Glass transitions in native silk fibres studied by dynamic mechanical thermal analysis

Guan, Juan; Wang, Yushu; Mortimer, Beth; Holland, Chris; Shao, Zhengzhong; Porter, David; Vollrath, Fritz

doi:10.1039/c6sm00019c

Cited by 49 publications

(43 citation statements)

References 59 publications

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“…There are likely several factors that lead to spider silk being tougher than silkworm silk, and several models of how the toughness is mediated have been put forward, e.g., [57,68,90,91,92]. One hypothesis states that the presence of poly-GA repeats in the repetitive part of fibroins, as compared to poly-A blocks present in spidroins, will create a lower binding strength of the beta sheets [68], which likely also affects the tensile properties.…”

Section: Tensile Properties Of Silk Fibers—why Is Spider Silk Tougmentioning

confidence: 99%

Silk Spinning in Silkworms and Spiders

Andersson

Johansson

Rising

2016

IJMS

135

141

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Spiders and silkworms spin silks that outcompete the toughness of all natural and manmade fibers. Herein, we compare and contrast the spinning of silk in silkworms and spiders, with the aim of identifying features that are important for fiber formation. Although spiders and silkworms are very distantly related, some features of spinning silk seem to be universal. Both spiders and silkworms produce large silk proteins that are highly repetitive and extremely soluble at high pH, likely due to the globular terminal domains that flank an intermediate repetitive region. The silk proteins are produced and stored at a very high concentration in glands, and then transported along a narrowing tube in which they change conformation in response primarily to a pH gradient generated by carbonic anhydrase and proton pumps, as well as to ions and shear forces. The silk proteins thereby convert from random coil and alpha helical soluble conformations to beta sheet fibers. We suggest that factors that need to be optimized for successful production of artificial silk proteins capable of forming tough fibers include protein solubility, pH sensitivity, and preservation of natively folded proteins throughout the purification and initial spinning processes.

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Section: Tensile Properties Of Silk Fibers—why Is Spider Silk Tougmentioning

confidence: 99%

Silk Spinning in Silkworms and Spiders

Andersson

Johansson

Rising

2016

IJMS

135

141

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“…Importantly, in polymer glasses there are effectively two independent measurements that determine the fitting parameter Λ: one from the value of T g , the other from the specific dependence of T g on the degree of polymerisation N . This characteristic dependence of polymer T g on the chain length N has been empirically seen since a long time ago, not only in synthetic polymers [32,33], but also in glassy biopolymers [34]. Very accurate matching values are obtained in this way, e.g.…”

Section: Marginal Rigidity Conditionmentioning

confidence: 67%

Polymer glass transition occurs at the marginal rigidity point with connectivity z* = 4

2016

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We re-examine the physical origin of the polymer glass transition from the point of view of marginal rigidity, which is achieved at a certain average number of mechanically active intermolecular contacts per monomer. In the case of polymer chains in a melt/poor solvent, each monomer has two neighbors bound by covalent bonds and also a number of central-force contacts modelled by the Lennard-Jones (LJ) potential. We find that when the average number of contacts per monomer (covalent and non-covalent) exceeds the critical value z* ≈ 4, the system becomes solid and the dynamics arrested - a state that we declare the glass. Coarse-grained Brownian dynamics simulations show that at sufficient strength of LJ attraction (which effectively represents the depth of quenching, or the quality of solvent) the polymer globule indeed crosses the threshold of z*, and becomes a glass with a finite zero-frequency shear modulus, G∝ (z-z*). We verify this by showing the distinction between the 'liquid' polymer droplet at z < z*, which changes shape and adopts the spherical conformation in equilibrium, and the glassy 'solid' droplet at z > z*, which retains its shape frozen at the moment of z* crossover. These results provide a robust microscopic criterion to tell the liquid apart from the glass for the linear polymers.

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“…Additionally, the probe bending issue was addressed with the deposition of SiO x stress compensation layer. Despite biocompatibility and 41 [ 38,43,44] Silk Natural polymer 200-240 Enzymatic: (40% weight loss in 25 days) 23 [44][45][46] Dextran-based hydrogel (≈50%) resorbability, the inherent brittleness of porous Si extensively limits its application to nonconformal devices. Therefore, these substrates are used when a rigid backing substrate is needed, such as the development of a fluid pressure sensor for intracranial pressure monitoring.…”

Section: Substratementioning

confidence: 99%

A Review of Bioresorbable Implantable Medical Devices: Materials, Fabrication, and Implementation

Singh

Bathaei

Istif

et al. 2020

Adv Healthcare Materials

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Implantable medical devices (IMDs) are designed to sense specific parameters or stimulate organs and have been actively used for treatment and diagnosis of various diseases. IMDs are used for long‐term disease screening or treatments and cannot be considered for short‐term applications since patients need to go through a surgery for retrieval of the IMD. Advances in bioresorbable materials has led to the development of transient IMDs that can be resorbed by bodily fluids and disappear after a certain period. These devices are designed to be implanted in the adjacent of the targeted tissue for predetermined times with the aim of measurement of pressure, strain, or temperature, while the bioelectronic devices stimulate certain tissues. They enable opportunities for monitoring and treatment of acute diseases. To realize such transient and miniaturized devices, researchers utilize a variety of materials, novel fabrication methods, and device design strategies. This review discusses potential bioresorbable materials for each component in an IMD followed by programmable degradation and safety standards. Then, common fabrication methods for bioresorbable materials are introduced, along with challenges. The final section provides representative examples of bioresorbable IMDs for various applications with an emphasis on materials, device functionality, and fabrication methods.

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Glass transitions in native silk fibres studied by dynamic mechanical thermal analysis

Cited by 49 publications

References 59 publications

Silk Spinning in Silkworms and Spiders

Silk Spinning in Silkworms and Spiders

Polymer glass transition occurs at the marginal rigidity point with connectivity z* = 4

A Review of Bioresorbable Implantable Medical Devices: Materials, Fabrication, and Implementation

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