Studies on spinning and rheological behaviors of regenerated silk fibroin/<Emphasis Type="Italic">N-</Emphasis>methylmorpholine-<Emphasis Type="Italic">N-</Emphasis>oxide·H<Subscript>2</Subscript>O solutions

In this paper, N-Methylmorpholine-N-Oxide (NMMO) was used as solvent for regenerated silk fibroin (RSF). Concentrated solutions with RSF content from 10 to 25 wt% were obtained by dissolving RSF film into NMMO monohydrate. The spinning and rheological properties of RSF/NMMO·H₂O solutions were studied by a simple piston type single filament spinning apparatus and HAAKE RS150L rheometer, respectively. The results are discussed to understand the influences of shear rate, temperature and RSF concentration on the rheological behaviors of RSF/NMMO·H₂O and to choose appropriate process condition for spinning. Spinning was performed using a dry-wet spinning process. The regenerated silk fibre was prepared successfully and the tenacity can reach to 3.07cN/dtex.     

Fabrication and characterization of fibroin solution and nanoparticle from silk fibers of Bombyx mori

The present investigation aims to study the effect of degumming time on the structural property of silk fiber obtained by silk cocoons of Bombyx mori, followed by preparation of the regenerated silk fibroin (RSF) solution which can be subsequently molded into silk nanoparticles. Silk fibers degummed with different media at different time intervals were investigated for the degumming loss and were characterized using Ffourier transform infrared (FTIR), differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). Maximum degumming was observed when the fibers were treated with sodium carbonate for 60 min. SEM and atomic force microscopy (AFM) images of RSF solution showed aggregation of silk globules resulting in formation of solvated macrochains and giving it an appearance of island-like morphology. Blank silk nanoparticles prepared from the RSF solution showed a smooth and spherical surface devoid of any adhesion using SEM, AFM, and transmission electron microscopy (TEM). The prepared silk nanoparticles may further be explored for loading drug entities and targeting.     

Fabrication and Fibroblast Attachment Property of Regenerated Silk Fibroin/Tetramethoxysilane Nanofibrous Biocomposites

In this study, regenerated silk fibroin (RSF)/tetramethoxysilane (TMOS) composite electrospun fibers with improved hydrophilicity were successfully prepared by electrospinning method, which was superior for fibroblast attachment. The electrospinning process caused adjacent fibers to “weld” at contact points, as confirmed by scanning electron microscope (SEM) analysis. Fourier transform infrared spectroscopy (FTIR) showed that TMOS has been well incorporated into the silk fibroin electrospun fibers. Thermogravimetric analysis (TGA) was carried out to quantify the water content in RSF/TMOS composite electrospun fibers. The cytotoxicity and L929 adhesion of three‐dimensional RSF/TMOS fibrous biocompoaites were investigated and compared to pure RSF membrane. The water contact angle of RSF/TMOS nanofibrous composites showed a sharp decrease compared to the pure RSF electrospun fibers, which has a great effect on the early stage of cell attachment behavior due to an relatively enhanced hydrophilicity.     

Rapid,High‐Resolution Magnetic Microscopy of Single Magnetic Microbeads

Magnetic microparticles or “beads” are used in a variety of research applications from cell sorting through to optical force traction microscopy. The magnetic properties of such particles can be tailored for specific applications with the uniformity of individual beads critical to their function. However, the majority of magnetic characterization techniques quantify the magnetic properties from large bead ensembles. Developing new magnetic imaging techniques to evaluate and visualize the magnetic fields from single beads will allow detailed insight into the magnetic uniformity, anisotropy, and alignment of magnetic domains. Here, diamond‐based magnetic microscopy is applied to image and characterize individual magnetic beads with varying magnetic and structural properties: ferromagnetic and superparamagnetic/paramagnetic, shell (coated with magnetic material), and solid (magnetic material dispersed in matrix). The single‐bead magnetic images identify irregularities in the magnetic profiles from individual bead populations. Magnetic simulations account for the varying magnetic profiles and allow to infer the magnetization of individual beads. Additionally, this work shows that the imaging technique can be adapted to achieve illumination‐free tracking of magnetic beads, opening the possibility of tracking cell movements and mechanics in photosensitive contexts.     

