Emerging chitin and chitosan nanofibrous materials for biomedical applications

Efficacy of a collagen-based dressing in an animal model of delayed wound healing

OBJECTIVE

The aim of this study was to evaluate in vitro and in vivo the efficacy of GBT013, a collagen-based dressing, for the treatment of chronic wounds, in a db/db mouse model of diabetes.

METHOD

Macroscopic and histologic analyses of db/db mice wound healing with GBT013 or saline gauze were assessed. The mRNA expression and the proliferation of dermal fibroblast were investigated. Matrix metalloproteinases (MMP)-2 and MMP-9 activities were quantified.

RESULTS

In db/db mice, GBT013 improves wound epithelialisation when compared with saline gauze. Histological analysis of scar tissue also shows an enhancement of remodelling associated with no sign of acute inflammation. In addition, GBT013 significantly decreases interleukin (IL)-6 and IL-8, significantly increases tissue inhibitors of metalloproteinases (TIMP)-1 and TIMP-2 fibroblast mRNA expression and significantly reduces in vitro MMP-2 and MMP-9 enzymatic activities. Moreover, GBT013 allows cell growth inside the matrix and stimulates proliferation of human dermal fibroblast.

CONCLUSION

By contributing to restore MMPs/TIMPs balance, GBT013 may function in all key stages of wound healing, such as inflammation, proliferation and tissue remodelling, and ultimately may provide a favourable environment for skin repair.

DECLARATION OF INTEREST

This work was supported by Genbiotech, the R&D subsidiary of Laboratoires Genévrier, a pharmaceutical company.

Highly cost-effective and high-strength hydrogels as dye adsorbents from natural polymers: chitosan and cellulose

Cost-effective chitosan/REC/cellulose hydrogels with high-strength are used for highly efficient dye adsorption.

Fish gelatin nanofibers prevent drug crystallization and enable ultrafast delivery

Eco-friendly and cost-effective electrospinning of aqueous fish gelatin could prevent the drug crystallization and exhibit the ultra-fast drug release behavior.

Remote controlled drug release from multi-functional Fe3O4/GO/Chitosan microspheres fabricated by an electrospray method

The construction of multifunctional microspheres for remote controlled drug release requires the exquisite selection of composite materials and preparation approaches. In this study, chitosan, an amino polysaccharide, was blended with inorganic nanocomponents, Fe₃O₄ and graphene oxide (GO) and electrosprayed to fabricate uniform microspheres with the diameters ranging from 100μm to 1100μm. An anti-cancer drug, doxorubicin (DOX), was loaded to the microspheres by an adsorption or embedding method. The microsphere is responsive to magnetic fields due to the presence of Fe₃O₄, and the incorporation of GO enhanced the drug loading capacity. The fast stimuli-responsive release of DOX can be facilely controlled by using NIR irradiation due to the strong photo-thermal conversion of Fe₃O₄ and GO_. In addition, ultrasound was used as another external stimulus for DOX release. The results suggest the Fe₃O₄/GO/Chitosan microspheres fabricated by the electrospray method provide an efficient platform for remote controlled drug release, which may have potential applications in drug eluting microspheres.

Fabrication of magnetic and fluorescent chitin and dibutyrylchitin sub-micron particles by oil-in-water emulsification

Chitin is a carbohydrate polymer with unique pharmacological and immunological properties, however, because of its unwieldy chemistry, the synthesis of discreet sized sub-micron particles has not been well reported. This work describes a facile and flexible method to fabricate biocompatible chitin and dibutyrylchitin sub-micron particles. This technique is based on an oil-in-water emulsification/evaporation method and involves the hydrophobization of chitin by the addition of labile butyryl groups onto chitin, disrupting intermolecular hydrogen bonds and enabling solubility in the organic solvent used as the oil phase during fabrication. The subsequent removal of butyryl groups post-fabrication through alkaline saponification regenerates native chitin while keeping particles morphology intact. Examples of encapsulation of hydrophobic dyes and nanocrystals are demonstrated, specifically using iron oxide nanocrystals and coumarin 6. The prepared particles had diameters between 300-400nm for dibutyrylchitin and 500-600nm for chitin and were highly cytocompatible. Moreover, they were able to encapsulate high amounts of iron oxide nanocrystals and were able to label mammalian cells.

