Silks are remarkable materials with desirable mechanical properties, yet the fine details of natural production remain elusive and subsequently inaccessible to biomimetic strategies. Improved ...knowledge of the natural processes could therefore unlock development of a host of bio inspired fibre spinning systems. Here, we use the Chinese silkworm Bombyx mori to review the pressure requirements for natural spinning and discuss the limits of a biological extrusion domain. This provides a target for finite element analysis of the flow of silk proteins, with the aim of bringing the simulated and natural domains into closer alignment. Supported by two parallel routes of experimental validation, our results indicate that natural spinning is achieved, not by extruding the feedstock, but by the pulling of nascent silk fibres. This helps unravel the oft-debated question of whether silk is pushed or pulled from the animal, and provides impetus to the development of pultrusion-based biomimetic spinning devices.The natural production of silks remains elusive and subsequently inaccessible to biomimetic strategies. Here the authors show that silks cannot be spun by pushing alone, and that natural spinning is dominated by pultrusion, which provides design guidelines for future biomimetic spinning systems.
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.
Silk biopolymers represent pioneer materials for medical applications. In this progress report, some of the mysteries of silk are unraveled and the past, current, and emerging clinical uses of silk are critically examined. This progress report also covers the historical context as well as the structure–function relationships critical for silks' performance in medicine.
Lepidopteran silks number in the thousands and display a vast diversity of structures, properties and industrial potential. To map this remarkable biochemical diversity, we present an identification ...and screening method based on the infrared spectra of native silk feedstock and cocoons. Multivariate analysis of over 1214 infrared spectra obtained from 35 species allowed us to group silks into distinct hierarchies and a classification that agrees well with current phylogenetic data and taxonomies. This approach also provides information on the relative content of sericin, calcium oxalate, phenolic compounds, poly-alanine and poly(alanine-glycine) β-sheets. It emerged that the domesticated mulberry silkmoth Bombyx mori represents an outlier compared with other silkmoth taxa in terms of spectral properties. Interestingly, Epiphora bauhiniae was found to contain the highest amount of β-sheets reported to date for any wild silkmoth. We conclude that our approach provides a new route to determine cocoon chemical composition and in turn a novel, biological as well as material, classification of silks.
The mechanism by which arthropods (e.g., spiders and many insects) can produce silk fibres from an aqueous protein (fibroin) solution has remained elusive, despite much scientific investigation. In ...this work, we used several techniques to explore the role of a hydration shell bound to the fibroin in native silk feedstock (NSF) from
silkworms. Small angle X-ray and dynamic light scattering (SAXS and DLS) revealed a coil size (radius of gyration or hydrodynamic radius) around 12 nm, providing considerable scope for hydration. Aggregation in dilute aqueous solution was observed above 65 °C, matching the gelation temperature of more concentrated solutions and suggesting that the strength of interaction with the solvent (i.e., water) was the dominant factor. Infrared (IR) spectroscopy indicated decreasing hydration as the temperature was raised, with similar changes in hydration following gelation by freezing or heating. It was found that the solubility of fibroin in water or aqueous salt solutions could be described well by a relatively simple thermodynamic model for the stability of the protein hydration shell, which suggests that the affected water is enthalpically favoured but entropically penalised, due to its reduced (vibrational or translational) dynamics. Moreover, while the majority of this investigation used fibroin from
, comparisons with published work on silk proteins from other silkworms and spiders, globular proteins and peptide model systems suggest that our findings may be of much wider significance.
Natural silk spinning offers several advantages over the synthetic fiber spinning, although the underlying mechanisms of this process are yet to be fully elucidated. Silkworm silks, specifically B. ...mori, comprise two main proteins: fibroin, which forms the fiber, and sericin, a coextruded coating that acts as a matrix in the resulting nonwoven composite cocoon. To date, most studies have focused on fibroin’s self-assembly and gelation, with the influence of sericin during spinning receiving little to no attention. This study investigates sericin’s effects on the self-assembly of fibroin via their natural phase-separation. Through changes in sample opacity, FTIR, and XRD, we report that increasing sericin concentration retards the time to gelation and β-sheet formation of fibroin, causing it to adopt a Silk I conformation. Such findings have important implications for both the natural silk spinning process and any future industrial applications, suggesting that sericin may be able to induce long-range conformational and stability control in silk fibroin, while being in a separate phase, a factor that would facilitate long-term storage or silk feedstocks.
