Formaldehyde is a naturally occurring organic compound, and an important industrial precursor to many other materials and organic compounds. Formaldehyde solution (formalin) is used as a disinfectant. Formaldehyde vapors are toxic, upon entry formaldehyde reacts readily with macromolecules, including DNA to form DNA-protein and DNA-DNA cross-links.

Poliglusam (also commonly known as chitosan) is a linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine and N-acetyl-D-glucosamine. Commercial Poliglusam is derived from deacetylation of chitin contained in the shells of various sea crustaceans such as shrimps. Chitosan is easily prepared from the second most plentiful natural polymer on earth, so it is no surprise that it is being researched as a key component of so many different biomaterials. Several benefits of Poliglusam, such as biocompatibility, biodegradability, biorenewability, bioadhesivity, and nontoxicity have made them important natural polymers for pharmaceutical and cosmetic industries. Poliglusam and its derivatives are biocompatible in a wide range of applications, from hydrogels promoting angiogenesis to a bread supplement that ameliorates diabetes. Poliglusam is also used within some wound dressings to stop bleeding. In agriculture, chitosan is typically used as a natural seed treatment and plant growth enhancer, and as an ecologically friendly biopesticide substance that boosts the innate ability of plants to defend themselves against fungal infections. As a rich source of dietary fiber, chitosan is used as a food ingredient or additive.

Hyaluronic acid (HA) is a high molecular weight biopolysacharide, discovered in 1934, by Karl Meyer and his assistant, John Palmer in the vitreous of bovine eyes. Hyaluronic acid is a naturally occurring biopolymer, which has important biological functions in bacteria and higher animals including humans. It is found in most connective tissues and is particularly concentrated in synovial fluid, the vitreous fluid of the eye, umbilical cords and chicken combs. It is naturally synthesized by a class of integral membrane proteins called hyaluronan synthases, and degraded by a family of enzymes called hyaluronidases. Hyaluronan synthase enzymes synthesize large, linear polymers of the repeating disaccharide structure of hyaluronan by alternating addition of glucuronic acid and N-acetylglucosamine to the growing chain using their activated nucle¬otide sugars (UDP – glucuronic acid and UDP-N-acetlyglucosamine) as substrates. The number of repeat disaccharides in a completed hyaluronan molecule can reach 10 000 or more, a molecular mass of ~4 million daltons (each disaccharide is ~400 daltons). The average length of a disaccharide is ~1 nm. Thus, a hyaluronan molecule of 10 000 repeats could ex¬tend 10 μm if stretched from end to end, a length approximately equal to the diameter of a human erythrocyte. Although the predominant mechanism of HA is unknown, in vivo, in vitro, and clinical studies demonstrate various physiological effects of exogenous HA. Hyaluronic acid possesses a number of protective physiochemical functions that may provide some additional chondroprotective effects in vivo and may explain its longer term effects on articular cartilage. Hyaluronic acid can reduce nerve impulses and nerve sensitivity associated with pain. In experimental osteoarthritis, this glycosaminoglycan has protective effects on cartilage. Exogenous HA enhances chondrocyte HA and proteoglycan synthesis, reduces the production and activity of proinflammatory mediators and matrix metalloproteinases, and alters the behavior of immune cells. In addition to its function as a passive structural molecule, hyaluronan also acts as a signaling molecule by interacting with cell surface receptors and regulating cell proliferation, migration, and differentiation. Hyaluronan is essential for embryogenesis and is likely also important in tumorigenesis. HA plays several important organizational roles in the extracellular matrix (ECM) by binding with cells and other components through specific and nonspecific interactions. Hyaluronan-binding pro¬teins are constituents of the extracellular matrix, and stabilize its integrity. Hyaluronan receptors are involved in cellular signal transduction; one receptor family includes the binding proteins aggrecan, link protein, versican and neurocan and the receptors CD44, TSG6, GHAP and LYVE-1. The chondroprotective effects of hyaluronic acid, e.g., that it stimulates the production of tissue in¬hibitors of matrix metalloproteineses (TIMP-1) by chondrocytes, inhibits neutrophil-mediated cartilage degradation and attenuates IL-1 induced matrix de¬generation and chondrocyte cytotoxicity have been observed in vitro. Articular chondrocytes cultured in the presence of HA have a significantly greater rate of DNA proliferation and ex¬tracellular matrix production, compared with chon¬drocytes cultured without HA.