Chitosan is a natural polycationic linear polysaccharide derived from chitin. The low solubility of chitosan in neutral and alkaline solution limits its application. Nevertheless, chemical modification into composites or hydrogels brings to it new functional properties for different applications. Chitosans are recognized as versatile biomaterials because of their non-toxicity, low allergenicity, biocompatibility and biodegradability. This review presents the recent research, trends and prospects in chitosan. Some special pharmaceutical and biomedical applications are also highlighted.

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Chitosan: An Update on Potential Biomedical and Pharmaceutical Applications.

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(15)00070-0.pdf

Crosslinking biopolymers for biomedical applications.

Nanotechnology refers to the fabrication, characterization, and application of substances in nanometer scale dimensions for various ends. The influence of nanotechnology on the healthcare industry is substantial, particularly in the areas of disease diagnosis and treatment. Recent investigations in nanotechnology for drug delivery and tissue engineering have delivered high-impact contributions in translational research, with associated pharmaceutical products and applications. Over the past decade, the synthesis of nanofibers or nanoparticles via electrostatic spinning or spraying, respectively, has emerged as an important nanostructuring methodology. This is due to both the versatility of the electrospinning/electrospraying process and the ensuing control of nanofiber/nanoparticle surface parameters. Electrosprayed nanoparticles and electrospun nanofibers are both employed as natural or synthetic carriers for the delivery of entrapped drugs, growth factors, health supplements, vitamins, and so on. The role of nanofiber/nanoparticle carriers is substantiated by the programmed, tailored, or targeted release of their contents in the guise of tissue engineering scaffolds or medical devices for drug delivery. This review focuses on the nanoformulation of natural materials via the electrospraying or electrospinning of nanoparticles or nanofibers for tissue engineering or drug delivery/pharmaceutical purposes. Here, we classify the natural materials with respect to their animal/plant origin and macrocyclic, small molecule or herbal active constituents, and further categorize the materials according to their proteinaceous or saccharide nature.

Electrosprayed nanoparticles and electrospun nanofibers based on natural materials: applications in tissue regeneration, drug delivery and pharmaceuticals

Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent.

Nanofibrillated cellulose: surface modification and potential applications

Manufacturing of hydrogel biomaterials with controlled mechanical properties for tissue engineering applications.

Plant fibers are hydrophilic in nature due to attraction/interaction between the hydroxyl groups of fiber components and water molecules. The hydrophilic nature of plant fibers often results in poor compatibility with hydrophobic polymer matrices. Therefore, it becomes necessary to modify the surface of plant fibers for better binding between fiber and matrix. Most of the chemical treatments involve mercerization, acetylation, benzoylation, isocyanate treatment and grafting of synthetic polymers. Surface modification of plant fibers using chemical treatments becomes less attractive because of a number of limitations. Environment friendly methods such as plasma treatment, treatments using fungi, enzymes and bacteria, can be used for the surface modification of plant fibers. In this article, we have reviewed various environmentally friendly methods for surface modification and their effect on the properties of plant fibers and reinforced polymer composites. The applications of modified plant fibers in textile industry and antimicrobial activities are also discussed in this article.

Surface modification of plant fibers using environment friendly methods for their application in polymer composites, textile industry and antimicrobial activities: A review

Non-covalent crosslinkers for electrospun chitosan fibers.

Few studies exist on the mechanical performance of crosslinked electrospun chitosan (CS) fibre mats. In this study, we show that the mat structure and mechanical performance depend on the different crosslinking agents genipin, epichlorohydrin (ECH), and hexamethylene-1,6-diaminocarboxysulphonate (HDACS), as well as the post-electrospinning heat and base activation treatments. The mat structure was imaged by field emission scanning electron microscopy and the mechanical performance was tested in tension. The elastic modulus, tensile strength, strain at failure and work to failure were found to range from 52 to 592 MPa, 2 to 30 MPa, 2 to 31 per cent and 0.041 to 3.26 MJ m−3, respectively. In general, neat CS mats were found to be the stiffest and the strongest, though least ductile, while CS–ECH mats were the least stiff, weakest, but the most ductile, and CS–HDACS fibre mats exhibited intermediary mechanical properties. The mechanical performance of the mats is shown to reflect differences in the fibre diameter, number of fibre–fibre contacts formed within the mat, as well as varying intermolecular bonding and moisture content. The findings reported here complement the chemical properties of the mats, described in part I of this study.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2012.0946

New crosslinkers for electrospun chitosan fibre mats. Part II: mechanical properties

Various-sourced pectin and polyethylene oxide electrospun fibers.

Biopolymer–ceramic composites are thought to be particularly promising materials for bone tissue engineering as they more closely mimic natural bone. Here, we demonstrate the fabrication by electrospinning of fibrous chitosan-hydroxyapatite composite scaffolds with low (1 wt %) and high (10 wt %) mineral contents. Scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and unidirectional tensile testing were performed to determine fiber surface morphology, elemental composition, and tensile Young's modulus (E) and ultimate tensile strength (σUTS), respectively. EDS scans of the scaffolds indicated that the fibers, crosslinked with either hexamethylene-1,6-diaminocarboxysulfonate (HDACS) or genipin, have a crystalline hydroxyapatite mineral content at 10 wt % additive. Moreover, FESEM micrographs showed that all electrospun fibers have diameters (122–249 nm), which fall within the range of those of fibrous collagen found in the extracellular matrix of bone. Young's modulus and ultimate tensile strength of the various crosslinked composite compositions were in the range of 116–329 MPa and 2–15 MPa, respectively. Osteocytes seeded onto the mineralized fibers were able to demonstrate good biocompatibility enhancing the potential use for this material in future bone tissue engineering applications. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3201–3211, 2015.

Marjorie A. Kiechel

Papers

Surface modification of plant fibers using environment friendly methods for their application in polymer composites, textile industry and antimicrobial activities: A review

Non-covalent crosslinkers for electrospun chitosan fibers.

New crosslinkers for electrospun chitosan fibre mats. Part II: mechanical properties

Various-sourced pectin and polyethylene oxide electrospun fibers.

Osteoblast biocompatibility of premineralized, hexamethylene-1,6-diaminocarboxysulfonate crosslinked chitosan fibers.