Summary Background Adults with relapsed or refractory B-precursor acute lymphoblastic leukaemia have an unfavourable prognosis. Blinatumomab is a bispecific T-cell engager antibody construct ...targeting CD19, an antigen consistently expressed on B-lineage acute lymphoblastic leukaemia cells. We aimed to confirm the activity and safety profile of blinatumomab for acute lymphoblastic leukaemia. Methods In a multicentre, single-arm, open-label phase 2 study, we enrolled adult patients with Philadelphia-chromosome-negative, primary refractory or relapsed (first relapse within 12 months of first remission, relapse within 12 months after allogeneic haemopoietic stem-cell transplantation HSCT, or no response to or relapse after first salvage therapy or beyond) leukaemia. Patients received blinatumomab (9 μg/day for the first 7 days and 28 μg/day thereafter) by continuous intravenous infusion over 4 weeks every 6 weeks (up to five cycles), per protocol. The primary endpoint was complete remission (CR) or CR with partial haematological recovery of peripheral blood counts (CRh) within the first two cycles. Analysis was by intention to treat. This trial is registered at ClinicalTrials.gov , number NCT01466179. Findings Between Jan 13, 2012, and Oct 10, 2013, 189 patients were enrolled and treated with blinatumomab. After two cycles, 81 (43%, 95% CI 36–50) patients had achieved a CR or CRh: 63 (33%) patients had a CR and 18 (10%) patients had a CRh. 32 (40%) of patients who achieved CR/CRh underwent subsequent allogeneic HSCT. The most frequent grade 3 or worse adverse events were febrile neutropenia (48 patients, 25%), neutropenia (30 patients, 16%), and anaemia (27 patients, 14%). Three (2%) patients had grade 3 cytokine release syndrome. Neurologic events of worst grade 3 or 4 occurred in 20 (11%) and four (2%) patients, respectively. Three deaths (due to sepsis, Escherichia coli sepsis, and Candida infection) were thought to be treatment-related by the investigators. Interpretation Single-agent blinatumomab showed antileukaemia activity in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia characterised by negative prognostic factors. Further assessment of blinatumomab treatment earlier in the course of the disease and in combination with other treatment approaches is warranted. Funding Amgen.
Controlled reeling is a powerful tool to investigate the details of silk processing. However, consistent forced reeling of silkworms is hindered by the significant degree of behaviorally induced ...variation caused by the animal. This paper proposes silkworm paralysis as a novel method to control the animal and thus in vivo spinning conditions. Using these methods, we achieve low and consistent reeling forces during the collection of over 500 m of individual silk fiber while monitoring filament variability, morphology, and properties. Novel techniques to measure the irregular silk cross-sectional areas lead to the more accurate calculation of the true engineering values and mechanical property variation of individual silk fibers. Combining controlled reeling and accurate thread measurement techniques allows us to present the relative contributions of processing and behavior in the performance envelope of Bombyx mori silk.
Silk is one of the most intriguing examples of biomolecular self-assembly, yet little is understood of molecular mechanisms behind the flow behavior generating these complex high-performance fibers. ...This work applies the polymer physics of entangled solution rheology to present a first microphysical understanding of silk in the linear viscoelastic regime. We show that silk solutions can be approximated as reptating polymers with “sticky” calcium bridges whose strength can be controlled through the potassium concentration. This approach provides a new window into critical microstructural parameters, in particular identifying the mechanism by which potassium and calcium ions are recruited as a powerful viscosity control in silk. Our model constitutes a viable starting point to understand not only the “flow-induced self-assembly” of silk fibers but also a broader range of phenomena in the emergent field of material-focused synthetic biology.
Gastropods, such as snails and slugs, can excrete mucus to aid in movement and adhesion. However, very few studies have examined the physical relationship between mucus composition and function. ...Here, we explore the role of mucus polymers (specifically their proteins) and their influence on the material properties of locomotive mucus. Using a range of spectroscopic, thermal, and rheological analytical tools, we characterised locomotive mucus from six gastropod species across four families. We report that all mucus tested consisted of 97%–99% water, and the remaining 1%–3% solid content contained a range of proteins (41–377 kDa, 18 of which are previously undocumented), which we propose contribute to its weak gel behaviour (1.58–36.33 Pa•s at 1 rad/s). Our results indicate that mucus properties are also grouped at the family level, suggesting that niche-specific adaptation occurs in these materials. We expect our study to offer a broader approach to how a correlation between properties is crucial for understanding the stability and functionality of snail mucus.
The unprecedented growth and socioeconomic impacts of polyolefins clearly outline a major success story in the world of polymer science. Polyolefins revolutionizes industries such as health care, ...construction, and food packaging. Despite the benefits of polyolefins, there is a rising concern for the environment due to high production volume (i.e., fossil fuel consumption), often short usage time, and problems related to waste management and accumulation in the natural environment. Creating a circular economy for polyolefins through effective recycling technologies has the potential to decrease the environmental impact of these materials. This perspective discusses polyolefins and their impact, existing and emerging recycling/upcycling solutions, and recycle‐by‐design alternatives that are challenging the status quo.
This perspective provides a broad overview of polyolefins including their success story, challenges associated with waste, current and emerging innovations in recycling technologies, and potential recycle‐by‐design replacements for the future.
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