New Methods Of Biosensor Based On Gold Nanoparticles And Fluorescent Polydopamin

Biosensor is a kind of transducer that can recognize the target by molecular probe and convert it into detectable signal.It has a wide application prospect in medicine,disease monitoring,environment and so on.Due to the unique properties of polydopamine（PDA NPs）,Au NPs and other nanomaterials,the applicability of biosensors and the sensitivity in the detection process are greatly improved.In this paper,on the basis of nanomaterials such as Au NPs and fluorescent polydopamine（FPDA NPs）,new quantitative analysis methods with simple operation and high sensitivity,such as colorimetric method and ratiometric fluorescence detection method,were constructed.The specific contents were described as follows:Heparin（Hep）,as an indispensable natural polysaccharide,plays an important role in anticoagulation,metabolism and other physiological processes.Hep is widely used in clinic as an anticoagulant and can be used in medical care after surgery.In Chapter2,a simple and fast synthesis method of Au NPs was developed,and the prepared Au NPs was further applied to Hep detection.Au NPs could be rapidly synthesized in 1min by using 2-morpholine ethylate（MES,p H=6.0）as reducing agent,protective agent and buffer solution.Based on this point,a new sensing platform for Hep detection was developed using the aggregation-induced color change of Au NPs.Au NPs were prone to aggregate with an obvious red-to-blue color change at high concentrations of sodium chloride（Na Cl）.However,the aggregation of Au NPs could be inhibited with the addition of Hep,and the solution turned into wine red.The color change of Au NPs in solution was used to quantitatively analyze and detect Hep.The nanosensor platform showed good selectivity and sentivity for Hep detection with a linear range of 0-1300μg?m L^-1 and a detection limit of 3.1x10^-3μg?m L^-1.In addition,the method has been successfully applied to the detection of Hep in human serum,proving great potential in biomedicine application.Tetracycline antibiotics have been widely used to treat bacterial infections and other diseases since their first synthesization in the 1940 s due to the low price and convenience.However,long-term use of tetracycline antibiotics increases bacterial resistance,resulting in adverse reactions.Once entering the human body,residues of tetracycline drugs will accumulate in the body,causing gastrointestinal and kidney discomfort.Therefore,rapid detection of tetracycline antibiotics is of great significance for the environment and human health.In Chapter 3,based on the fluorescence of FPDA NPs and Eu MOF using as signal output units,a ratiometric fluorescence sensor was constructed for the detection of tetracyclines.By the coordination of Eu³⁺with tetracycline（TC）or oxytetracycline（OTC）and HEPES buffer solution,Eu MOF with red fluorescence emission was synthesized.Meanwihle,the fluorescence of FPDA NPs was decreased,which was used to detect TC and OTC.The sensor displayed good selectivity and sensitivity.The detection range of the sensor for TC detection is 0～100μM with the detection limit is 0.44μM.And the range of the sensor for OTC is 0～70μM with the detection limit is 0.6μM.Moreover,the detection performances of the sensor in lake water,tap water and other actual samples were further verified.The experimental results showed that the sensor showed good detection performance in lake water and tap water,proving the application potential in actual water quality samples.Cerium（Ce）is one of the lanthanide metals,the main ionic forms of which are Ce³⁺and Ce⁴⁺.Ce⁴⁺has a good bactericidal effect,but excessive accumulation will destroy cell structure and be harmful to organisms.Therefore,it is very necessary to explore a method for rapid detection of Ce⁴⁺.L-ascorbic acid（AA）is a vital substance in the body to sustain growth and metabolism and to protect against cancer and various diseases.The amount of AA can be used as a standard to assess whether a person is healthy or not in medicine.In Chapter 4,a ratiometric fluorescence sensor based on the regulation of the mimic oxidase activity of Ce⁴⁺-based nanocomplex was developed for Ce⁴⁺and AA detection.Ce⁴⁺was coordinated with HEPES buffer solution and FPDA NPs to form FPDA NPs-Ce⁴⁺-HEPES nanocomplex.The nanocomplex displayed mimic activity of oxidase and could greatly enhance the oxidation capacity of OPD substrate.The OPD was oxidized to produce 2,3-diaminophenazine（DAP）,which emited yellow fluorescence,simultaneously,the fluorescence of FPDA NPs is effectively quenched by Ce⁴⁺.Contrastly,AA coulc reduce Ce⁴⁺to Ce³⁺,and the formed PDA NFs-Ce³⁺-HEPES nanocomples did not have the catalytic oxidation activity of OPD,and Ce³⁺did not have the fluorescence quenching property of FPDA NPs.Highly sensitive detection of Ce⁴⁺and AA were achieved by the change of fluorescence ratio of DAP and FPDA NPs.The sensor exhibited a linear range of 0-600μM with a detection limit of 96.2 n M for Ce⁴⁺and a linear range of 0-150μM with a detection limit of 2.23μM for AA.To further explore the practical application ability of the sensor,Ce⁴⁺was detected in tap water and lake water,and AA was detected in orange juice and human serum.The results showed that this proposed method had a great potential in practical sample detection.