SILK.IT project: Silk Italian Technology for industrial biomanufacturing

Silk fibroin is a natural protein that constitutes the core fibre of the silkworm cocoon. Recently, a great deal of attention is being paid to the use of the regenerated silk fibroin (RSF) solution that can be obtained by water-processing of the cocoon fibre. Indeed, thanks to its chemical and physical properties it has been shown that substrates obtained by RSF can be used as biomaterials for several biomedical and technological applications. In this context, silk fibroin could be exploited as raw material that can become a platform for eco-sustainable manufacturing.The project SILK.IT, coordinated by the CNR-ISOF, within the framework of the Flagship Project “Factory of the Future”, a research programme approved by the Interministerial Committee for Economic Planning (CIPE), aims to support this assumption by developing methods and protocols to use this silk fibroin as new material for advanced biotechnologies and sustainable manufacturing.The main goal of the project is to establish and control the whole-chain underpinning the silk fibroin-based technology, and to promote its up-scaling from the laboratory to industrial scale, targeting bio-photonics for biomedical application.The recent results obtained by the project are herein reported as key building block towards proposed achievement to establish a sustainable and process-controlled silk-based bio-manufacturing of the future.     

Silk microfibrous mats with long-lasting antimicrobial function

The controlled release of antibiotic drugs to injured sites has great advantages over the conventional intravenous administration of antibiotics,which is associated with systemic toxicity,for wound care.Electrospun nanofibrous/microfibrous mats,with a similar structure to the native extracellular matrix,is a promising wound dressing.Herein,drug-loaded halloysite nanotubes(HNTs)incorporated into regenerated silk fibroin(RSF)microfibrous mats were prepared by electrospinning to achieve sustained drug release and long-lasting antimicrobial protection.A broad-spectrum antibiotic,tetracycline hydrochloride(TCH),was selected as the model drug.Transmission electron microscopic images revealed that the TCH-loaded HNTs were homogeneously embedded in the RSF electrospun microfibers without significant changes in morphology.The drug release profiles showed that the RSF microfibrous mats with TCH-loaded HNTs exhibited a significantly reduced burst phase and a long release time over two weeks compared to the pure TCH-loaded HNTs and the TCH-loaded RSF microfibrous mats without HNTs.These results were attributed to the two-step release of TCH first from the HNTs and then RSF matrix in the electrospun mats.Finally,the antimicrobial properties of the RSF microfibrous mats with TCH-loaded HNTs were evaluated using both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria.The results demonstrated long-lasting antimicrobial activity for at least one week,showing the great potential of TCH-loaded RSF microfibrous mat as a wound dressing material.Therefore,these TCHloaded RSF microfibrous mats with excellent biocompatibility and sustained antimicrobial protection are extremely attractive systems for clinical applications.     

Influence of Formulation and Other Factors on the Release of Chlorpheniramine Mateate from Polymer Coated Beads

Controlled release beads containing chlorpheniramine maleate, coated with Eudragit RL and RS, were prepared using the Wurster process. The effect of membrane thickness, polymer ratio of the coating material, agitation speed and pH of the dissolution medium on drug release were investigated using the USP dissolution basket method. The in vitro release of drug was described adequately by a previously published equation. The release rate constant (K) was dependent on the membrane thickness, the polymer ratio and pH of the dissolution medium. On the other hand, agitation speed used in this study did not have any influence on the release of the drug.     