STATEMENT OF SIGNIFICANCE

We describe a technique to prepare sub-micron particles of highly acetylated chitin (>90%) and dibutyrylchitin and demonstrate their utility as carriers for imaging. Chitin is a polysaccharide capable of stimulating the immune system, a property that depends on the acetamide groups, but its insolubility limits its use. No method for sub-micron particle preparation with highly acetylated chitins have been published. The only approach for the preparation of sub-micron particles uses low acetylation chitins. Dibutyrylchitin, a soluble chitin derivative, was used to prepare particles by oil in water emulsification. Butyryl groups were then removed, forming chitin particles. These particles could be suitable for encapsulation of hydrophobic payloads for drug delivery and cell imaging, as well as, adjuvants for vaccines.

Myocardial tissue engineering using electrospun nanofiber composites

Emerging trends for cardiac tissue engineering are focused on increasing the biocompatibility and tissue regeneration ability of artificial heart tissue by incorporating various cell sources and bioactive molecules. Although primary cardiomyocytes can be successfully implanted, clinical applications are restricted due to their low survival rates and poor proliferation. To develop successful cardiovascular tissue regeneration systems, new technologies must be introduced to improve myocardial regeneration. Electrospinning is a simple, versatile technique for fabricating nanofibers. Here, we discuss various biodegradable polymers (natural, synthetic, and combinatorial polymers) that can be used for fiber fabrication. We also describe a series of fiber modification methods that can increase cell survival, proliferation, and migration and provide supporting mechanical properties by mimicking micro-environment structures, such as the extracellular matrix (ECM). In addition, the applications and types of nanofiber-based scaffolds for myocardial regeneration are described. Finally, fusion research methods combined with stem cells and scaffolds to improve biocompatibility are discussed. [BMB Reports 2016; 49(1): 26-36]

Mechanically Robust 3D Nanostructure Chitosan-Based Hydrogels with Autonomic Self-Healing Properties

Fabrication of hydrogels based on chitosan (CS) with superb self-healing behavior and high mechanical and electrical properties has become a challenging and fascinating topic. Most of the conventional hydrogels lack these properties at the same time. Our objectives in this research were to synthesize, characterize, and evaluate the general properties of chitosan covalently cross-linked with zinc phthalocyanine tetra-aldehyde (ZnPcTa) framework. Our hope was to access an unprecedented self-healable three-dimensional (3D) nanostructure that would harvest the superior mechanical and electrical properties associated with chitosan. The properties of cross-linker such as the structure, steric effect, and rigidity of the molecule played important roles in determining the microstructure and properties of the resulting hydrogels. The tetra-functionalized phthalocyanines favor a dynamic Schiff-base linkage with chitosan to form a 3D porous nanostructure. Based on this strategy, the self-healing ability, as demonstrated by rheological recovery and macroscopic and microscopic observations, is introduced through dynamic covalent Schiff-base linkage between NH₂ groups in CS and benzaldehyde groups at cross-linker ends. The hydrogel was characterized using FT-IR, NMR, UV/vis, and rheological measurements. In addition, cryogenic scanning electron microscopy (cryo-SEM) was employed as a technique to visualize the internal morphology of the hydrogels. Study of the surface morphology of the hydrogel showed a 3D porous nanostructure with uniform morphology. Furthermore, incorporating the conductive nanofillers, such as carbon nanotubes (CNTs), into the structure can modulate the mechanical and electrical properties of the obtained hydrogels. Interestingly, these hydrogel nanocomposites proved to have very good film-forming properties, high modulus and strength, acceptable electrical conductivity, and excellent self-healing properties at neutral pH. Such properties can be finely tuned through variation of the cross-linker and CNT concentration, and as a result these structures are promising candidates for potential applications in various fields of research.

