Silk fibroin protein

Correction for 'Preparation of hexagonal GeO 2 particles with particle size and crystallinity controlled by peptides, silk and silk-peptide chimeras' by Estefania Boix et al., Dalton Trans., 2014, 43, 16902-16910. The following acknowledgment was inadvertently omitted from the paper. We gratefully acknowledge receipt of an EPSRC research grant (EP/E048439/1) 'A novel approach to nanoscale materials assembly using bioengineered spider silk fusion proteins: a generic approach' for the aspects of research on the silk chimeras presented in this article.

The objective of the present study is to investigate the possibility of preparing pure protein microspheres from regenerated silk fibroin (RSF). It is found that RSF microspheres, with predictable and controllable sizes ranging from 0.2 to 1.5 mm, can be prepared via mild selfassembling of silk fibroin molecular chains. The merits of this novel method include a rather simple production apparatus and no potentially toxic agents, such as surfactants, initiators, crosslinking agents, etc. The results show that the particle size and size distribution of RSF microspheres are greatly affected by the amount of ethanol additive, the freezing temperature and the concentration of silk fibroin. Finally, the mechanism of RSF microspheres formation is also discussed based on our experimental results.

Nacre is the main component of the pearl oyster shells and it is synthesized by specialized soluble and insoluble shell matrix proteins. Insoluble proteins from the decalcification of the shell are the less studied proteins due to the technical problems to isolate them from the organic matrix. In this study, an insoluble shell matrix protein from Pinctada mazatlanica, pearlin (Pmaz-pearlin), was successfully cloned from the mantle tissue, and the native protein isolated from the shell was functionally characterized. The full coding sequence of Pmaz-pearlin mRNA consists of 423 base pairs, which encode to a 16.3 kDa pearlin. Analysis of the deduced amino acid sequence revealed that Pmaz-pearlin contained four acidic regions, an NG repeat domain, and Cys conserved residues, the latter potentially forms four disulfide bridges which might stabilize the protein structure. The isolated protein from the shell is a glycoprotein of ~ 16.74 kDa which can produce aragonite and calcite crystals...

A protein-polymer blend system based on silkworm silk fibroin (SF) and polylactic acid (PLA) was systematically investigated to understand the interaction and miscibility of proteins and synthetic biocompatible polymers in the macro-and micro-meter scales, which can dramatically control the cell responses and enzyme biodegradation on the biomaterial interface. Silk fibroin, a semicrystalline protein with beta-sheet crystals, provides controllable crystal content and biodegradability; while noncrystallizable PDLLA provides hydrophobicity and thermal stability in the system. Differential scanning calorimetry (DSC) combined with scanning electron microscope (SEM) showed that the morphology of the blend films was uniform on a macroscopic scale, yet with tunable micro-phase patterns at different mixing ratios. Fourier transform infrared analysis (FTIR) revealed that structures of the blend system, such as beta-sheet crystal content, gradually changed with the mixing ratios. All blended samples have better stability than pure SF and PLA samples as evidenced by thermogravimetric analysis. Protease XIV enzymatic study showed that the biodegradability of the blend samples varied with their blending ratios and microscale morphologies. Significantly, the topology of the micro-phase patterns on the blends can promote cell attachment and manipulate the cell growth and proliferation. This study provided a useful platform for understanding the fabrication strategies of protein-synthetic polymer composites that have direct biomedical and green chemistry applications.

Silk fibroin (SF) is a sustainable material explored with success in the textile and biomedical industries. This protein has outstanding mechanical and electrical properties that could be used for advanced technological applications. In this work, silk fibroin fibrous membranes were processed by electrospinning, with conditions obtained through orthogonal experimental design. Due to their high-water affinity, the membranes were stabilized against aqueous environments by exposure to methanol (MeOH) in vapor phase. Individual SF fibres present an apparent piezoelectric constant (d33) of 38 ± 2 pm/V for the as-spun ones and 28 ± 3 pm/V for those submitted to MeOH in vapor phase, a piezoelectric voltage coefficient (g ) 33 of 1.05 and 0.53 Vm.N -1 , respectively, a mechano-sensibility of 0.15 V kPa -1 , an energy storage capacity of 85 μJ, and an efficiency up to 21%. When the SF is submitted to MeOH in vapor phase, no effect was observed in the protein secondary structures. This work represents a new insight into the origin of the piezoelectric properties of SF and opens new opportunities for applications in microelectronics engineering for self-powered epidermal electronics, implantable medical devices, and personalized health care systems.

