Effect of processing on silk-based biomaterials: reproducibility and biocompatibility.
01 Oct 2011-Journal of Biomedical Materials Research Part B (NIH Public Access)-Vol. 99, Iss: 1, pp 89-101
TL;DR: The degumming conditions significantly affected cell viability on the silk fibroin material and the ability to form three-dimensional porous scaffolds from the silk Fibroin, but did not affect macrophage activation or β-sheet content in the materials formed.
Abstract: Silk fibroin has been successfully used as a biomaterial for tissue regeneration. In order to prepare silk fibroin biomaterials for human implantation a series of processing steps are required to purify the protein. Degumming to remove inflammatory sericin is a crucial step related to biocompatibility and variability in the material. Detailed characterization of silk fibroin degumming is reported. The degumming conditions significantly affected cell viability on the silk fibroin material and the ability to form three-dimensional porous scaffolds from the silk fibroin, but did not affect macrophage activation or β-sheet content in the materials formed. Methods are also provided to determine the content of residual sericin in silk fibroin solutions and to assess changes in silk fibroin molecular weight. Amino acid composition analysis was used to detect sericin residuals in silk solutions with a detection limit between 1.0% and 10% wt/wt, while fluorescence spectroscopy was used to reproducibly distinguish between silk samples with different molecular weights. Both methods are simple and require minimal sample volume, providing useful quality control tools for silk fibroin preparation processes.
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TL;DR: This protocol includes methods to extract silk from B. mori cocoons to fabricate hydrogels, tubes, sponges, composites, fibers, microspheres and thin films, used directly as biomaterials for implants, as scaffolding in tissue engineering and in vitro disease models, as well as for drug delivery.
Abstract: Silk fibroin, derived from Bombyx mori cocoons, is a widely used and studied protein polymer for biomaterial applications. Silk fibroin has remarkable mechanical properties when formed into different materials, demonstrates biocompatibility, has controllable degradation rates from hours to years and can be chemically modified to alter surface properties or to immobilize growth factors. A variety of aqueous or organic solvent-processing methods can be used to generate silk biomaterials for a range of applications. In this protocol, we include methods to extract silk from B. mori cocoons to fabricate hydrogels, tubes, sponges, composites, fibers, microspheres and thin films. These materials can be used directly as biomaterials for implants, as scaffolding in tissue engineering and in vitro disease models, as well as for drug delivery.
2,165 citations
Journal Article•
TL;DR: In this article, B. mori silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity.
Abstract: We report a study of self-assembled beta-pleated sheets in B. mori silk fibroin films using thermal analysis and infrared spectroscopy. B. mori silk fibroin may stand as an exemplar of fibrous proteins containing crystalline beta-sheets. Materials were prepared from concentrated solutions (2−5 wt % fibroin in water) and then dried to achieve a less ordered state without beta-sheets. Crystallization of beta-pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally or by exposure to methanol. The fractions of secondary structural components including random coils, alpha-helices, beta-pleated sheets, turns, and side chains were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra. The silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity. The increment of the reversing heat capacity ΔCp0(Tg) at the glass transition fo...
837 citations
TL;DR: This progress report provides a critical but detailed insight into the biomedical use of silk, including the development pipeline of this new industry for clinical use.
Abstract: Humans have long appreciated silk for its lustrous appeal and remarkable physical properties, yet as the mysteries of silk are unraveled, it becomes clear that this outstanding biopolymer is more than a high-tech fiber. This progress report provides a critical but detailed insight into the biomedical use of silk. This journey begins with a historical perspective of silk and its uses, including the long-standing desire to reverse engineer silk. Selected silk structure-function relationships are then examined to appreciate past and current silk challenges. From this, biocompatibility and biodegradation are reviewed with a specific focus of silk performance in humans. The current clinical uses of silk (e.g., sutures, surgical meshes, and fabrics) are discussed, as well as clinical trials (e.g., wound healing, tissue engineering) and emerging biomedical applications of silk across selected formats, such as silk solution, films, scaffolds, electrospun materials, hydrogels, and particles. The journey finishes with a look at the roadmap of next-generation recombinant silks, especially the development pipeline of this new industry for clinical use.
450 citations
TL;DR: The state of the art in terms of materials options for use in biodegradable medical devices is surveyed, focusing on degradation mechanisms and their control, and silk is highlighted as an important polymer, owing to its mechanical robustness, bioactive component sequestration, degradability without problematic metabolic products and biocompatibility.
