Chitin scaffolds in tissue engineering

Evaluation of wound healing potential of β-chitin hydrogel/nano zinc oxide composite bandage

PURPOSE

β-chitin hydrogel/nZnO composite bandage was fabricated and evaluated in detail as an alternative to existing bandages.

METHODS

β-chitin hydrogel was synthesized by dissolving β-chitin powder in Methanol/CaCl(2) solvent, followed by the addition of distilled water. ZnO nanoparticles were added to the β-chitin hydrogel and stirred for homogenized distribution. The resultant slurry was frozen at 0°C for 12 h. The frozen samples were lyophilized for 24 h to obtain porous composite bandages.

RESULTS

The bandages showed controlled swelling and degradation. The composite bandages showed blood clotting ability as well as platelet activation, which was higher when compared to the control. The antibacterial activity of the bandages were proven against Staphylococcus aureus (S. aureus) and Escherichia coli (E.coli). Cytocompatibility of the composite bandages were assessed using human dermal fibroblast cells (HDF) and these cells on the composite bandages were viable similar to the Kaltostat control bandages and bare β-chitin hydrogel based bandages. The viability was reduced to 50-60% in bandages with higher concentration of zinc oxide nanoparticles (nZnO) and showed 80-90% viability with lower concentration of nZnO. In vivo evaluation in Sprague Dawley rats (S.D. rats) showed faster healing and higher collagen deposition ability of composite bandages when compared to the control.

CONCLUSIONS

The prepared bandages can be used on various types of infected wounds with large volume of exudates.

Chitosan, hyaluronan and chondroitin sulfate in tissue engineering for cartilage regeneration: a review

Injection of hyaluronan into osteoarthritic joints restores the viscoelasticity, augments the flow of joint fluid, normalizes endogenous hyaluronan synthesis, and improves joint function. Chitosan easily forms polyelectrolyte complexes with hyaluronan and chondroitin sulfate. Synergy of chitosan with hyaluronan develops enhanced performances in regenerating hyaline cartilage, typical results being structural integrity of the hyaline-like neocartilage, and reconstitution of the subchondral bone, with positive cartilage staining for collagen-II and GAG in the treated sites. Chitosan qualifies for the preparation of scaffolds intended for the regeneration of cartilage: it yields mesoporous cryogels; it provides a friendly environment for chondrocytes to propagate, produce typical ECM, and assume the convenient phenotype; it is a good carrier for growth factors; it inactivates metalloproteinases thus preventing collagen degradation; it is suitable for the induction of the chondrogenic differentiation of mesenchymal stem cells; it is a potent means for hemostasis and platelet delivery.

Effect of electrospun non-woven mats of dibutyryl chitin/poly(lactic acid) blends on wound healing in hairless mice

The aim of this study was to examine the proliferative ability of dibutyryl chitin (DBC) on scratch wounds in HaCaT keratinocytes and to evaluate the effect of nanoporous non-woven mat (DBCNFM) on skin wound healing in hairless mice using the advantages of DBCNFM, such as high porosity and high surface area to volume. The cell spreading activity of DBC was verified through a cell spreading assay in scratched human HaCaT keratinocytes. Scratch wound experiments showed that DBC notably accelerates the spreading rate of HaCaT keratinocytes in a dose dependent manner. The molecular aspects of the healing process were also investigated by hematoxylin & eosin staining of the healed skin, displaying the degrees of reepithelialization and immunostaining on extracellular matrix synthesis and remodeling of the skin. Topical application of DBCNFM significantly reduced skin wound rank scores and increased the skin remodeling of the wounded hairless mice in a dose dependent way. Furthermore, DBCNFM notably increased the expression of the type 1 collagen and filaggrin. These results demonstrate that DBC efficiently accelerates the proliferation of HaCaT keratinocytes and DBCNFM notably increases extracellular matrix synthesis on remodeling of the skin, and these materials are a good candidate for further evaluation as an effective wound healing agent.

Porous collagen scaffold reinforced with surfaced activated PLLA nanoparticles

Porous collagen scaffold is integrated with surface activated PLLA nanoparticles fabricated by lyophilizing and crosslinking via EDC treatment. In order to prepare surface-modified PLLA nanoparticles, PLLA was firstly grafted with poly (acrylic acid) (PAA) through surface-initiated polymerization of acrylic acid. Nanoparticles of average diameter 316 nm and zeta potential −39.88 mV were obtained from the such-treated PLLA by dialysis method. Porous collagen scaffold were fabricated by mixing PLLA nanoparticles with collagen solution, freeze drying, and crosslinking with EDC. SEM observation revealed that nanoparticles were homogeneously dispersed in collagen matrix, forming interconnected porous structure with pore size ranging from 150 to 200 μm, irrespective of the amount of nanoparticles. The porosity of the scaffolds kept almost unchanged with the increment of the nanoparticles, whereas the mechanical property was obviously improved, and the degradation was effectively retarded. In vitro L929 mouse fibroblast cells seeding and culture studies revealed that cells infiltrated into the scaffolds and were distributed homogeneously. Compared with the pure collagen sponge, the number of cells in hybrid scaffolds greatly increased with the increment of incorporated nanoparticles. These results manifested that the surface-activated PLLA nanoparticles effectively reinforced the porous collagen scaffold and promoted the cells penetrating into the scaffold, and proliferation.

Biomedical exploitation of chitin and chitosan via mechano-chemical disassembly, electrospinning, dissolution in imidazolium ionic liquids, and supercritical drying

Recently developed technology permits to optimize simultaneously surface area, porosity, density, rigidity and surface morphology of chitin-derived materials of biomedical interest. Safe and ecofriendly disassembly of chitin has superseded the dangerous acid hydrolysis and provides higher yields and scaling-up possibilities: the chitosan nanofibrils are finding applications in reinforced bone scaffolds and composite dressings for dermal wounds. Electrospun chitosan nanofibers, in the form of biocompatible thin mats and non-wovens, are being actively studied: composites of gelatin + chitosan + polyurethane have been proposed for cardiac valves and for nerve conduits; fibers are also manufactured from electrospun particles that self-assemble during subsequent freeze-drying. Ionic liquids (salts of alkylated imidazolium) are suitable as non-aqueous solvents that permit desirable reactions to occur for drug delivery purposes. Gel drying with supercritical CO₂ leads to structures most similar to the extracellular matrix, even when the chitosan is crosslinked, or in combination with metal oxides of interest in orthopedics.