Simultaneous Detection Of Adenosine And Vascular Endothelial Growth Factor In Serum Samples Based On Photonic Crystal Encoded Microspheres

The occurrence of lung cancer is associated with the abnormal expression of adenosine and VEGF165 in human serum.Therefore,the simultaneous detection of these two tumor markers is significant for the early diagnosis and treatment of lung cancer.Since photonic crystal microspheres have unique photonic band gap and exhibit various structure colors,they have been developed into encoding carriers for multiple targets assays.In this thesis,we prepared silica photonic crystal microspheres with controllable sizes and good monodispersity by using a microfluidic droplet technique.The simultaneous detection of adenosine and VEGF165 in serum samples was achieved by the structure color encoding of photonic crystal microspheres and the specific recognition of nucleic acid aptamers.In chapter 1,the significance of detection of adenosine and VEGF165 and their research progress were introduced.Then the concept of nucleic acid aptamers and their applications in chemical sensing,biological imaging and biomedicine were outlined.Next we summarized the preparation methods and the analytical applications of photonic crystals.Finally,we proposed the research significance and design ideas of this work.In chapter 2,photonic crystal microspheres with good monodispersity were prepared by using a microfluidic chip.Suspensions of silica nanoparticles with different diameters were respectively introduced into the microfluidic chip,and sheared into droplets by the oil phase.After the solvent in the droplets was completely evaporated,photonic crystal microspheres with different structure colors were respectively formed.The microspheres were characterized by scanning electron microscope,reflective spectra and optical microscope.On this basis,the microspheres were functionalized respectively with hydroxyl,amino and carboxyl groups,and these microspheres were characterized by Fourier transform infrared spectroscopy and X-ray spectrometer.In chapter 3,FAM-labelled aptamers were immobilized on the functionalized photonic crystal microspheres via chemical bonds.The effects of concentrations of adenosine aptamer,VEGF165 aptamer and GO on the fluorescence intensity of microspheres were investigated.When the concentrations of adenosine aptamer and VEGF165 aptamer were respectively 400 nmol L-1 and 600 nmol L-1,the fluorescence intensity of the microspheres reached saturation.When the concentration of GO was 0.1 mg mL-1,the fluorescence of the microspheres was almost completely quenched.Based on the specific recognition ability of the aptamer to the target,and the fluorescence resonance energy transfer between FAM and GO,a simple"turn-on" fluorescent aptasensor was constructed,and the rapid and sensitive detection of adenosine and VEGF165 was realized.The linear equation for the detection of adenosine is y=-0.351+0.0960x,and the linear range is 20.0-150 nmol L-1,R2=0.993.The linear equation for the detection of VEGF165 is y=0.983+13.4x,and the linear range is 0.130-1.30 nmol L-1,R2=0.992.The detection limits are 6.1 nmol L-1 for adenosine and 38 pmol L-1 for VEGF165.At last,based on the distinguishing ability of photonic crystal microspheres to the analytes,the method was used to determine the concentrations of adenosine and VEGF165 in serum samples.The recovery rates of adenosine are 83.0%and 92.1%,and the recovery rate of VEGF165 is 97.5%,which indicates that the method has good practicability.In chapter 4,the method based on photonic crystal encoded microspheres and aptamer fluorescence sensing for simultaneous detection of multiple targets was summarized,and its application prospect in the future was predicted as well.