Abstract: Biodegradable materials, including natural and synthetic polymers and hydrolyzable metals, constitute the main components of temporary, implantable medical devices. Besides the intrinsic properties of the materials, the most critical factor determining the successful clinical outcome of implantable and degradable devices is the host response, particularly the immune response, which largely depends on the material features and degradation mechanisms. In this Review, we first survey the state of the art in terms of materials options for use in biodegradable medical devices, focusing on degradation mechanisms and their control. In particular, we highlight silk, which is emerging as an important polymer, owing to its mechanical robustness, bioactive component sequestration, degradability without problematic metabolic products and biocompatibility. We then discuss the host response to these biodegradable materials in terms of dynamic tissue–implant interfaces. Next, we examine the clinical translation of three leading biodegradable material systems — natural and synthetic biodegradable polymers and biodegradable metals — and the related challenges in the context of orthopaedic fixation devices, cardiovascular stents and biodegradable electronic devices. Looking to the future, we propose updated material design strategies to improve the clinical outcomes for these biodegradable medical devices. Clinical outcomes with implantable and degradable devices largely depend on host response. This Review surveys material options and degradation mechanisms relevant to host responses to biodegradable devices, examines clinical translation of leading biodegradable materials and proposes updated material-design strategies to improve device performance.
350 citations
TL;DR: Overall, the diverse array of silk materials shows excellent bioresponses in vivo with low immunogenicity and the ability to be remodeled and replaced by native tissue making it suitable for numerous clinical applications.
327 citations
References
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TL;DR: Studies with well-defined silkworm silk fibers and films suggest that the core silk fibroin fibers exhibit comparable biocompatibility in vitro and in vivo with other commonly used biomaterials such as polylactic acid and collagen.
3,067 citations
TL;DR: An understanding of the proteins involved in osteoblast adhesion opens up new possibilities for the grafting of these proteins (or synthesized peptide) onto vector materials, to increase their in vivo bioactivity or to promote cell integration within the vector material during the development of hybrid materials.
2,361 citations
"Effect of processing on silk-based ..." refers background in this paper
...The way in which proteins adsorb to biomaterial surfaces has been shown previously to affect subsequent cellular responses.(32,33) Furthermore, protein adsorption has also been shown to be mediated by biomaterial surface charge....
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TL;DR: Silks are fibrous proteins with remarkable mechanical properties produced in fiber form by silkworms and spiders that are biocompatible when studied in vitro and in vivo.
2,236 citations
"Effect of processing on silk-based ..." refers methods in this paper
...Silk fibroin is harvested from Bombyx mori silkworm cocoons and assembled into a spectrum of material formats using a variety of fabrication techniques.(1) The silk fibroin is present within B....
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TL;DR: Results indicate that THP‐1 is a leukemic cell line with distinct monocytic markers, and the ability to restore T‐lymphocyte response to Con A.
Abstract: A human leukemic cell line (THP-1) cultured from the blood of a boy with acute monocytic leukemia is described. This cell line had Fc and C3b receptors, but no surface or cytoplasmic immunoglobulins. HLA haplotypes of THP-1 were HLA-A2, -A9, -B5, -DRW1 and -DRW2. The monocytic nature of the cell line was characterized by: (1) the presence of alpha-naphthyl butyrate esterase activities which could be inhibited by NaF; (2) lysozyme production; (3) the phagocytosis of latex particles and sensitized sheep erythrocytes; and (4) the ability to restore T-lymphocyte response to Con A. The cells did not possess Epstein-Barr virus-associated nuclear antigen. These results indicate that THP-1 is a leukemia cell line with distinct monocytic markers. During culture, THP-1 maintained these monocytic characteristics for over 14 months.
2,209 citations
TL;DR: This review illustrates the mediation of cell responses to biomaterials by adsorbed proteins, in the context of osteoblasts and selected materials used in orthopedic implants and bone tissue engineering.
Abstract: An appropriate cellular response to implanted surfaces is essential for tissue regeneration and integration. It is well described that implanted materials are immediately coated with proteins from blood and interstitial fluids, and it is through this adsorbed layer that cells sense foreign surfaces. Hence, it is the adsorbed proteins, rather than the surface itself, to which cells initially respond. Diverse studies using a range of materials have demonstrated the pivotal role of extracellular adhesion proteins--fibronectin and vitronectin in particular--in cell adhesion, morphology, and migration. These events underlie the subsequent responses required for tissue repair, with the nature of cell surface interactions contributing to survival, growth, and differentiation. The pattern in which adhesion proteins and other bioactive molecules adsorb thus elicits cellular reactions specific to the underlying physicochemical properties of the material. Accordingly, in vitro studies generally demonstrate favorable cell responses to charged, hydrophilic surfaces, corresponding to superior adsorption and bioactivity of adhesion proteins. This review illustrates the mediation of cell responses to biomaterials by adsorbed proteins, in the context of osteoblasts and selected materials used in orthopedic implants and bone tissue engineering. It is recognized, however, that the periimplant environment in vivo will differ substantially from the cell-biomaterial interface in vitro. Hence, one of the key issues yet to be resolved is that of the interface composition actually encountered by osteoblasts within the sequence of inflammation and bone regeneration.
1,423 citations
"Effect of processing on silk-based ..." refers background in this paper
...The way in which proteins adsorb to biomaterial surfaces has been shown previously to affect subsequent cellular responses.(32,33) Furthermore, protein adsorption has also been shown to be mediated by biomaterial surface charge....
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