Recent Advances in Polymeric Materials Used as Electron Mediators and Immobilizing Matrices in Developing Enzyme Electrodes

Different classes of polymeric materials such as nanomaterials, sol-gel materials, conducting polymers, functional polymers and biomaterials have been used in the design of sensors and biosensors. Various methods have been used, for example from direct adsorption, covalent bonding, crossing-linking with glutaraldehyde on composites to mixing the enzymes or use of functionalized beads for the design of sensors and biosensors using these polymeric materials in recent years. It is widely acknowledged that analytical sensing at electrodes modified with polymeric materials results in low detection limits, high sensitivities, lower applied potential, good stability, efficient electron transfer and easier immobilization of enzymes on electrodes such that sensing and biosensing of environmental pollutants is made easier. However, there are a number of challenges to be addressed in order to fulfill the applications of polymeric based polymers such as cost and shortening the long laboratory synthetic pathways involved in sensor preparation. Furthermore, the toxicological effects on flora and fauna of some of these polymeric materials have not been well studied. Given these disadvantages, efforts are now geared towards introducing low cost biomaterials that can serve as alternatives for the development of novel electrochemical sensors and biosensors. This review highlights recent contributions in the development of the electrochemical sensors and biosensors based on different polymeric material. The synergistic action of some of these polymeric materials and nanocomposites imposed when combined on electrode during sensing is discussed

A novel BCS code in F-OFDM system: a promising candidate for 5G wireless communication systems

Due to the rapid growth in wireless communication systems, Long Term Evolution (LTE), mainly based on Orthogonal Frequency Division Multiplexing (OFDM), no longer meets wireless communication systems request and higher data rate requirements. Thus, to support a number of users, higher throughput, reliability, and lower latency, 5G is a candidate to meet these features. Furthermore, OFDM does not meet the demand of 5G because of its high Out Of Band Emission (OOBE) and Peak to Average Power Ratio (PAPR). Filtered-OFDM (f-OFDM) is considered an alternative waveform for OFDM and a candidate technique for 5G because of its lower OOBE and similar features of familiar OFDM. However, there is a trade-off among reducing OOBE, Bit Error Rate (BER) degradation, and rising PAPR. Therefore, a novel BCS code has been proposed in this thesis for the filtered-OFDM system to improve BER performance with maintaining its low OOBE. It is created using a new methodology that differs from conventional concatenated RS/BCH codes. Hence, an inner RS (7, 1) code has been proposed to achieve compatibility with an outer BCH (15, 5) code and appended by interleaver to create a novel BCS code with low complexity. The results showed that using a novel BCS code in LTE system reduces BER, significantly improved to be better than single and concatenated RS/BCH codes with low decoding complexity. On the other hand, using a novel BCS code in f-OFDM system achieved 0.8dB coding gain at 8×10-3 BER and 1dB coding gain at 2×10-3 BER versus conventional OFDM system in both BPSK and QPSK modulation schemes, respectively. Meanwhile, the proposed system reduced both OOBE and PAPR lower than the conventional OFDM system. In conclusion, due to its low OOBE, improving BER, and minimizing PAPR better than conventional OFDM system, the proposed system is presented as a high competitor candidate of 5G wireless communication systems

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Biological and microbial fuel cells

Biological fuel cells have attracted increasing interest in recent years because of their applications in environmental treatment, energy recovery, and small-scale power sources. Biological fuel cells are capable of producing electricity in the same way as a chemical fuel cell: there is a constant supply of fuel into the anode and a constant supply of oxidant into the cathode; however, typically the fuel is a hydrocarbon compound present in the wastewater, for example. Microbial fuel cells (MFCs) are also a promising technology for efficient wastewater treatment and generating energy as direct electricity for onsite remote application. MFCs are obtained when catalyst layer used into classical fuel cells (polymer electrolyte fuel cell) is replaced with electrogenic bacteria. A particular case of biological fuel cell is represented by enzyme-based fuel cells, when the catalyst layer is obtained by immobilization of enzyme on the electrode surface. These cells are of particular interest in biomedical research and health care and in environmental monitoring and are used as the power source for portable electronic devices. The technology developed for fabrication of enzyme electrodes is described. Different enzyme immobilization methods using layered structures with self-assembled monolayers and entrapment of enzymes in polymer matrixes are reviewed. The performances of enzymatic biofuel cells are summarized and approaches on further development to overcome current challenges are discussed. This innovative technology will have a major impact and benefit to medical science and clinical research, health care management, and energy production from renewable sources. Applications and advantages of using MFCs for wastewater treatment are described, including organic matter removal efficiency and electricity generation. Factors affecting the performance of MFC are summarized and further development needs are accentuated

