A Miniaturized Dual-Wavelength Photoacoustic Spectroscopic System For The Detection Of Carcinoembryonic Antigen

Photoacoustic spectroscopy is a new method for non-destructive sample analysis.Because of its non-destructive analysis and no influence from analyte morphology and scattered light,it can be widely applied for the analysis of high-reflective and opaque samples.In recent years,the use of photoacoustic spectroscopy for the analysis of biological samples has attracted widespread attention.In this thesis,based on the homemade photoacoustic cell,a miniaturized dual-wavelength photoacoustic spectroscopic system is developed for the quantitative detection of carcinoembryonic antigen(CEA)by means of the specific recognition ability of aptamers.In the first chapter,we introduces the principle,characteristics,development and application of photoacoustic spectroscopy,and the application of gold nanoparticles(AuNPs)in photoacoustic spectroscopy.In the second chapter,we describes the miniature photoacoustic spectroscopic detection system used and the principle of photoacoustic signal produced from liquid materials.In the experiment,a miniaturized liquid photoacoustic cell was designed and fabricated.A complete photoacoustic spectroscopic system included two lasers with wavelengths of 520 nm and 638 nm as light source,a chopper for laser modulation,a microphone for receiving the photoacoustic signal,and a lock-in amplifier for readout.The present system was used for measuring the photoacoustic signals of different concentrations of AuNPs,and a good linear relationship was obtained with a correlation coefficient(R2)of 0.9984.The results verified the feasibility of quantitative analysis by the present photoacoustic spectroscopic detection system.In the third chapter,we determines the cancer marker CEA by using the present photoacoustic spectroscopic system.Different concentrations of CEA were mixed with 6μmol L-1 aptamer.Then 17.5 nmol L-1 AuNPs and 0.9 mol L-1 potassium chloride(KCl)were sequentially added to the above reaction solution.With the increase of CEA concentration,the color of the reaction solution changes from wine red to purple,and the photoacoustic signal changes accordingly.Quantitative analysis of CEA was achieved based on the photoacoustic signal ratio measured at 520 nm and 638 nm laser radiation.Under the optimal experimental conditions,the linear range of the method is 10～50 ng mL-1,the correlation coefficient R2 is 0.9929,the relative standard deviation RSD is 2.6%(n=9,30 ng mL-1),and the detection limit is 3 ng mL-1(3σ,n=7).In order to evaluate the selectivity of the method,the potential interference of some coexisting substances was investigated by using the present system.The results proved that the method has high selectivity to CEA.The spiking recovery test was conducted to detect CEA in human saliva,with recoveries of 93～110%.It indicates that the present method has favorable accuracy and reliability.These results demonstrate the feasibility of the present method for detecting liquid biological samples,providing an effective approach for analyzing other liquid biological samples.