Bone mineralisation is a well-orchestrated procedure triggered by a protein-based template inducing the nucleation of hydroxyapatite (HA) nanocrystals on the matrix. In an attempt to fabricate superior nanocomposites from silk fibroin, textile braided structures made of natively spun fibres of Bombyx mori silkworm were compared against regenerated fibroin (lyophilised and films) underpinning the influence of intrinsic properties of fibroin matrices on HA nucleation. We found that native braids could bind Ca 2+ ions through electrostatic attraction, which initiated the nucleation and deposition of HA, as evidenced by discrete shift in amide peaks via ATR-FTIR. This phenomenon also suggests the involvement of amide linkages in promoting HA nucleation on fibroin. Moreover, CaCl 2 -SBF immersion of native braids resulted in preferential growth of HA along the c-axis, forming needle-like nanocrystals and possessing Ca/P ratio comparable to commercial HA. Though regenerated lyophilised matrix also witnessed prominent peak shift in amide linkages, HA growth was restricted to (211) plane only, albeit at a significantly lower intensity than braids. Regenerated films, on the other hand, provided no crystallographic evidence of HA deposition within 7 days of SBF immersion. The present work sheds light on the primary fibroin structure of B.mori which probably plays a crucial role in regulating template-induced biomineralisation on the matrix. We also found that intrinsic material properties such as surface roughness, geometry, specific surface area, tortuosity and secondary conformation exert influence in modulating the extent of mineralisation. Thus our work generates useful insights and warrants future studies to further investigate the potential of bone mimetic, silk/mineral nanocomposite matrices for orthopaedic applications.

The bone is a complex and dynamic structure subjected to constant stress and remodeling. Due to the worldwide incidence of bone disorders, tissue scaffolds and engineered bone tissues have emerged as solutions for bone grafting, which require sophisticated scaffolding architectures while keeping high mechanical performance. However, the conjugation of a bone-like scaffold architecture with efficient mechanical properties is still a critical challenge for biomedical applications. In this sense, the present study focused on the modulating the architecture of silk fibroin (SF) scaffolds crosslinked with horseradish peroxidase and mixed with zinc (Zn) and strontium (Sr)-doped β-tricalcium phosphate (ZnSr.TCP) to mimic bone structures. The ZnSr.TCP-SF hydrogels were tuned by programmable ice-templating parameters, and further freeze-dried, in order to obtain 3D scaffolds with controlled pore orientation. The results showed interconnected channels in the ZnSr.TCP-SF scaffolds that mimic the porous network of the native subchondral bone matrix. The architecture of the scaffolds was characterized by microCT, showing tunable pore size according to freezing temperatures (-196 ºC: ~80.2 ± 20.5 µm; -80 ºC: ~73.1 ± 20.5 µm; -20 ºC: ~104.7 ± 33.7 µm). The swelling ratio, weight loss, and rheological properties were also assessed, revealing efficient scaffold integrity and morphology after aqueous immersion. Thus, the ZnSr.TCP-SF scaffolds made of aligned porous structure were developed as affordable candidates for future applications in clinical osteoregeneration and in vitro bone tissue modelling.

Polyvinylidene fluoride or simply PVDF is one of the most important semicrystalline polymers which generate piezoelectricity when a pressure or mechanical force applied on it. It has four crystalline phases α, β, ɣ and δ depending on the chain conformation structure. Among them α is non polar phase and β and ɣ are polar phase. Piezoelectricity in PVDF arises due to the β and ɣ phase formation. Several materials have been introduced for the preparation of nanogenerator. Among them PVDF (polyvinylidene fluoride) is most interesting material used in nanogenerator preparation due to its flexibility, bio-compatiable, nontoxic in nature. It is used in nanogenerator application due to its good ferroelectric, piezoelectric and pyroelectric properties. In this article we describe little bit concept about PVDF, its piezoelectricity and PVDF based nanogenerator. Application of piezoelectric nanogenerator is also briefly described here.

This study investigated the functional and histological properties of an implantation of silk fibroin/gelatin (SF/G) scaffold enriched with chondrocytes into a rat’s knee joint.  The animals were divided into 3 groups as 1) a sham group which received an incision on the joint capsule, 2) a blank SF/G group which had a burr hole on the cartilage and transplanted with a blank scaffold, and 3) SF/G+C group which had a burr hole on the cartilage and transplanted with chondrocyte-rich fibroin scaffold.  At the 1st, 2nd, 3rd, and 4th week after surgery, each animal was subjected to locomotor activity tests by running on a treadmill for 5 min and followed by climbing on a rotating rod for 5 min, respectively.  The results of treadmill test showed that some animals in each group could not walk or run as long duration as 5 min period in the 1st week.  However, all of them could run normally on the treadmill in the 2nd week.  For the rotarod test, most of the animals in SF/G+C group could not...

The components of musculoskeletal system that consists of bone, ligament tendons and muscles are most vulnerable to injury from sports and related activities. Replacing the injured tissues more specifically the bone is a challenge to tissue engineers. Aiming at regeneration of bone tissues, silk fibroin from Bombyx mori, a novel biocompatible natural polymer has been explored either alone or as organic/inorganic composites for optimal growth of bone cells or differentiation of stem cells to bone cells in vitro. In the process, raw silk fibroins need to be were degummed, usually by alkali treatment method, to ameliorate the cytotoxicity from sericin. Most recently, the nanofibers of silk from electrospinning has shown a promise for bone tissue engineering. To get nanofibers, the degummed silk is usually dissolved in compatible solutions i.e. CaCl2 in H2O or LiBr in C2H5OH at different concentrations followed by dialysis to remove toxic ions. The ion free silk solution can be Electrospun alone or can be blended with various biopolymers for the fabrication of nanofibre biodegradable composite. Other approaches like crosslinking an array of biopolymers with silk or freeze drying the silk fibroins are also in pipeline to develop a novel silk based scaffold for bone tissue engineering.

