Detection Methods Of Cells Based On The Photothermal Effect Of Nano Materials

Metastasis is the main leading cause of cancer-associated death.Circulating tumor cells(CTCs)are intermediate process which provide essential condition for cancer metastasis.As a consequence,the detection of CTCs is significant for studying the mechanism of cancer metastasis,evaluating the therapeutic effect,concluding the prognosis,and monitoring the metastasis of cancer.Salmonellosis caused by the bacteria Salmonella is one of the most common foodborne diseases.Traditional detection methods are time-consuming and laborious.In the wake of developments in detection technology,detection of Salmonella could be finished in 48 h,which still cannot meet the requirement for rapid detection.Detection methods of the above two types of cells both need to be high sensitive,rapid and simple.Thus,establishing high sensitive,rapid and simple detection methods would be significant.Currently,choosing label materials with better performance for producing signals is a way to improve detection sensitivity.Detection methods based on the photothermal effect of nano label materials were high sensitive rapid,rapid,and simple.A variety of nano materials with commendable photothermal effect have been utilized for the thermal therapy of malignant tumors.But reports using the photothermal effect for detection were comparatively few.Two kinds of detection methods based on the photothermal effect were established to achieve the detection of CTCs/Salmonella typhimurium: one was based on the photothermal effect of graphene,and the other was based on the photothermal effect of magnetic nano materials.On the basis of traditional membrane filtration and immune-magnetic separation,the detections of CTCs/Salmonella typhimurium were realized by the thermal contrast detection based on the photothermal effect of nano materials.The above detection methods had a number of advantages such as rapid,simple and sensitive.The paper mainly consisted of three parts,as follows:In the chapter one,the capture and detection of CTCs/Salmonella,nano materials and the photothermal effect,and the application of the photothermal effect were summarized.The emphasis was the photothermal effects of nanogold/graphene/magnetic nano materials and their research progress and the research progress of the application of the photothermal effect in detection methods.In the chapter two,a strategy based on the photothermal effect of graphene functionalized magnetic microbeads for detection of CTCs was designed and constructed.The high capture efficiency and sensitive detection were achieved simultaneously by combined use of membrane filtration,magnetic separation and the photothermal effect of graphene.The graphene oxides(GOs)were modified with antiepithelial cell adhesion molecule(EpCAM)antibodies,and the magnetic microbeads were modified with anti-IgG antibodies.The immune-GO-magnetic microbead complexes were synthesized through the anti-EpCAM-anti-IgG interaction.The immune complexes could specifically recognize the EpCAM antigens on the surface of 4T1 cells.Following incubation,membrane filtration was used to retain cells surrounded by the immune-GO-magnetic microbead complexes,and then the remaining impurities were eliminated by a further magnetic separation step.A laser pen was used to irradiate the GOs on the cell-retained membrane to produce temperature change.The number of cancer cells was determined by a thermal camera,according to the standard curve of temperature change and cell number.The cell incubation time,substrate,laser power and irradiation time,nano materials,GOs’ concentration and the amount of immune complexes were optimized.At the same time,the standard curves in culture medium/human blood of temperature change and cell number were established.The optimal incubation time was 1 h,the optimal substrate was cotton absorbent pad,the optimal laser power and irradiation time were 1.5 W·cm-2 and 2 min,the optimal nano material was GOs,the optimal GOs’ concentration was 100 μg·mL-1,the optimal amount of immune complexes was 50 μL/(500 cells).Under optimal conditions,the limit of detection could reach 100 cells.4T1 cells spiked in human blood could be successfully detected in 1.5 h,and the recovery was between 90.8% and 116.5%.In the chapter three,a strategy based on the photothermal effect of magnetic nano materials for detection of Salmonella typhimurium was designed and constructed.The high capture efficiency,sensitive detection and sample inactivation were achieved simultaneously by combined use of membrane filtration,magnetic separation and the photothermal effect of magnetic nano materials.The magnetic nano materials were modified with anti-Salmonella typhimurium antibodies.The immune magnetic nano materials could specifically recognize antigens on the surface of Salmonella typhimurium.The high capture efficiency,sensitive detection and sample inactivation were achieved simultaneously by use of magnetic nano materials.Following incubation,membrane filtration was used to retain Salmonella typhimurium surrounded by the immune magnetic nano materials,and then the remaining impurities were eliminated by a further magnetic separation step.A laser pen was used to irradiate the immune magnetic nano materials on the cell-retained membrane to produce temperature change.The number of Salmonella typhimurium was determined by a thermal camera,according to the standard curve of Salmonella typhimurium number and temperature change.The magnetic nano materials,laser power and irradiation time,and the amount of immune magnetic nano materials were optimized.At the same time,the standard curve in PBS/drinking water of temperature change and Salmonella typhimurium number was established.The optimal grain size of magnetic nano material was 200~300 nm,the optimal laser power and irradiation time were 2.5 W·cm-2 and 2 min,the optimal amount of immune magnetic nano materials was 10 μL/(1000 Salmonella typhimurium).Under optimal conditions,the limit of detection could reach 300 Salmonella typhimurium.Salmonella typhimurium spiked in drinking water could be successfully detected in 1.5 h,and the recovery was between 96.2%~106.4%.