Biosensor case results

Update Stella Givanoudi - February 2018

(A) Development of an aptamer-based biosensor for seafood quality control

A novel impedimetric biosensor was developed by the BIOS group (Professor P. Wagner) at KU Leuven. The Differential Impedimetric Sensor Cell, a.k.a. DISC, includes two chips with up to 4 sensing spots. The aptamer functionalized chips are placed inside the modules on either side of a flowcell with a capacity of 310 μl. The temperature of the sample solution inside the flowcell can be kept constant at the desired value. A Faraday cage protects the device from external electronic noise. The DISC is accompanied by a costume-made Electronic Base Unit, see Picture 1, for which also the software and a user interface were developed. It can be connected to syringe pumps (up to five) for the automatic exchange of fluids inside the flowcell. The impedance, temperature and pumping settings are controlled through the software, which also enables the real-time monitoring of the impedance and temperature data inside the flowcell. 

Pic 1: On the left, the Differential Impedimetric Sensor Cell “DISC” connected to the Electronic Base Unit (on the right).

Update Stella Givanoudi - January 2018

(A) Development of an aptamer-based biosensor for seafood quality control

A DNA-conjugated gold nanoparticles-based colorimetric assay was applied for the detection of histamine in buffer solution using two of the pre-selected histamine aptamers. A concentration-dependent response was observed. In the same assay no response was observed for the structurally similar compound, L-histidine, confirming the aptamer’s specificity for histamine. The same assay was performed for the cadaverine and putrescine aptamers, which were tested against the biogenic amines cadaverine and putrescine, respectively.

Engineering of Functional Interfaces 2017 - Stella Givanoudi - August 2017

At the 28th and 29th of August, Stella participated at a conference on Engineering of Functional Interfaces, Marburg (Germany). 

She presented a poster and pitch on "Selection and characterization of aptamers for the detection of biogenic amines".  
The poster can be found here.

Update Stella Givanoudi - June 2017

(A) Development of an aptamer-based biosensor for seafood quality control 

We have selected 21 aptamers able to recognize three biogenic amines: Histamine, Cadaverine and Putrescine. For this purpose, we conducted magnetic-bead-based SELEX (Systematic Evolution of Ligands by EXponential enrichment). The aptamers were obtained by selection from an initial random DNA oligonucleotide library. In preparation for SELEX, the amino acids L-histidine, L-lysine and L-ornithine (which are the precursors of histamine, cadaverine and putrescine, respectively) were immobilized with EDC coupling on the surface of magnetic beads covered with -NH2 functional groups. The immobilization was verified by FT-IR ATR spectroscopy and UV/VIS spectroscopy.

Pic 1: Immobilization of amino acids on the surface of Magnetic beads.

Post-SELEX characterization for all aptamers was accomplished with fluorescence-based binding assay in order to determine the affinity of the aptamers for the target-compounds. Selected aptamers are also being tested with quartz-crystal microbalance with energy dissipation monitoring (QCM-D) and Impedance in order to determine the selectivity of the selected aptamers for the target-compounds. The selected aptamers will be used for the construction of a novel impedimetric sensor.

(B) The development of surface imprinted polymer based biosensors for Campylobacter species 

The set-up for the imprinting of the bacteria in the polyurethane layer was tested using the Escherichia coli strain 8739. The imprinting of three Campylobacter species (Campylobacter coli, Campylobacter jejuni and Campylobacter lari) was tried using inactivated bacteria. For this purpose, inactivation experiments were conducted. The attempts for inactivating the bacteria include inactivation through heating at 55°C, 65°C, 75°C, 85°C at various incubation times and the use of the following reagents 100% EtOH, 5mM Silver nitrate and formaldehyde. Inactivation of the bacteria was checked with microscopy and plating in CCDA agar medium. From the above methods, incubation of the bacteria with formaldehyde were the most successful. It was important to verify through microscopy that the bacteria maintain their shape after the inactivation. This is crucial for the successful imprinting and the detection of the bacteria from the biosensor.