Molecularly imprinted polymer beads: suspension polymerization using a liquid perfluorocarbon as the dispersing phase

A suspension polymerization technique suitable for molecular imprinting is described, based on the use of a liquid perfluorocarbon as the dispersing phase. This dispersant does not interfere with the interactions between functional monomers and print molecules required for the recognition process during molecular imprinting. The method produces polymer beads, with almost quantitative yield, which can be used after only a simple washing step. An acrylate polymer with perfluorocarbon and poly(oxyethylene) ester groups was used to stabilize an emulsion of functional monomer, cross-linker, print molecule, initiator, and porogenic solvent in perfluoro(methylcyclohexane). Initiation of polymerization by UV irradiation resulted in polymer beads. The average bead size could be controlled between about 50 and 5 μm by varying the amount of stabilizing polymer. SEM of the beads indicated spherical particles with morphology typical of beads made by suspension polymerization. The technique was applicable to a range of conditions typically used for molecular imprinting. A detailed chromatographic study of the polymer beads confirmed that α values and resolution factors were similar to those achieved with traditional ground and sieved imprinted polymers. Small (5 μm) beaded packings gave low back pressure and rapid diffusion, giving good separation even at high flow rates.     

Influence of Formulation and Other Factors on the Release of Chlorpheniramine Mateate from Polymer Coated Beads

Abstract

Controlled release beads containing chlorpheniramine maleate, coated with Eudragit RL and RS, were prepared using the Wurster process. The effect of membrane thickness, polymer ratio of the coating material, agitation speed and pH of the dissolution medium on drug release were investigated using the USP dissolution basket method. The in vitro release of drug was described adequately by a previously published equation. The release rate constant (K) was dependent on the membrane thickness, the polymer ratio and pH of the dissolution medium. On the other hand, agitation speed used in this study did not have any influence on the release of the drug.     

Extensive collection of femtolitre pad secretion droplets in the beetle Leptinotarsa decemlineata allows nanolitre microrheology

Pads of beetles are covered with long, deformable setae, each ending in a micrometric terminal plate coated with secretory fluid. It was recently shown that the layer of the pad secretion covering the terminal plates is responsible for the generation of strong attractive forces. However, less is known about the fluid itself because it is produced in an extremely small quantity. We present here the first experimental investigation of the rheological properties of the pad secretion in the Colorado potato beetle Leptinotarsa decemlineata (Coleoptera, Chrysomelidae). Because the secretion is produced in an extremely small amount at the level of the terminal plate, we first developed a procedure based on capillary effects to collect the secretion for rheological experiments. In order to study the collected fluid (less than 1 nl) through passive microrheology, we managed to incorporate micrometric probes (melamine beads) that were initially in the form of a dry powder. Finally, the bead thermal motions were observed optically and recorded to determine the mechanical properties of the surrounding medium. We achieved this quantitative measurement with the collected volume, which is much smaller than the usual 1 µl sample volume required for this technique. Surprisingly, the beetle secretion was found to behave as a purely viscous liquid, of high viscosity (about 100 times that of water). This suggests that no specific complex fluid behaviour is needed by this adhesive system during beetle locomotion. We describe a scenario for the contact formation between the spatula at the setal tip and a smooth substrate, during the insect walk. We show that the attachment dynamics of the insect pad computed from the high measured viscosity is in good agreement with the observed insect pace. We finally discuss the consequences of the viscosity of the secretion on the insect adhesion.     

Characterization of the high-temperature behaviour of a glass-filled polymer composite

The decomposition kinetics and material properties of a decomposing, expanding glass-filled polymer composite have been measured. In addition, the morphology as a function of the stage of decomposition and the decomposition-induced material damage have been monitored visually by scanning electron microscopy. The combination of these data was used to characterize the high-temperature behaviour of the material.     

Preparations of bifunctional polymeric beads simultaneously incorporated with fluorescent quantum dots and magnetic nanocrystals

Bifunctional polystyrene beads simultaneously incorporated with fluorescent CdTe quantum dots (Q-dots) and superparamagnetic Fe(3)O(4) nanocrystals were prepared by a modified mini-emulsion polymerization method, in which polymerizable surfactants were used as both phase transfer agent for aqueous colloidal nanoparticles and emulsifier. In addition, silica coating was also introduced to Fe(3)O(4) nanocrystals for regulating the internal structure of the composite beads. Transmission electron microscopy, confocal fluorescence microscopy and conventional spectroscopy were used to characterize the composite beads, as well as the polymerizable surfactant-coated CdTe Q-dots and silica-coated Fe(3)O(4) nanoparticles. Different mixing methods were also attempted in order to vary the size of the resultant bifunctional beads.     

