Studies On The Determination Of TNT By Functional Gold Nanoparticles-based Aptasensors

As one of the most commonly used explosives,2,4,6-trinitrotoluene(TNT)has been widely used for terrorism activities.Due to its risk of human health through the invading of digestive tract,respiratory tract,and skin,the selective and ultrasensitive detection of TNT has attracted tremendous attention in recent years.In this thesis,two types of Au NPs-based sensors were investigated via the combination of the aptamer and the nanotechology for the quantitative determination of TNT.The main contents of our work are listed as follows:1.As an important component of TNT sensor,the synthesis and the stability of Au NPs–TNT aptamer composites were intensively studied in this section.In detail,a reduction method was used to the preparation of three kinds of Au NPs with different particle sizes.Then,a self-assembly method was used to anchor peptide aptamers of TNT on the surface of Au NPs via Au–S bonds.The characterization results showed that the morphology of the as-prepared Au NPs were uniform,and the dispersion liquid were homogeneous and stable.The Au NPs–TNT aptamer composites were slightly agglomerated when the Au NPs were in 5 nm.While the dispersion and stability of the composites were improved when the other two sizes(15 and 25 nm)of Au NPs were used.The effects of aptamer concentration,pH,and salt concentration on the stability of the composites were also studied,and the results showed that the composites were stably dispersed at a 10-5 g/mL aptamer content,pH > 8,and salt concentrations < 4 mmol/L.2.Based on the Au NPs as functional elements,a colorimetric aptamer sensor was fabricated for the detection of TNT.The TNT aptamers–Au NPs composites were stable in a salt solution.After the addition of TNT into the above composites,the color of the solution was changed from burgundy to purple-black due to agglomeration of composites and the specific binding of the aptamers and TNT.The concentration of TNT was quantitatively monitored with a UV-Vis spectrophotometer according to the absorbance ratio A650/A523,under optimized conditions,including salt concentration,pH,and incubation time.The linear range was 350-650 ng/mL,and the limit of detection was 330 ng/mL.The proposed sensor of TNT possessed lots of advantages,such as simple operation,low cost,and easy judgment from the appearance,and it had a wide application prospect.3.Based on the Au NPs as functional elements,a surface plasmon resonance(SPR)aptamer sensor was investigated for the detection of TNT.The proposed sensor was based on the interaction between the TNT aptamer–Au NPs composite and the surface modification of the chip,and the determination of TNT was achieved via the indirect competition.The effect of Au NPs size on the SPR signal was investigated.And the experimental conditions,such as pH,injection time,sampling flow rate,and incubation time were also optimized.Under the optimal conditions,the linear range of the proposed sensor was 500 pg/mL to 10 ng/mL and the limit of detection was 58 pg/mL.The proposed sensor exhibited high sensitivity and good selectivity for the trace level detection of TNT.Moreover,the SPR detection system can be miniaturized to achieve online fast detection.