Ioulia Tzouvadaki

Label-Free Ultrasensitive Memristive Aptasensor

We present the very first worldwide ever-reported electrochemical biosensor based on a memristive effect and DNA aptamers. This novel device is developed to propose a completely new approach in cancer diagnostics. In this study, an affinity-based technique is presented for the detection of the prostate specific antigen (PSA) using DNA aptamers. The hysteretic properties of memristive silicon nanowires functionalized with these DNA aptamers provide a label-free and ultrasensitive biodetection technique. The ultrasensitive detection is hereby demonstrated for PSA with a limit of detection down to 23 aM, best ever published value for electrochemical biosensors in PSA detection. The effect of polyelectrolytes on our memristive devices is also reported to further show how positive or negative charges affect the memristive hysteresis. With such an approach, combining memristive nanowires and aptamers, memristive aptamer-based biosensors can be proposed to detect a wide range of cancer markers with unprecedent ultrasensitivities to also address the issue of an early detection of cancer.

Memristive Biosensors Integration With Microfluidic Platform

The integration of nanoscale sensors with microfluidic platforms is a powerful tool for the design of robust biosensing devices that present high reliability and the advantage of a quick data acquisition. In addition, microfluidic based lab-on-a-chip sensors require minute amounts of clinical samples and cancer biosensing products. However, the integration of nanostructures in such more complex configurations may significantly complicate the electrical readout process. The aim of the present work is to develop improved devices for cancer prognosis based on nanofabricated Memristive Biosensors integrated for the first time with a microfluidic structure. The effective readout of the Memristive Biosensors electrical response is enabled through a series of specially designed metal line extensions realized accordingly in order to fully retain the sensing output signal.

Computational Study on the Electrical Behavior of Silicon Nanowire Memristive Biosensors

In this paper, a complete study is carried out investigating the relationship between the biosensing and the electrical characteristics of freestanding two-terminal Schottky-barrier silicon nanowires. This paper successfully reproduces computationally the electrical behavior obtained experimentally from the nanowire devices before and after the surface biomodification. Throughout modeling and simulations, this paper confirms that the experimental results obtained from the electrical characterization of bare two-terminal Schottky-barrier silicon nanowires present current-to-voltage characteristics fully equivalent to that of a pure memristor device, according to the literature. Furthermore, this paper shows that the voltage gap appearing in the current-to-voltage characteristics for nanowires with biomodified surface is related to capacitive effects due to minority carriers in the nanowire and it is also indicated that those effects are strongly affected by the concentration of antigens uptaken on the device surface. Overall, this paper confirms the implication of the memristive effect for biosensing applications and therefore, demonstrates the memristive biosensors.

Performance of Carbon Nano-Scale Allotropes in Detecting Midazolam and Paracetamol in Undiluted Human Serum

Nano-materials are highly exploited to enhance sensing performance of electrochemical electrodes by increasing the electro-active surface area (EASA). In this paper, an analytical calculation of the deposited EASA is presented and experimentally validated by comparing two kinds of nano-structured electrochemical sensors modified with multi-walled carbon nano-tubes (MWCNTs) and fullerenes. Further, the two differently nano-structured electrodes, prepared with equal optimum EASA, have been adopted as novel approach in the detection of paracetamol (APAP) and midazolam (MZ), two largely adopted and complementary sedative drugs. We have used the novel approach to let emerge the different nano-scale structures’ sensing performance at the same equivalent EASA. The analytical method for EASA calculation has been recently validated by our group on different nano-materials; hence the aim of the actual work is to present, for the first time, its efficient applicability also in comparing the performance of different allotropes of the same nature (carbon-based) in drug sensing, e.g., MZ and APAP. This paper also includes the comparison in undiluted human serum (HS), proposed here as complex bio-sample, to confirm the validity of our novel approach close to real applications. With respect to fullerenes, the MWCNTs-modified electrodes obtained the best limit of detection values in HS detection, as 0.3518

Nano-fabricated memristive biosensors for biomedical applications with liquid and dried samples

\mu \text{M}

“Bio-functionalization study of Memristive-Biosensors for early detection of prostate cancer”

and 0.5367 mm for APAP and MZ, respectively. Scanning electron microscopy analysis also confirmed the higher quality of MWCNTs-based surface in terms of homogeneity and denser coverage of the surface with respect to fullerene-based one, with a better-packed aggregate of assembled structures.

An efficient electronic measurement interface for memristive biosensors

Nanowire based platforms are widely reported for sensing applications and for their potential in the bio-detection field. In the present work, memristive nanowire devices are implemented for label-free sensing in liquid samples as well as in dried samples via leveraging the modification of the hysteresis in the devices electrical response as a consequence of the surface modification. First, pH sensing in liquid conditions is demonstrated. In addition, the memristive devices are bio-functionalized using antibodies for Prostate Specific Antigen (PSA) as case of study. In this way, the nanowires are converted to memristive biosensors paving the way for future molecular diagnostics applications in general, and for detection of prostate cancer disease in particular.

Modeling memristive biosensors

Silicon nanowires are reported for their application in bio sensing area and their potential in the detection of various biomolecules. In the present work, freestanding two-terminal Schottky-barrier silicon nanowire arrays exhibiting memristive behavior are fabricated to obtain Memristive-Biosensors. Scanning electron microscopy reveal details on the morphology of the fabricated structures. The memristive devices are functionalized with anti-free-Prostate Specific Antigen (PSA) antibody by two strategies: a) direct passive adsorption on the device surface, and b) bio-affinity approach using Biotin-Streptavidin combination. The electrical behavior of the so-obtained Memristive-Biosensors is examined dealing with the two systems of bio-functionalization. The presence of biomolecules linked to the surface of the nanostructures is detected by a voltage gap appearing in the memristive electrical characteristics. The system shows the potential for applications in molecular diagnostics especially due to possibilities for detection in the femto molar ranges that allow early detection of the cancer disease.

Memristive Biosensors for PSA-IgM Detection

Reducing sensing time is one major concern in clinical diagnostics. In the present work, a robust measurement system is developed aiming at the faster and easier signal acquisition of memristive biosensors. Sensing chips consisting of nanofabricated silicon wires exhibiting memristive electrical response and metallic extension electrodes allowing an integrated measurement procedure are designed and fabricated. Furthermore, the electrical response of these particular nanofabricated structures is for the first time acquired using an embedded-system-based measurement front-end. The suggested prototype significantly simplifies the measurement procedure and provides conveniently the response signal of the devices. Such optimized co-design of memristive biosensors with electronic platforms hold great promise for PoC (point-of-care) applications.

The memristive effect as a novelty in drug monitoring

In the present work, a computational study is carried out investigating the relationship between the biosensing and the electrical characteristics of two-terminal Schottky-barrier silicon nanowire devices. The model suggested successfully reproduces computationally the experimentally obtained electrical behavior of the devices prior to and after the surface bio-modification. Throughout modeling and simulations, it is confirmed that the nanofabricated devices present electrical behavior fully equivalent to that of a memristor device, according to literature. Furthermore, the model introduced successfully reproduces computationally the voltage gap appearing in the current to voltage characteristics for nanowire devices with bio-modified surface. Overall, the present study confirms the implication of the memristive effect for bio sensing applications, therefore demonstrating the Memristive Biosensors.