非线性黏弹复合材料有效性质

提出了一个细观力学模型 , 用于预测非线性黏弹聚合物基复合材料的有效性质。该方法利用广义割线模量方法对单积分型热力学本构进行线性化 , 并运用 Laplace变换技术将黏性问题转化为弹性问题。利用热力学本构拟合高密度聚乙烯的实验数据 , 得到基体的材料参数。 利用该模型计算了玻璃微珠填充高密度聚乙烯复合材料(GB/HDPE)在恒应变率下的应力应变关系 , 计算结果与文献实验结果吻合较好。数值计算结果表明 GB/HDPE复合材料表现出明显的非线性力学行为。 该细观力学模型可以很好地预测复合材料非线性黏弹性性质。      

Facile fabrication of the porous three-dimensional regenerated silk fibroin scaffolds

In the present work, we report a new facile method to fabricate porous three-dimensional regenerated silk fibroin (RSF) scaffolds through n-butanol- and freezing-induced conformation transition and phase separation. The effects of RSF concentration, freezing temperature and n-butanol addition on the microstructure, the secondary structures of silk fibroin and apparent mechanical properties of the RSF scaffolds were investigated by SEM, ¹³C CP-MAS NMR spectra and mechanical testing, respectively. By adjusting the RSF concentration and n-butanol addition, the pore size of the scaffold could be controlled in the range from of 10 μm to 350 μm with 84%–98% of porosity. The tensile strength of the wet scaffold reached the maximum of 755.2 ± 33.6 kPa when the concentration of RSF solution was increased to 15% w/w. Moreover, post-treatment with ethanol further induced conformation transition of RSF from random coil or helix to β-sheet. The porous scaffolds prepared by this facile and energy-saving method with good biocompatibility will have great potential for application in tissue engineering.     

Effect of cationic groups on the adhesivity of peritoneal macrophages to polymeric beads

This study demonstrates the adhesion of macrophages to polymer beads from a copolymer of hydroxyethyl methacrylate and dimethyl aminoethyl methacrylate intraperitoneally injected into the rat. Dimethyl aminoethyl methacrylate exhibited a stimulatory effect on macrophage adhesion 5 h after injection of the beads. Electron microscopy demonstrated protein adsorption on the surface of the beads. Protein fibres between the cell surface and beads were observed. The experimental system used minimizes the influence of tissue damage at macrophage recognition of polymers. This method seems to be suitable for short-term investigation of macrophage-polymer interaction.     

Simulation of bead-and-spring chain models for semidilute polymer solutions in shear flow

We report preliminary results of simulations of the steady-state rheological behavior for semidilute polymer solutions of head-and-spring chain models in planar Couette now. The simulations include examination of the effects of excluded volume. hydrodynamic interactions and density. Hydrodynamic interactions are modeled by the Rotne -Prager Yamakawa tensor. The simulations are based on the nonequilibrium Brownian dynamics algorithm of Ermak and McCammon. In addition to the spring potential between neighboring beads in the chain. the interaction between any two beads in the solution is modeled using a shifted, repulsive Leonard-Jones potential. Lees Edward sliding brick boundary conditions are used for consistency with the Couette flow field.Paper presented at the Twelfth Symposium on Thermophysical Properties. June 19–24. 1994, Boulder. Colorado. U.S.A.     

