Collagen-based adhesives, often called collagen glues, are medical products used to seal tissues and manage bleeding during surgery. Derived from a protein naturally abundant in the body, these materials offer a biological alternative to traditional methods like sutures or staples. Their use is expanding for various clinical situations, especially those involving delicate or hard-to-reach tissues.
Defining Collagen Glue: Composition and Sources
Collagen is the most plentiful protein in mammals and serves as a primary structural component in tissues like skin, bones, and tendons. The glues developed from this protein primarily use Type I collagen, which is favored for its ability to provide tensile strength and stability at a wound site.
The collagen used in medical adhesives is sourced from various animals. Bovine (cow) and porcine (pig) sources are common due to their abundance and structural similarity to human collagen. Marine animals like fish are also a source, as their collagen has high biocompatibility and low immunogenicity. Advanced formulations may use recombinant human collagen, produced in a lab to eliminate disease transmission risks and ensure consistency.
Collagen glues are often formulated with other substances to improve their functional properties. These include crosslinking agents to enhance mechanical strength and durability. Additives may also be incorporated to control the gelation process—how the liquid glue solidifies—or to modify its handling characteristics for easier surgical application.
Mechanism of Action: How Collagen Glues Adhere
Collagen glues adhere to biological tissues through a combination of physical and chemical interactions. When applied, the adhesive integrates with the native extracellular matrix, which is the natural scaffold holding cells together. This process forms covalent and noncovalent bonds between the glue and the tissue, creating a stable seal.
Upon application, the glue undergoes crosslinking, which solidifies the material and strengthens its internal structure. This process creates links between individual collagen molecules, preventing them from slipping under stress and enhancing the seal’s durability. The setting time is influenced by factors like body temperature, and some hydrogels are designed to gel within minutes.
The effectiveness of a collagen adhesive is defined by several properties. Adhesive strength is how well it sticks to tissue, while cohesive strength is the internal durability of the glue. Elasticity is also important, allowing the sealed tissue to move without breaking the bond. These characteristics are adjusted by modifying the formulation for specific applications.
Medical and Surgical Applications
In the operating room, collagen glues are used for several tasks. A primary application is as a surgical sealant to prevent air or fluid leaks. For instance, in lung surgery, it can close small air leaks, and in neurosurgery, it can prevent cerebrospinal fluid leakage. Surgeons also use these glues in vascular procedures to seal suture lines in blood vessels.
Another use is for hemostasis, the process of stopping bleeding. Collagen promotes the aggregation of platelets, the cell fragments in blood that form clots. When applied to a bleeding surface, the glue helps control blood loss from small vessels. This is particularly useful on fragile tissues where sutures might cause more damage.
Collagen adhesives also serve as an alternative to stitches for closing external and internal wounds. In ophthalmic surgery, they can close incisions in the cornea. A collagen-based hydrogel patch can seal corneal perforations, offering a regenerative alternative to synthetic glues that may have cytotoxic effects.
Biological Interaction: Biocompatibility and Degradation
Biocompatibility is the ability of a material to exist in the body without causing a harmful immune response. Because collagen is a natural protein, it has low antigenicity, meaning it is unlikely to be recognized as a foreign substance by the immune system. This quality reduces the risk of inflammation and rejection.
Collagen-based adhesives are biodegradable. The body has enzymes, like collagenases, that are responsible for breaking down collagen. These enzymes gradually degrade the adhesive over time, allowing the body to absorb it as tissues heal. This process eliminates the need for a second procedure to remove the material.
The degradation rate is an important design consideration, as the adhesive must remain intact long enough to support the wound while it heals. This rate can be controlled by adjusting the degree of crosslinking in the formulation. A more highly crosslinked glue is more resistant to enzymatic breakdown and will persist for a longer period.