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...

/pdf/determining-beta-sheet-crystallinity-in-fibrous-proteins-by-2aov4wvj48.pdf

Determining Beta Sheet Crystallinity in Fibrous Proteins by Thermal Analysis and Infrared Spectroscopy

Three-dimensional bioprinting uses additive manufacturing techniques for the automated fabrication of hierarchically organized living constructs. The building blocks are often hydrogel-based bioinks, which need to be printed into structures with high shape fidelity to the intended computer-aided design. For optimal cell performance, relatively soft and printable inks are preferred, although these undergo significant deformation during the printing process, which may impair shape fidelity. While the concept of good or poor printability seems rather intuitive, its quantitative definition lacks consensus and depends on multiple rheological and chemical parameters of the ink. This review discusses qualitative and quantitative methodologies to evaluate printability of bioinks for extrusion- and lithography-based bioprinting. The physicochemical parameters influencing shape fidelity are discussed, together with their importance in establishing new models, predictive tools and printing methods that are deemed instrumental for the design of next-generation bioinks, and for reproducible comparison of their structural performance.

Printability and Shape Fidelity of Bioinks in 3D Bioprinting.

Bone tissue engineering (BTE) is a rapidly growing field aiming to create a biofunctional tissue that can integrate and degrade in vivo to treat diseased or damaged tissue. It has become evident that scaffold fabrication techniques are very important in dictating the final structural, mechanical properties, and biological response of the implanted biomaterials. A comprehensive review of the current accomplishments on scaffold fabrication techniques, their structure, and function properties for BTE is provided herein. Different types of biomaterials ranging from inorganic biomaterials to natural and synthetic polymers and related composites for scaffold processing are presented. Emergent scaffolding techniques such as electrospinning, freeze-drying, bioprinting, and decellularization are also discussed. Strategies to improve vascularization potential and immunomodulation, which is considered a grand challenge in BTE scaffolding, are also presented.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.202010609

Scaffold fabrication technologies and structure/function properties in bone tissue engineering

Hydrogels are a three-dimensional and crosslinked network of hydrophilic polymers. They can absorb a large amount of water or biological fluids, which leads to their swelling while maintaining their 3D structure without dissolving (Zhu and Marchant, Expert Rev Med Devices 8:607–626, 2011). Among the numerous polymers which have been utilized for the preparation of the hydrogels, polysaccharides have gained more attention in the area of pharmaceutics; Sodium alginate is a non-toxic, biocompatible, and biodegradable polysaccharide with several unique physicochemical properties for which has used as delivery vehicles for drugs (Kumar Giri et al., Curr Drug Deliv 9:539–555, 2012). Owing to their high-water content and resembling the natural soft tissue, hydrogels were studied a lot as a scaffold. The formation of hydrogels can occur by interactions of the anionic alginates with multivalent inorganic cations through a typical ionotropic gelation method. However, those applications require the control of some properties such as mechanical stiffness, swelling, degradation, cell attachment, and binding or release of bioactive molecules by using the chemical or physical modifications of the alginate hydrogel. In the current review, an overview of alginate hydrogels and their properties will be presented as well as the methods of producing alginate hydrogels. In the next section of the present review paper, the application of the alginate hydrogels will be defined as drug delivery vehicles for chemotherapeutic agents. The recent advances in the application of the alginate-based hydrogels will be describe later as a wound dressing and bioink in 3D bioprinting.

/pdf/alginate-based-hydrogels-as-drug-delivery-vehicles-in-cancer-ofytezw246.pdf

Alginate-based hydrogels as drug delivery vehicles in cancer treatment and their applications in wound dressing and 3D bioprinting

Wounds are one of the most common health issues, and the cost of wound care and healing has continued to increase over the past decade. The first step in wound healing is haemostasis, and the development of haemostatic materials that aid wound healing has accelerated in the past 5 years. Numerous haemostatic materials have been fabricated, composed of different active components (including natural polymers, synthetic polymers, silicon-based materials and metal-containing materials) and in various forms (including sponges, hydrogels, nanofibres and particles). In this Review, we provide an overview of haemostatic materials in wound healing, focusing on their chemical design and operation. We describe the physiological process of haemostasis to elucidate the principles that underpin the design of haemostatic wound dressings. We also highlight the advantages and limitations of the different active components and forms of haemostatic materials. The main challenges and future directions in the development of haemostatic materials for wound healing are proposed. Uncontrolled bleeding is a major cause of death, incentivizing the development of biomaterials that aid haemostasis and wound healing. This Review highlights the active components and forms of haemostatic materials, with a focus on their chemical design, and considers future trends in their development.

