| In recent years,cardiovascular disease has become the number one cause of death in the world,including various types such as coronary heart disease（also called ischemic heart disease）,cerebrovascular disease,rheumatic heart disease,congenital heart disease and so on.Acute myocardial infarction（AMI）is a serious manifestation of coronary heart disease,which is caused by myocardial damage and necrosis due to acute and persistent ischemia and hypoxia in the coronary artery.Patients with AMI usually have sudden symptoms such as severe chest pain,palpitations,nausea,and dyspnea,but these symptoms cannot be diagnosed with AMI.Electrocardiogram（ECG）is a commonly used method for clinical heart disease examination,but it can only detect obvious myocardial damage and is difficult to detect hidden lesions.In addition,ECG results may also be affected by environmental interference,psychological state,and diagnostic level,suggesting that they cannot be used as the basis for the diagnosis of AMI.As we known,AMI may cause irreversible myocardial damage,even life-threatening.Therefore,it is necessary to develop analytical methods for AMI detection with high sensitivity and high specificity to reduce the mortality and disability rate of AMI.At present,myoglobin,creatine kinase isoenzyme and cardiac troponin have been used as biomarkers for the diagnose of AMI.Among them,cardiac troponin I（c Tn I）is considered to be the"gold standard"for the detection of AMI.In recent years,biosensors have attracted much attention due to their excellent advantages,such as simple,fast,low-cost and sensitive.Compared with traditional immunosensors,aptasensors exhibit the advantages of high sensitivity,high specificity,convenience and fast,and easy construction,which have been widely used in the diagnosis of AMI.Therefore,this thesis had constructed electrochemical aptasensors for sensitive and selective detection of c Tn I by combining the advantages of aptamers（e.g.controllable structure,simple design,and easy preparation）and noble metal nanomaterials（e.g.high conductivity,excellent electrochemical properties）.The main work is divided into the following parts:1.Platinum nanocubes-decorated molybdenum disulfide nanocomposites（Mo S2-Pt NCs）have been synthesized by utilizing the advantages of the graphene-like two-dimensional molybdenum disulfide（Mo S2）nanosheets with large surface area,rich catalytic active centers,good chemical stability,easy surface functionalization,excellent biocompatibility and platinum nanocubes with excellent electrochemical performancef,which can significantly enhance the electronic conductivity of nanocomposites.On the basis of successful synthesis,an electrochemical aptasensor was constructed for highly sensitive and specific detection of c Tn I by assembling aptamers on the surface of Mo S2-Pt NCs nanocomposites through Pt-S bonds.With the addition of target c Tn I,an aptamer-c Tn I complex was formed due to the specific reaction between the aptamer and c Tn I,leading to the decrease of electrochemical signal.The reason is ascribed to the electron transfer between potassium ferricyanide and electrode surface was hindered by this aptamer-c Tn I complex.According to the change of electrochemical signal,this aptasensor was used to qualitatively and quantitatively detect c Tn I.Under optimal conditions,the constructed electrochemical aptasensor can detect c Tn I concentration in the range of 10-2–104 ng/m L with a detection limit of 1.98 pg/m L.Moreover,the electrochemical aptasensor has excellent selectivity,suggesting that it can efficiently distinguish cardiac troponin C（c Tn C）from cardiac troponin T（c Tn T）,bovine serum（BSA）,and human serum（HSA）.The electrochemical aptasensor also can analyze c Tn I in simulated samples with accepted results,proving that it can be used in the early diagnosis of acute myocardial infarction.2.In order to achieve early diagnosis of AMI and improve prognosis of patients,it is necessary to develop a simple,fast,portable and on-site device for point-of-care detection（POCT）of c Tn I.In this chapter,an electrochemical sensor was developed by combining with the advantages of low-cost screen-printed electrode（SPCE）,high-specificity aptamers and simple electrochemical method.First,three-dimensional gold nanoflowers（Au NFs）with uniform size and uniform distribution are electrodeposited on the surface of SPCE to improve the specific surface area,electrical conductivity and chemical stability of SPCE.Then,the anti-c Tn I aptamer labeled with methylene blue（MB）was assembled on SPCE via Au-S bond.With the addition of c Tn I,the conformational structure of aptamer was changed with the specific binding reaction of aptamer and c Tn I,which greatly hinders the electron transfer between MB and the electrode surface.As a result,the electrochemical signal decreased.According to the electrochemical signal changes of MB,the sensor can sensitively detect c Tn I concentration ranging from 10 pg/m L and 100 ng/m L with a detection limit of 8.46 pg/m L.The constructed electrochemical sensor can also selectively distinguish the target c Tn I from c Tn T,c Tn C,HSA and other proteins.Combined with a portable smartphone and a USB-like electrochemical workstation,the sensor can directly detect c Tn I in human serum samples as low as 10μL without washing.These results showed that the constructed sensor has a great application potential in the field of POCT. |
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