Methacrylated hyaluronic acid (HAMA) is a modified biomaterial derived from hyaluronic acid, a glycosaminoglycan (long-chain sugar molecule) found throughout the body’s tissues. Natural hyaluronic acid is involved in processes like cell movement and lubrication. HAMA is created through a chemical process that alters these properties to make it more suitable for biomedical applications.
This alteration provides new characteristics without compromising the material’s biocompatibility. This allows it to be used in sensitive biological environments with minimal adverse reactions.
Creating a Photocrosslinkable Material from Hyaluronic Acid
Natural hyaluronic acid (HA) dissolves quickly within the body and lacks the structural stability needed for certain biomedical applications. To overcome these limitations, scientists chemically modify it through a process called methacrylation. This process attaches methacrylate groups to the HA molecule’s backbone through esterification, making the resulting HAMA molecule sensitive to light.
When a liquid HAMA solution containing a photoinitiator is exposed to ultraviolet (UV) or visible light, a rapid reaction called photocrosslinking occurs. The methacrylate groups on different HAMA molecules link together, solidifying the liquid into a stable, three-dimensional network called a hydrogel. A hydrogel is a gel that holds a large amount of water. This light-curing ability allows for precise control over solidification, potentially turning a liquid into a solid in seconds.
Unique Characteristics of HAMA Hydrogels
HAMA hydrogels possess distinct properties useful for medical applications. A primary feature is their tunable mechanical stiffness. Scientists control the hydrogel’s firmness by adjusting the HAMA concentration or the duration of light exposure. This allows for creating gels that match the softness of brain tissue or the firmness of cartilage.
Derived from a molecule abundant in the human body, HAMA hydrogels exhibit high biocompatibility. The material is well-tolerated by living tissues and is not recognized as a foreign substance. This minimizes the risk of an immune response or inflammation.
The hydrogels are also biodegradable, breaking down naturally over time within the body. The degradation rate can be controlled by altering the degree of methacrylation and the gel’s crosslinking density. This allows the hydrogel to dissolve at a pace that matches new tissue growth, so it is gradually replaced by the body’s own structures.
Applications in Tissue Engineering and Bioprinting
In tissue engineering, HAMA hydrogels function as a scaffold, providing a temporary structure for new tissue to grow. Live cells can be mixed into the liquid HAMA solution before it is solidified. The mixture can then be molded into a specific anatomical shape, like a piece of cartilage, and solidified with light, trapping the cells within a biocompatible environment.
This principle extends to 3D bioprinting, where HAMA is a component of materials known as bioinks. A 3D printer deposits the bioink, a mix of HAMA and living cells, layer by layer to construct biological structures. After printing, the structure is exposed to light to crosslink the HAMA, solidifying it and fixing the cells in place. This technique can be used to create structures that promote bone cell differentiation.
HAMA can be combined with other materials like collagen or gelatin to refine a bioink’s properties. This blending can enhance the mechanical strength or biological signaling of the printed construct. These capabilities make HAMA-based hydrogels a promising material for engineered tissue replacements.
Use in Drug Delivery and Wound Healing
HAMA hydrogels also serve as vehicles for localized drug delivery. Therapeutic agents like medications or growth factors can be incorporated into the HAMA solution before it gels. Once formed, the hydrogel acts as a reservoir for the entrapped drug and can be injected or used in a wound dressing.
As the hydrogel biodegrades, the therapeutic payload is released in a controlled and sustained manner at the target site. This method provides a steady supply of the drug over an extended period. Because the degradation rate is adjustable, the timing and dosage of the drug’s release can be precisely controlled.
For wound healing, HAMA hydrogels can be applied to an injury as a dressing. The hydrogel covers the wound, creating a protective barrier against infection while maintaining a moist environment conducive to healing. These dressings can also be loaded with antibiotics or growth factors to prevent infection and stimulate tissue repair.