Tissue reconstruction is among the increasing applications of polymer nanofibers. Fibrous scaffolds (mats) can be easily produced using the electrospinning method with structure and biomechanical properties similar to those of a cellular matrix. Electrospinning is widely used in the production of nanofibers and the GAP-method electrospinning is one of the means of producing fully aligned nanofibers. In this research, using the GAP-method, knitted fibrous scaffolds were made of silk fibroin, which is a biocompatible and biodegradable polymer. To extract fibroin from cocoons, the sodium chloride solution as well as dialysis and freeze-drying techniques were employed. The molecular weight of the extracted fibroin was measured with the SDS-Page electrophoresis technique. Moreover, the pure fibroin structure was examined using the ATR-FTIR method, and the viscosity of the solution used for electrospinning was measured with the Brookfield rotational viscometer. The scaffolds were prepared through electrospinning of the silk fibroin in pure formic acid solution. The following three structures were electrospun: 1) a random structure; 2) a knitted structure with an interstitial angle of 60 degrees; 3) a knitted structure with an interstitial angle of 90 degrees. Morphology of the resulting fibers was studied with a SEM (scanning electron microscope). Fibroin scaffolds are degradable in water. Therefore, they were fixated through immersion in methanol to be prepared for assays. The mechanical properties of the scaffolds were also studied using a tensile strength test device. The effect of methanol on the strength properties of the samples was also assessed. The hydrophilic potential of the samples was measured via a contact angle test. To increase the hydrophilicity of the scaffold surfaces, the cold oxygen plasma technique was employed. Finally, the biocompatibility and cell adhesion of the resulting scaffolds were examined through a HEK 293 cell culture, and the results were analyzed through the MTT, DAPI staining, and SEM imaging techniques. Results revealed that the oriented knitted structure contributed to the increase in Young's modulus and the maximum strength of scaffolds as compared to the random samples. Moreover, this structure can also be a suitable alternative to the typical chemical means of increasing strength.

Study compares the quality and quantity of sericin obtained from four sources, namely mulberry silk cocoons, silk flats, reeling silk waste and woven silk fabric. Sericin has been extracted using the conventional HTHP machine as well as IR heating machine. Results show that among the four sources, the maximum yield of sericin (28%) is obtained from silk fabric followed by 25% sericin obtained from silk flats. IR machine extraction gives ~13 times higher yield of sericin as compared to that obtained by HTHP at 100 0 C for 60 min. Sample obtained from IR extraction is also compared with the standard sample in terms of its physical properties, morphological structure, protein quality, protein structure, molecular weight and thermal behaviour using various analytical methods. The study proposes a protocol for assessing the quality of sericin protein. Since the source as well as the method of extraction can affect the properties of sericin, this protocol can be used to assess and determine the quality parameters of various sericin samples.

To effectively repair or replace damaged tissues, it is necessary to design scaffolds with tunable structural and biomechanical properties that closely mimic the host tissue. In this paper, we describe a newly synthesized photocrosslinkable interpenetrating polymer network (IPN) hydrogel based on gelatin methacrylate (GelMA) and silk fibroin (SF) formed by sequential polymerization, which possesses tunable structural and biological properties. Experimental results revealed that IPNs, where both the GelMA and SF were independently crosslinked in interpenetrating networks, demonstrated a lower swelling ratio, higher compressive modulus and lower degradation rate as compared to the GelMA and semi-IPN hydrogels, where only GelMA was crosslinked. These differences were likely caused by a higher degree of overall crosslinking due to the presence of crystallized SF in the IPN hydrogels. NIH-3T3 fibroblasts readily attached to, spread, and proliferated on the surface of IPN hydrogels as demonstrated by F-actin staining and analysis of mitochondrial activity (MTT). In addition, photolithography combined with lyophilization techniques was used to fabricate 3D micropatterned and porous micro-scaffolds from GelMA-SF IPN hydrogels, furthering their versatility for use in various microscale tissue engineering applications. Overall, this study introduces a class of photocrosslinkable, mechanically robust and tunable IPN hydrogels that could be useful for various tissue engineering and regenerative medicine applications.

Local order and dynamics in polymers under mechanical stress is studied by NMR. Permanent magnets in aHalbach arrangement permits NMR investigation without the limits present in highfield NMR. In particular the confined stray field permit the application of NMR in a stretching apparatus and a rheometer. Mechanical stress on elastomers results in partial chain ordering and consequently reduced chain mobility, which results in stronger residual dipolar couplings are manifested in the stronger buildup of double quantum coherences and in a shortening of the slower component of the transverse relaxation time. The crystalline and amorphous fractions of semicrystalline polymers are distinguished by their transverse relaxation times. Under mechanical load there is a significant shortening of the transverse relaxation time of the amorphous fraction, which partially relaxes with time, when the load is kept constant. In an alternative experiment mechanical stress is induced on a polymer melt or solution in a Couette cell. This requires a dedicated high-temperature rheo-NMR probe. Changes in the polymer mobility during the melting and subsequent shear are followed in the proton T2 using a CPMG experiment. Double quantum experiments yield information on residual dipolar coupling and hence the dynamic chain order parameter.