Nanomaterial-Based Vaccine Adjuvants

Vaccination is a biological process that administrates antigenic materials to stimulate an individual's immune system to develop immunity to a specific pathogen. It is the most effective tool to prevent illness and death from infectious diseases or diseases leading to cancers. Because many recombinant and synthetic antigens are poorly immunogenic, adjuvant is essentially added to vaccine formula that can potentiate the immune responses, offer better protection against pathogens and reduce the amount of antigens needed for protective immunity. To date, there are nearly 100 different types of adjuvants associated with about 400 vaccines that are either commercially available or under development. Among these adjuvants, many of them are particulates and nano-scale in nature. Nanoparticles represent a wide range of materials with novel physicochemical properties that exhibit immunostimulatory effects. However, the mechanistic understandings on how their physicochemical properties affect immunopotentiation remain elusive. In this article, we aim to review current development status of nanomaterial-based vaccine adjuvants, and further discuss their acting mechanisms, understanding of which will benefit the rational design of effective vaccine adjuvants with improved immunogenicity for prevention of infectious disease as well as therapeutic cancer treatment.

Mechanochemical synthesis of chitosan submicron particles from the gladius of Todarodes pacificus

The present work focused on the synthesis of β-chitosan submicron particles (CSPs) from Todarodes pacificus using mechanochemical techniques. The gladius was submitted to a sequence of mechanical and chemical treatments to synthesize β-chitin (CT), which was further deacetylated to form spherical chitosan submicron particles with an average diameter of ⩽100 nm. The surface morphology of β-chitin and CSPs was observed using electron microscopy. The degree of deacetylation (DD%), evaluated from the absorbance peak of a Fourier Transform Infrared (FTIR) spectrum, was 80 ± 2.5%. Physicochemical characterization exhibited good crystallinity, positive zeta potential and low molecular weight, as well as reduced ash content and high water-binding capacity. CSPs exhibit significant antimicrobial properties toward all tested pathogenic bacterial and fungal microorganisms. Antioxidant analysis revealed high reducing power and excellent scavenging and chelating ability. Hence, CSPs synthesized from gladius of Todarodes pacificus using mechanochemical techniques are promising candidates for biomedical applications.

Chitosan/alginate based multilayers to control drug release from ophthalmic lens

In this study we investigated the possibility of using layer-by-layer deposition, based in natural polymers (chitosan and alginate), to control the release of different ophthalmic drugs from three types of lens materials: a silicone-based hydrogel recently proposed by our group as drug releasing soft contact lens (SCL) material and two commercially available materials: CI26Y for intraocular lens (IOLs) and Definitive 50 for SCLs. The optimised coating, consisting in one double layer of (alginate - CaCl2)/(chitosan+glyoxal) topped with a final alginate-CaCl2 layer to avoid chitosan degradation by tear fluid proteins, proved to have excellent features to control the release of the anti-inflammatory, diclofenac, while keeping or improving the physical properties of the lenses. The coating leads to a controlled release of diclofenac from SCL and IOL materials for, at least, one week. Due to its high hydrophilicity (water contact angle≈0) and biocompatibility, it should avoid the use of further surface treatments to enhance the useŕs comfort. However, the barrier effect of this coating is specific for diclofenac, giving evidence to the need of optimizing the chemical composition of the layers in view of the desired drug.

Chitosan-chitin nanocrystal composite scaffolds for tissue engineering

Chitin nanocrystals (CNCs) with length and width of 300 and 20nm were uniformly dispersed in chitosan (CS) solution. The CS/CNCs composite scaffolds prepared utilizing a dispersion-based freeze dry approach exhibit significant enhancement in compressive strength and modulus compared with pure CS scaffold both in dry and wet state. A well-interconnected porous structure with size in the range of 100-200μm and over 80% porosity are found in the composite scaffolds. The crystal structure of CNCs is retained in the composite scaffolds. The incorporation of CNCs leads to increase in the scaffold density and decrease in the water swelling ratio. Moreover, the composite scaffolds are successfully applied as scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs images reveal that CNCs can markedly promote the cell adhesion and proliferation of the osteoblast on CS. The biocompatible composite scaffolds with enhanced mechanical properties have potential application in bone tissue engineering.