Rational design of artificial redox-mediating systems toward upgrading photobioelectrocatalysis

Photobioelectrocatalysis has recently attracted particular research interest owing to the possibility to achieve sunlight-driven biosynthesis, biosensing, power generation, and other niche applications. However, physiological incompatibilities between biohybrid components lead to poor electrical contact at the biotic-biotic and biotic-abiotic interfaces. Establishing an electrochemical communication between these different interfaces, particularly the biocatalyst-electrode interface, is critical for the performance of the photobioelectrocatalytic system. While different artificial redox mediating approaches spanning across interdisciplinary research fields have been developed in order to electrically wire biohybrid components during bioelectrocatalysis, a systematic understanding on physicochemical modulation of artificial redox mediators is further required. Herein, we review and discuss the use of diffusible redox mediators and redox polymer-based approaches in artificial redox-mediating systems, with a focus on photobioelectrocatalysis. The future possibilities of artificial redox mediator system designs are also discussed within the purview of present needs and existing research breadth

Development of electrochemical nitrite biosensors using cytochrome c nitrite reductase from Desulfovibrio desulfuricans ATCC 27774

Dissertação apresentada para a obtenção do Grau de Doutor em Química Sustentável pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaREQUIMTE ; Fundação para a Ciência e Tecnologia -(POCI/QUI/58026/2004 and SFRH/BD/28921/2006

ELECTROCHEMICAL CHIRAL BIOSENSORS

Recognition of chiral molecules in biological assemblies has been a subject of extensive research. The aim of this work was to fabricate and characterise biocompatible composite materials suitable for chiral recognition. Collagen, the most abundant chiral, extracellular protein, was chosen as a possible matrix. The chiral recognition properties were evaluated by a comparative study in collagen, collagen incorporated in tetramethyl orthosilicate (TMOS) and TMOS. In electrochemical studies, ferrocene was incorporated to facilitate electron transfer. The recognition characteristics of two chiral enzymes, L-lactate oxidase and D-glucose oxidase were tested using circular dichroism (CD), Fourier Transform Infra-Red (FTIR) spectroscopy and electrochemical methods. A surprising result revealed an inversion of chiral selectivity. The effect of various parameters such as immobilisation, temperature, chemical modification, solvent systems, on enantioselectivity is well known. Stereoinversions caused by the ‘sergeants and soldiers’ effect in gel-forming p-conjugated molecules caused by co-assembly has been reported by several groups. The inversion of stereoselectivity observed in this study is probably due to a combination of the microenvironment and electrostatic interactions of the enzyme, mediator and substrate with the chiral collagen matrix. The results may have important implications for biosensing, asymmetric syntheses and understanding the nature of chiral interactions in biological systems

Prospects of Nanotechnology in Clinical Immunodiagnostics

Nanostructured materials are promising compounds that offer new opportunities as sensing platforms for the detection of biomolecules. Having micrometer-scale length and nanometer-scale diameters, nanomaterials can be manipulated with current nanofabrication methods, as well as self-assembly techniques, to fabricate nanoscale bio-sensing devices. Nanostructured materials possess extraordinary physical, mechanical, electrical, thermal and multifunctional properties. Such unique properties advocate their use as biomimetic membranes to immobilize and modify biomolecules on the surface of nanoparticles. Alignment, uniform dispersion, selective growth and diameter control are general parameters which play critical roles in the successful integration of nanostructures for the fabrication of bioelectronic sensing devices. In this review, we focus on different types and aspects of nanomaterials, including their synthesis, properties, conjugation with biomolecules and their application in the construction of immunosensing devices. Some key results from each cited article are summarized by relating the concept and mechanism behind each sensor, experimental conditions and the behavior of the sensor under different conditions, etc. The variety of nanomaterial-based bioelectronic devices exhibiting novel functions proves the unique properties of nanomaterials in such sensing devices, which will surely continue to expand in the future. Such nanomaterial based devices are expected to have a major impact in clinical immunodiagnostics, environmental monitoring, security surveillance and for ensuring food safety