Cryogelation within cryogels: Silk fibroin scaffolds with single-, double- and triple-network structures

Yetiskin, Berkant; Akıncı, Caner; Okay, Oğuz

doi:10.1016/j.polymer.2017.09.023

Cited by 36 publications

(37 citation statements)

References 53 publications

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“…Okay also described a directional freezing/cryogelation method to produce high‐strength silk fibroin cryogels with a degree of mechanical anisotropy. The compressive modulus of cryogels formed at 16.7 wt% RSF concentration was 45 MPa, but the tensile properties were not shown . Consequently, achieving highly stretchable RSF hydrogels for wide‐range applications is still in its infancy.…”

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confidence: 99%

Highly Stretchable and Tough Physical Silk Fibroin–Based Double Network Hydrogels

Zhao

Guan

2019

Macromol. Rapid Commun.

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a facile way to construct strong RSF hydrogels simply by adding sodium dodecyl sulfate (SDS) into high molecular weight RSF solutions. The resulting hydrogels demonstrated high tensile strength of ≈0.74 MPa and fair extensibility of 140%. [6] Shao et al. also found that ionic liquid (IL)/water mixtures could generate RSF-based gels, whose tensile strength and breaking elongation reached up to 0.4 MPa and 147%, respectively. [11] Okay et al. reported a novel strategy to design mechanically robust and stretchable silk fibroin/hyaluronic acid hydrogels with chemical cross-links and physical cross-links (β-sheet domains). [7] The hybrid hydrogels exhibited a high extensibility up to around 400% and tensile strength of 65 kPa after equilibrium swelling. Okay also described a directional freezing/cryogelation method to produce high-strength silk fibroin cryogels with a degree of mechanical anisotropy. The compressive modulus of cryogels formed at 16.7 wt% RSF concentration was 45 MPa, but the tensile properties were not shown. [12] Consequently, achieving highly stretchable RSF hydrogels for wide-range applications [13] is still in its infancy.An alternative strategy to prepare strong and tough hydrogels is the double network (DN) hydrogel, which introduces a flexible and stretchable second network. These DN hydrogels demonstrated high fracture strength (0.1-10 MPa) and high water content (60-90%). [14][15][16][17][18][19] A series of DN gels using biomacromolecules (agar, cellulose) had been developed. [20,21] Chen et al. developed RSF-based DN hydrogels via introducing a hydrophobically associated gel of polyacrylamide (HPAAm) as the second network. [10] The DN hydrogels were conveniently synthesized by the one-pot method coupled with photo-polymerization, and the resultant RSF/HPAAm DN gels showed a tensile strength of ≈1.17 MPa, and breaking elongation of ≈1900%, but non-equilibrium RSF/HPAAm DN gels contained excessive residual monomers. It is notable that although the RSF gels could be rapidly achieved via introducing SDS, the gelation that takes only a few minutes is difficult to control. It is quite difficult to achieve uniform mixing between SDS micelles and the hydrophobic monomers via the one-step method, which often resulted in poor homogeneity of the gels. In addition, the swelling of as-prepared hydrogels in water destroys the RSF/SDS network so that equilibrium hydrogels cannot be obtained. In contrast, if the first RSF/SDS network can be stabilized first during the swelling of hydrogels, the Regenerated silk fibroin (RSF) is a promising biomedical material, but the poor mechanical properties of RSF hydrogels may hinder the use as structural components. Herein, an equilibrium RSF hydrogel is prepared and optimized based on the double network (DN) concept. After sufficient soaking in water and removal of small molecules, the equilibrium RSF DN hydrogels prove stable in water, strong, highly extensible, and tough with 0.26-0.44 MPa tensile strength, 500-900% elongation, and 2 MJ m −3 work of extension. The...

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confidence: 99%

Highly Stretchable and Tough Physical Silk Fibroin–Based Double Network Hydrogels

Zhao

Guan

2019

Macromol. Rapid Commun.

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“…Bone tissue engineering is, therefore, an active area of research. [15,16] One of the most important elements of BTE is the design of a biocompatible scaffold that provides appropriate mechanical support with optimum pore size and interconnected porosity. Porosity was calculated by measuring the weight and volume of individual cylindrical scaffolds.…”