Electrophoretic Deposition of Chitosan Coatings Modified with Gelatin Nanospheres To Tune the Release of Antibiotics

Orthopedic and dental implants are increasingly used in the medical field in view of their high success rates. Implant-associated infections, however, still occur and are difficult to treat. To combat these infections, the application of an active coating to the implant surface is advocated as an effective strategy to facilitate sustained release of antibacterial drugs from implant surfaces. Control over this release is, however, still a major challenge. To overcome this problem, we deposited composite coatings composed of a chitosan matrix containing gelatin nanospheres loaded with antibiotics onto stainless steel plates by means of the electrophoretic deposition technique. The gelatin nanospheres were distributed homogeneously throughout the coatings. The surface roughness and wettability of the coatings could be tuned by a simple adjustment of the weight ratio between the gelatin nanospheres and chitosan. Vancomycin and moxifloxacin were released in sustained and burst-type manners, respectively, while the coatings were highly cytocompatible. The antibacterial efficacy of the coatings containing different amounts of antibiotics was tested using a zone of inhibition test against Staphylococcus aureus, which showed that the coatings containing moxifloxacin exhibited an obvious inhibition zone. The coatings containing a high amount of vancomycin were able to kill bacteria in direct contact with the implant surface. These results suggest that the antibacterial capacity of metallic implants can be tuned by orthogonal control over the release of (multiple) antibiotics from electrophoretically deposited composite coatings, which offers a new strategy to prevent orthopedic implant-associated infections.

Recent advances in liposome surface modification for oral drug delivery

Oral delivery via the gastrointestinal (GI) tract is the dominant route for drug administration. Orally delivered liposomal carriers can enhance drug solubility and protect the encapsulated theraputic agents from the extreme conditions found in the GI tract. Liposomes, with their fluid lipid bilayer membrane and their nanoscale size, can significantly improve oral absorption. Unfortunately, the clinical applications of conventional liposomes have been hindered due to their poor stability and availability under the harsh conditions typically presented in the GI tract. To overcome this problem, the surface modification of liposomes has been investigated. Although liposome surface modification has been extensively studied for oral drug delivery, no review exists so far that adequately covers this topic. The purpose of this paper is to summarize and critically analyze emerging trends in liposome surface modification for oral drug delivery.

Antibacterial effects of electrospun chitosan/poly(ethylene oxide) nanofibrous membranes loaded with chlorhexidine and silver

To prevent percutaneous device associated infections (PDAIs), we prepared electrospun chitosan/poly(ethylene oxide) (PEO) nanofibrous membrane containing silver nanoparticles as an implantable delivery vehicle for the dual release of chlorhexidine and silver ions. We observed that the silver nanoparticles were distributed homogeneously throughout the fibers, and a fast release of chlorhexidine in 2days and a sustained release of silver ions for up to 28days. The antibacterial efficacy of the membranes against Staphylococcus aureus showed that the membranes exhibited an obvious inhibition zone upon loading with either chlorhexidine (20μg or more per membrane) or AgNO3 (1 and 5wt% to polymer). Furthermore, long-term antibacterial effect up to 4days was verified using membranes containing 5wt% AgNO3. The results suggest that the membranes have strong potential to act as an active antibacterial dressing for local delivery of antibacterial agents to prevent PDAIs.

Cytotoxic Effects of Phosphonate-Functionalized Mesoporous Silica Nanoparticles

In this work, we synthesized pristine mesoporous silica nanoparticles (MSN) and functionalized these with phosphonate groups (MSN-Phos). We report, for the first time, cell death in MCF-7 cells (human breast adenocarcinoma cell line) when exposed to the empty MSN and MSN-Phos nanoparticles. In comparison, the same nanoparticles were found to elicit few deleterious effects on normal human foreskin fibroblast cells (BJ cells). MCF-7 cells were found to exhibit a concentration-dependent uptake, whereas no detectable nanoparticle uptake was observed in the BJ cells, irrespective of treatment dosage. A disruption of the cell cycle in the MCF-7 cells was determined to be the cause of cell death from the nanoparticle exposure, thereby suggesting the role of nondrug loaded MSN and MSN-Phos as effective anticancer drugs.

Needleless electrospinning for scaled-up production of ultrafine chitosan hybrid nanofibers used for air filtration

This filter media showed better performance than commercial HEPA for nanoparticles filtration.

