AixSense 2019

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[[File:|200px|thumb|right|Logo of AixSense]]

AixSense 2019

AixSense is a team from the RWTH Aachen University competing in the SensUs 2019 event. For SensUs 2019, AixSense 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

Anti-Adalimumab (Anti-AM) is used to immobilize the surface of the graphene based transducers where the analyte then flowed over. Changes in the impedance before and after the flow are measured using an Impedance Analyzer. Adalimumab specific transducers will then show increase of impedance against different concentrations of Adalimumab molecular binding within clinical ranges (0.1μg/ml to 10 μg/ml).


Molecular Recognition

The molecules used in the biosensor are the Anti-Adalimumab Type 1 Antibody, the TNF-α - Tumour Necrosis Factor alpha (TNF-α), and silver Nanoparticles.

The Type 1 anti-adalimumab (Anti-AM) antibodies inhibit the binding of the drug adalimumab(AM) to its target, TNF-α, and therefore detect the free drug. This protein was used to bio-immobilize the Graphene based transducers.

The tumour Necrosis Factor alpha (TNF-α), is an inflammatory cytokine produced by macrophages/monocytes during acute inflammation and is responsible for a diverse range of signalling events within cells, leading to necrosis or apoptosis.The affinity of TNF-α to adalimumab was taken advantage of by tagging it with optically active silver nanoparticles and then flowing it over the Graphene based transducers containing the Anti-AM complex.

The Silver Nanoparticles (Ag NPs) were used as the optical tags with receptor proteins specific to AM.


Physical Transduction

Differential pulse voltammetry (DPV) is used for the readout and an equimolar mixture of the potassium ferricyanide/ferrocyanide redox couple acts as a probe for the signal generation. The current is measured as a function of time and potential between the indicator and reference electrode. As the potential increases towards the redox potential of the probe, it starts undergoing redox and a current up to a peak value is produced. The current is subsequently brought into a diffusion-controlled state and as a result, the total current response takes its shape as a peak. The immunocomplex restricts the surface availability for the redox probe, which lowers the number of redox events and therefore reduces the current signal. Measurements are performed after the immobilization procedure to achieve a baseline which is compared to the signal obtained after analyte incubation on the electrode. Samples with known concentrations of the analyte are used to prepare a calibration curve which can then be used to quantify the amount of the analyte in an unknown sample.

Cartridge

The screen-printed electrodes are disposable. Incubation of the sample on the electrode is performed outside of the potentiostat. The sample is applied by the technician on the tabletop after which the sample is incubated in a sealed container in 4 degree celsius. After sample incubation, the electrode is manually washed off with PBS into a waste container. The electrode is inserted into the adapter on the potentiostat and quantification can be performed. After running the measurement, the electrode can simply be discarded into biological waste. The electrode chips could potentially be regenerated and therefore, reused.

Reader Instrument

The size of the biosensor is 95mmx75mmx75mm. It consists of a sealed potentiostat and an electrode chip. The only handling required by the user is related to the electrode chip. The output of the measurement can be viewed and analyzed with the PSTrace software (PalmSens). The data from known concentrations of the analyte can be used to externally produce a calibration curve which can then be used to infer the analyte concentrations of an unknown sample based on peak differences. Additionally, an app has been developed which can measure the raw data in real-time during the measurement using Bluetooth. The data obtained can be automatically converted to the concentration of adalimumab in blood. The app provides graphs on current and past measurements, making the interpretation of the optimal drug usage straightforward to assess.

Prizes