The American Physical Society Surface Induced Self-Assembly of Fibrinogen Fibers in the Absence of Thrombin JASEUNG KOO, MIRIAM RAFAILOVICH, DENNIS GALANAKIS, Stony Brook University -Wound healing is a complex process imitated by the formation of fibrin fibers that are involved in clot formation and fibroblast migration. Normally this process is triggered by thrombin cleavage of the E domain on the fibrinogen molecules, which allows them to spontaneously selfassemble into the fibers. Here we demonstrate that this process can also be initiated in the absence of thrombin. We show that by simply placing the proteins in contact with hydrocarbon functionalized clay surfaces, molecular reorientation occurs which allows fibers to form from the intact fibrinogen protein. Furthermore, using monoclonal antibodies, we determined which regions on the αC domains are involved in the formation of the new fibrinogen fibers. This allowed us to extend these findings to general hydrophobic surfaces, such as those presented by most hydrocarbon polymers. On the other hand, the carboxyl terminal part of the Aα chain, can interact with amine containing polymers, and suppress formation of the fibers.

Wound healing is a complex process imitated by the formation of fibrin fibers that are involved in clot formation and fibroblast migration. Normally this process is triggered by thrombin cleavage of the E domain on the fibrinogen molecules, which allows them to spontaneously self-...

In this study, silk fibroin was extracted by CaCl2 solution from Bombyx mori cocoons and then dialyzed in deionized water for 96 hrs. The resulting solution was lyophilized to yield a sponge which can be dissolved in water to achieve a 10% water-based silk fibroin solution. To evaluate the
rheological behaviour of this solution, a viscosity test was performed which showed the typical shear-thinning behavior of the SF, and to ensure that the product is silk fibroin, FTIR analysis was done.
based on this protocol, the final solution is water-based so that it can be used in biomedical fields and also cells can be loaded on it.
Keywords: Silk Fibroin, Rheological

Acute lymphoblastic leukemia (ALL) is the white blood cell cancer in children. L-asparaginase (L-ASNase) is one of the first drugs used in ALL treatment. Anti-tumor activity of L-ASNase is not specific and indicates limited stability in different biological environments, in addition to its quick clearance from blood. The purpose of the present study was to achieve a new L-ASNase polymer bioconjugate to improve pharmacokinetic, increase half-life and stability of the enzyme. The conjugations were achieved by the cross-linking agent of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) which activates the carboxylic acid groups of polymeric nanoparticles to create amide bond. EDC conjugated the L-ASNase to two biodegradable polymers including; Ecoflex ® and poly (styrene-co-maleic acid) (PSMA) nanoparticles. To achieve optimal L-ASNase nanoparticles the amounts of each polymer and the crosslinker were optimized and the nanoparticles were characterized according to their particle size, zeta potential and percent of conjugation of the enzyme. The results showed that conjugated enzyme had more stability against pH changes and proteolysis. It had lower Km value (indicating more affinity to the substrate) and greater half-life in plasma and phosphate buffered saline, in comparison to native enzyme. Generally, the conjugated enzyme to PSMA nanoparticles showed greater results than Ecoflex ® nanoparticles.

Macro/microporous silk/nano-sized calcium phosphate scaffolds (SC16) with bioactive and superior physicochemical properties are currently being developed. In this study, we evaluated the new bone formation ability in rat femur of the SC16 scaffolds in vivo, using silk fibroin scaffolds (S16) as control. The CaP distribution profile in the scaffolds was characterized by micro-computed tomography and the CaP phase was found to be distributed homogeneously in the SC16 scaffolds. Mineralization was only observed in SC16 scaffolds, and both scaffolds gradually degraded with time. By staining the explants, new bone growth was observed directly on the SC16 surface and with higher density than that observed on the S16 scaffolds. These results demonstrated that the SC16 hybrid scaffolds are osteoconductive and can be good candidates for bone tissue engineering as they promote superior de novo bone formation.

Orb-web weaving spiders synthesize and use a variety of silks, each having different propertie s suited to their particular functions. Three of these silks were collected from two different species of spiders an d subjected to physical/mechanical testing . The major ampullate (dragline), minor ampullate, and cocoon silks o f both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compar e their physical properties . The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus . Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to brea k the fiber than that of Nephila .

Orb-web weaving spiders synthesize and use a variety of silks, each having different propertie s suited to their particular functions . Three of these silks were collected from two different species of spiders an d subjected to physical/mechanical testing . The major ampullate (dragline), minor ampullate, and cocoon silks o f both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compar e their physical properties . The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus . Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to brea k the fiber than that of Nephila .