Electrospinning of natural polymers for advanced wound care: towards responsive and adaptive dressings

Nanofibrous dressings produced by electrospinning proteins and polysaccharides are highly promising candidates in promoting wound healing and skin regeneration.

A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.

Intracellular targeted co-delivery of shMDR1 and gefitinib with chitosan nanoparticles for overcoming multidrug resistance

Nowadays, multidrug resistance and side effects of drugs limit the effectiveness of chemotherapies in clinics. P-glycoprotein (P-gp) (MDR1), as a member of the ATP-binding cassette family, acts on transporting drugs into cell plasma across the membrane of cancer cells and leads to the occurrence of multidrug resistance, thus resulting in the failure of chemotherapy in cancer. The main aims of this research were to design a nanodelivery system for accomplishing the effective co-delivery of gene and antitumor drug and overcoming multidrug resistance effect. In this study, shMDR1 and gefitinib-encapsulating chitosan nanoparticles with sustained release, small particle size, and high encapsulation efficiency were prepared. The serum stability, protection from nuclease, and transfection efficiency of gene in vitro were investigated. The effects of co-delivery of shMDR1 and gefitinib in nanoparticles on reversing multidrug resistance were also evaluated by investigating the cytotoxicity, cellular uptake mechanism, and cell apoptosis on established gefitinib-resistant cells. The results demonstrated that chitosan nanoparticles entrapping gefitinib and shMDR1 had the potential to overcome the multidrug resistance and improve cancer treatment efficacy, especially toward resistant cells.

A dynamic and self-crosslinked polysaccharide hydrogel with autonomous self-healing ability

Natural polymeric hydrogels with self-healing capability that can recover the functionalities and structures of gels after damage are extremely attractive due to their emerging applications in the biomedical field. Here we report a self-healable polymeric hydrogel by self-crosslinking two natural polymers acrylamide-modified chitin (AMC) containing amino groups and oxidized alginate containing dialdehyde groups. The generation of the self-crosslinked hydrogel relies on the dynamic covalent linkage through Schiff base between the polysaccharide chains. The self-healing capability of the crosslinked hydrogel depends on the molar ratio of AMC and oxidized alginate and the surrounding pH. Under certain circumstances, the damaged hydrogel shows a complete recovery and can be stretched to a favorable extent, which is seldom observed for polysaccharide self-healing hydrogel. Notably, we find that the self-healing ability can be "stored" by freeze-drying and "activated" by rehydration. In addition, we demonstrate that the hydrogel can be used as a soft template to guide the repair of inorganic materials like hydroxyapatite. We anticipate that this self-healable hydrogel consisting of biocompatible and biodegradable polysaccharides can be applied to various biomedical fields.

Antimicrobial activity and cytotoxicity of nanofibrous mats immobilized with polysaccharides-rectorite based nanogels

Rectorite (REC)-encapsulated lysozyme (LY)-alginate (ALG) nanogels (NGs) were prepared by adding ALG-REC composites suspensions into LY solutions at the mass ratio of 1:2. The morphology of the NGs and the NGs-assembled nanofibrous mats were studied by transmission electron microscope and field emission scanning electron microscopy, respectively. The composition of NGs-immobilized nanofibrous mats was detected by X-ray photoelectron spectroscopy. The NGs-assembled nanofibrous mats with the addition of REC could enhance the inhibition against Escherichia coli and Staphylococcus aureus. Additionally, NGs-coated mats reduced the toxicity of cellulose mats on mouse lung fibroblasts using MTT assay. Besides, the addition of REC in the NGs improved the cell compatibility of NGs-assembled nanofibrous mats.

