J. S. Church, A. S. Voda, A. Sutti, J. George, B. L. Fox, K. Magniez

In order to overcome interfacial incompatibility issues in natural fibre reinforced polymer bio-composites, surface modifications of the natural fibres using complex and environmentally unfriendly chemical methods is necessary. In this paper, we demonstrate that the interfacial properties of cellulose-based bio-composites can be tailored through surface adsorption of polyethylene glycol (PEG) based amphiphilic block copolymers using a greener alternative methodology. Mixtures of water or water/acetone were used to form amphiphilic emulsions or micro-crystal suspensions of PEG based amphiphilic block copolymers, and their deposition from solution onto the cellulosic substrate was carried out by simple dip-coating. The findings of this study evidence that, by tuning the amphiphilicity and the type of building blocks attached to the PEG unit, the flexural and dynamic thermo-mechanical properties of cellulose-based bio-composites comprised of either polylactide (PLA) or high density polyethylene (HDPE) as a matrix, can be remarkably enhanced. The trends, largely driven by interfacial effects, can be ascribed to the combined action of the hydrophilic and hydrophobic components of these amphiphiles. The nature of the interactions formed across the fibre–matrix interface is discussed. The collective outcome from this study provides a technological template to significantly improve the performance of cellulose-based bio-composite materials.

D. Yu, J. Y. Cai, X. Liu, J. S. Church, L. Wang

This paper introduces a new approach for immobilizing a quaternary ammonium moiety on a keratinous substrate for enhanced medical applications. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in the keratin, followed by reaction with[2-(acryloyloxy)ethyl]trimethylammonium chloride through thiol-ene click chemistry. The modified substrate was characterized with Raman and infrared spectroscopy, and assessed for its antibacterial efficacy and other performance changes. The results have demonstrated that the quaternary ammo-nium moiety has been effectively attached onto the keratin structure, and the resultant keratin substrate exhibits a multifunctional effect including antibacterial and antistatic properties, improved liquid moisture management property, improved dyeability and a non-leaching characteristic of the treated substrate.

D. Yu, J. Y. Cai, J. S. Church, L. Wang

This paper reports on a new method for improving the antistatic and liquid moisture management properties of keratinous materials. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in keratin with tris(2-carboxyethyl) phosphine hydrochloride and subsequent grafting of hydrophilic groups onto the reduced keratin by reaction with an acrylate sulfonate or acrylamide sulfonate through thiol−ene click chemistry. The modified substrates were characterized with Raman spectroscopy and scanning electron microscopy and evaluated for their performance changes in liquid moisture management, surface resistivity, and wet burst strength. The results have revealed that the thiol−acrylate reaction is more efficient than the thiol−acrylamide reaction, and the keratinous substrate modified with an acrylate sulfonate salt exhibits significantly improved antistatic and liquid moisture management properties.

H. E. Trueman, A. A. Walker, S. Weisman, P. M. Campbell, Z. Dong, M. G. Huson, A. L. Woodhead, J. S. Church

The use of coiled coil proteins as the basis of silk materials is an engineering solution that has evolved convergently in at least five insect lineages — the stinging hymenopterans (ants, bees, hornets), argid sawflies, fleas, lacewings, and praying mantises — and persisted throughout large radiations of these insect families. These coiled coil silk proteins share a characteristic distinct from other coiled coil proteins, in that they are fabricated into solid materials after accumulating as highly concentrated solutions within dedicated glands. Here, we relate the amino acid sequences of these proteins to the secondary and tertiary structural information available from biophysical methods such as X-ray scattering, nuclear magnetic resonance and Raman spectroscopy. We investigate conserved and convergently evolved features within these proteins and compare these to the features of classic coiled coil proteins including tropomyosin and leucine zippers. Our analysis finds that the coiled coil domains of insect silk proteins have several common structural anomalies including a high prevalence of alanine residues in core positions. These atypical features of the coiled coil fibrous proteins – which likely produce deviations from canonical coiled-coil structure – likely exist due to selection pressures related to the process of silk fabrication and the final function of the proteins.

T. D. Sutherland, A. Sriskantha, J. S. Church, T. Strive, H. Trueman, T. Kameda

Viruses are important for a range of modern day applications. However, their utility is limited by their susceptibility to temperature degradation. In this study, we report a simple system to compare the ability of different dried protein films to stabilize viruses against exposure to elevated temperatures. Films from each of three different silks, silkworm, honeybee silk and hornet silk, stabilized entrapped viruses at 37 °C better than films of albumin from bovine serum (BSA) and all four proteins provided substantially more stabilization than no protein controls. A comparison of the molecular structure of the silks and BSA films showed no correlation between the ability of the proteins to stabilize the virus and the secondary structure of the protein in the films. The mechanism of stabilization is discussed and a hypothesis is suggested to explain the superior performance of the silk proteins.

T. D. Rapson, J. S. Church, H. E. Trueman, H. Dacres, T. D. Sutherland, S. C. Trowell

In this work we investigate the use of coiled-coil silk proteins,produced in recombinant Escherichia coli,as a new material for immobilizing biosensors. Myoglobin was embedded in transparent honeybee silk protein films. Immobilized myoglobin maintained a high affinity for nitric oxide (K_D NO=52 μM) and good sensitivity with a limit of detection of 5 mM. The immobilized myoglobin–silk protein film was stable and could be stored as a dry film at room temperature for at least 60 days. The effect of immobilization on the structure of myoglobin was fully investigated using UV/visible, Fourier Transform Infrared and Raman spectroscopy, which indicated a weakening in the strength of the iron–histidine bond. This study demonstrates that recombinant coiled-coil silk proteins provide a safe and environmentally friendly alternative to sol–gels for stabilizing hemeproteins for use as optical biosensors.

A. P. Pierlot, A. L. Woodhead, J. S. Church

The realized mechanical properties of CNT macrostructures such as webs and yarns remain significantly lower than those of the individual CNTs. Structural changes induced by thermal annealing under inert atmosphere were assessed using Raman spectroscopy. Annealing above 1000 °C resulted in a marked decrease in the D/G ratio which can be attributed to an increase in the crystallite size or the distance between defects. The band component parameters obtained by spectral deconvolution reveal that the D band peak maximum shifts to slightly higher energy with increased annealing temperature. In contrast, the energy of the G band did not change. The full widths at half height (FWHH) of the D and G bands are seen to decrease with increasing annealing temperature. The tensile properties of the yarns have been investigated and it was found that the yarn tenacity did not improve with these structural changes. The effect of impurities in the annealing system such as oxygen, adsorbed water or organic surface contamination was also investigated.

Y-S. Li, J. S. Church, Andrea L. Woodhead, N. E. Vecchio, J. Yang

Tris-[3-(trimethoxysilyl)propyl] isocyanurate (TTPI) has been used as a precursor to prepare a sol using ethanol as the solvent under acidic conditions. The sol–gel was applied for the surface treatment of aluminum and copper. Infrared and Raman spectra have been recorded for pure TTPI and the TTPI sol, xerogel and TTPI sol–gel coated metals. From the vibrational spectra, TTPI is likely to have the C1 point group. Vibrational assignments are suggested based on group frequencies, the expected reactions in the sol–gel process and the vibrational studies of some related molecules. From the experimental infrared spectra of xerogels annealed at different temperatures and from the thermal-gravimetric analysis, it is found that the TTPI xerogel decomposes at around 450 °C with silica being the major decomposition product. A cyclic voltammetric study of the metal electrodes coated with different concentrations of TTPI ranging from 5% to 42% (v/v) has shown that the films with high concentrations of sol would provide better corrosion protection for aluminum and copper.