The use of bowel segments to perform bladder augmentation is associated with several metabolic and surgical complications. A great variety of synthetic materials, biodegradable or not, have been tested. Collagen-based biomaterials have shown effectiveness for the regeneration and obtainment of a functional bladder. Assess the functional and histological response of the rabbit bladder to anionic collagen membrane (ACM), either when it is anastomosed to the bladder or it is placed onto bladder after vesicomyectomy. In 15 male rabbit a partial cystectomy was performed. After 4 weeks they were divided in 3 groups. Group 1 (G1) - bladder augmentation with ACM. Group 2 (G2) ACM is placed onto bladder after vesicomyectomy. Group 3 (G3) control group. Maximal bladder capacity (MBC) and weight were assessed with 4 (M1), 8 (M2) and 12 (M3) weeks after partial cystectomy. In M3 was performed the sacrifice and extraction of the bladder and kidneys for anatomopathologic study. There were neither...

Butterflies constitute approximately 10% of lepidopteran insects, and along with silkworms, they can produce silk; however, this feature is often ignored. In the present study, we observed two primary methods used by butterflies to hang pupae on trees using silk: pupa adheraena (Danaus chrysippus) and pupa contigua (Papilio polytes). Anchoring the abdominal ends of pupae with a silk pad was the most common method used in both cases, whereas wrapping silk around the body using a silk girdle was a method unique to pupa contigua. The connection between the cremaster and silk pad was observed to be similar to that between the hook and loop of a Velcro fastener, except that the cremaster hook is anchor-shaped rather than being a single hook. Such a connection will remain secure, ensuring the safety of the pupae during exposure to wind and rain. Through determining the mechanical properties of silk, the performance of butterfly silk was found to be weaker than that of silkworm silk. Therefore, the P. polytes silk girdle adopts the strategy of merging a dozen silk threads to improve its strength and toughness, thereby making it difficult to break. In addition, we explained how the protein sequence and structure of butterfly silk impact its performance. In conclusion, we discovered that butterfly pupae develop unique body features to establish secure bonds with silk. This enables them to effectively undergo metamorphosis and endure harsh weather conditions and surroundings.

Silk fibroin (SF)-based or-coated biomaterials are likely to be endowed with properties fitting tissue engineering applications. In this work we investigated the interactions between SF-coated polyurethane (PU) membranes and foams, and four different strains of normal human adult fibroblasts The aim of this work was to explore the interactions between normal adult human fibroblasts and the SF-coated substrates.

In this project, we propose to explore the modular characteristic of spider silk proteins, through synthetic biology techniques, by combining and directing its properties to the desired application. The aim of this project is to generate a modular bionanomaterial able to immobilize proteins. This bionanomaterial will be composed of modular recombinant proteins from spider silk, which will be the immobilization support to other proteins, in this project an antimicrobial protein (enzybiotic). By combining these proteins and their properties, the primary focus will be the use of this technology for the development of artificial skin for burn victims.

Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications....

The bone is a complex and dynamic structure subjected to constant stress and remodeling. Due to the worldwide incidence of bone disorders, tissue scaffolds and engineered bone tissues have emerged as solutions for bone grafting, which require sophisticated scaffolding architectures while keeping high mechanical performance. However, the conjugation of a bone-like scaffold architecture with efficient mechanical properties is still a critical challenge for biomedical applications. In this sense, the present study focused on the modulating the architecture of silk fibroin (SF) scaffolds crosslinked with horseradish peroxidase and mixed with zinc (Zn) and strontium (Sr)-doped β-tricalcium phosphate (ZnSr.TCP) to mimic bone structures. The ZnSr.TCP-SF hydrogels were tuned by programmable ice-templating parameters, and further freeze-dried, in order to obtain 3D scaffolds with controlled pore orientation. The results showed interconnected channels in the ZnSr.TCP-SF scaffolds that mimic the porous network of the native subchondral bone matrix. The architecture of the scaffolds was characterized by microCT, showing tunable pore size according to freezing temperatures (-196 ºC: ~80.2 ± 20.5 µm;-80 ºC: ~73.1 ± 20.5 µm;-20 ºC: ~104.7 ± 33.7 µm). The swelling ratio, weight loss, and rheological properties were also assessed, revealing efficient scaffold integrity and morphology after aqueous immersion. Thus, the ZnSr.TCP-SF scaffolds made of aligned porous structure were developed as affordable candidates for future applications in clinical osteoregeneration and in vitro bone tissue modelling.

Orb-web weaving spiders synthesize and use a variety of silks, each having different propertie s suited to their particular functions. Three of these silks were collected from two different species of spiders an d subjected to physical/mechanical testing . The major ampullate (dragline), minor ampullate, and cocoon silks o f both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compar e their physical properties . The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus . Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to brea k the fiber than that of Nephila .

Novel porous bilayered scaffolds, fully integrating a silk fibroin (SF) layer and a silk-nano calcium phosphate (silk-nanoCaP) layer for osteochondral defect (OCD) regeneration, were developed. Homogeneous porosity distribution was achieved in the scaffolds, with calcium phosphate phase only retained in the silk-nanoCaP layer. The scaffold presented compressive moduli of 0.4MPa in the wet state. Rabbit bone marrow mesenchymal stromal cells (RBMSCs) were cultured on the scaffolds, and good adhesion and proliferation were observed. The silk-nanoCaP layer showed a higher alkaline phosphatase level than the silk layer in osteogenic conditions. Subcutaneous implantation in rabbits demonstrated weak inflammation. In a rabbit knee critical size OCD model, the scaffolds firmly integrated into the host tissue. Histological and immunohistochemical analysis showed that collagen II positive cartilage and glycosaminoglycan regeneration presented in the silk layer, and de novo bone ingrowths and ...

