Development and optimization of a solid composite tyrosinase biosensor for phenol detection in flow injection systems

Bulk-modified epoxy-graphite tyrosinase biosensors were fabricated by four different procedures. The influence of these fabrication procedures on the analytical performance of the enzyme electrode in an amperometric wall-jet flow cell has been studied. The bioprobe performance is assessed by cyclic voltammetry. Higher current densities and narrower peaks were obtained when the enzyme was introduced in the dry state into the epoxy-graphite material, instead of introducing it previously dissolved in the buffer. In the F1 system responses of 11.79 μA cm⁻² and 1.43 μA cm⁻² are then obtained for catechol and phenol respectively for 50 μL injections of 20 μM solutions. Moreover, if gold/palladium is introduced into the epoxy-graphite, a further increase in current is achieved resulting in 27.70μA cm⁻² and 4.90μA cm⁻²for catechol and phenol, respectively. This biosensor can operate in aqueous as well as in mixed aqueous-organic environments.     

Miscanthus stem fragment – Reinforced polypropylene composites: Development of an optimized preparation procedure at small scale and its validation for differentiating genotypes

The production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity.     

A Novel Label-free Chronoamperometric Immunosensor Based on a Biocomposite Material for Rapid Detection of Carcinoembryonic Antigen

In this research, poly(diallyldimethylammonium chloride)-capped gold nanoparticles, nickel ferrite particles, and carbon nanotubes were combined to form a PANC metal composite. The prepared metal composite modified onto a glassy carbon electrode was electropolymerized with poly(o-phenylenediamine) and immobilized with horseradish peroxidase, anti-carcinoembryonic antigen antibody, and bovine serum albumin to create the label-free immunosensors for rapid detection of carcinoembryonic antigen (CEA) using chronoamperometry. This developed biocomposite material modified onto a glassy carbon electrode presented an excellent electrocatalytic response to the redox reaction of hydrogen peroxide as a sensing probe, from which the kinetic parameters including of a charge transfer rate constant, a diffusion coefficient value, an electroactive surface area, and a surface concentration were calculated to be 1.85 s⁻¹, 4.28×10⁻⁶ cm² s⁻¹, 0.14 cm² and 1.87×10⁻⁸ mol cm⁻², respectively. The developed immunosensors also exhibited a wide linear range of CEA concentration from 0.01 to 25 ng mL⁻¹ with high sensitivity (96.21 μA cm⁻² ng⁻¹ mL) and low detection limit (0.72 pg mL⁻¹), excellent selectivity without interfering effects from possible species (amoxicillin, ascorbic acid, aspirin, caffeine, cholesterol, dopamine, glucose, and uric acid), outstanding stability (n=100, %I>50 %), repeatability (%RSD=0.34, n=10), reproducibility (%RSD=4.06, n=10), and rapid analysis (25 s each operation time). This proposed method was successfully applied for CEA detection in whole blood samples with satisfactory results, suggesting that this developed sensing platform may be considered to be exploited for fabrication of other label-free electrochemical immunosensors for the real sample analysis.     

Coconut shell particles reinforced cardanol–formaldehyde resole resin biocomposites: Effect of treatment on thermal properties

The current work focuses on the thermal behavior of biocomposites based on cardanol formaldehyde resin (CFR) reinforced with untreated and treated coconut shell particles (CSP). CFR has been synthesized by condensing cardanol with formaldehyde in the presence of NH₄OH catalyst (ratio of 1:1.6:0.36). Fabricating biocomposites is performed by compression moulding technique. The CSP with particle size of 50?µm is used in various proportions: 30 and 40?wt%. The CSP is immersed in 5?wt% NaOH solution for 5?h. Fourier transform infrared spectroscopy is used to characterize chemical formation of the new biocomposites. Thermogravimetric analysis and differential thermal analysis are applied to measure the thermal stability of composites. The thermal stability exhibits a slight decrease with particles loading from 30 to 40?wt% against neat CFR. This work gives a path for the possibility of CSP usage in low-value products in composite manufacturing.     

Effect of Butyl Methacrylate on Properties of Regenerated Cellulose Coconut Shell Biocomposite Films

In this study, butyl methacrylate acid (BMA) is used as chemical modifier of regenerated cellulose (RC) coconut shell (CS) biocomposite films. The effect of CS content and BMA on tensile properties and crystallinity index (CrI) of RCCSbiocomposite films were investigated. It is found that the increasing of CS content up to 3 wt% increased the tensile strength and modulus of elasticity but decreased at higher content of CS. Elongation at break decreased with increasing of CS content and increased at 4 wt% of CS. Cystallinity index (CrI) of biocomposite films also increased with increasing CS up to 3 wt% content. At similar CS content, treated RC CS biocomposite films with BMA were found to have higher tensile properties and crystallinity index (CrI) than the untreated biocomposite films. The modification by BMA improved interfacial interaction and dispersion of CS in RC biocomposite films.     

