نمونه متن انگلیسی مقاله
Recently, chitosan has become attractive due to being biodegradable, biocompatible and renewable. However, the weak mechanical properties of chitosan films limit their large-scale application. In this work, a strategy of blending TEMPO, oxidized CNF (TOCN) and chitosan was developed to fabricate nanocomposite films in order to improve the mechanical properties and maintain biocompatibility. The TOCN/chitosan nanocomposite films exhibited excellent optical transmittance (>85%) and extremely high tensile strength of 235 MPa. The good compatibility of TOCN and chitosan chains, good dispersion of chitosan aggregates and the presence of stiff TOCN crystal domains are the main reasons for getting improved mechanical strength of composite films. The films showed good biocompatible properties based on the cell activity assay results. Furthermore, they were stable in PBS buffer for more than 6 months without significant degradation. The TOCN/chitosan nanocomposite films with these excellent properties could be employed in medical applications.
In the past decades, the environmental pollution produced by petroleum-based plastic materials has become more and more serious because they are not biodegradable and can remain in the environment for hundreds of years. One possible solution for this issue is to promote bio-based materials that are renewable, biodegradable and abundant in nature. Chitosan is promising in the bio-based materials list because it is a derivative of chitin microfibrils from crustaceans . It has a lot of advantages including biodegradability, biocompatibility and antimicrobial properties . Moreover, it can be easily made into films by simple methods such as solvent casting, electrospraying and direct immersion [3–5].
Chitosan-based films have been explored as promising substrates for various applications. For example, they were applied for removing dyes and metal ions from polluted water , used as carriers for drug delivery [7,8] and for applications in regenerative medicine . They were also fabricated into food packaging films that have antibacterial properties [10,11]. However, weak mechanical properties are a major problem of chitosan-based films which limits their further practical application. Intensive efforts have been made to resolve this issue. For instance, some nanofillers such as nano-hydroxyapatite , nano metal oxides [13, 14], graphene oxide [15,16] and mineral clays  show good reinforcement effects on chitosan films. In addition, there are some other additives that can simultaneously enhance the mechanical properties and maintain the biocompatibility of chitosan, such as glycerol , xylitol and sorbitol , cross-linking agent vanillin , hydroxyethyl-cellulose and polyvinyl alcohol (PVA) .
In summary, TOCN/chitosan nanocomposite films with significantly improved physicochemical properties were prepared via carefully controlled processing of the TOCN and chitosan dispersion. The main findings are listed as: (1) All the nanocomposite films maintained good transparency with the addition of TOCN. The viscosity of the hybrid suspensions increased and remained constant at different temperatures, which indicates that the nanocomposites are suitable for in vivo applications. (2) Chitosan and TOCN chains showed good compatibility with strong hydrogen bonding interactions. Benefiting from the good dispersion and higher crystallinity, the nanocomposite films exhibited improved mechanical properties compared to the neat chitosan films and commercial fabric fibers used for wound healing. (3) The nanocomposite films showed excellent biocompatibility, verified by the nontoxic behavior against mouse monocyte Raw264.7 cells and excellent stability in PBS buffer, indicating their potential use in biomedical applications, such as contact lens, drug release, etc. It also shows the possibility to replace current commercial wound healing materials. Overall, the addition of nanocellulose can overcome chitosan’s main mechanical weakness and lead to a total biocompatible nanocomposite with the advantages of being obtained from bio-sources, contributing to sustainability and environmental safety concerns.