Deglycosylation of glucose oxidase to improve biosensors and biofuel cells

We demonstrate that a more efficient redox hydrogel structure can be achieved by engineering the size and the surface charge of the bioelectrocatalyst. Deglycosylated glucose oxidase (GOx) modified electrode exhibits higher current density than native GOx, for the same molar composition of the hydrogel. This improvement is very likely due to a more efficient hydrogel structure rather than a better intrinsic electron transfer between the FAD/FADH₂ redox center and the redox mediator.     

Crosslink effect and albumin adsorption onto chitosan/alginate multilayered systems: an in situ QCM-D study

The adsorption of HSA onto CHI/ALG multilayer assemblies was assessed in situ using QCM-D. It was found that the behavior of HSA on biomaterials surface can be tuned by adjusting parameters of the polyelectrolyte system such as pH, layer number, crosslinker and polymer terminal layer. Our results confirmed the key role of electrostatic interactions during HSA adsorption, since oppositely charged surfaces were more effective in promoting protein adhesion. QCM-D data revealed that crosslinking (CHI/ALG)(5) CHI films allows HSA to become adsorbed in physiological conditions. Our results suggested that the biological potential of biopolymers and the mild conditions of the LbL technique turn these natural nanoassemblies into a suitable choice to be used as pH-sensitive coatings.     

SOLUTIONS OF A SYSTEM OF FORCED BURGERS EQUATION IN TERMS OF GENERALIZED LAGUERRE POLYNOMIALS

In this article, we obtain explicit solutions of a linear PDE subject to a class of radial square integrable functions with a monotonically increasing weight function |x|n-1eβ|x|2/2,β≥ 0, x ∈ Rn. This linear PDE is obtained from a system of forced Burgers equation via the Cole-Hopf transformation. For any spatial dimension n 1, the solution is expressed in terms of a family of weighted generalized Laguerre polynomials. We also discuss the large time behaviour of the solution of the system of forced Burgers equation.     

Nanoporous aluminosilicate catalyst with 3D cage-type porous structure as an efficient catalyst for the synthesis of benzimidazole derivatives

Herein we demonstrate for the first time, the synthesis of benzimidazoles through the coupling of aldehydes with o-phenylenediamine by using highly acidic nanoporous aluminosilicate with 3D structure and cage-type pores as the catalyst. The catalyst resulted in excellent yields in short reaction times presumably due to its high acidity, large pore diameter, high surface area, and cage-type 3D porous structure.     

Influences of organometallic polymer‐derived catalyst dispersion on SWNT growth

Catalyst formation kinetics of a ferrocene‐containing homopolymer, polyferrocenylethylmethylsilane (PFEMS), is investigated as it relates to the catalysis of single walled carbon nanotubes (SWNTs) through a chemical vapor deposition (CVD) process. The formation and efficiency of the PFEMS‐based iron catalyst is compared with that of the corresponding polystyrene (PS)‐b‐PFEMS diblock copolymer. The PFEMS homopolymer contains 23 wt % iron, while PS‐b‐PFEMS, with a 25 vol % PFEMS content, is only 6% iron. Despite its lower iron content, spin‐cast PS‐b‐PFEMS films on SiO₂/Si substrates produce more active iron sites than spin‐cast PFEMS films during CVD growth of SWNTs. This is related to the self‐assembly of the block copolymer, where PFEMS domains are well dispersed in the PS matrix, which degrades at a CVD temperature of 920 °C to leave catalytically active elemental iron behind. On the contrary, the pure PFEMS films contain a high percentage of iron and silicon, which tend to transform into ceramic‐coated iron at this high temperature, thus rendering the iron inactive towards SWNT growth. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 758–765, 2007     

N-doping and coalescence of carbon nanotubes: synthesis and electronic properties

Self-assembly pyrolytic routes to large arrays (<2.5 cm²) of aligned CN_x nanotubes (15–80 nm OD and <100 μm in length) are presented. The method involves the thermolysis of ferrocene/melamine mixtures (5:95) at 900–1000 °C in the presence of Ar. Electron energy loss spectroscopy (EELS) reveals that the N content varies from 2–10%, and can be bonded to C in two different fashions (double-bonded and triple-bonded nitrogen). The electronic densities of states (DOS) of these CN_x nanotubes, using scanning tunneling spectroscopy (STS), are presented. The doped nanotubes exhibit strong features in the conduction band close to the Fermi level (0.18 eV). Using tight-binding and ab initio calculations, we confirm that pyridine-like (double-bonded) N is responsible for introducing donor states close to the Fermi Level. These electron-rich structures are the first example of n-type nanotubes. Finally, it will be shown that moderate electron irradiation at 700–800 °C is capable of coalescing single-walled nanotubes (SWNTs). The process has also been studied using tight-binding molecular dynamics (TBMD). Vacancies induce the coalescence via a zipper-like mechanism, which has also been observed experimentally. These vacancies trigger the organization of atoms on the tube lattices within adjacent tubes. These results pave the way to the fabrication of nanotube heterojunctions, robust composites, contacts, nanocircuits and strong 3D composites using N-doped tubes as well as SWNTs. Received: 10 October 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

General description of the adsorption of proteins at their iso-electric point in nanoporous materials

A simple but remarkably precise geometric pore-filling model is proposed and experimentally validated for the adsorption of proteins at their iso-electric point (pI) in nanoporous materials. Three different globular proteins-lysozyme, myoglobin, and bovine serum albumin-are used as model proteins to study protein adsorption on two types of ordered mesoporous materials-silica and carbon-which allows us to study the effects of protein and surface structure on the protein adsorption mechanism. The geometric pore-filling model confirms that proteins are closely packed inside the pore channels of mesoporous materials, leading to an exceptionally large protein loading capacity. A relationship for the amount of adsorbed protein as a function of protein size, nanopore volume, and pore diameter is derived. The pore space gradually fills up to complete packing of the available pore space at the highest protein concentration. The high precision of the geometric pore-filling model demonstrates its utility to predict the protein adsorption capacity of ordered nanoporous materials.     

Dual responsive nanostructured surfaces for biomedical applications

In this paper, we describe the construction and characteristics of thermoresponsive, thin nanostructured films prepared by layer-by-layer sequential assembly of chitosan-graft-NIPAAm and alginate. FTIR and (1)H NMR spectra have confirmed the introduction of NIPAAm moieties onto the chitosan backbone. The LCST of the synthesized copolymer was found to be around 31-33 °C. The formation of the polyelectrolyte multilayers containing the copolymer and alginate was followed in situ by quartz crystal microbalance with dissipation monitoring technique and ex situ by UV-vis measurements. Our results revealed the linear increase of the multilayer film growth and the influence of the presence of salt. Moreover, AFM analysis has confirmed that PNIPAAm is able to reconform upon temperature swaps even when combined with other layers in a polyelectrolyte multilayer, demonstrating that the nanoassemblies are thermoresponsive. Preliminary results showed that, upon reducing culture temperature below PNIPAAm LCST, a gradual detachment of cell sheets from these PNIPAAm-based coatings has occurred.