Bicomponent aligned nanofibers of N-carboxyethylchitosan and poly(vinyl alcohol)

Reviewing Chitin/Chitosan Nanofibers and Associated Nanocomposites and Their Attained Medical Milestones

Chitin/chitosan research is an expanding field with wide scope within polymer research. This topic is highly inviting as chitin/chitosan's are natural biopolymers that can be recovered from food waste and hold high potentials for medical applications. This review gives a brief overview of the chitin/chitosan based nanomaterials, their preparation methods and their biomedical applications. Chitin nanofibers and Chitosan nanofibers have been reviewed, their fabrication methods presented and their biomedical applications summarized. The chitin/chitosan based nanocomposites have also been discussed. Chitin and chitosan nanofibers and their binary and ternary composites are represented by scattered superficial reports. Delving deep into synergistic approaches, bringing up novel chitin/chitosan nanocomposites, could help diligently deliver medical expectations. This review highlights such lacunae and further lapses in chitin related inputs towards medical applications. The grey areas and future outlook for aligning chitin/chitosan nanofiber research are outlined as research directions for the future.

Electrospun anisotropic architectures and porous structures for tissue engineering

Recent advances in electrospun anisotropic architectures and porous structures, as well as their applications in tissue engineering, are presented.

A novel fixed-bed reactor design incorporating an electrospun PVA/chitosan nanofiber membrane

In this research, a novel fixed-bed reactor was designed with a nanofiber membrane composed of a polyvinyl alcohol (PVA)/chitosan nanofiber blend prepared using an electrospinning technique. The applied voltage, tip-collector distance, and solution flow rate of the electrospinning process were 18 kV, 14.5 cm, and 0.5 mL h(-1), respectively. Brunauer-Emmett-Teller (BET) theory, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize and analyze the nanofiber membranes. Homogeneous electrospun nanofibers with an average diameter of 99.47 nm and surface area of 214.12 m(2)g(-1) were obtained. Adsorption experiments were carried out in a batch system to investigate the effect of different adsorption parameters such as pH, adsorbent dose, biomass dose, contact time, and temperature. The kinetic data, obtained at the optimal pH of 6, were analyzed by pseudo first-order and pseudo second-order kinetic models. Three isotherm models and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were applied to describe the equilibrium data of the metal ions adsorbed onto the PVA/chitosan nanofiber membrane.

Emerging chitin and chitosan nanofibrous materials for biomedical applications

Over the past several decades, we have witnessed significant progress in chitosan and chitin based nanostructured materials. The nanofibers from chitin and chitosan with appealing physical and biological features have attracted intense attention due to their excellent biological properties related to biodegradability, biocompatibility, antibacterial activity, low immunogenicity and wound healing capacity. Various methods, such as electrospinning, self-assembly, phase separation, mechanical treatment, printing, ultrasonication and chemical treatment were employed to prepare chitin and chitosan nanofibers. These nanofibrous materials have tremendous potential to be used as drug delivery systems, tissue engineering scaffolds, wound dressing materials, antimicrobial agents, and biosensors. This review article discusses the most recent progress in the preparation and application of chitin and chitosan based nanofibrous materials in biomedical fields.

Micro- and nanofabrication of chitosan structures for regenerative engineering

Repair and regeneration of human tissues and organs using biomaterials, cells and/or growth factors is the ultimate goal of tissue engineers. One of the grand challenges in this field is to closely mimic the structures and properties of native tissues. Regenerative engineering-the convergence of tissue engineering with advanced materials science, stem cell science, and developmental biology-represents the next valuable tool to overcome the challenges. This article reviews the recent progress in developing advanced chitosan structures using various fabrication techniques. These chitosan structures, together with stem cells and functional biomolecules, may provide a robust platform to gain insight into cell-biomaterial interactions and may function as excellent artificial extracellular matrices to regenerate complex human tissues and biological systems.

