AUSense 2019

AUSense 2019

AUSense is a team from The American University in Cairo competing in the SensUs 2019 event. For SensUs 2019, AUSense investigated the possibilities for creating a biosensor which is able to measure the concentration of Adalimumab. The full TRD can be found [ via this link]

Method

Electrochemical detection methods were utilized for this biosensor. The biosensor relies on the interaction between an antigen and the antibody, with the antigen used being TNF-α, and the antibody being Humira.

Molecular Recognition

Carbon screen printed electrodes functionalized with gold nanoparticles alongside 11-mercaptoundecanoic acid (C11H22O2S) aid in the immobilization of TNF-α on the surface of the electrode. All the dilutions made were with phosphate-buffered saline (PBS, pH 7.4). Upon the introduction of the blood sample spiked with Humira, which is the target antibody, the immobilized TNF-α complexes with Humira, thereby forming an insulator layer that impedes electron transfer between the redox species and the electrode surface, reducing the electrochemical current generated in the absence of the target antibody. By exploiting this observed phenomenon, a calibration curve is generated in order to establish rapid and accurate ways of determining the concentration of Humira present in blood samples.

Physical Transduction

Electron transfer resulting from the interaction of the redox species with the electrode produces a current in the microampere range. The electrode is inserted in a cartridge/electrode holder, which is then connected to a small handheld potentiostat that can measure current in the pico ampere range (this is to improve accuracy). The potentiostat is connected to a computer, which utilizes a certain software program that runs the tests.

Cartridge

The disposable device wherein the sample fluid is treated is a basic carbon screen printed electrode coated with several layers each contributing to a specific function. The basic carbon electrode is first treated with gold nanoparticles. After being treated with gold, the electrode is then also treated with 11-mercaptoundecanoic acid (C11H22O2S). This acid facilitates in the immobilization o f TNF-α on the surface of the electrode. This sequence of layering results in the final disposable electrode wherein the blood sample resides.

Reader Instrument

The size of the biosensor is 90 x 65 mm.

The EmStat Pico Development Kit(Potentiostat) is the circuit board used to test a difference in the potential difference. The kit is offered with a PSTrace software for electrochemistry which helps with running the experiment by creating optimal settings and a script to control the EmStat. The used language for the device is MethodSCRIPT scripting language. This language allows the developer to program a readable script for users. The device is designed to be user friendly in that the user places the chip inside the device easily and the results appear on the computer after. There is one input and one output on opposite sides of the device. The chip is placed in the input side and the output has a USB connection with the computer. It is manufactured using laser cutting and made from acrylic.