Development of new strategies for electrochemical aptasensing.
27 May 2016
Campus Groenenborger, V0.08 - Groenenborgerlaan 171 - 2020 Antwerpen
Organization / co-organization:
Department of Chemistry
Karolien De Wael & Ronny Blust
PhD defence of Mrs. Sanaz Pilehvar - Department of Chemistry
In the present thesis, new strategies were developed and used to achieve efficient electrochemical aptasensing of low molecular weight target compounds. The sensitive detection of small molecule pollutants is one of the key challenges for environmental monitoring and biotechnology. The main issues which were tackled in this thesis were identification and improvement of different parameters affecting the quality of the ssDNA aptamer monolayer on the surface of the sensor and subsequent performance of the electrochemical aptasensing platform. In order to reach these goals, different experimental results were obtained. As a first step, a new and efficient pretreatment procedure for ssDNA immobilization on the surface of gold electrodes was developed. This pretreatment procedure is mainly based on the electrochemical cleaning followed by the activation of gold electrode surfaces for effective and reproducible ssDNA assembly. Taking into account the importance of ssDNA aptamer structure on its interaction with their target molecule, a new prestructuring strategy for ssDNA aptamers was developed based on the use of DNA intercalator agents such as proflavine. The effect of the developed strategies on the efficiency of the aptasensing towards CAP detection was also evaluated. The sensitivity of the impedimetric aptasensor towards CAP detection is enhanced when the above strategies are applied.
In order to further improve the immobilization of ssDNA, surface modifications of gold nanoparticles were explored and a novel electrochemical aptasensing approach was proposed. This approach is based on the covalent attachment of gold nanoparticles on the electrode surface as an amplification and an immobilization platform for self-assembly of thiolated aptamers. The proposed aptasensing device demonstrated a number of advantages: (a) low detection limits, (b) simple experimental procedures, without requirements for chemical labelling of DNA or the target, (c) high stability and selectivity, (d) ability to sense OFL in real environmental samples, showing that the approach is promising for environmental monitoring. In addition, the special features of multi-walled carbon nanotubes were used to construct a highly efficient electrochemical aptasensor strategy in order to detect OH-PCB in human blood serum. The MWCNTs provide a high surface area for aptamer immobilization and fast heterogeneous electron transfer. The proposed aptasensing strategies provide remarkable properties such as fast response, broad linear range, good reproducibility, acceptable stability and low detection limit.