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The growing bioeconomic demand for lightweight materials with combined sustainability, large-scale production, ease in functionalization and competitive mechanical properties has seen the revival of cellulose as a scaffold for several applications. In particular, due to its multifunctional features, cellulose has found application in sensor and biosensor fabrication. Nonetheless, the great variety of cellulose properties and formulations makes the choice of the best suited cellulose-based material for a specific sensing strategy a difficult task. This review offers a critical discussion and guide for the reader towards the understanding of which of the multiple cellulose derivatives and properties can be exploited for the optimal performance of the desired sensing device. We introduce the unique molecular structure, nanoarchitecture and main properties of cellulose and its derivatives. The different functionalization approaches for anchoring receptors on cellulose derivatives and the processing methodologies for fabricating cellulose-based sensors are explored. As far as the use and performance of cellulose-based functional materials in sensors is concerned, we discuss the recent advances of optical and electrochemical sensors and biosensors for biomedical and environmental monitoring. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical studies of laccase–mediator systems are aimed at understanding the mechanism of their redox transformation and their efficiency in both homogeneous and heterogeneous reactions; this topic has paramount application spanning from bleaching of paper pulp and the enzymatic degradation of lignin to the biosensors and biofuel cell development. In this paper four different laccases from Trametes hirsuta (ThL), Trametes versicolor (TvL), Melanocarpus albomyces (r-MaL) and Rhus vernicifera (RvL) were characterized from both biochemical and electrochemical points of view. Two of them (TvL and ThL) are high redox potential and two (RvL and r-MaL) are low redox potential laccases. The outline of this work is focused on the determination of catalytic and bioelectrochemical properties of these four enzymes in homogenous solution as well as immobilized onto electrode surface in the presence of a set of different redox mediators. The results measured in the homogenous reaction system correlated well with those measured with the immobilized enzymes. In addition, they are in good agreement with those reported with reference techniques, suggesting that the electrochemical methods employed in this work can be applied well in place of the traditional techniques commonly used for the kinetic characterization of laccases. These results are also discussed in terms of the known amino acid sequences and three-dimensional (3D) structures of the laccases. [Copyright &y& Elsevier]

In this paper, we present a surface-plasmon-resonance-based immunosensor for the real-time detection of cortisol and cortisone levels in urine and saliva samples. The method proposed here is simple, rapid, economic, sensitive, robust, and reproducible thanks also to the special features of the polycarboxylate-hydrogel-based coatings used for the antibody immobilization. The sensor surface displays a high level of stability during repeated regeneration and affinity reaction cycles. The immunosensor shows high specificity for cortisol and cortisone; furthermore, no significant interferences from other steroids with a similar chemical structure have been observed. The suitability of the hydrogel coating for the prevention of nonspecific binding is also investigated. A good correlation is noticed between the results obtained by the proposed method and the reference liquid chromatography/tandem mass spectrometry method for the analysis of cortisol and cortisone in urine and saliva samples. Standard curves for the detection of cortisol and cortisone in saliva and urine are characterized by a detection limit less than 10 μg l−1, sufficiently sensitive for both clinical and forensic use. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A highly stable functional composite film was prepared using polyazetidine prepolymer (PAP) with peroxidase from horseradish (HRP) and/or glucose oxidase (GOx). The good permeability of the PAP layer to classical electrochemical mediators, as evaluated by the determination of the diffusion coefficient of different redox molecules, is of great importance in view of the use of PAP as an immobilizing agent in second-generation biosensor development. Cyclic voltammetry of the HRP–PAP layer on a glassy carbon electrode (GCE) showed a pair of stable and quasi-reversible peaks for the HRP–Fe(III)/Fe(II) redox couple at about −370mV vs. Ag/AgCl electrode in pH 6.5 phosphate buffer. The electrochemical reaction of HRP entrapped in the PAP film exhibited a surface-controlled electrode process. This film and the successive modifications (HRP–PAP self-assembled monolayer (SAM) modified Au electrode) were used as a biological catalyst (hydrogen peroxide transducers) for glucose biosensors, after coupling to GOx. Both HRP/GOx–PAP and HRP/GOx–PAP SAM third generation biosensors were prepared and characterized. The use of PAP as immobilizing agent offers a biocompatible micro-environment for confining the enzyme and foreshadows the great potentiality of this immobilizing agent not only in theoretical studies on protein direct electron transfer but also from an applications point of view in the development of second- and third-generation biosensors. [Copyright &y& Elsevier]

Abstract: Bioelectrochemical properties of Trametes versicolor Laccase (TvL) and Trametes hirsuta Laccase (ThL) immobilized by using polyazetidine prepolymer (PAP) onto multi-walled carbon nanotubes (MWCNTs) screen printed electrode (SPE) surface, have been studied with several redox mediators by cyclic voltammetry (CV). The efficient entrapment of laccase in the PAP layer was confirmed by determination of both kinetic parameters (maximum current and Michaelis–Menten apparent constant) and analytical performances by chronoamperometry. The Laccase-modified MWCNTs electrode provides an effective biosensor for determination of polyphenols and catecholamines in real matrices; performances of the considered biosensors for real samples analysis are also compared and discussed. [Copyright &y& Elsevier]