetroxide using the oxidative self-polymerization property of dopamine,and gold nanoparticles were grown in situ using the reducing property of polydopamine to form Fe3O4@PDA@Au(FPA)SERS substrates were formed.In this process,the size and gap of gold nanoparticles on the surface were regulated by the addition of HAucl4,and four SERS substrates with different sizes and gaps of gold particles,FPA-50,FPA-100,FPA-150 and FPA-200,were synthesized.The substrates with the best SERS intensity were screened using crystalline violet(CV)as the standard,and the sensitivity and reproducibility of the screened SERS substrates were investigated using CV as the probe molecule.The substrates were characterized morphologically by scanning electron microscopy(TEM)and transmission electron microscopy(SEM),and then by Fourier transform infrared spectrometer(FTIR Spectrometer),X-ray diffractometer(XRD),UV-VisSpectrophotometer and energy spectrometer.The substrates were characterized structurally.In order to further validate the universality and sensitivity of the substrates,malachite green and thiram were additionally selected for SERS detection.Finally,the prepared SERS substrates with magnetically enriched FPA were used to achieve the detection of benzodiazepines in serum.Result: Four FPAs SERS substrates with different gold particle size gaps were synthesized and screened with a CV concentration of 10-6 M for the substrates.When the amount of tetrachloroauric acid was 150 μL(FPA-150),the gold nanoparticle size was 35 nm and the gap was about 10 nm,and the SERS signal of the substrate was the best.And combined with the FDTD simulation results,the electric field region of FPA-150 SERS substrate was the strongest,so we chose FPA-150 as the SERS substrate for the assay.FPA-150 is a multifunctional SERS substrate with low detection limits of 10-8M for both malachite green and the pesticide thiram,and the SERS substrate has good universality and sensitivity.The detection limit of the FPA-150 substrate reached 10-10 M for the probe molecular CV,and the relative standard deviation(RSD)was 7.88% at a displacement of 1619 cm-1,all fluctuating within the error tolerance(15%),indicating that the substrate has good sensitivity and reproducibility.The SERS assay has good basal universality and sensitivity.The results showed that the substrate can be used for the rapid detection of benzodiazepines diazepam and eszopiclone in methanol solution down to 10 ng/m L,and even for the detection of the mixture of the two drugs in serum with the detection line down to 1μg/m L.The results showed that the substrate can be used for the rapid detection of acute neutrophiles by magnetic separation technique with certain clinical application prospects.Conclusion: This study investigated the synthesis and application of Fe3O4@PDA@Au core-shell satellite SERS substrate,which has high sensitivity and good reproducibility due to the generation of a large number of SERS hot spots and its own superparamagnetic substrate.The magnetic properties of the screened FPA-150 substrate can effectively extract and separate targets from complex environmental samples,greatly improving the efficiency and accuracy of the assay and reducing the interference of the substrate in the sample.The substrate is versatile for both malachite green and pesticide thiram detection at concentrations as low as 10-8 M.Two benzodiazepines,diazepam and eszopiclone,were mixed and detected in human serum with detection limits as low as 1 μg/m L.FPA-150 has potential applications as an efficient SERS substrate for actual drug detection.