Signal Amplification Strategy Of Nanomaterials-Based Optical Immunosensor For Application In Early Detection Of Cancer

The biomarker in human blood or body fluids is a class of cancer-related substance,wherein protein is the most common type of biomarkers.The patients who accept therapy in the early stage of disease have significantly improved survival rate,which means that early detection of cancer is necessary.Therefore,the development of ultra-high sensitive and high selective biosensors is imminent.In recent years,the rapid development of nanotechnology provides huge supports for the development of biosensors.In this paper,we synthesized a variety of nano-materials to label or fix biomolecules,and utilized the principle of the sandwich immunoassay to construct optical immunosensors realizing the sensitive detection of Alzheimer's disease and prostate cancer related biomarkers.The main contents are summarized as follows:1.CdTe@SiO2 assisted fluorescent immunosensor for quantification of prostate specific antigenCompared with CdTe quantum dots,CdTe@SiO2 composite quantum dots have stronger fluorescence intensity.The silicon shell coated on the surface of CdTe quantum dots can prevent the deterioration of optical properties and the decreasing of fluorescence quantum yield of quantum dots caused by photooxidation,meanwhile the silicon shell can reduce the leakage of heavy metals.We utilize the principle of the sandwich immunoassay to construct a fluorescent immunosensor to achieve highly sensitive detection of prostate specific antigen,using the CdTe@SiO2 composite quantum dots as fluorescent markers.The fluorescent immunosensor shows the linear response range of 0.01?5 ng/mL and detection limit of 0.005 ng/mL.2.Graphene quantum dots assisted fluorescent immunosensor for quantification of phosphorylated proteinSilicon nanomaterials with good biological compatibility and large specific surface area can be used as nanocarriers to load signal substances and biological molecules.Graphene quantum dots have many unique advantages,such as relatively low toxicity,good biological compatibility,excellent chemically inert and stable fluorescence,and the surface is rich in carboxyl group,so the graphene quantum dots can be used as fluorescent markers to generate fluorescent signal.Therefore,silicon nanomaterials can be used as nanocarriers to immobilize antibody and graphene quantum dots,then obtain graphene quantum dots-antibody-silica beads nanocomposites,using the sandwich-type immunoassay method we can achieve the sensitive detection of phosphorylated protein.3.The peroxidase-like catalytic activity of graphene quantum dots and application in immunosensorThe graphene quantum dots prepared by pyrolysis L-glutamic acid have peroxidase-like catalytic activity,and the surface contains amino and carboxyl functional groups which can be conjugated with biomolecules.Hence the graphene quantum dots can be used as labels.Magnetic nanoparticles have a large surface area,and they are easy to separate and clean under the effect of external magnetic field,also have good peroxidase-like catalytic activity.Therefore,we constructed a colorimetric immunosensor using the magnetic nanoparticles as nanocarriers and the graphene quantum dots as labels,the synergistic effects of the magnetic nanomaterials and graphene quantum dots largely amplified the signal.This immunosensor avoids complicated operation and time-consuming testing process,shows potential application in clinical detection.