Fuyuan Ding

Chitin-based fast responsive pH sensitive microspheres for controlled drug release.

Ionically crosslinked chitin microspheres were prepared by using electrostatic droplet method and the drug release from the microspheres was controlled by adjusting external pH. Specifically, chitin was dissolved in NaOH/urea solution at low temperature and functionalized with acrylamide moieties. Acrylamide-modified chitin microspheres with a diameter of 400-500 μm can be obtained at the voltage of 6 kV and the pump speed of 5 mL h(-1). The formed microspheres were ionically crosslinked with Fe(3+) and then complexed with polycationic polysaccharide chitosan. The structure of the microspheres was characterized by FT IR, SEM, and EDS analyses. Besides, the drug release behavior of the microspheres exhibited a fast responsive and pH sensitive release of vancomycin. It took 30 h for complete release of vancomycin in pH 4.0 buffer and pH 1.2 HCl solution while a fast release (10 min) occurred in pH 7.4 buffer. The results showed that the microspheres could be used in drug delivery.

Antibacterial hydrogel coating by electrophoretic co-deposition of chitosan/alkynyl chitosan

Despite much effort has been paid to develop aseptic implant devices, the infection associated with medical implant still remains a significant problem. Here, we report a potential coating material derived from a natural biopolymer chitosan. Firstly, chitosan functionalized with alkynyl moiety (ACS) was prepared by reaction between chitosan and 3-bromopropyne. The structure of the alkynyl chitosan was characterized by FT-IR, (1)H NMR, XRD, TGA and element analysis. The minimum inhibitory concentration (MIC) of ACS with a degree of substitution (DS) of 0.40 was 0.03% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Subsequently, the alkynyl chitosan was co-deposited with chitosan on stainless steel wire to fabricate a composite hydrogel. The composite hydrogel exhibited better antibacterial activities than pure chitosan hydrogel.

Recent advances in engineered chitosan-based nanogels for biomedical applications

In the last few decades, chitosan-based nanostructured materials have attracted significant attention and have been applied in different biomedical fields. Chitosan-based nanogels with appealing physical and biological characteristics have been developed for various biomedical applications due to their excellent properties related to biocompatibility, biodegradability, antibacterial activity, low immunogenicity, large surface area, and stimuli responsiveness. Numerous approaches, such as physical gelation, self-assembly, polymerization, ionic gelation and microemulsion, have been employed to fabricate chitosan-based nanogels with multiple functionalities. These nanogels are promising as effective vehicles for drug delivery, cell culture, bioimaging and therapy. This paper reviews recent progress in the preparation and application of engineered chitosan-based nanogels in biomedical fields.

Tunable thermosensitive behavior of multiple responsive chitin

Chitin can be dissolved and homogeneously functionalized in NaOH/urea aqueous solvent. Previously, we reported that chitin modified with acrylamide (AMC) possesses high water solubility and can undergo a sol-gel transition responding to pH and cationic ions. In this report, we further explored the thermosensitive behavior of this multiple responsive chitin. We showed that the sol-gel transition temperature of AMC can be facilely adjusted by the degree of substitution (DS), pH, polymer concentration and the presence of anions or cations. Importantly, AMC can form a hydrogel at 37 °C and return to solution at 4 °C by adjusting experimental parameters. We anticipate this multiple responsive chitin may have potential applications in injectable materials and smart drug delivery.

Emerging Chitosan-Based Films for Food Packaging Applications

Recent years have witnessed great developments in biobased polymer packaging films for the serious environmental problems caused by the petroleum-based nonbiodegradable packaging materials. Chitosan is one of the most abundant biopolymers after cellulose. Chitosan-based materials have been widely applied in various fields for their biological and physical properties of biocompatibility, biodegradability, antimicrobial ability, and easy film forming ability. Different chitosan-based films have been fabricated and applied in the field of food packaging. Most of the review papers related to chitosan-based films are focusing on antibacterial food packaging films. Along with the advances in the nanotechnology and polymer science, numerous strategies, for instance direct casting, coating, dipping, layer-by-layer assembly, and extrusion, have been employed to prepare chitosan-based films with multiple functionalities. The emerging food packaging applications of chitosan-based films as antibacterial films, barrier films, and sensing films have achieved great developments. This article comprehensively reviews recent advances in the preparation and application of engineered chitosan-based films in food packaging fields.

Electrochemically induced reversible formation of carboxymethyl chitin hydrogel and tunable protein release

Carboxymethyl chitin is one of the most important derivatives of chitin that has been widely used in the fields of biomedicine and environmental treatment. In this contribution, carboxymethyl chitin was homogenously synthesized in NaOH–urea aqueous solution for the first time. The product was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), 1H nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC) and a titration method. Carboxymethyl chitin showed water solubility and cationic sensitivity. Reversible sol–gel transition could be performed by sequentially adding cations and a reducing agent. Further, we demonstrated that the reversible sol–gel transition of carboxymethyl chitin could be controlled on the surface of a stainless steel electrode by using an electrochemical method. Once an anodic signal was imposed to the electrode, sol–gel transition occurred due to the crosslinking of carboxymethyl chitin with Fe2+/Fe3+. The gel formation can be facilely controlled by voltage, concentration of carboxymethyl chitin and deposition time. Protein could be entrapped in the hydrogel simultaneously during the in situ formation of hydrogel. Protein release accelerated when a cathodic signal was imposed due to the electrochemically induced conversion of Fe2+/Fe3+ to Fe. The present result represents a “green” and simple process to synthesize carboxymethyl chitin and the prepared chitin derivative may have potential applications in electrochemically controlled drug delivery systems.

Electrochemical writing on edible polysaccharide films for intelligent food packaging

Polysaccharide films used as intelligent food packaging possess the advantages of renewability, safety and biodegradability. Printing on the polysaccharidic food packaging is challenging due to the high demand for edible-ink and the need for a suitable printing technique. In this work, we propose an electrochemical method for writing on polysaccharide film. Unlike conventional printing, this electrochemical writing process relies on the pH responsive color change of anthocyanin embedded in the chitosan/agarose hydrogel. By biasing a negative potential to a stainless wire (used as a pen) contacting the surface of the chitosan/agarose/ATH hydrogel, the locally generated pH change induced the color change of ATH and wrote programmed information on the hydrogel. We demonstrate the writing can be temporary in the hydrogel but stable when the hydrogel is dried. We further demonstrate that the written film is applicable for the detection of the spoilage of crucian fish. The reported electrochemical writing process provides a novel method for printing information on polysaccharide film and great potential for intelligent food packaging.

Recent advances in chitosan-based self-healing materials

Over the past few decades, self-healing materials derived from chitosan have attracted a great deal of attention due to their excellent physical and biological properties related to their self-healing ability, biodegradability, biocompatibility and antibacterial activity. This review discusses the most recent progress in the preparation and application of chitosan-based self-healing materials. Various strategies that have been used to prepare chitosan-based self-healing materials are reviewed, including the construction of dynamic covalent and non-covalent bonds. Applications of chitosan-based self-healing hydrogels and coatings in tissue engineering, drug delivery systems and anti-corrosion are also discussed.