Green electrospun pantothenic acid/silk fibroin composite nanofibers: fabrication, characterization and biological activity

Silk fibroin (SF) from Bombyx mori has many established excellent properties and has found various applications in the biomedical field. However, some abilities or capacities of SF still need improving to meet the need for using practically. Indeed, diverse SF-based composite biomaterials have been developed. Here we report the feasibility of fabricating pantothenic acid (vitamin B5, VB5)-reinforcing SF nanofibrous matrices for biomedical applications through green electrospinning. Results demonstrated the successful loading of D-pantothenic acid hemicalcium salt (VB5-hs) into resulting composite nanofibers. The introduction of VB5-hs did not alter the smooth ribbon-like morphology and the silk I structure of SF, but significantly decreased the mean width of SF fibers. SF conformation transformed into β-sheet from random coil when composite nanofibrous matrices were exposed to 75% (v/v) ethanol vapor. Furthermore, nanofibers still remained good morphology after being soaked in water environment for five days. Interestingly, as-prepared composite nanofibrous matrices supported a higher level of cell viability, especially in a long culture period and significantly assisted skin cells to survive under oxidative stress compared with pure SF nanofibrous matrices. These findings provide a basis for further extending the application of SF in the biomedical field, especially in the personal skin-care field.

Drying and denaturation characteristics of α-lactalbumin, β-lactoglobulin, and bovine serum albumin in a convective drying process

Drying and denaturation kinetics of aqueous droplets of α-lactalbumin (α-lac), β-lactoglobulin (β-lg), and bovine serum albumin (BSA) were measured in a convective drying environment. Single droplets having an initial droplet diameter of 2 ± 0.1 mm and containing 10% (w/v) protein concentration were dried using conditioned air (65 and 80 °C, 2-3% RH, 0.5 m/s velocity) for 600 s. The denaturation of these proteins was measured by using reversed-phase HPLC. At the end of 600 s of drying 13.3 and 19.4% α-lac was found to be lost due to denaturation at 65 and 80 °C, respectively. Up to 31.0% of β-lg was found to be denatured, whereas BSA was not found to be significantly (p > 0.05) denatured in these drying conditions. The formation and strength of skin and the associated morphological features were found to be linked with the degree of denaturation of these proteins. The secondary structure of these proteins was significantly (p < 0.05) affected and altered by the drying stresses. The β-sheet and random coil contents were increased in α-lac by 6.5 and 4.0%, respectively, whereas the α-helix and β-turn contents decreased by 5.5 and 5.0%, respectively. The β-sheet and random coil contents in β-lg were increased by 7.5 and 2.0%, respectively, whereas the α-helix and β-turn contents decreased by 3.5 and 6.0%, respectively. In the case of BSA the β-sheet, α-helix, and random coil contents were found to increase, whereas the β-turn content decreased.

Self-assembled multimicellar vesicles via complexation of a rigid conjugated polymer with an amphiphilic block copolymer

A viable method of encapsulating block copolymer micelles inside vesicles using a conjugated polymer is reported in this study. Self-assembly and complexation between an amphiphilic block copolymer poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) and a rod-like conjugated polymer polyaniline (PANI) in aqueous solution were studied using transmission electron microscopy, atomic force microscopy and dynamic light scattering. The complexation and morphology transformation were driven by electrostatic interaction between PANI and the PAA block of the block copolymer. Addition of PANI to PMMA-b-PAA induced the morphology transformation from micelles to irregular vesicles through vesicles, thick-walled vesicles (TWVs) and multimicellar vesicles (MMVs). Among the observed morphologies, MMVs were observed for the first time. Morphology transformation was studied as a function of aniline/acrylic acid molar ratio ([ANI]/[AA]). Micelles were observed for the pure block copolymer, while vesicles and TWVs were observed at [ANI]/[AA] = 0.1 and 0.3, respectively. MMVs were observed at [ANI]/[AA] = 0.5 and irregular vesicles were observed for molar ratios at 0.7 and above. Clearly, a conjugated polymer like polyaniline can induce a morphology transformation even at its lower concentrations and produce complex morphologies.

A first step towards a simple in-line shape compensation routine for the roll forming of high strength steel

The roll forming process is increasingly used in the automotive industry for the manufacture of structural and crash components from Ultra High Strength Steel (UHSS). Due to the high strength of UHSS (<1GPa) even small and commonly observed material property variations from coil to coil can result in significant changes in material yield and through that affect the final shape of the roll formed component. This requires the re-adjustment of tooling to compensate for shape defects and maintain part geometry resulting in costly downtimes of equipment. This paper presents a first step towards an in-line shape compensation method that based on the monitoring of roll load and torque allows for the estimation of shape defects and the subsequent re-adjustment of tooling for compensation. For this the effect of material property variation on common shape defects observed in the roll forming process as well as measurable process parameters such as roll load and torque needs to be understood. The effect of yield strength and material hardening on roll load and torque as well as longitudinal bow is investigated via experimental trials and numerical analysis. A regression analysis combined with Analysis of Variance (ANOVA) techniques is employed to establish the relationships between the process and material parameters and to determine their percentage influence on longitudinal bow, roll load and torque. The study will show that the level of longitudinal bow, one of the major shape defects observed in roll forming, can be estimated by variations in roll load and torque.

