New Directions in Aesthetic Medicine: A Novel and Hybrid Filler Based on Hyaluronic Acid and Lactose Modified Chitosan

A Covalently Cross-Linked Hyaluronic Acid/Carboxymethyl Cellulose Composite Hydrogel as a Potential Filler for Soft Tissue Augmentation

The use of fillers for soft tissue augmentation is an approach to restore the structure in surgically or traumatically created tissue voids. Hyaluronic acid (HA), is one of the main components of the extracellular matrix, and it is widely employed in the design of materials with features similar to human tissues. HA-based fillers already find extensive use in soft tissue applications, but are burdened with inherent drawbacks, such as poor thermal stability. A well-known strategy to improve the HA properties is to reticulate it with 1,4-Butanediol diglycidyl ether (BDDE). The aim of this work was to improve the design of HA hydrogels as fillers, by developing a crosslinking HA method with carboxymethyl cellulose (CMC) by means of BDDE. CMC is a water soluble cellulose ether, whose insertion into the hydrogel can lead to increased thermal stability. HA/CMC hydrogels at different ratios were prepared, and their rheological properties and thermal stability were investigated. The hydrogel with an HA/CMC ratio of 1/1 resulted in the highest values of viscoelastic moduli before and after thermal treatment. The morphology of the hydrogel was examined via SEM. Biocompatibility response, performed with the Alamar blue assay on fibroblast cells, showed a safety percentage of around 90% until 72 h.

Modification of hyaluronic acid to enable click chemistry photo-crosslinking of hydrogels with tailorable degradation profiles

Hyaluronic acid (HA) is a naturally occurring mucopolysaccharide that, due to its inherent bioactivity and extracellular matrix-like structure, has the potential to be utilised extensively in tissue engineering. However, this glycosaminoglycan lacks the properties required for cellular adhesion and photo-crosslinking by UV light, which significantly hinders this polymers applicability. This research presents a method for modifying hyaluronic acid via thiolation and methacrylation to generate a novel photo-crosslinkable polymer with improved physicochemical properties, biocompatibility and the potential to customize biodegradability according to the ratio of monomers used. A decrease in stiffness proportional to increasing thiol concentration was observed when testing the compressive strength of hydrogels. Conversely, it was noted that the storage moduli of hydrogels increased proportionally to thiol concentration indicating a greater degree of cross-linking with the addition of thiol. The addition of thiol to HA increased the biocompatibility of the material in both neuronal and glial cell lines and improved the degradability of methacrylated HA. Due to the enhanced physicochemical properties and biocompatibility imparted by the introduction of thiolated HA, this novel hydrogel system could have numerous bioengineering applications.