Surface coatings for biomedical implants have been used to prevent premature failure of implant due to bacterial biofilm formation and foreign body reaction. Delamination, cracking, crazing, etc. are frequent problems associated with coatings when implants are subjected to mechanical deformation either during surgical handling or during use. We demonstrate here, a novel process that results in the formation of a coating that is stable under mechanical stresses in tensile, torsion and bending modes. The coating process involves a combination of two conventional coating processes-namely dip coating and electro-spinning. Polydimethylsiloxane was selected as the substrate owing to its wide use in biomedical implants. Silk fibroin, a natural biocompatible protein polymer obtained from Bombyx mori silkworm, was used for demonstrating the process of coating. The coating was also further functionalized using a green biomoleculeglycomonoterpene prepared using citronellal and glucose. These functional compounds are being touted as the next generation antibiofilm molecules on account of quorum sensing inhibitory activity. We have demonstrated that the quorum quenching activity of the biomolecule is retained during the processing steps and the coatings exhibited excellent antibiofilm activity against common infection causing bacterium P. aeruginosa

ESR studies have been done on natural and UV-irradiated silk fibroins and wool keratins at the temperature range of À1961C to 201C. The intensities of ESR signals obtained from the irradiated samples at À1961C remarkably increase with respect to those of natural samples. While the signals mainly consist of triplet peaks at À1961C, a doublet arises around the room temperatures. For the first time, at room temperature without any external effect the complicated ESR spectra of fibrous proteins (wool keratin and silk fibroin) whose components are as follows have been observed: (1) (for white wool keratin) a central doublet with DH m ¼ 1:1 mT and g ¼ 2:0075; DH m ¼ 5 mT and g ¼ 2:1911; (2) a wide peak with DH m E66 mT and gE2:1575; (3) the 'sulfur' peak given in the literature with DH m ¼ 2:2 mT and g ¼ 2:0218; (4) the signal with DH m ¼ 0:6 mT and g ¼ 2:0065; and for silk fibroin, (a) a very wide signal with DH m E70 mT and gE2:084; (b) a very sharp signal with DH m E1:1 mT and gE2:01; and (c) relatively narrower signal with DH m E5 mT and gE2:336: It has been shown by recombination kinetic method that 30-50% of the free radicals formed by UV-irradiation do not undergo recombination up to 2201C and 1501C for silk fibroin and wool keratin, respectively, even they keep their concentration constant for long period of time (weeks, months, even longer). In this article, considering above-mentioned results, the mechanism of signals observed in natural wool keratin and silk fibroin without any external effects is examined. We can briefly explain the role of the subject of the article, by considering fibrous proteins and some applications of the reactions by free radical occurring in these proteins under the effects of different factors in medicine and biology and the important role of oxidation and the other kinds of degradations on these processes, as well as the significant applications of ESR investigations on comprehending the processes by free radical.

Hidrogel adalah jaringan polimer hidrofilik yang terikat silang dan memiliki kapasitas mengembang (swelling) dengan menyerap air atau cairan biologis namun tidak larut karena adanya ikatan silang. Tujuan dari penelitian ini adalah untuk mendapatkan formulasi basis sediaan pembalut luka hidrogel dengan teknik beku leleh menggunakan kappa karagenan sebagai polimer alam pembentuk gel. Basis hidrogel dibuat dengan memvariasikan konsentrasi PVP, PVA dan kappa karagenan. Basis hidrogel yang terbentuk dilakukan evaluasi meliputi uji organoleptik, rasio swelling dan fraksi gel. Formula basis hidrogel dengan karakteristik terbaik yaitu PVP 1%, Kappa karagenan 2%, KCl 0,2%, agar 1%, PEG 400 1% dan gliserin 1% dengan 5 siklus freezing and thawing. Basis hidrogel yang dihasilkan memiliki bentuk yang padat dan kaku, warna bening kekuningan dan bau khas karagenan, nilai rasio swelling sebesar 4,91 g dan fraksi gel 65,39%.

