Improved chitosan nerve conduits through crosslinking

Artificially produced nerve conduits are promising alternatives to autologous nerve grafts in the treatment of damaged nerves. In this study, the physiochemical properties of chitosan/poly-ε-caprolactone nerve conduits will be improved by using the chitosan crosslinker genipin.

 

Improved physiochemical properties of chitosan@PCL nerve conduits by crosslinking natural molecules

Bianchini, M.; Zinno, C.; Micera, S.; Redolfi Riva, E. Improved Physiochemical Properties of Chitosan@PCL Nerve Conduits by Natural Molecule Crosslinking. Biomolecules 2023, 13, 1712. https://doi.org/10.3390/biom13121712

Damaged nerves lead to the loss of sensorimotor functions, organ control or neuropathic pain. These impairments are associated with less severe long-term consequences that affect up to 300,000 people in Europe every year. The primary clinical treatment method is the use of autologous nerve grafts to restore the lost nerve functions of limbs or organs. However, autologous nerve grafts have disadvantages such as low availability, unsuitable size ratios and loss of sensorimotor abilities at the site where the autograft was harvested. With the help of tissue engineering and regenerative medicine, so-called nerve conduits (NC) have been developed as an alternative to autologous transplants to close larger gaps in nerve injuries. Natural polymers are considered promising materials for NCs due to their good biocompatibility and cell compatibility against neuronal cells, as well as a safe biodegradability process.
Chitosan is particularly interesting because of its excellent nerve regeneration properties, which have already been demonstrated in animal models, for example. The reasons for this are the physio-chemical properties of chitosan. The rheological properties are comparable to those of natural glucosaminoglycan and promote the adhesion and proliferation of neuronal and Schwann cells. The cell viability correlates with the degree of deacetylation of chitosan. This increases with a DDA of (<85 %) due to greater stability in a physiological environment. In addition, degradation slows down and crystallinity is reduced. However, the use of chitosan and NCs is generally limited by their comparatively low mechanical strength.
In a previous study, a Chitosan (CTS)/poly-ε-caprolactone (PCL) NC (CTS@PLC-NC) was successfully fabricated using extrusion-based 3D bioprinting and freeze-drying. Besides good mechanical properties and adjustability of the structural characteristics of the NCs, the nerve regeneration was worse compared to the use of autografts. To improve this, the CTS@PLC-NC was additionally modified with the chitosan crosslinker genipin (GEN). Genipin interacts with the primary amino group of chitosan and, as a crosslinker, ensures improved thermal and mechanical stability. In addition, it has low toxicity compared to other crosslinkers. A chitosan of the quality Chitoceuticals with a DDA of ≥ 92.5 % from Heppe Medical Chitosan GmbH was used in this study.

RESULTS

• Successful preparation of CTS@PLC-NC+GEN, obtaining a dark blue-green, sponge-like network
• Compared to the previously prepared CTS@PLC-NCs (large, elliptical pores), the NCs cross-linked with Genipin have small, circular pores
• Significantly reduced porosity of CTS@PLC-NC+GEN compared to CTS@PLC-NC
• Lower hydration of the networks with Genipin
• Significantly slower biodegradability due to the use of Genipin
• Improvement of the stability of the chitosan matrix under physiological conditions, as well as the compressive strength and bending stiffness of the NCs through cross-linking

Conclusions: In this study, it was shown that the physiochemical properties of CTS@PCL NCs can be significantly improved by genipin crosslinking by changing the porosity, reducing the pore shape and increasing the stability and toughness of the chitosan matrix in a simulated physiological environment. However, the quality of nerve regeneration in vivo also needs to be investigated.

Link to article: Biomolecules | Free Full-Text | Improved Physiochemical Properties of Chitosan@PCL Nerve Conduits by Natural Molecule Crosslinking (mdpi.com)