Self-chemisorption of azurin on functionalized oxide surfaces for the implementation of biomolecular devices

Abstract In this work, we investigate the formation of redox protein Azurin (Az) monolayers on functionalized oxygen exposing surfaces. These metallo-proteins mediate electron transfer in the denitrifying chain of Pseudomonas bacteria and exhibit self-assembly properties, therefore they are good candidates for bio-electronic applications. Azurin monolayers are self-assembled onto silane functionalized surfaces and characterized by atomic force microscopy (AFM). We show also that a biomolecular field effect transistor (FET) in the solid state can be implemented by interconnecting an Azurin monolayer immobilized on SiO 2 with two gold nanoelectrodes. Transport experiments, carried out at room temperature and ambient pressure, show FET behavior with conduction modulated by the gate potential

Retention of nativelike conformation by proteins embedded in high external electric fields.

In this Communication, we show that proteins embedded in high external electric fields are capable of retaining a nativelike fold pattern. We have tested the metalloprotein azurin, immobilized onto SiO2 substrates in air with proper electrode configuration, by applying static fields up to 106–107V∕m. The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. Such results are also discussed and supported by theoretical predictions of the inner protein fields

Pile-Ups Formation in AFM-Based Nanolithography: Morpho-Mechanical Characterization and Removal Strategies

In recent decades, great efforts have been made to develop innovative, effective, and accurate nanofabrication techniques stimulated by the growing demand for nanostructures. Nowadays, mechanical tip-based emerged as the most promising nanolithography technique, allowing the pattern of nanostructures with a sub-nanometer resolution, high reproducibility, and accuracy. Unfortunately, these nanostructures result in contoured pile-ups that could limit their use and future integration into high-tech devices. The removal of pile-ups is still an open challenge. In this perspective, two different AFM-based approaches, i.e., Force Modulation Mode imaging and force-distance curve analysis, were used to characterize the structure of pile-ups at the edges of nanogrooves patterned on PMMA substrate by means of Pulse-Atomic Force Lithography. Our experimental results showed that the material in pile-ups was less stiff than the pristine polymer. Based on this evidence, we have developed an effective strategy to easily remove pile-ups, preserving the shape and the morphology of nanostructures

Nano-scaled Biomolecular Field-Effect Transistors: Prototypes and Evaluations

As modern electronics rapidly approach the ultimate level of integration (typically thought to be at the nanoscale level), the fascinating world of biomolecules provides new opportunities and directions for further miniaturization. In this work we review our results in the field of biomolecular electronics, starting from the fabrication of nanojunctions up to the implementation of hybrid devices

Pulse-Atomic Force Lithography: A Powerful Nanofabrication Technique to Fabricate Constant and Varying-Depth Nanostructures

The widespread use of nanotechnology in different application fields, resulting in the integration of nanostructures in a plethora of devices, has addressed the research toward novel and easy-to-setup nanofabrication techniques to realize nanostructures with high spatial resolution and reproducibility. Owing to countless applications in molecular electronics, data storage, nanoelectromechanical, and systems for the Internet of Things, in recent decades, the scientific community has focused on developing methods suitable for nanopattern polymers. To this purpose, Atomic Force Microscopy-based nanolithographic techniques are effective methods that are relatively less complex and inexpensive than equally resolute and accurate techniques, such as Electron Beam lithography and Focused Ion Beam lithography. In this work, we propose an evolution of nanoindentation, named Pulse-Atomic Force Microscopy, to obtain continuous structures with a controlled depth profile, either constant or variable, on a polymer layer. Due to the modulation of the characteristics of voltage pulses fed to the AFM piezo-scanner and distance between nanoindentations, it was possible to indent sample surface with high spatial control and fabricate highly resolved 2.5D nanogrooves. That is the real strength of the proposed technique, as no other technique can achieve similar results in tailor-made graded nanogrooves without the need for additional manufacturing steps

