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Silk fibroin interactions with metallic surfaces can provide utility for medical materials and devices. Toward this goal, titanium alloy (Ti6Al4 V) was covalently grafted with polyacrylamide via electrochemically reducing 4‐nitrobenzene diazonium salt in the presence of acrylamide. Analysis of the modified surfaces with FT‐IR spectra, SEM and AFM were consistent with surface grafting. Functionalised titanium samples with a silk fibroin membrane, with and without impregnated therapeutics, were used to assess cytocompatibility and drug delivery. Initial cytocompatibility experiments using fibroblasts showed that the functionalised samples, both with and without silk fibroin coatings, supported significant increases between 72–136 % in cell metabolism, compared to the controls after 7 days. A 7‐days release profiling showed consistent bacterial inhibition through gentamicin release with average inhibition zones of 239 mm2. Over a 5‐week period, silk fibroin coated samples, both with and without growth factors, supported better human mesenchymal stem cell metabolism with increases reaching 1031 % and 388 %, respectively, compared to samples without the silk fibroin coating with. [ABSTRACT FROM AUTHOR]

Bonding dissimilar materials has been a persistent challenge for decades. This paper presents a method to modify a stainless steel surface (316 L), routinely used in medical applications to enable the significant adhesion of a biopolymer (silk fibroin). The metallic surface was first covalently grafting with polyacrylamide, to enable a hydrogen bonding compatible surface. The polymerisation was initiated via the irreversible electrochemical reduction of a 4‐nitrobenzene diazonium salt (20 mM), in the presence of an acrylamide monomer (1 M) at progressively faster scan rates (0.01 V/s to 1 V/s). Examination of the modified samples by FT‐IR was consistent with successful surface modification, via observations of the acrylamide carbonyl (1600–1650 cm−1) was observed, with more intense peaks correlating to slower scan rates. Similar observations were made with respect to increasing surface polarity, assessed by water contact angle. Reductions of >60° were observed for the grafted surfaces, relative to the unmodified control materials, indicating a surface able to undergo significant hydrogen bonding. The adhesion of silk to the metallic surface was quantified using a lap shear test, effectively using silk fibroin as an adhesive. Adhesion improvements of 5–7‐fold, from 4.1 MPa to 29.3 MPa per gram of silk fibroin, were observed for the treated samples, highlighting the beneficial effect of this surface treatment. The methods developed in this work can be transferred to any metallic (or conductive) surface and can be tailored to complement any desired interface. [ABSTRACT FROM AUTHOR]

In this study we report the extraction and characterization of sericin using water alone, from two non-mulberry silks - Antheraea assamensis (A. assamensis) and Philosamia ricini (P. ricini) compared with Bombyx mori (B. mori) silk. Degumming at 130 °C offered the highest sericin removal for A. assamensis; P. ricini had the lowest sericin removal among the varieties, because of its lower overall sericin content. Along with sericin degumming, fiber tensile properties were also reported. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of sericin revealed minimal sericin degradation even for degumming temperatures above 100 °C. The spectra from Fourier Transform Infrared Spectroscopy (FTIR) confirmed random coil motifs for B. mori sericin but a higher proportion of β-sheets in A. assamensis and P. ricini sericin which is likely to contribute to their lower water solubility. Thus, high temperature, water-based processing can be a potential approach for chemical- free degumming of silk fibers and to obtain high molecular weight sericin for different biomaterial applications. [ABSTRACT FROM AUTHOR]

Reported is a fast and versatile protocol to surface modify pre-cast silk membranes targeting tyrosine residues. Enriched alkyne silk membranes were prepared using this method and azides possessing a range of functional groups were tethered to the membrane surface using click chemistry to give a range of water contact angles from 85 ± 3° to 34 ± 6°. [ABSTRACT FROM AUTHOR]