What makes a good graphene-binding peptide? Adsorption of amino acids and peptides at aqueous graphene interfaces

Investigation of the non-covalent interaction of biomolecules with aqueous graphene interfaces is a rapidly expanding area. However, reliable exploitation of these interfaces in many applications requires that the links between the sequence and binding of the adsorbed peptide structures be clearly established. Molecular dynamics (MD) simulations can play a key role in elucidating the conformational ensemble of peptides adsorbed at graphene interfaces, helping to elucidate these rules in partnership with experimental characterisation. We apply our recently-developed polarisable force-field for biomolecule-graphene interfaces, GRAPPA, in partnership with advanced simulation approaches, to probe the adsorption behaviour of peptides at aqueous graphene. First we determine the free energy of adsorption of all twenty naturally occurring amino acids (AAs) via metadynamics simulations, providing a benchmark for interpreting peptide-graphene adsorption studies. From these free energies, we find that strong-binding amino acids have flat and/or compact side chain groups, and we relate this behaviour to the interfacial solvent structuring. Second, we apply replica exchange with solute tempering simulations to efficiently and widely sample the conformational ensemble of two experimentally-characterised peptide sequences, P1 and its alanine mutant P1A3, in solution and adsorbed on graphene. For P1 we find a significant minority of the conformational ensemble possesses a helical structure, both in solution and when adsorbed, while P1A3 features mostly extended, random-coil conformations. In solution this helical P1 configuration is stabilised through favourable intra-peptide interactions, while the adsorbed structure is stabilised via interaction of four strongly-binding residues, identified from our metadynamics simulations, with the aqueous graphene interface. Our findings rationalise the performance of the P1 sequence as a known graphene binder.

In vitro simulator with numerical stress analysis for evaluation of stent-assisted coiling embolization in cerebral aneurysm treatments

There are several complications associated with Stent-assisted Coil Embolization (SACE) in cerebral aneurysm treatments, due to damaging operations by surgeons and undesirable mechanical properties of stents. Therefore, it is necessary to develop an in vitro simulator that provides both training and research for evaluating the mechanical properties of stents.

Multi-output interval type-2 fuzzy logic system for protein secondary structure prediction

A new multi-output interval type-2 fuzzy logic system (MOIT2FLS) is introduced for protein secondary structure prediction in this paper. Three outputs of the MOIT2FLS correspond to three structure classes including helix, strand (sheet) and coil. Quantitative properties of amino acids are employed to characterize twenty amino acids rather than the widely used computationally expensive binary encoding scheme. Three clustering tasks are performed using the adaptive vector quantization method to construct an equal number of initial rules for each type of secondary structure. Genetic algorithm is applied to optimally adjust parameters of the MOIT2FLS. The genetic fitness function is designed based on the Q3 measure. Experimental results demonstrate the dominance of the proposed approach against the traditional methods that are Chou-Fasman method, Garnier-Osguthorpe-Robson method, and artificial neural network models.

Complex coacervation between flaxseed protein isolate and flaxseed gum

Flaxseed protein isolate (FPI) and flaxseed gum (FG) were extracted, and the electrostatic complexation between these two biopolymers was studied as a function of pH and FPI-to-FG ratio using turbidimetric and electrophoretic mobility (zeta potential) tests. The zeta potential values of FPI, FG, and their mixtures at the FPI-to-FG ratios of 1:1, 3:1, 5:1, 10:1, 15:1 were measured over a pH range 8.0-1.5. The alteration of the secondary structure of FPI as a function of pH was studied using circular dichroism. The proportion of a-helical structure decreased, whereas both β-sheet structure and random coil structure increased with the lowering of pH from 8.0 to 3.0. The acidic pH affected the secondary structure of FPI and the unfolding of helix conformation facilitated the complexation of FPI with FG. The optimum FPI-to-FG ratio for complex coacervation was found to be 3:1. The critical pH values associated with the formation of soluble (pHc) and insoluble (pHΦ1) complexes at the optimum FPI-to-FG ratio were found to be 6.0 and 4.5, respectively. The optimum pH (pHopt) for the optimum complex coacervation was 3.1. The instability and dissolution of FPI-FG complex coacervates started (pHΦ2) at pH2.1. These findings contribute to the development of FPI-FG complex coacervates as delivery vehicles for unstable albeit valuable nutrients such as omega-3 fatty acids.