Detection Of Vascular Endothelial Growth Factor Based On Metal-enhanced Fluorescence Of MnO₂ Nanosheets

Vascular endothelial growth factor(VEGF),which acts as a crucial regulator of physiological angiogenesis and vascular permeabilization during skeleton growth,reproductive functions and embryogenesis,has been regarded as significant biomarker for tumor diagnosis.Therefore,the establishment of an efficient method for VEGF detection is helpful to early cancer diagnosis.In this work,we firstly discovered MnO2 nanosheets which always acted as fluorescence quencher,could also be confirmed as substrates for fluorescence enhancement.MnO2 nanosheets were encapsulated in a Lyz coat in order to form MnO2@Lyz composites which were set as substrates,building a new method for VEGF165 determination.In the first chapter,a brief introduction is given to the effect of metal-enhanced fluorescence.Then some common nanomaterials based on metal-enhanced fluorescence have been discussed.Secondly,the research background,synthesis methods and important applications of MnO2 nanosheets have also been introduced.Thirdly,the significance and common test methods of VEGF165 detection have been illustrated.In the second chapter,the preparation and characterization of MnO2 nanosheets and MnO2@Lyz composites were discussed.The MnO2 nanosheets were prepared by oxidation of manganese chloride,and the MnO2@Lyz composites were synthesized via mixing of MnO2 nanosheets and Lyz with the effect of electrostatic interaction and hydrogen bonding.The as-prepared composites were characterized by Fourier transform infrared spectrometry,UVvis absorption spectra,scanning electron microscopy,transmission electron microscopy,X-Ray diffraction analysis and Zeta potential.In the third chapter,MnO2@Lyz composites were employed as substrates for fluorescence enhancement and adsorbed aptamer which was labeled by FAM.After VEGF165 was added to the system,we calculated VEGF165 levels through increased fluorescence intensity.Based on LOD＝3σ/k,obtained LOD of MnO2@Lyz/FAM-aptamer composites was 8.49 pg·mL-1,which was found to be much lower than most of fluorescence detection methods.The recovery of real sample detection was in the range from 97.5%to 106%,there results indicated the prepared MnO2 nanosheets-based optical biosensor has great potential to be further applied for VEGF165 determination in real biological environments.