Grafting chitosan with polyethylenimine in an ionic liquid for efficient gene delivery

Modifying chitosan (CS) with polyethylenimine (PEI) grafts is an effective way to improve its gene transfection performance. However, it is still a challenge to conduct the grafting with fine control and high efficiency, particularly for the modification of water-insoluble CS. Herein, a novel method to graft CS with PEI (1.8 kDa, PEI-1.8) was developed by using ionic liquid 1-butyl-3-methyl imidazolium acetate ([BMIM]Ac) as a reaction solvent, water-insoluble CS as a reaction substrate and 1,1-carbonyldiimidazole (CDI) as a linking agent. The grafting reaction was greatly accelerated and the reaction time was largely shortened to 4 h by taking advantages of the good solubility of CS, the enhanced nucleophilicity of amino groups and the preferential stability of the activated complexes in the ionic liquid. The chitosan-graft-polyethylenimine (CS-g-PEI) products were characterized by 1H NMR, FTIR and GPC. PEI-1.8 was quantitatively grafted to CS through urea linkages, and the grafting degree (GD) was conveniently tuned by varying the molar ratios of PEI-1.8 to D-glucosamine units of CS in the range of 9.0 × 10(-3) to 9.0 × 10(-2). Compared with CS, the synthesized CS-g-PEI copolymers showed higher pDNA-binding affinity, which increased with the GD as shown in Agarose gel electrophoresis. The dynamic light scattering (DLS) experiment demonstrated that the CS-g-PEI/pDNA polyplexes had suitable particle sizes and proper ζ-potentials for cell transfection. The CS-g-PEI copolymer with a medium GD of 4.5% conferred the best gene transfection, with the efficiency 44 times of CS and 38 times of PEI-1.8 in HEp-2 cells. The cytotoxicity of CS-g-PEI was tested and found nearly as low as that of CS and much lower than that of PEI.

Supramolecular cationic assemblies against multidrug-resistant microorganisms: activity and mechanism of action

The growing challenge of antimicrobial resistance to antibiotics requires novel synthetic drugs or new formulations for old drugs. Here, cationic nanostructured particles (NPs) self-assembled from cationic bilayer fragments and polyelectrolytes are tested against four multidrug-resistant (MDR) strains of clinical importance. The non-hemolytic poly(diallyldimethylammonium) chloride (PDDA) polymer as the outer NP layer shows a remarkable activity against these organisms. The mechanism of cell death involves bacterial membrane lysis as determined from the leakage of inner phosphorylated compounds and possibly disassembly of the NP with the appearance of multilayered fibers made of the NP components and the biopolymers withdrawn from the cell wall. The NPs display broad-spectrum activity against MDR microorganisms, including Gram-negative and Gram-positive bacteria and yeast.

Anticancer and anti-inflammatory properties of chitin and chitosan oligosaccharides

Previous reports indicate that N-acetyl-d-glucosamine oligomers (chitin oligosaccharide; NACOS) and d-glucosamine oligomers (chitosan oligosaccharide; COS) have various biological activities, especially against cancer and inflammation. In this review, we have summarized the findings of previous investigations that have focused on anticancer or anti-inflammatory properties of NACOS and COS. Moreover, we have introduced recent evaluation of NACOS and COS as functional foods against cancer and inflammatory disease.

Characterization and preparation of bio-tubular scaffolds for fabricating artificial vascular grafts by combining electrospinning and a 3D printing system

The last decade has seen artificial blood vessels composed of natural polymer nanofibers grafted into human bodies to facilitate the recovery of damaged blood vessels. However, electrospun nanofibers (ENs) of biocompatible materials such as chitosan (CTS) suffer from poor mechanical properties. This study describes the design and fabrication of artificial blood vessels composed of a blend of CTS and PCL ENs and coated with PCL strands using rapid prototyping technology. The resulting tubular vessels exhibited excellent mechanical properties and showed that this process may be useful for vascular reconstruction.

Reinforced chitosan beads by chitin nanofibers for the immobilization of β-glucosidase

Chitin nanofibers prepared from partially deacetylated α-chitin were used as fillers to form DEChN/CS(chitosan) composite beads for application as immobilization supports.

Self-assembled zein–sodium carboxymethyl cellulose nanoparticles as an effective drug carrier and transporter

In this work, biodegradable nanoparticles (NPs) were assembled with sodium carboxymethyl cellulose (CMC) and zein to produce zein–CMC NPs.

Cell uptake mechanisms of glycosylated cationic pDNA–cyclodextrin nanoparticles

β-Cyclodextrin-based glycoCDplexes are internalized through several redundant pathways whose relative prevalence depends on the coating sugar and on the cell line.