Publications in March 2015

In March 2015, 201 articles about chitosan and chitosan derivatives have been published. The main topics address chitosan in evaluation studies, nanoparticles, pharmaceutical preparations and tissues. Among the top countries of chitosan research are again: China (51 articles), India (23) and USA (21).

Table: Leading journals, publishing the highest number of chitosan-related articles in March 2015. Source: GoPubMed

Chitosan-modified scaffolds for tissue engineering are intensively studied in numerous publications. Some medical applications require a specific degree of elasticity and at the same time mechanical resilience. The two following studies invented novel chitosan-modified substrates, which proved to be useful as cellular matrices for specific tissue engineering.   

Incorporation of chitosan in biomimetic gelatin/chondroitin-6-sulfate/hyaluronan cryogel for cartilage tissue engineering.

Kuo C.Y., Chen C.H, Hsiao C.Y. et al.; Carbohydrate Polymers. Vol. 117:722-30. March 2015

In the present study a cryogel scaffold was designed for cartilage tissue engineering. The extracellular matrix of cartilage was mimicked by a scaffold composed of gelatin, chondroitin-6-sulfate and hyaluronan. Cryogels are synthesized at subzero temperatures to obtain a frozen and a liquid phase of the solvent. Dissolved substances concentrate in the liquid microphase and lead to gel formation by chemical reactions. Macroporous structures are formed upon thawing of frozen solvent crystals. Gelatin is composed of denatured collagen, which is the major component of cartilage. Chondroitin-6-sulfate is a glycosaminoglycan and provides pressure resistance in cartilage tissue. Hyaluronan is a major component of the extracellular matrix and promotes cell proliferation and migration. The scaffold was additionally modified by chitosan (0.20 degree of acetylation) to improve cell adhesion and matrix properties in general.

Results for GCH-chitosan cryogel compared to GCH cryogel:

• Higher porosity and larger pore size
• Higher ultimate strain and elasticity
• Lower stress relaxation
• Diminished chondrocytes growth and proliferation
• Up-regulated secretion of glycosaminoglycan and type II collagen
• GCH-chitosan grafts help to regenerate articular cartilage defects in vivo

Conclusions: Cryogels generated from GCH-chitosan display improved physical and mechanical properties compared to GCH cryogels. They possess similar biomechanical characteristics like cartilage. The growth arrest of chondrocytes and the enhanced secretion of glycosaminoglycan and type II collagen indicates a process of cellular redifferentiation. As GCH-chitosan grafts can functionally repair articular cartilage defects in rabbits, they might be beneficial for cartilage tissue engineering.

Source: http://www.ncbi.nlm.nih.gov/pubmed/25498693

Bacterial Cellulose As a Support for the Growth of Retinal Pigment Epithelium.

Gonçalves S., Padrão J., Rodrigues I.P. et al.; Biomacromolecules. [Epub ahead of print] March 2015
Macular degeneration is a medical condition, which causes blurred vision or even irreversible blindness. In this study a novel substrate for retinal pigment epithelium (RPE) cells was analysed, which were composed of bacterial cellulose (BC). Such RPE-loaded BC-scaffold could serve as grafts to replace damaged photoreceptors of the retina.
BC-nanofibers are synthesised by Gluconacetobacter xylinus bacteria and possess advantageous properties for biomedical applications. The nontoxic, elastic polymer is permeable for gases and fluids, it is hydrophilic and not biodegradable in the human body. To improve RPE cell adhesion, the surfaces of BC fibres were additionally modified by acetylation or polysaccharide adsorption using chitosan or carboxymethyl cellulose.

Results:

• All surface-modified BC substrates display:
  • similar porous structure
  • similar permeation coefficients for solutions
  • enhanced cell adhesion and proliferation
• Acetylated BC:  
  • decreased hydrophilicity and swelling
  • smaller tensile strength and elongation at break
• Polysaccharide BC
  • high hydrophilic degree
  • increased protein adsorption

Conclusion: Cell adhesion and proliferation was significantly improved by all kinds of BC-surface modification. However, acetylated or chitosan-modified BC substrates were slightly superior to the carboxymethyl-cellulose modification. RPE cells adhered to BC surfaces as monolayers and did not penetrate into the pores. Since BC substrates are viable carriers for RPE cells, BC-RPE grafts might also be suitable to replace degenerated photoreceptors in vivo.

Source: http://www.ncbi.nlm.nih.gov/pubmed/25748276