Hyaluronic acid modified with hydroxypropyl methacrylate as a potential biomaterial for tissue engineering applications

introduce Hyaluronic acid (HA), also known as hyaluronan, is a natural polymer that plays a vital role in maintaining tissue hydration, lubrication, and elasticity. It is found in almost all body tissues and is found in particularly high levels in connective tissues such as skin, cartilage and synovial fluid. Over the years, HA has become a valuable therapeutic agent for a wide range of medical and cosmetic applications, with a growing body of research demonstrating its safety and efficacy. This article aims to provide a detailed overview of the physiology, molecular structure, biosynthesis, and therapeutic uses of HA.

Physiology of Hyaluronic Acid

 Hyaluronic acid is a versatile molecule that is widely distributed throughout the body. It has a variety of functions, including: 

- Tissue hydration: HA is hydrophilic, which means it has a high affinity for water molecules. This property allows it to absorb and retain water in tissues, providing hydration and volume to the skin and cushioning the joints. 

- Lubrication: HA is a component of synovial fluid that lubricates and cushions joints, reducing friction and wear. 

- Wound Healing: HA is involved in all stages of wound healing, from inflammation and granulation to remodeling and scarring. Promote cell migration, proliferation, differentiation and matrix deposition, and promote tissue regeneration after injury. 

- Inflammation Modulation: HA has been shown to play a role in modulating immune responses, modulating inflammation and inhibiting the formation of reactive oxygen species (ROS).

Molecular structure of hyaluronic acid Hyaluronic acid is a linear polysaccharide composed of repeating disaccharide units of glucuronic acid (GlcA) and N-acetylglucosamine (GlcNAc).  GlcA residues bear a carboxyl group, which can be ionizing or neutral, depending on the acidity (pH) of the microenvironment.  GlcNAc residues carry an amino group that can be acetylated or sulfated, depending on the tissue type. The disaccharide units are linked together by β-1,4-glycosidic bonds, forming long chains of up to 25,000 sugars.  The molecular weight of HA varies widely, from a few kDa to several MDa, depending on the tissue and developmental stage.

Biosynthesis of Hyaluronic Acid 

Hyaluronic acid is synthesized by a group of enzymes called hyaluronan synthases (HAS).  There are three isoforms of HAS (HAS1, HAS2, and HAS3), each with distinct tissue distribution and regulation.  HAS are transmembrane proteins that insert their active sites into the inner surface of the plasma membrane, where they polymerize HA chains using glucose and UDP-N-acetylglucosamine as substrates. Newly synthesized HA chains extrude from the cell surface, where they can interact with the extracellular matrix (ECM) or bind cell surface receptors such as CD44 or RHAMM, depending on their molecular weight and charge density.

Therapeutic Uses of Hyaluronic Acid Hyaluronic acid has a wide range of therapeutic applications, including: - Ophthalmology: HA is used as a viscoelastic agent in cataract and glaucoma surgery, as a tear substitute in dry eye, and as a drug delivery vehicle for ophthalmic drugs. 

- Orthopedics: HA is used as an intra-articular injection for the treatment of joint pain and osteoarthritis, and as a coating material for orthopedic implants and biomaterials. 

- Dermatology: HA is used in skin care products as a moisturizer, anti-aging agent and wound healing promoter, and in cosmetic surgery as a dermal filler and scar reducer.

 - Dentistry: HA is used as a biomaterial for dental implants, periodontal regeneration and pulp capping, as well as a lubricant for dental instruments and a stabilizer for impression materials. 

- Drug delivery: HA can be chemically or physically modified to enhance its binding, solubility, or permeability, making it a versatile vehicle for drug delivery systems in various disease states such as cancer, inflammation, and infection.

In summary 

Hyaluronic acid is a natural polymer with remarkable properties that make it a valuable therapeutic agent in a wide range of medical and cosmetic applications.it has the ability to hydrate