Modification of Low Molecular Weight Chitosan with Glycidyl Methacrylate

Chitosan is a derivative of chitin, a polysaccharide sourced from shrimp and crabs, among other organisms. A biocompatible and antimicrobial material, chitosan has been used as a hydrogel for 3D-printed scaffolds with medical applications. Recent successes with 3D-printing chitosan include the polymer in mixtures with other hydrogels, such as alginate and gelatin. This investigation targets low molecular weight chitosan, generated by controlled depolymerization, and modified with glycidyl methacrylate (GMA) side chains as the base hydrogel for 3D printing.

Materials & Methods

High molecular weight chitosan was dissolved in 1.5 wt% acetic acid to form a 1.5 wt % solution. Aliquots of this solution were reacted with 0.2M NaNO₂. The depolymerization reaction stoichiometry indicates that 1 mole of glycosidic bonds is cleaved per mole of HONO consumed (Allan, 1995). A range of low molecular weight (LMW) chitosan solutions were formed: targeting molecular masses of 10, 20, 30, and 40 kDa.

Glycidyl methacrylate was added to each LMW chitosan solution with a 3.8:1 molar ratio of GMA per glucosamine subunit. Samples were precipitated with ammonia, centrifuged, and washed four times with water before freezing and lyophilization. All solutions will be characterized as 1.5 wt% GMA-chitosan dissolved in 1.5 wt% acetic acid.

Printing and material characterization

0.1% lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) was added to GMA-chitosan solutions prior to exposure with 405nm light for 8 minutes. An Anycubic Photon was used for 3D printing. For tensile testing, GMA-chitosan solutions were injected into a mold and exposed to a 405nm LED.

Results & Discussion

Early tests with the low molecular weight GMA-chitosan have not produced a gel sturdy enough to be removed from a mold or to withstand the shear stress required for stereolithographic (SLA) printing. Presently, the dissolution of the GMA-chitosan with a molar reaction ratio of 3.8:1 has been limited. Future tests with the LMW GMA-chitosan will be run at higher concentrations and lower degrees of methacrylation. Upon discovery of a preferred reaction ratio and concentration, tensile strength of the gel and rheological analysis of the solution before gelation will be reported, along with material characterization.

Allan, G. G., Peyron, M. (1995). Molecular weight manipulation of chitosan II: prediction and control of extent of depolymerization of nitrous acid. Carbohydrate Research 277.