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In recent years, natural polymer-based electrospun fibers (EFs) with huge specific surface area, good biocompatibility, and biological activity obtained from electrospinning process exhibit tremendous vitality in the field of biomedical areas. Herein, the parameters of electrospinning from two perspectives, polymer solution such as solvent, polymeric relative molecular mass, concentration, viscosity, and conductivity of the solution, and electrospinning process such as spinning voltage, spinning flow rate, needle tip to collector distance, temperature, and humidity are first detailed. Next, the raw materials consisting of polysaccharides such as cellulose, hyaluronic acid, alginate, and chitosan as well as proteins such as collagen, gelatin, silk fibroin, and keratin are summarized. The preparation method and related characteristics of EFs with multistage structures such as porous, core-shell, Janus, bamboo-like and other structures are introduced. The biomedical applications of these natural polymer-based EFs mainly including tissue engineering, drug sustained release, wound dressings, and biomedical sensors are systematically recapitulated. Finally, the outlook on natural EFs is further proposed., (© 2022 Wiley-VCH GmbH.)

Natural extracts gallnut tannins (GTs) were used as functional components to prepare chitosan/gallnut tannins (CS/GTs) composite fiber by blended solution spinning. Chitosan fiber has great potential to be used as absorbent suture and dressing due to its good biocompatibility. However, the weak mechanical properties limited its application. Chitosan and GTs were blended in aqueous solution of acetic acid to spin the composite fiber. The results indicated that CS/GTs fiber can be easily prepared due to the appropriate rheology characteristics for blended solution. Compared with pure chitosan fiber, CS/GTs fiber with 10% GTs showed lower hydrophilicity and higher dry, wet breaking strength by more than 40% due to ionic cross-linking between chitosan and GTs. The bacterial reduction to Staphylococcus aureus increased from 49.0 to 99.7% and about double green and red fluorescent intensity were observed for CS/GTs fiber. GTs have great potentiality in improving the properties of chitosan fiber., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this paper, rod-like chitin whisker was used as a filler to reinforce the chitosan membrane, and a series of composite membranes were prepared by casting-evaporation method. Mechanical testing shows that tensile strength of the resulting composite membrane with 3 wt% chitin whisker content reaches up to 110.3 MPa, which is about 2.8 times than that of neat chitosan membrane (38.5 MPa), and moisture regain of all composite membranes presents a decreasing tendency with increasing content of chitin whisker. Furthermore, SEM was used to investigate the morphology difference between neat chitosan membrane and composite membranes, to understand the reinforce mechanism of chitin whisker. Wide angle x-ray diffraction and Fourier transform infrared spectroscopy were used to visualize the structure change before and after the compositing processes. Besides, the bacterostatic test shows that this composite membrane presents effective inhibitory effect on Staphylococcus aureus, Escherchia coli and Corinebaterium michiganence respectively, which indicates it a promising material for packaging and wound dressing., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A binary ionic liquid system was confirmed to be a promising solvent to dissolve chitosan, and the regenerated chitosan fibers were prepared by wet and dry-wet spinning technique respectively. The SEM results show that the chitosan fibers prepared by wet spinning technique present striated surface and round cross section, and the chitosan fibers prepared by dry-wet spinning technique present smooth surface and irregular cross section. The mechanical testing results show that the regenerated chitosan fibers present relatively high tenacity, especially, these prepared by dry-wet spinning process present excellent strength and initial modulus, i.e. 2.1cN/dtex and 83.5cN/dtex, which is stronger than that of most reported chitosan fibers. The FT-IR results show that the dissolution of chitosan in the binary ionic liquid system is due to the protonation of NH₂ groups in the chitosan chains. Furthermore, a possible reaction during the dissolution and regeneration process is proposed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In this study, glycine hydrochloride (Gly·HCl) is confirmed to be a promising solvent for dissolving native chitosan and preparing regenerated chitosan membrane. As compared with the chitosan membrane prepared from traditional acetic acid, the membrane prepared from Gly·HCl by dry technique shows excellent tensile strength and initial modulus, i.e. 103.8MPa and 3.2GPa, respectively, which is superior to any chitosan membrane and most chitosan blend membranes reported in literatures. Besides, scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FT-IR) were used to visualize the difference between the two kind of regenerated chitosan membranes. The SEM results show that the membrane prepared from Gly·HCl by dry technique presents a novel structure, which ensures its high tenacity. Furthermore, the chitosan microporous membranes were also prepared using PEG as porogen., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

ABSTRACT Keratin particles with microscale are prepared by ball mill and its influences on the chitosan membrane is evaluated. Composite membranes with various content of keratin are fabricated, and their physical and chemical properties such as morphology, wettability, crystallization, thermal stability, tensile strength, and break elongation are investigated. Optical microscope and situ topographic scan mode of nano-test system are used to examine the dispersion and aggregation of keratin on the surface of chitosan membrane. The result of contact angle (CA) and mechanical testing show that the incorporation of keratin particles decrease the CA from 98.1° to 58.2°. Tensile strength and break elongation of the composite membrane reaches a maximum of 65 ± 8 MPa and 15% when the keratin content is 6%, an increase of 80% and 88% compared with the pristine chitosan membrane. Both the increase in tensile strength and break elongation is result of the incorporation of keratin particles known for their excellent compatibility between keratin and chitosan matrix. These kind of composite material combines the antibacterial properties of chitosan with cell culture preference of keratin which may have potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44667. [ABSTRACT FROM AUTHOR]

Abstract: Chitosan membrane possesses huge potential application in many fields, such as biomedicine, wastewater purification and environmental protection, however, the poor mechanical property restricts its further development. In this study, chitin whisker was prepared by hydrolysis method, and was firstly used as an interlayer to fabricate the multilayered chitosan membrane through layer-by-layer method, which is inspired by the natural materials' hierarchical structure. From the results of mechanical testing, it is shown that tensile strength of the multilayered chitosan membranes reaches up to 122.8MPa, which is about 2.5 times than that of neat chitosan membrane (i.e. 49.5MPa), and the elongation at break is sharply increased as well. [Copyright &y& Elsevier]

Abstract: A binary system consisting of acidic ionic liquid glycine hydrochloride (Gly·HCl) and neutral ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) is proposed to be cosolvent for chitosan and cellulose, the spinning solution of chitosan/cellulose can be prepared in one step. The regenerated chitosan/cellulose composite fiber with 9.4wt.% chitosan was prepared through dry–wet spinning process. SEM shows that the chitosan is scattered on the surface and interior of the composite fiber. WAXD shows that the degree crystallization of the composite fibers is far less than that of raw materials. The result of elemental analysis (EA) indicates that there is little weight loss of chitosan during the spinning process. Moreover, the prepared composite fiber presents good thermal stability, i.e. its T onset is 305.1°C, and excellent mechanical property, i.e. its tensile strength is 4.63cN/dtex. All the results show that Gly·HCl/[Bmim]Cl binary system is a promising solvent for the preparation of chitosan/cellulose composite fiber. [Copyright &y& Elsevier]