Developing hydrogel which combines superior mechanical performance and biocompatibility attracts researchers’ attention in recent years. Here, a novel biocompatible hydrogel with excellent mechanical performance, comprised of regenerated silk fibroin (RSF) and hydroxypropyl methyl cellulose (HPMC), is fabricated by simply mixing and heating. It is found that both of compressive modulus and tensile modulus of the optimal RSF/HPMC hydrogel are over 1.0 MPa. Meanwhile, the break energy is up to 3500 J m⁻², which is higher than that of some natural elastomers, such as cartilage, cork, and skin. The investigation of gelation mechanism reveals that more uniformly dispersed crosslinks dominated by smaller β-sheet structures, which is attributed to the synergistic effects of hydrogen bonding and hydrophobic interaction between HPMC and RSF molecules, contribute to the superior mechanical performance of RSF/HPMC hydrogel. This biocompatible high strength silk protein based hydrogel diversifies the robust hydrogels and holds a great promise as candidates for load-bearing materials in biomedical field.

As an analogue of the main protein contained in naturally formed nacre, reconstituted silk fibroin (SF) from the Bombyx mori silkworm silk shows a strong preference for the formation of the aragonite form of CaCO₃ crystals and allows fine control over their size and morphology. The aragonite phase could be generated via two different routes: direct growth or dissolution and recrystallization, depending on the concentration of Ca²⁺ and SF. Generally, lower concentrations of Ca²⁺ and SF favor the formation of aragonite needles and their aggregates, of which the lattice structure of the precursor is similar to that of the organic matrix in natural shell. Higher concentrations lead to the formation of aragonite aggregates via a dissolution and recrystallization process through intermediates of lens-like vaterite. Molecular modeling shows that the β-strand conformers of silk fibroin molecules has an excellent match with the ionic spacing in the aragonite (010) plane, which can promote growth along the (001) long axis of aragonite crystals. This synergy between silk fibroin and the aragonite phase may help our understanding of the function of organic matrices involved in the biomineralization process, and facilitate the fabrication of synthetic materials with the potential for high performance mechanical properties.

The ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) was initiated by n-hexylamine in N,N-dimethyformamide under normal pressure at 0 °C. The products were characterizated by gel permeation chromatography, matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS), nuclear magnetic resonance etc. MALDI-TOF MS gave direct evidence that the side reactions during the polymerization of BLG-NCA could be greatly reduced by decreasing the reaction temperature, e.g. from room temperature to 0 °C. As a result, over 90% of the products were amino-terminated poly(γ-benzyl-L-glutamate) (PBLG) with low polydispersity index when the polymerization was carried out at 0 °C, which could be used to re-initiate the polymerization of other NCAs. Then several well-defined PBLG-containing block copolypeptides were successfully synthesized in a convenient way. Copyright © 2012 Society of Chemical Industry

The orthopedic infection, such as osteomyelitis, especially those caused by Methicillin-resistant Staphylococcus aureus (MRSA), remains a major complication of open fractures. Local vancomycin delivery is considered to provide better methods when avascular zones prevent the delivery of drugs from conventional routes of administration. Chitosan (CS) delivery system has been developed with the disadvantages, such as mechanically weakness, lacking osteoconductivity, and the initial burst of antibiotics into the environment. The aim of this study was to confirm that the prepared CS/β-tricalcium phosphate (β-TCP) composites coated with poly (ε-caprolactone) (PCL), similar to natural bone in components, had a three-dimensional porous structure and could be used as drug carriers to deliver vancomycin in a sustained and controlled manner effectively for 6 weeks at levels to inhibit MRSA proliferation. We prepared porous CS/β-TCP composites by incorporating β-TCP into the system, and coated the composites with PCL of three different concentrations. The morphological structure of composites, including pore size and porosity, was examined. The result showed that CS/β-TCP coated with 2.5w/v% PCL solution had the best coating effect and it retarded the release of vancomycin in a near zero-order mechanism from 0 to 14 days. The drug delivery was significantly delayed after coated with 2.5w/v% PCL. The quantitative release of vancomycin was extended to 42 days. Therefore PCL coating could be used to retard the release of vancomycin from CS/β-TCP composites in a sustained and controlled manner. Porous CS/β-TCP coated with PCL might be one of the candidate vancomycin carriers for treating MRSA-related osteomyelitis. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

Antheraea pernyi (A. pernyi) silk is produced and used by “wild” silkworms to construct a cocoon, but the primary structure of its protein is rather similar to that of spider major ampullate silk used to build web and dragline. Studies on this specific silk may provide valuable knowledge about the structure-property relationship for the whole animal silk family. In this work, A. pernyi silk fibers with few macroscale defects are obtained by forcibly reeling, and are investigated in detail. It is found that such silk fibers display breaking stress and toughness of the same magnitude as spider major ampullate silks and forcibly reeled mulberry silk. The other mechanical properties, such as elasticity, supercontraction, and the effect of water on modulus are between those of spider major ampullate silks and mulberry silk. Therefore, an interpretation of the connection between the primary structures of silk proteins and the mechanical properties of silks is proposed here based on the ordered fraction, which in turn is determined by both the protein sequence and spinning process of the silk.

Microspheres of calcium carbonate (CaCO₃)/sodium polyacrylate (PAAs)/H₂O composite were synthesized by adding PAAs to the supersaturated solution of CaCO₃. It was found that the sizes of microsphere were influenced by the concentration and average molecular weight (M_w) of PAAs. Particularly, the polymorph of CaCO₃ in the microspheres could be regulated by M_w of PAAs, that is, the formation of aragonite was induced by PAAs with lower M_w, while the amorphous calcium carbonate (ACC) was facilitated by PAAs with a higher one. Both polymorphs in produced microspheres were stable in air for longer than 3 months. In addition, it was revealed that the formation of calcite crystals was suppressed by a highly concentrated solution of PAAs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Mollusk shell is one of the best studied of all calcium carbonate biominerals. Its silk-like binder-matrix protein plays a pivotal role during the formation of aragonite crystals in the nacre sheets. Here, we provide novel experimental insights into the interaction of mineral and protein compounds using a model system of reconstituted Bombyx mori silk fibroin solutions serving as templates for the crystallization of calcium carbonate (CaCO₃). We observed that the inherent (self-assembling) aggregation process of silk fibroin molecules affected both the morphology and crystallographic polymorph of CaCO₃ aggregates. This combination fostered the growth of a novel, rice-grain-shaped protein/mineral hybrid with a hollow structure with an aragonite polymorph formed after ripening. Our observations suggest new hypotheses about the role of silk-like protein in the natural biomineralization process, but it may also serve to shed light on the formation process of those ‘ersatz’ hybrids regulated by artificially selected structural proteins.