| Carcinoembryonic antigen(CEA)is a biomarker that is highly expressed in cancer patients.Label-free,highly sensitive,and specific detection of CEA biomarkers can greatly aid in preventing disease deterioration and reducing mortality.In addition,it has the advantages of high sensitivity,low dose as well as simple operation for the detection of CEA based on the terahertz(THz)metamaterials(meta)biosensors on account of the unique characteristics of biomolecules in THz band and the high enhancement effect of meta on electromagnetic response.However,using conventional methods,such as direct drip addition or biological functionalization on the surface of metamaterials,is unable to meet the current demand for high sensitivity,high specificity and low cost detection.Thus,in response to the above problems,in this thesis,the Carcinoembryonic antigen(CEA)is taken as the research object,and we utilized comprehensively the advantages of high specificity and affinity of biological aptamers,high enhanced sensing characteristics of gold nanoparticles,unique properties of THz time domain spectroscopy,as well as the high sensitivity of meta sensing chips for chemical composition identification to carry out the integrated research on THz-meta biosensing.The main contents of this thesis are as follows:1.An 8-shaped meta biosensor excited by toroidal resonance is proposed to achieves an ultrahigh quality factor of 15.04 due to the magnetic field formed an electrical confinement.To characterize the sensing capability of the proposed THz toroidal meta-biosensor,the performance of refractive index sensing was evaluated by numerical simulations.The results show that the relationship between the frequency shift and the refractive index(n)can be fitted linearly,where sensitivity is therefore calculated as high as 300 GHz/RIU;In addition,the sensitivity shows a growth trend with increasing analyte thickness,along with a slow down in the increment rate.Finally,the discrete hemispheres located randomly at the meta surface were used to further explore the influence of Gold nanoparticles on the sensing performance.2.Gold nanoparticles(AuNPs)were prepared by reducing chlorauric acid with sodium citrate.Its influencing factors of preparation,particle size morphology as well as concentration were characterized.In addition,the size of gold nanoparticles can be controlled by changing the dose of sodium citrate in the reaction,which show certain relationship between them;In addition,the prepared AuNPs are characterized and interpreted by TEM,UV-Vis as well as DLS.Finally,gold nanoparticles have been successfully functionalized based on bio-modification technology,which can be used for specific recognition of CEA.3.The THz toroidal meta-biosensor integrated with functionalized AuNPs was utilized to demonstrate the ultrahigh-sensitivity and high-specificity detection of the CEA biomarker.Through experimental measurement,the CEA with or without gold nanoparticles were detected,showing that the enhancement effect of gold nanoparticles on Meta biosensors was up to 115 times.In addition,the logarithmic function relationship between CEA concentration and meta transmission spectrum frequency shift Δf are obtained,which realize the quantitative and qualitative detection of CEA,achieving a limit of detection of 0.17 ng and high specificity for different proteins.Finally,the reusability of the meta biosensor is verified,which have a relative standard deviation(RSD)of less than 1.99%,indicating superior stability.To sum up,the proposed AuNP-integrated THz toroidal meta-biosensor achieves ultrahigh-sensitivity and high-specificity detection of the CEA biomarker,which demonstrates the noteworthy potential for utilization in early cancer detection,as well as in the development of a reliable cancer screening chip that is label-free,highly sensitive,noninvasive,and rapid. |
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