Azurin for Biomolecular Electronics: a Reliability Study

The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its resilience to high electric fields and ambient conditions, which are crucial reliability issues. Concerning the effect of electric fields, two models of different complexity agree indicating an unexpectedly high robustness. Experiments in device-like conditions confirm that no structural modifications occur, according to fluorescence spectra, even after a 40-min exposure to tens of MV/m. Ageing is then investigated experimentally, at ambient conditions and without field, over several days. Only a small conformational rearrangement is observed in the first tens of hours, followed by an equilibrium state

Metalloprotein-based electronic nanodevices

A key challenge of the current research in nanoelectronics is the realization of biomolecular devices. The use of electron-transfer proteins, such as the blue copper protein, azurin (Az), is particularly attractive because of its natural redox properties and self-assembly capability. This chapter dis- cusses results of fabrication, characterization, and modeling of devices based on this redox protein. The prototype of biomolecular devices operate in the solid state and in air. The charge transfer process in protein devices can be engineered by using proteins with different redox centers (metal atoms) and by controlling their orientation in the solid state through different immobilization methods. A biomolecular electron rectifier has been demonstrated by interconnecting two gold nanoelectrodes with an Az monolayer immobilized on SiO2. The device exhibits a clear rectifying behavior with discrete current steps in the positive wing of the current— voltage (I-V) curve, which is ascribed to resonant tunneling through the redox active center. On the basis of these results, an Az-based three- terminal device has been designed. The three-terminal device exhibits an ambipolar behavior as a function of the gate bias, thus opening the way to the implementation of a new generation of logic architectures. This peculiar characteristic allows the implementation of a fully integrated nanoscopic logic gate

Systematic versus on-demand early palliative care: results from a multicentre, randomised clinical trial

Background Early palliative care (EPC) in oncology has been shown to have a positive impact on clinical outcome, quality-of-care outcomes, and costs. However, the optimal way for activating EPC has yet to be defined. Methods This prospective, multicentre, randomised study was conducted on 207 outpatients with metastatic or locally advanced inoperable pancreatic cancer. Patients were randomised to receive ‘standard cancer care plus on-demand EPC’ (n = 100) or ‘standard cancer care plus systematic EPC’ (n = 107). Primary outcome was change in quality of life (QoL) evaluated through the Functional Assessment of Cancer Therapy – Hepatobiliary questionnaire between baseline (T0) and after 12 weeks (T1), in particular the integration of physical, functional, and Hepatic Cancer Subscale (HCS) combined in the Trial Outcome Index (TOI). Patient mood, survival, relatives' satisfaction with care, and indicators of aggressiveness of care were also evaluated. Findings The mean changes in TOI score and HCS score between T0 and T1 were −4.47 and −0.63, with a difference between groups of 3.83 (95% confidence interval [CI] 0.10–7.57) (p = 0.041), and −2.23 and 0.28 (difference between groups of 2.51, 95% CI 0.40–4.61, p = 0.013), in favour of interventional group. QoL scores at T1 of TOI scale and HCS were 84.4 versus 78.1 (p = 0.022) and 52.0 versus 48.2 (p = 0.008), respectively, for interventional and standard arm. Until February 2016, 143 (76.9%) of the 186 evaluable patients had died. There was no difference in overall survival between treatment arms. Interpretations Systematic EPC in advanced pancreatic cancer patients significantly improved QoL with respect to on-demand EPC

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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Memristor-based pixel for event-detection vision sensor

We report on a vision sensor architecture relying on a pixel-embedded memristive device to perform dynamic background subtraction as basic image processing components, aimed at detecting anomalous events in the scene. A Light-To-Frequency Converter generates digital pulses, which are linearly proportional with the light intensity. During the exposure time, a certain number of pulses, with proper width and amplitude, drive the memristor MS, changing its resistance. The value of MS is then compared with two memristors, MH and ML, used as thresholds. After each frame, the values of MH and ML are adjusted in order to satisfy ML < MS < MH. The rate at which the two memristors are updated is application-dependent and can be digitally programmed. If the value of MS trespasses either MH or ML, due to a light change, the pixel behaviour is recognized as anomalous (hot-pixel) By aggregating the hot-pixels of the image, anomalous events can be detected through standard processing techniques. The pixel architecture has been designed in a 0.35µm standard CMOS process and validated through simulation