Small-diameter (less than 6 mm in diameter) vascular grafts are highly desirable due to the large demand for surgical revascularization; however, there are no available artifi cial grafts. Vascular grafts of 1.5 mm diameter prepared by our group with silk fi broin fi ber have been proved to be excellent grafts with remarkably high patency and remodeling, based on rat implantation experiment (Enomoto et al., 2010). In this study, a silk fi broin vascular graft with 3 mm diameter which can be used for the coronary arteries or lower extremity arteries is prepared with a double-raschel knitted Bombyx mori silk fi ber tube coated with B. mori silk fi broin sponge. Here the silk sponge is prepared from an aqueous solution of the silk fi broin and poly(ethylene) glycol diglycidyl ether as porogen. Suffi cient strength, proper elasticity, and protection from loose ends in the implantation process are obtained for the silk fi broin graft; low water permeability and relatively large compliance are also attained. These excellent physical properties make silk fi broin grafts suitable to be implanted in a canine model. grafts larger than 6 mm in internal diameter (ID). [ 1 ] Specifi cally, the patencies of e-PTFE and Dacron grafts (6 mm ID) were 26-46% and 42-62%, respectively, at 5 years follow-up time. [ 2 ] However, grafts with smaller than 6 mm ID fail early due to thrombus formations and intimal hyperplasia. [ 3 , 4 ] Animal studies have shown only a 20-25% patency rate with 1 mm diameter PTFE grafts, while all vein grafts in a similar size remained patent. [ 5,6 ] Silk fi broin (SF) fi ber from Bombyx mori has a long history of use in textiles. SF fi ber also has a long history of use as a suture material because of its high strength and toughness. [ 7 ] Moreover, SF has been reported to have many inherent superior properties as a biomaterial in terms of mechanical properties, environmental stability, biocompatibility, low immunogenicity, and biodegradability; [ 8-11 ] therefore, many applications of SF biomaterials have been examined. [ 12-16 ] SF has been previously studied as biomaterial substrates for cell growth related to tissue engineering. Electrospun and porous silk composite scaffolds have been used for ingrowth of human mesenchymal stem cells (hMSCs) to osteogenic tissue formation in vitro. Both scaffolds supported high calcium deposition and cell differentiation. [ 16-19 ] In our previous studies, [ 20,21 ] we prepared SF grafts by braiding, fl attening, and winding the SF fi bers onto a cylindrical polymer tube followed by coating with an SF aqueous solution. The grafts, which are 1.5 mm in ID and 10 mm in length, were implanted into rat abdominal aorta. An excellent patency (85.1%; n = 27) at 1 year after grafting with SF fi bers was obtained. This patency rate was remarkably higher than that of e-PTFE grafts (30%; n = 10, p < 0.01). Endothelial cells and smooth muscle cells were organized early on the inner layer of the SF graft. Sirius-red staining revealed that the collagen content of fi broin grafts signifi cantly increased 1 year after implantation, with a decrease in SF content. [ 20 ] However, this graft has some problems when used with larger diameter (3 mm) for the coronary arteries or lower extremity arteries because of its relatively weak strength, lack of elasticity, and tendency for the end of the graft to become loose during the implantation process, which are not very serious problems in

Materials such as expanded polytetrafluoroethylene and glutaraldehyde-fixed bovine pericardium are currently used for cardiac tissue regeneration. However, patches made from these materials remain permanently without being absorbed by the body and must be replaced overtime because of degeneration or lack of growth. To improve the long-term outcomes for cardiac tissue regeneration, biocompatible and biodegradable materials must be used. In this study, we used two biocompatible polymers, silk fibroin (SF), which is biodegradable and segmented polyurethane, to prepare nonwoven sheets that were then insolubilized by water vapor or methanol treatment. The tensile stress increased significantly on adding segmented polyurethane to pure SF and the water vapor processed sheets showed higher extension on strain than the methanol-processed sheets. The different insolubilization treatments also resulted in different SF structures. Our results show that it is possible to obtain the physical properties required for cardiac tissue repair patch by varying the insolubilization treatment.

found regarding tissue infiltration and internal diameter. The TG SF revealed migration of the endothelial cells into the center part of the vessels at the early stage. Also, tissue infiltration and remodeling is expected using SF. The 3 cm length vascular grafts can be evaluated as a new experimental system.

ABSTRACTMaterials such as expanded polytetrafluoroethylene and glutaraldehyde‐fixed bovine pericardium are currently used for cardiac tissue regeneration. However, patches made from these materials remain permanently without being absorbed by the body and must be replaced overtime because of degeneration or lack of growth. To improve the long‐term outcomes for cardiac tissue regeneration, biocompatible and biodegradable materials must be used. In this study, we used two biocompatible polymers, silk fibroin (SF), which is biodegradable and segmented polyurethane, to prepare nonwoven sheets that were then insolubilized by water vapor or methanol treatment. The tensile stress increased significantly on adding segmented polyurethane to pure SF and the water vapor processed sheets showed higher extension on strain than the methanol‐processed sheets. The different insolubilization treatments also resulted in different SF structures. Our results show that it is possible to obtain the physi...

Vascular grafts under 5 mm or less in diameter are not developed due to a problem caused by early thrombus formation, neointimal hyperplasia, etc. Bombyx mori silk fibroin (SF) which has biodegradability and tissue infiltration is focused as tube and coating material of vascular grafts. Coating is an important factor to maintain the strength of the anastomotic region of vascular grafts, and to prevent the blood leak from the vascular grafts after implantation. Therefore, in this research, we focused on the SF concentration of the coating solution, and tissue infiltration and remodeling were compared among each SF concentration. Silk poly (-ethylene) glycol diglycidyl ether (PGDE) coating with concentrations of 1.0%, 2.5%, 5.0%, and 7.5% SF were applied for the double-raschel knitted small-sized vessel with 1.5 mm diameter and 1cm in length. The grafts were implanted in the rat abdominal aorta and removed after 3 weeks or 3 months. Vascular grafts patency was monitored by ultrasound, and morphological evaluation was performed by histopathological examination. SF concentration had no significant effects on the patency rate. However, tissue infiltration was significantly higher in the sample of 2.5% SF in 3 weeks, and 1.0% and 2.5% SF in 3 months. Also, in comparison of length inside of the graft, stenosis were not found in 3 weeks, however, found with 5.0% and 7.5% in 3 months. From these results, it is clear that 2.5% SF coating is the most suitable concentration, based on the characteristics of less stenosis, early tissue infiltration, and less neointimal hyperplasia.

