Highly Sensitive Detection For Alpha-fetoprotein By Fluorescence Sensor Based On Aptamer

Alpha-fetoprotein（AFP）is a type of plasma protein produced by the fetus’s yolk sac and excreted by the liver in pregnant women.A type of plasma protein excreted by the liver is one of the indicators for fetal Down’s syndrome.However,with the development and birth of the fetus,the content of AFP in the human body gradually decreases.According to statistics,the content of healthy adults is as low as 25 ng/m L so that it does not reach the detection limit of AFP.However,studies have found that the content of AFP in the human body of patients with cancer such as hepatocellular carcinoma can be as high as 500 ng/m L,so the content of AFP is an important detection index for certain cancers in adults.Aptamer has been widely used in the field of tumor marker detection due to its advantages of in vitro batch synthesis,easy modification and low cost.This research is mainly based on the principle of fluorescence resonance energy transfer（FRET）,using several different nanomaterials（carbon nanotubes,gold nanoparticles,graphene oxide and ferroferric oxide,etc.）,aptamers and aggregation induces fluorescent molecules and designs several aptamer sensors for AFP detection to realize the sensitive detection of AFP.1.Detection of alpha-fetoprotein aptamer labeled with aggregation induced emission and azide functionalized single-walled carbon nanotubes.The azidated functionalized single-walled carbon nanotubes（SWNTs）and the fluorescence-labeled aptamers underwent click reaction without Cu（I）catalysis,and the fluorescence was quenched.After the addition of AFP sample,aptamers preferred to bind specifically to the protein,and the conformation changed,making some aptamers far away from the surface of SWNTs,and the fluorescence recovered to some extent.The sensing platform uses the functional modification and quenching properties of carbon nanotubes while avoiding the toxicological effects caused by heavy metal ion catalysis such as copper（I）.Its detection limit is 25.909 ng/L,and the linear range of AFP is 0.1-8 ng/m L.2.Detection of alpha-fetoprotein by aptamer fluorescence sensor based on composite nanomaterials and multifunctional peptides.Firstly,gold nanoparticles（Au NPs）aggregated to bind nucleic acid aptamers more efficiently under Na Cl induction conditions,with a detection limit of 4.805 ng/L.Subsequently,a new type of nanomaterial,graphadiyne oxide,which also has a quenching effect,was introduced into the system and combined with gold nanoparticles to form a GDY@Au NPs complex,with a detection limit of 3.645 ng/L.On this basis,the porous coordination network（PCN）and GDY@Au NPs are formed into a“three-in-one”composite material（GDY@Au NPs@PCN）,and compare the sensitivity of detecting AFP through the above three types of nanomaterials with a detection limit of 3.399 ng/L.Finally,a“sandwich”sensing system based on GDY@Au NPs@PCN,aptamers and AFP was developed to further explore the sensitivity detection of AFP and its detection limit is1.528 ng/L,the linear range of AFP is 0.01-0.8 ng/m L.3.Detection of alpha-fetoprotein based on the sandwich structure of AIEgen nanosphere-labeled nucleic acid aptamer combined with magnetic gold nanocomposite.Using the synthesized magnetic Fe₃O₄@MPTMS@Au NPs composite material,and through the combination of AFP and AIEgen-linked aptamer,the fluorescence intensity can achieve the purpose of detecting AFP based on the characteristics of low background signal and high sensitivity detection of the"sandwich"structure in the previous chapter.The detection limit is 1.429 ng/L,and the linear range is 0.005-0.1ng/m L.4.Detection of alpha-fetoprotein using a fluorescent biosensor based on graphite-diacetylene oxide composite material and aptamer.The Partial complementary sequence is fixed on the surface of GDY@Au NPs,and the AIEgen modified aptamer is complementary to Partial complementary sequence to make it close to the surface of GDY@Au NPs,and the fluorescence is quenched.When AFP was added,the aptamer specifically bound to AFP,resulting in changes in its own structure,and thus far away from the surface of the nanomaterial,and the fluorescence was restored.At the same time,carbon nanotubes dissolved by sericin were introduced.On the one hand,sericin provides good compatibility for carbon nanotubes and can remove certain nonspecific differences,provide excellent stabilizer and remove certain nonspecific adsorption at the same time.On the other hand,carbon nanotubes formed a complex with the surface of GDY@Au NPs to improve the sensitivity of AFP detection.The detection limits of the sensor platform are calculated to be 6.045 ng/L and 3.296 ng/L,and the linear ranges are 0.01-0.8 ng/m L and 0.005-0.8 ng/m L,respectively.In summary,four types of fluorescent biosensors have been constructed based on the FRET principle using a variety of nanomaterials and fluorescent molecules,which can achieve high-sensitivity detection of AFP and at the same time have good selectivity.The development of AFP detection methods and technologies is helpful for the early detection,diagnosis and treatment of related diseases and improving the survival rate of related patients,which is of great significance to human health.