Haemostatic materials for wound healing applications

Biomedical hydrogels as sole repair matrices or combined with pre-seeded cells and bioactive growth factors are extensively applied in tissue engineering and regenerative medicine. Hydrogels normally provide three dimensional structures for cell adhesion and proliferation or the controlled release of the loading of drugs or proteins. Various physiochemical properties of hydrogels endow them with distinct applications. In this review, we present the commonly used crosslinking method for hydrogel synthesis involving physical and chemical crosslinks and summarize their current progress and future perspectives.

Advances in crosslinking strategies of biomedical hydrogels

Halloysite nanotubes (HNTs) are natural occurring mineral clay nanotubes that have excellent application potential in different fields. However, HNTs are heterogeneous in size, surface charge, and formation of surfacial hydrogen bond, which lead to weak affinity and aggregation at a certain extent. It is very important to modify the HNTs’ surface to expand its applications. In this review, the structural characteristics, performance, and the related applications of surface-modified HNTs are reviewed. We focus on the surface-modified variation of HNTs, the effects of surface modification on the materials and related applications in various regions. In addition, future prospects and the meaning of surface modification were also discussed in HNTs studies. This review provides a reference for the application of HNTs modifications in the field of new nanomaterials.

Recent Advances on Surface Modification of Halloysite Nanotubes for Multifunctional Applications

Forming biomolecular hydrogels with a combination of high strength and biocompatibility is still a challenge. Herein, we demonstrated a green gas (CO2)-mediated chemical cross-linking strategy that...

Green Gas-Mediated Cross-Linking Generates Biomolecular Hydrogels with Enhanced Strength and Excellent Hemostasis for Wound Healing.

Accelerated skin wound healing by soy protein isolate-modified hydroxypropyl chitosan composite films.

A series of ultrafine polyvinyl alcohol (PVA)/graphene oxide (GO) nanofibrous scaffolds (PGNSs) with different GO content (0, 0.25, 0.5, and 1.0%) was fabricated via an electrospinning process. The morphology, composition, mechanical behavior, surface wettability and protein adsorptivity of these scaffolds were investigated. The results showed that the diameter of the nanofibers in the PGNSs was 230 ± 68, 197 ± 46, 188 ± 38 or 164 ± 54 nm when the GO content in the scaffolds was 0, 0.25, 0.5 or 1.0%, respectively. The ATR-Fourier transform infrared spectra, Raman spectra, and X-ray diffraction results revealed the successful introduction of GO into the PVA matrix. Mechanical testing indicated that GO increased the tensile strength while reducing the ductility of the scaffolds. The biological properties of the scaffolds were evaluated by water contact angle measurements, protein adsorption assays, hemolysis ratio testing, cell co-culturing and in vivo skin repair in animal models. The results showed that the GO-modified scaffolds had favorable hydrophilicity and enhanced protein-enrichment ability. No visible hemolysis was observed for any of the scaffolds. Cellular behavior on the scaffolds revealed that the PGNSs were suitable for the growth and adhesion of L929 fibroblasts. Moreover, the PGNS containing a 0.25% GO content was the most suitable scaffold for cell viability and adhesion. In vivo wound repair assessments showed that the wound contraction rate when treated by the PGNS containing a 0.25% GO content exceeded 90% within 9 days, suggesting excellent potential of the PGNS for skin tissue engineering.

/pdf/graphene-oxide-modified-electrospun-polyvinyl-alcohol-2pkqt5ybw8.pdf

Zijian Wang

Papers

Advances in crosslinking strategies of biomedical hydrogels

Recent Advances on Surface Modification of Halloysite Nanotubes for Multifunctional Applications

Green Gas-Mediated Cross-Linking Generates Biomolecular Hydrogels with Enhanced Strength and Excellent Hemostasis for Wound Healing.

Accelerated skin wound healing by soy protein isolate-modified hydroxypropyl chitosan composite films.

Graphene oxide-modified electrospun polyvinyl alcohol nanofibrous scaffolds with potential as skin wound dressings