A proposed new method for the crosslinking of chitosan microspheres

Glyceraldehyde as an Efficient Chemical Crosslinker Agent for the Formation of Chitosan Hydrogels

The rheological changes that occur during the chemical gelation of semidilute solutions of chitosan in the presence of the low-toxicity agent glyceraldehyde (GCA) are presented and discussed in detail. The entanglement concentration for chitosan solutions was found to be approximately 0.2 wt.% and the rheological experiments were carried out on 1 wt.% chitosan solutions with various amounts of GCA at different temperatures (25 °C and 40 °C) and pH values (4.8 and 5.8). High crosslinker concentration, as well as elevated temperature and pH close to the pKa value (pH ≈ 6.3-7) of chitosan are three parameters that all accelerate the gelation process. These conditions also promote a faster solid-like response of the gel-network in the post-gel region after long curing times. The mesh size of the gel-network after a very long (18 h) curing time was found to contract with increasing level of crosslinker addition and elevated temperature. The gelation of chitosan in the presence of other chemical crosslinker agents (glutaraldehyde and genipin) is discussed and a comparison with GCA is made. Small angle neutron scattering (SANS) results reveal structural changes between chitosan solutions, incipient gels, and mature gels.

Preparation and encapsulation techniques of chitosan microsphere for enhanced bioavailability of natural antioxidants

Reactive oxygen species (ROS), induced by medical and life irradiation, have led to diverse diseases. Natural antioxidants (NAs) have been widely used to protect the body from the harmful effects of ROS. NAs have biocompatible properties but their bioavailability in the body is very low. This article discusses possible solutions to improve the bioavailability using several preparation and encapsulation techniques for microspheres using chitosan as a carrier. The first is the emulsion technique that controls particle size (0.5-1000 μm) according to the speed (RPM) of the agitator. The second technique discussed is spray drying-a very simple method that can control particle size (5-5000 μm) according to the nozzle size and discharge pressure. The third is the extrusion technique, which can control particle size (250-2500 μm) according to the syringe pore size. These techniques have enormous potential for use as drug delivery systems (DDS) in the functional food and biomedical field industries.

Polysaccharide-Based Controlled Release Systems for Therapeutics Delivery and Tissue Engineering: From Bench to Bedside

Polysaccharides or polymeric carbohydrate molecules are long chains of monosaccharides that are linked by glycosidic bonds. The naturally based structural materials are widely applied in biomedical applications. This article covers four different types of polysaccharides (i.e., alginate, chitosan, hyaluronic acid, and dextran) and emphasizes their chemical modification, preparation approaches, preclinical studies, and clinical translations. Different cargo fabrication techniques are also presented in the third section. Recent progresses in preclinical applications are then discussed, including tissue engineering and treatment of diseases in both therapeutic and monitoring aspects. Finally, clinical translational studies with ongoing clinical trials are summarized and reviewed. The promise of new development in nanotechnology and polysaccharide chemistry helps clinical translation of polysaccharide-based drug delivery systems.

Chitosan-Coated Collagen Membranes Promote Chondrocyte Adhesion, Growth, and Interleukin-6 Secretion

Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan solutions then crosslinked with glutaraldehyde vapor. Fourier transform infrared (FTIR) analyses showed elevated absorption at 1655 cm-1 of the carbon-nitrogen (N=C) bonds formed by the reaction between the (NH₂) of the chitosan and the (C=O) of the glutaraldehyde. A significant peak in the amide II region revealed a significant deacetylation of the chitosan. Scanning electron microscopy (SEM) images of the chitosan-coated membranes exhibited surface variations, with pore size ranging from 20 to 50 µm. X-ray photoelectron spectroscopy (XPS) revealed a decreased C-C groups and an increased C-N/C-O groups due to the reaction between the carbon from the collagen and the NH2 from the chitosan. Increased rigidity of these membranes was also observed when comparing the chitosan-coated and uncoated membranes at dried conditions. However, under wet conditions, the chitosan coated collagen membranes showed lower rigidity as compared to dried conditions. Of great interest, the glutaraldehyde-crosslinked chitosan-coated collagen membranes promoted chondrocyte adhesion, growth, and interleukin (IL)-6 secretion. Overall results confirm the feasibility of using designed chitosan-coated collagen membranes in future applications, such as cartilage repair.

Optimization of levofloxacin-loaded crosslinked chitosan microspheres for inhaled aerosol therapy

The aim of this work was the development of innovative levofloxacin-loaded swellable microspheres (MS) for the dry aerosol therapy of pulmonary chronicPseudomonas aeruginosainfections in Cystic Fibrosis patients. In a first step, a factorial design was applied to optimize formulations of chitosan-based MS with glutaraldehyde as crosslinker. After optimization, other crosslinkers (genipin, glutaric acid and glyceraldehyde) were tested. Analyses of MS included aerodynamic and swelling properties, morphology, drug loading, thermal and chemical characteristics,in vitroantibacterial activity and drug release studies. The prepared MS presented a drug content ranging from 39.8% to 50.8% of levofloxacin in an amorphous or dispersed state, antibacterial activity and fast release profiles. The highest degree of swelling was obtained for MS crosslinked with glutaric acid and genipin. These formulations also presented satisfactory aerodynamic properties, making them a promising alternative, in dry-powder inhalers, to levofloxacin solution for inhalation.