Bioresorbable materials are a class of substances designed to dissolve or degrade within the human body over a specific period. These materials perform a temporary function, such as supporting healing tissue, before gradually breaking down and being absorbed or excreted by the body. This characteristic eliminates the need for additional surgeries to remove the implant, offering a distinct advantage in various medical applications.
Understanding Bioresorption: The Process
The breakdown of bioresorbable materials within the body occurs through two mechanisms: hydrolysis and enzymatic degradation. Hydrolysis involves the chemical reaction of the material with water molecules, causing it to slowly break apart into smaller, soluble fragments. This process is influenced by factors such as the material’s chemical structure and its exposure to bodily fluids.
Enzymatic degradation involves enzymes present in the body breaking down the material. Cells can engulf and degrade biomaterial particles, while others may secrete enzymes and acids that facilitate the breakdown. The degradation rate can be controlled by adjusting the material’s composition, porosity, and molecular weight, allowing it to match the body’s healing timeline. Once broken down, the resulting non-toxic byproducts are naturally processed and eliminated by the body, often as water and carbon dioxide.
Materials That Resorb
A variety of materials are engineered to exhibit bioresorbable properties, falling into categories of polymers, metals, and ceramics. Polymers are commonly used, with examples like polylactic acid (PLA), polyglycolic acid (PGA), and polycaprolactone (PCL). PLA degrades into lactic acid, PGA into glycolic acid, and PCL offers a slower degradation rate and high flexibility.
Certain metals, such as magnesium and iron alloys, are also being explored for their bioresorbable characteristics, offering high strength alongside their ability to degrade. Bioresorbable ceramics, including calcium phosphate and bioactive glass, find applications in bone tissue engineering and dental procedures. These materials can be tailored for specific mechanical properties and degradation rates.
Where Bioresorbable Materials Are Used
Bioresorbable materials have found widespread application across various medical fields. Dissolvable sutures, a familiar example, are commonly used in surgical procedures to close wounds, eliminating the need for removal stitches. In cardiovascular medicine, absorbable stents provide temporary support to blood vessels after procedures like angioplasty, allowing the vessel to heal and remodel before the stent gradually disappears. These stents can also deliver drugs to the vessel wall over time.
Orthopedic applications also benefit from these materials, with bioresorbable bone screws and plates used to stabilize fractures and promote bone healing. These devices provide support during the initial healing phase and then resorb, allowing the bone to fully take over its load-bearing function. Bioresorbable materials are also integrated into drug delivery systems, where they can release therapeutic agents in a controlled manner over an extended period. This allows for continuous medication at the site of action, reducing the need for repeated drug administrations.
Advantages in Medical Treatment
The use of bioresorbable materials offers advantages over traditional, permanent implants in medical treatments. A primary benefit is avoiding a second surgery for implant removal, which reduces patient trauma, surgical risks, and healthcare costs. This is particularly beneficial for pediatric patients who might otherwise outgrow permanent devices, requiring additional interventions.
Bioresorbable materials can also reduce the risk of long-term complications often associated with permanent foreign bodies. These complications include chronic inflammation, infection, or issues arising from implant fatigue over time. By disappearing, these materials allow the body’s natural tissues to heal and gradually assume the full functional role, promoting more natural tissue regeneration. The predictable degradation of these implants can also progressively transfer mechanical load to the healing bone, aiding in its regeneration.