The degumming process to remove sericin decreases silk fiber strength; however, the impact of degumming on the mechanical properties of regenerated silk biomaterials has not been established. This study investigated the effect of degumming temperature, time, alkaline component and alkaline concentration on the mechanical properties of silk fibroin films. Sericin removal was estimated using weight loss; 10 samples with 12.2–29.4% weight loss were then further characterized in terms of fiber mechanical properties, fiber surface morphology, molecular weight distribution and film tensile strength. A negative correlation was found between weight loss and fiber tensile strength. This loss of fiber strength under harsher degumming conditions had a direct impact on the tensile strength of regenerated films. Mild degumming conditions (weight loss of 12.2%) led to higher film strength (8.9 MPa), whereas aggressive degumming conditions (with 29.4% weight loss) resulted in significantly weaker films (4.3 MPa). The presence of some residual sericin, after mild degumming, is likely to affect the mechanical properties of the regenerated silk films. These results will assist in the development of materials with mechanical and biocompatibility properties tuned to specific biomedical applications. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases are a major global health challenge. Blood vessel disease and dysfunction are major contributors to this healthcare burden, and the development of tissue-engineered vascular grafts (TEVGs) is required, particularly for the replacement of small-diameter vessels. Silk fibroin (SF) is a widely used biomaterial for TEVG fabrication due to its high strength and biocompatibility. However, the stiffness of SF is much higher than that of native blood vessels (NBVs), which limits its application for vascular tissue engineering. In this study, SF was plasticized with glycerol to produce TEVGs exhibiting similar stiffness and ultimate tensile strength to those of NBVs. The electrospun SF/glycerol TEVGs exhibited mechanical properties comparable to NBVs and supported the in vitro proliferation of essential vascular cells-endothelial and smooth muscle cells. After 5 days of culture, the TEVGs exhibited an endothelial monolayer in the lumen, demonstrating their potential for functional vascular tissue regeneration. Our study demonstrates the feasibility of producing TEVGs from SF with tailored mechanical properties, paving the way for more functional and durable TEVGs for future clinical applications., (© 2024 The Author(s). Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

A 160 kDa enzyme with beta-glucosidase activity was purified from the midgut gland of the land crab Gecarcoidea natalis. The enzyme was capable of releasing glucose progressively from cellobiose, cellotriose or cellotetraose. Although beta-glucosidases (EC 3.2.1.21) have some activity towards substrates longer than cellobiose, the enzyme was classified as a glucohydrolase (EC 3.2.1.74) as it had a preference for larger substrates (cellobiose

Terrestrial decapods consume a wide variety of plant and animal material. The potential adaptations of carnivorous, omnivorous, and herbivorous terrestrial crustaceans were studied by examining the functional morphology of the gastric mill. Two closely related species from each feeding preference group were examined to identify which features of the mill were due to phylogeny and which were due to adaptation. The morphology of the gastric mill matched the diet well; the gastric mills of the carnivorous species (Geograpsus grayi and Geograpsus crinipes) possessed a blunt, rounded medial tooth and flattened lateral teeth with a longitudinal grinding groove. These features make them well suited to a carnivorous diet of soft animal tissue as well as hard material, such as arthropod exoskeleton. In contrast, the mill of the herbivorous gecarcinids (Gecarcoidea natalis and Discoplax hirtipes) consisted of a medial tooth with sharp transverse ridges and lateral teeth with sharp interlocking cusps and ridges and no grinding surface. These features would efficiently shred fibrous plant material. The morphology of the mill of the omnivorous coenobitids (Coenobita perlatus and Birgus latro) was more generalized toward a mixed diet. However, the mill of B. latro was more adapted to deal with highly nutritious food items, such as nuts and heavily calcified decapods. Its mill possessed lateral teeth with extended ridges, which sat close to the calcified cardiopyloric valve to form a flattened floor. Hard items trapped in the mill would be crushed against this surface by the medial tooth.

Laminarinase and endo-beta-1,4-glucanase were purified and characterised from the midgut gland of the herbivorous land crab Gecarcoidea natalis and the crayfish Cherax destructor. The laminarinase isolated from G. natalis was estimated to have a molecular mass of 41 kDa by SDS-PAGE and 71 kDa by gel filtration chromatography. A similar discrepancy was noted for C. destructor. Possible reasons for this are discussed. Laminarinase (EC 3.2.1.6) from G. natalis had a V(max) of 42.0 micromol reducing sugars produced min(-1) mg protein(-1), a K(m) of 0.126% (w/v) and an optimum pH range of 5.5-7, and hydrolysed mainly beta-1,3-glycosidic bonds. In addition to the hydrolysis of beta-1,3-glycosidic bonds, laminarinase (EC 3.2.1.39) from C. destructor was capable of significant hydrolysis of beta-1,4-glycosidic bonds. It had a V(max) of 19.6 mumol reducing sugars produced min(-1) mg protein(-1), a K(m) of 0.059% (w/v) and an optimum pH of 5.5. Laminarinase from both species produced glucose and other short oligomers from the hydrolysis of laminarin. Endo-beta-1,4-glucanase (EC 3.2.1.4) from G. natalis had a molecular mass of 52 kDa and an optimum pH of 4-7. It mainly hydrolysed beta-1,4-glycosidic bonds, but was also capable of significant hydrolysis of beta-1,3-glycosidic bonds. Two endo-beta-1,4-glucanases, termed 1 and 2, with respective molecular masses of 53+/-3 and 52 kDa, were purified from C. destructor. Endo-beta-1,4-glucanase 1 was only capable of hydrolysing beta-1,4-glycosidic bonds and had an optimum pH of 5.5. Endo-beta-1,4-glucanases from both species produced some glucose, cellobiose and other short oligomers from the hydrolysis of carboxymethyl cellulose.