Effect of Chitosan Properties on Immunoreactivity.

Area of Science:

• Biomaterials Science
• Immunology
• Polymer Chemistry

Background:

• Chitosan is a versatile biopolymer with applications in drug delivery, tissue engineering, and vaccine development.
• Its immunoreactivity is poorly understood due to conflicting literature, hindering clinical translation.
• Key biochemical properties like degree of deacetylation (DDA), viscosity, and endotoxin levels require clarification regarding their immunomodulatory effects.

Purpose of the Study:

• To investigate the influence of chitosan's biochemical properties (DDA, viscosity, endotoxin levels) on immune responses.
• To determine the specific factors responsible for chitosan-induced immunoreactivity in antigen-presenting cells (APCs).
• To establish criteria for inert chitosan suitable for preclinical and clinical applications.

Main Methods:

• Chitosan solutions with varying DDA, viscosity, and endotoxin levels were prepared.
• Mouse and human APCs (macrophages and dendritic cells) were exposed to these chitosan solutions.
• Tumor necrosis factor-alpha (TNF-α) release from APCs was quantified as a measure of immunoreactivity.

Main Results:

• Only endotoxin content significantly influenced chitosan-induced immune responses.
• Degree of deacetylation (DDA) and viscosity did not correlate with APC activation.
• Chitosan with low endotoxin levels (<0.01 EU/mg), 80–97% DDA, and 20–600 cP viscosity demonstrated minimal immunoreactivity.

Conclusions:

• Endotoxin contamination is the primary driver of chitosan immunoreactivity, not its inherent biochemical properties like DDA or viscosity.
• Low-endotoxin chitosan (<0.01 EU/mg) is essentially inert and suitable for broader biomedical applications.
• Standardized characterization and purification of chitosan are crucial for reliable preclinical and clinical use.