Biorecognition is a central event in biological processes in the living systems that is also widely exploited in technological and health applications. We demonstrate that the Electrolyte Gated Organic Field Effect Transistor (EGOFET) is an ultrasensitive and specific device that allows us to quantitatively assess the thermodynamics of biomolecular recognition between a human antibody and its antigen, namely, the inflammatory cytokine TNFα at the solid/liquid interface. The EGOFET biosensor exhibits a superexponential response at TNFα concentration below 1 nM with a minimum detection level of 100 pM. The sensitivity of the device depends on the analyte concentration, reaching a maximum in the range of clinically relevant TNFα concentrations when the EGOFET is operated in the subthreshold regime. At concentrations greater than 1 nM the response scales linearly with the concentration. The sensitivity and the dynamic range are both modulated by the gate voltage. These results are explained by establishing the correlation between the sensitivity and the density of states (DOS) of the organic semiconductor. Then, the superexponential response arises from the energy-dependence of the tail of the DOS of the HOMO level. From the gate voltage-dependent response, we extract the binding constant, as well as the changes of the surface charge and the effective capacitance accompanying biorecognition at the electrode surface. Finally, we demonstrate the detection of TNFα in human-plasma derived samples as an example for point-of-care application.

Organic electronic transistors are rapidly emerging as ultra-high sensitive label-free biosensors suited for point of care or in-field deployed applications. Most organic biosensors reported to date are based on immunorecognition between the relevant biomarkers and the immobilized antibodies, whose use is hindered by large dimensions, poor control of sequence and relative instability. Here, we report an Electrolyte Gated Organic Field Effect Transistor (EGOFET) biosensor where the recognition units are surface immobilized peptide aptamers (Affimerä proteins) instead of antibodies. We demonstrate our peptide aptasensor for the detection of the pro-inflammatory cytokine Tumor Necrosis Factor alpha (TNFa) with a 1pM limit of detection. Ultra-low sensitivity is met even in complex solutions such as cell culture media containing 10 % serum, demonstrating the remarkable ligand specificity of our device. The device performances, together with the simple one-step immobilization strategy of the recognition moieties and the low operational voltages, all prompt EGOFET peptide aptasensors as candidates for early diagnostics and monitoring at the point-of-care.

Low‐cost, minimally invasive sensors able to provide real‐time monitoring of wound infection can enable the optimization of healthcare resources in chronic wounds management. Here, a novel printed organic electrochemical transistors (OECT) biosensor for monitoring uric acid (UA), a bacterial infection biomarker in wounds, is demonstrated in artificial wound exudate. The sensor exploits the enzymatic conversion of UA to 5‐hydroxyisourate, catalyzed by Uricase entrapped in a dual‐ionic‐layer hydrogel membrane casted onto the gate. The sensor response is based on the catalytic oxidation of the hydrogen peroxide, generated as part of the Uricase regeneration process, at the Pt modified gate. The proposed dual membrane avoids the occurrence of nonspecific faradic reactions as, for example, the direct oxidation of UA or other electroactive molecules that would introduce a potentially false negative response. The biosensor is robust and its response is reproducible both in phosphate buffer saline and in complex solutions mimicking the wound exudate. The sensor has a high sensitivity in the range encompassing the pathological levels of UA in wounds (<200 μm) exhibiting a limit of detection of 4.5 μm in artificial wound exudate. All these characteristics make this OECT‐based biosensor attractive for wound monitoring interfaced to the patient.

(2017), Label-free detection of interleukin-6 using electrolyte gated organic field effect transistors, Biointerphases, 12 (5)

In this work, we demonstrate the ultrasensitive and selective detection of dopamine by means of a neuro-inspired device platform without the need of a specific recognition moiety. The sensor is a whole organic device featuring two electrodes made of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-PEDOT:PSS-patterned on a polydymethylsiloxane-PDMS-flexible substrate. One electrode is pulsed with a train of voltage square waves, to mimic the presynaptic neuron behavior, while the other is used to record the displacement current, mimicking the postsynaptic neuron. The current response exhibits the features of synaptic Short-Term Plasticity (STP) with facilitating or depressing response according to the stimulus frequency. We found that the response characteristic time υ depends on dopamine (DA) concentration in solution. The dose curve exhibits superexponential sensitivity at the lowest concentrations below 1 nM. The sensor detects [DA] down to 1 pM range. We assess the sensor also in the presence of ascorbic acid (AA) and uric acid (UA). Our sensor does not respond to UA, but responds to AA only at concentration above 100 μM. However, it is still able to detect DA down to 1 pM range in the presence of [AA] = 100 μM and 100 pM in the presence of [UA] = 3 μM, these values for AA and UA being the physiological levels in the cerebrospinal fluid and the striatum, respectively.