同轴静电纺再生丝素/丝胶蛋白纤维的制备及其形态结构表征

模仿蚕丝的组成和结构,利用同轴静电纺丝法制备了以再生丝素蛋白（RSF）为＂芯＂、丝胶蛋白（SS）为＂皮＂的双组分静电纺纤维。通过扫描电镜和透射电镜研究了内层纺丝液流速（Qc）、电压（U）、接收距离（D）以及场强（E）等参数对同轴静电纺RSF/SS纤维形态结构的影响。研究结果表明纤维的平均直径在1400～2100nm左右,皮-芯层结构清晰;Qc对纤维皮-芯层结构的影响较大,过大的内层纺丝液流速会因外层丝胶对内层丝素的包裹不均匀而导致偏芯现象;随E的增加（U增加或D减小）,纤维的直径及其分布显著减小,皮-芯层结构清晰;相同E下,高电压、长距离利于纤维的细化,使直径变细且分布均匀,皮-芯层结构明显。     

Evaluating the orientation and dispersion of carbon nanotubes inside nanocomposites by a focused-ion-beam technique

Poly ether ether ketone (PEEK)/multi-walled carbon nanotubes (MWNTs) nanocomposites were fabricated to characterize and understand the orientation and dispersion of carbon nanotubes (CNTs) in a polymer matrix. A focused-ion-beam (FIB) technique was used for milling the nanocomposite by a focused gallium ion beam, and the MWNTs were carefully observed. The PEEK preferentially disappeared when the Ga⁺ ion beam milled the composite, and MWNTs were exposed on the surface of composites. Using this method, it is very easy to estimate and directly evaluate the orientation of the MWNTs in the polymer matrix even though they are embedded in the polymer matrix. Transmission electron microscopy (TEM) was employed to characterize the detailed position of the nanotubes in the PEEK matrix.     

Bead compacts. II. Evaluation of rapidly disintegrating nonsegregating compressed bead formulations

In this study, three techniques for the prevention or mitigation of polymer coat fracture on compaction of sustained-release beads into tablets were investigated. All techniques in this paper were evaluated without the addition of any cushioning excipients, but rather by spray coating these excipients to avoid segregation during product manufacturing. First, it was shown that use of swellable polymers such as polyethylene oxide (PEO) serves a unique and effective role in preventing polymer coat rupture. PEO was spray coated between the ethylcellulose (EC) and microcrystalline cellulose (MCC) coats to evaluate its cushioning effect. The compacted PEO layered beads, on dissolution, disintegrated into individual beads with sustained drug release of up to 8 hr. It is postulated that the PEO was hydrated and formed a gel that acts as a sealant for the cracks formed in the ruptured polymer coating (sealant-effect compacts). Second, EC-coated drug-layered beads were also overcoated with cushioning excipients such as polyethylene glycol (PEG) and MCC with an additional coating of a disintegrant. These beads were compressed at pressures of 125, 500, and 1000 pounds into caplets and, on dissolution testing, disintegrated into individual beads when the dissolution medium was switched from simulated gastric to intestinal fluid. The dissolution profiles show that the polymer coat was partly disrupted on compaction, leading to a total drug release in 8-10 hr. Third, EC-coated beads were also granulated with cushioning excipient and compressed. This approach also resulted in a ruptured polymer coat on the beads, but at higher compaction pressure produced a partially disintegrating matrix caplet that showed a nearly zero-order sustained drug release for 24 hr. The effect of bead size and polymer coat thickness was also investigated.     

In-process rheometry as a PAT tool for hot melt extrusion

Real time measurement of melt rheology has been investigated as a Process Analytical Technology (PAT) to monitor hot melt extrusion of an Active Pharmaceutical Ingredient (API) in a polymer matrix. A developmental API was melt mixed with a commercial copolymer using a heated twin screw extruder at different API loadings and set temperatures. The extruder was equipped with an instrumented rheological slit die which incorporated three pressure transducers flush mounted to the die surface. Pressure drop measurements within the die at a range of extrusion throughputs were used to calculate rheological parameters, such as shear viscosity and exit pressure, related to shear and elastic melt flow properties, respectively. Results showed that the melt exhibited shear thinning behavior whereby viscosity decreased with increasing flow rate. Increase in drug loading and set extrusion temperature resulted in a reduction in melt viscosity. Shear viscosity and exit pressure measurements were found to be sensitive to API loading. These findings suggest that this technique could be used as a simple tool to measure material attributes in-line, to build better overall process understanding for hot melt extrusion.