Section: Discussionmentioning

confidence: 99%

Silk Fibroin 3D Microparticle Scaffolds with Bioactive Ceramics: Chemical, Mechanical, and Osteoregenerative Characteristics

et al. 2020

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Bone regeneration in large bone cavities presents a major challenge. These bony voids are either filled with an autograft/ allograft (patient's own bone from another anatomical location or cadaveric bone, respectively), or synthetic bone graft substitute called "bone void filler." Autografts are the 'gold standard' for bone grafting, but have inherent limitations of donor site morbidity and limited supply. [1] More recently, synthetic ceramics have shown promise for this application of bone void filling because of their chemical similarity to ceramics present in natural bone. Commonly used bioceramics include hydroxyapatite (HA), beta tricalcium phosphate (TCP), and more recently calcium sulfate (CaS). These materials are biocompatible, and support cell adhesion, proliferation, and growth of bone cells. Although these bioceramics are used as bone void fillers, they have certain limitations: they are intrinsically brittle and lack the required mechanical properties. Also, some of them have faster bioresorption rate (e.g., CaS and TCP), whereas others do not completely bioresorb (e.g., HA). In this context, to achieve native bone-like properties, current trend in bone tissue engineering (BTE) is to use a composite of bioceramic and a biocompatible polymer. [2,3] Silk fibroin (SF)-a natural biopolymerhas come up as potential candidate for BTE, owing to its biocompatibility, mechanical properties, tunable biodegradation rate, and ease of processability. The silk from the Bombyx mori silkworm, commonly known as a mulberry silkworm, can be produced with good quality in large quantities. [4-6] Efficacy of SF-based biomaterials has been proven in various tissue regeneration models. [7,8] SF can be easily modulated to obtain required functionality and different forms. [9,10] Different SF-based biomaterials including SF films, [11] SF-3D scaffold, [12,13] and SF-reinforced biomaterials [14] have proven to be successful for bone regeneration purpose. We have earlier reported a method to prepare silk fibroin microparticle scaffolds that have shown a high potential in BTE. [12] These SF microparticle scaffolds have excellent mechanical properties, pore interconnectivity, and a superior ability to promote osteoregeneration. The objective of this work was to prepare regenerated silk fibroin (RSF) microparticle scaffolds filled with nano-HA or CaS. [12,13] The addition of these fillers would further enhance the mechanical properties of these scaffolds and would thereby contribute toward the osteoregenerative potential. We compare and evaluate the performance of these microparticles and scaffolds vis-à-vis pure SF scaffolds. We have characterized the microparticles and their scaffolds for the

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“…Silk, obtained from silkworms, consists mainly of the proteins sericin and fibroin and has recently been studied in many applications of tissue engineering and regenerative medicine. Silk fibroin-based cryogels were synthesized by freeze-thawing [ 8 , 115 ] and using butanediol diglycidyl ether as a cross-linker [ 109 ]. The addition of ethylene glycol diglycidyl ether into the cryotropic gelation system triggers the conformational transition of fibroin from a random coil to the beta-sheet structure and, consequently, the gelation of fibroin during the freeze-thawing process [ 116 ].…”

Section: Biodegradable Cryogelsmentioning

confidence: 99%

Design and Assessment of Biodegradable Macroporous Cryogels as Advanced Tissue Engineering and Drug Carrying Materials

Zoughaib

Yergeshov

2021

Gels

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Cryogels obtained by the cryotropic gelation process are macroporous hydrogels with a well-developed system of interconnected pores and shape memory. There have been significant recent advancements in our understanding of the cryotropic gelation process, and in the relationship between components, their structure and the application of the cryogels obtained. As cryogels are one of the most promising hydrogel-based biomaterials, and this field has been advancing rapidly, this review focuses on the design of biodegradable cryogels as advanced biomaterials for drug delivery and tissue engineering. The selection of a biodegradable polymer is key to the development of modern biomaterials that mimic the biological environment and the properties of artificial tissue, and are at the same time capable of being safely degraded/metabolized without any side effects. The range of biodegradable polymers utilized for cryogel formation is overviewed, including biopolymers, synthetic polymers, polymer blends, and composites. The paper discusses a cryotropic gelation method as a tool for synthesis of hydrogel materials with large, interconnected pores and mechanical, physical, chemical and biological properties, adapted for targeted biomedical applications. The effect of the composition, cross-linker, freezing conditions, and the nature of the polymer on the morphology, mechanical properties and biodegradation of cryogels is discussed. The biodegradation of cryogels and its dependence on their production and composition is overviewed. Selected representative biomedical applications demonstrate how cryogel-based materials have been used in drug delivery, tissue engineering, regenerative medicine, cancer research, and sensing.

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Cryogelation within cryogels: Silk fibroin scaffolds with single-, double- and triple-network structures

Cited by 36 publications

References 53 publications

Highly Stretchable and Tough Physical Silk Fibroin–Based Double Network Hydrogels

Highly Stretchable and Tough Physical Silk Fibroin–Based Double Network Hydrogels

Silk Fibroin 3D Microparticle Scaffolds with Bioactive Ceramics: Chemical, Mechanical, and Osteoregenerative Characteristics

Design and Assessment of Biodegradable Macroporous Cryogels as Advanced Tissue Engineering and Drug Carrying Materials

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