Hybrid nanofibrous yarns based on N-carboxyethylchitosan and silver nanoparticles with antibacterial activity prepared by self-bundling electrospinning

Hybrid nanofibrous materials with antibacterial activity consisting of yarns from N-carboxyethylchitosan (CECh) and poly(ethylene oxide) (PEO) that contain 5 wt% or 10 wt% silver nanoparticles (AgNPs) were prepared. This was achieved by electrospinning using formic acid as a solvent and as a reducing agent for silver ions. AgNO₃ was used as an Ag(+)-containing salt. Its concentration was selected to be 0.02 mol/L or 0.04 mol/L in order the content of the AgNPs in the electrospun nanofibers to be 5 wt% or 10 wt%, respectively. The self-bundling of the fibers into yarns with a mean diameter of ca. 35 μm was enabled only by using a grounded needle electrode. The reduction of the silver ions to an elemental silver was evidenced by UV-vis spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The transmission electron microscopy (TEM) analyses revealed that AgNPs formed at AgNO₃ concentration of 0.02 mol/L were with a mean diameter of 4±0.5 nm and were distributed uniformly within the fiber. The increase of AgNO₃ concentration to 0.04 mol/L led to the preparation of AgNPs with a higher mean diameter and a broader diameter distribution as well as to aggregate formation. The performed studies on the antibacterial activity of CECh/PEO/AgNPs fibrous materials against Staphylococcus aureus showed that at AgNPs content of 5 wt% the mats had bacteriostatic, and at AgNPs content of 10 wt%-bactericidal activity.

Electrospinning of polysaccharides for regenerative medicine

Electrospinning techniques enable the production of continuous fibers with dimensions on the scale of nanometers from a wide range of natural and synthetic polymers. The number of recent studies regarding electrospun polysaccharides and their derivatives, which are potentially useful for regenerative medicine, is increasing dramatically. However, difficulties regarding the processibility of the polysaccharides (e.g., poor solubility and high surface tension) have limited their application. In this review, we summarize the characteristics of various polysaccharides such as alginate, cellulose, chitin, chitosan, hyaluronic acid, starch, dextran, and heparin, which are either currently being used or have potential to be used for electrospinning. The recent progress of nanofiber matrices electrospun from polysaccharides and their biomedical applications in tissue engineering, wound dressings, drug delivery, and enzyme immobilization are discussed.

Nanofibrous membranes from aqueous electrospinning of carboxymethyl chitosan

Carboxymethyl chitosan (CMCS) with varying molecular weights (M(v) = 40-405 kDa) and degrees of substitution (DS = 0.25-1.19) has been synthesized by alkalization of chitosan, followed by carboxymethylation with monochloroacetic acid. At DS up to 1.19, the locations where carboxymethylation took place were influenced by the alkalization temperature, i.e., both C2 and C6 substitution at ambient temperature (N,O-carboxymethylated) and mainly C6 substitution at the lower temperature, -15 °C (O-carboxymethylated). Generally, carboxymethylation was more favorable at the primary C6 hydroxyl than the C2 position with increasing DS. CMCS synthesized from 405 kDa CS was soluble in water at DS≥0.73 whereas those from 40 and 89 kDa became water-soluble at lower DS of 0.25 and 0.36, respectively. Electrospinning of aqueous solutions of CMCS was facilitated with the addition of water-soluble polymers, including PEO, PAA, PAAm and PVA. The optimal fiber formation was observed at equal mass composition of O-CMCS (89 kDa at 0.36 DS) and PVA, producing nanofibers with an average diameter of 130 nm. Heat-induced esterification (at 140 °C for 30 min) produced inter-molecular covalent cross-links within and among fibers, rendering the fibrous membrane water-insoluble. Membranes containing higher CMCS carboxyl to PVA hydroxyl ratio retained better fiber morphology upon extended water exposure, indicating more favorable inter-molecular cross-links. The fibrous membranes generated with less substituted CMCS were more hydrophilic and retained a greater extent of the desirable amine functionality.