Small-diameter (less than 6 mm in diameter) vascular grafts are highly desirable due to the large demand for surgical revascularization; however, there are no available artificial grafts. Vascular grafts of 1.5 mm diameter prepared by our group with silk fibroin fiber have been proved to be excellent grafts with remarkably high patency and remodeling, based on rat implantation experiment (Enomoto et al., 2010). In this study, a silk fibroin vascular graft with 3 mm diameter which can be used for the coronary arteries or lower extremity arteries is prepared with a double-raschel knitted Bombyx mori silk fiber tube coated with B. mori silk fibroin sponge. Here the silk sponge is prepared from an aqueous solution of the silk fibroin and poly(ethylene) glycol diglycidyl ether as porogen. Sufficient strength, proper elasticity, and protection from loose ends in the implantation process are obtained for the silk fibroin graft; low water permeability and relatively large compliance are als...

The present study aimed to produce small-diameter grafts made of a silk fibroin by electrospinning. In order to reinforce the electrospun silk fibroin graft (ES), the graft was coated with a silk sponge (ESSC). Physical properties such as a diameter of the electrospun silk fibers were influenced by a concentration of fibroin solution. Ultimate tensile strength (UTS) of the ESSC graft was improved compared to the ES graft. However, the ESSC graft was less compliant than the ES graft. Importantly, water permeability of the ESSC graft was within the range of which endothelialization was promoted in previous studies.

Silk fibroin (SF) was obtained in reeled form from Bursa Institute for Silkworm Research (Bursa/Turkey). Hyaluronic acid (HA) sodium salt (M W : 1600000 Da, form Streptococcus equi) was provided by Fluka-BioChemica (Buchs, Switzerland) in powder form. Di-sodium hydrogen phosphate, phosphate dihydrogen phosphate (acid and base components for phosphate buffer), ethanol (absolute GR for analysis) and sulfuric acid (98+%) were from Merck (Darmstadt, Germany). Calcium chloride-2-hydrate and sodium chloride were supplied from Riedel-de Haën (Seelze, Germany), sodium carbonate (99.5+%) was from Aldrich-Chemie (Steinheim, Germany) and timolol

HA-mineralised composite electrospun scaffolds have been introduced for bone regeneration due to their ability to mimic both morphological features and chemical composition of natural bone ECM. Micro-sized HA is generally avoided in electrospinning due to its reduced bioactivity compared to nano-sized HA due to the lower surface area. However, the high surface area of nanoparticles provides a very high surface energy, leading to agglomeration. Thus, the probability of nanoparticles clumping leading to premature mechanical failure is higher than for microparticles at higher filler content. In this study, two micron-sized hydroxyapatites were investigated for electrospinning with PLA at various contents, namely spray dried HA (HA1) and sintered HA (HA2) particles to examine the effect of polymer concentration, filler type and filler concentration on the morphology of the scaffolds, in addition to the mechanical properties and bioactivity. SEM results showed that fibre diameter and surface roughness of 15 and 20 wt% PLA fibres were significantly affected by incorporation of either HA. The apatite precipitation rates for HA1 and HA2-filled scaffolds immersed in simulated body fluid (SBF) were similar, however, it was affected by the fibre diameter and the presence of HA particles on the fibre surface. Degradation rates of HA2-filled scaffolds in vitro over 14 days was lower than for HA1filled scaffolds due to enhanced dispersion of HA2 within PLA matrix and reduced cavities in PLA/HA2 interface. Finally, increasing filler surface area led to enhanced thermal stability as it reduced thermal degradation of the polymer.

The research aim was to investigate preparation and characterisation of ovalbumin-loaded alginate microspheres produced by aerosolisation and study its in vitro release. Calcium chloride was use as crosslinking agent with crosslinking time of 30 and 120 minutes. Aerosolization technique offers a simple, fast, produce homogenous microspheres and a safe technique with no organic solvent involved. Ovalbuin-loaded-alginate microspheres were evaluated in terms of size, morphology, encapsulation efficiency, loadings of protein and yield of microspheres. In vitro release study was conducetd in simulated gastric fluid (HCl pH 1.2) and simulated intestinal fluid (PBS pH 7.4). Results showed that smaller particle size (12-23 µm) and higher encapsulation efficiency, loading and yield was produced by inceasing alginate and crosslinker concentration as well as increasing crosslinking time from 30 minutes to 120 minutes. Furthermore, by increasing alginate concentration and crosslinking time, rel...