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.     

Functionalized alginate/chitosan biocomposites consisted of cylindrical struts and biologically designed for chitosan release

A novel alginate/chitosan composite scaffold was developed. The composite scaffolds were fabricated at low temperature using a three-axis robot system connected to a micro-dispenser and a core/shell nozzle. The structure of the composite scaffolds included hollow struts; deposited chitosan on the inner walls (core region) of the struts reacted electrostatically with the alginate layer (shell region). The fabricated, highly porous composite scaffolds exhibited excellent mechanical properties and controllable chitosan release, which was closely dependent on the weight fraction of the alginate in the shell region. The tensile strength in the dry state was ∼1.8-fold greater than that of pure alginate scaffold due to the ionic interaction between alginate and chitosan. To determine the feasibility of using the developed scaffold in tissue regeneration applications, in vitro cellular responses were evaluated using osteoblast-like-cells (MG63). The cell proliferation on the composite scaffold was ∼3.4-fold greater than that on the pure alginate scaffold. Alkaline phosphate activity and calcium deposition of the composite scaffold after 14 and 21 days of cell culture were significantly enhanced (1.6- and 1.8-fold greater, respectively) compared with those of the pure alginate scaffold. These results suggested that the alginate/chitosan composite scaffolds with a controlled chitosan release have great potential for use in regenerating various tissues.     

Influence of Glycerol Content on Properties of Wheat Gluten/Hydroxyethyl Cellulose Biocomposites

Environmentally friendly biocomposites were prepared by blending wheat gluten（WG）as a matrix, hydroxyethyl cellulose（HEC）as a filler,and glycerol as a plasticizer,followed by thermo-molding of the mixture at 120°C for crosslinking the matrix.Moisture absorption,tensile properties,dynamic mechanical analysis,and dynamic rheology were evaluated in relation to the glycerol content.Tensile strength and modulus drop dramatically with increasing glycerol content,which is accompanied by significant depression in the glass transition temperature and improvement in the extensibility of the biocomposites.     

Synthesis of a chitin-based biocomposite for water treatment: Optimization for fluoride removal

The optimum composition of a chitin-based biocomposite was determined based on both its fluoride adsorption capacity and its chemical resistance in acid aqueous solution. Parameters such as the chitin content, additive content, catalyst content, chitin particle size, degree of acetylation of chitin and effect of pH on adsorption were evaluated. It was possible to chemically reinforce chitin while keeping an acceptable fluoride adsorption capacity onto the chitin-based biocomposites. Optimum chitin content (60%) was limited by the polymer-biopolymer anchoring capacity. An amine-based additive was used to improve the biocomposite adsorption capacity; however, its inclusion was not suitable in terms of biocomposite chemical resistance. The chitin particle size had no effect on adsorption capacity, and the degree of acetylation of chitin notably modified biocomposite adsorption capacity. On the other hand, the biocomposite chemical resistance was notably improved compared to pure chitin. The physicochemical properties of the optimum chitin-based biocomposite showed its potential for being used in continuous adsorption processes.     

An Experimental Investigation of Deformation and Fracture of Nacre–Mother of Pearl

Nacre, also known as mother-of-pearl, is a hard biological composite found in the inside layer of many shells such as oyster or abalone. It is composed of microscopic ceramic tablets arranged in layers and tightly stacked to form a three-dimensional brick wall structure, where the mortar is a thin layer of biopolymers (20–30 nm). Although mostly made of a brittle ceramic, the structure of nacre is so well designed that its toughness is several order of magnitudes larger that the ceramic it is made of. How the microstructure of nacre controls its mechanical performance has been the focus of numerous studies over the past two decades, because such understanding may inspire novel composite designs though biomimetics. This paper presents in detail uniaxial tension experiment performed on miniature nacre specimens. Large inelastic deformations were observed in hydrated condition, which were explained by sliding of the tablets on one another and progressive locking generated by their microscopic waviness. Fracture experiments were also performed, and for the first time the full crack resistance curve was established for nacre. A rising resistance curve is an indication of the robustness and damage tolerance of that material. These measurements are then discussed and correlated with toughening extrinsic mechanisms operating at the microscale. Moreover, specific features of the microstructure and their relevance to associated toughening mechanisms were identified. These features and mechanisms, critical to the robustness of the shell, were finely tuned over millions of years of evolution. Hence, they are expected to serve as a basis to establish guidelines for the design of novel man-made composites.