Bioresorbable implants are revolutionizing modern medicine by providing effective treatment options that safely dissolve in the body after fulfilling their purpose. These implants support tissue healing, prevent complications, and eliminate the need for surgical removal. But what exactly are these implants made of? Let’s explore the common materials used to manufacture bioresorbable implants, focusing on polymers, metals, and ceramics in simple language.
What Are Bioresorbable Implants?
Bioresorbable implants are medical devices designed to perform their function temporarily inside the body. After their job, they gradually degrade and are absorbed or eliminated safely by natural body processes. This avoids the need for a second surgery to remove the implant, reduces risks of infection or implant-related complications, and often improves patient comfort.
The materials used must be biocompatible meaning they don’t harm the body and degrade at a controlled rate matching tissue healing time.
Polymers: The Most Common Materials
Polymers are the backbone of most bioresorbable implants. These are large molecules made by linking many smaller units called monomers. The most popular polymers in bioresorbable implants include:
Polylactic Acid (PLA)
PLA is one of the earliest and most widely used bioresorbable polymers. It is made from natural sources like corn starch or sugarcane, making it eco-friendly. PLA breaks down into lactic acid, a substance your body can easily process.
- Uses: PLA is used in surgical sutures, bone fixation devices, and scaffolds to support tissue growth. It provides strong mechanical support but degrades relatively slowly, making it ideal for applications needing longer healing times.
Polyglycolic Acid (PGA)
PGA degrades faster than PLA due to its chemical structure, breaking down into glycolic acid.
- Uses: It is commonly used in fast-absorbing sutures and other short-term implants. PGA's quicker degradation makes it suitable where rapid healing is expected.
Poly(lactic-co-glycolic) Acid (PLGA)
PLGA is a copolymer made by combining PLA and PGA units. By adjusting their ratio, manufacturers can tune how quickly the implant breaks down.
- Uses: PLGA is widely used in drug delivery systems and implants that require customized degradation timing.
Polycaprolactone (PCL)
PCL degrades slowly over months to years and provides flexibility and durability in implants.
- Uses: Ideal for long-term implants and drug delivery scaffolds, PCL is FDA-approved and used in vascular and soft tissue applications.
Others: Polydioxanone (PDO) and Polyhydroxyalkanoates (PHA)
PDO is flexible and mostly used in absorbable sutures and orthopedic devices. PHA is a group of biopolyesters produced by bacteria or synthetically, used in surgical screws and drug delivery.
Metals: Strong and Bioabsorbable
While polymers dominate, bioresorbable metals are gaining traction for implants needing higher strength.
Magnesium (Mg) Alloys
Magnesium alloys are incredibly promising as they have good mechanical strength and are biocompatible. Magnesium naturally corrodes in the body into harmless minerals.
- Uses: Used in cardiovascular stents and orthopedic implants to provide strong support that dissolves safely after healing.
Zinc (Zn) and Iron (Fe) Alloys
Zinc and iron-based alloys are also studied for bioresorbable uses. They degrade slower but offer useful mechanical properties.
- Challenges: Control over degradation rate and ensuring safe corrosion products remain key research areas.
Ceramics: Bone-like and Bioactive
Bioceramics are materials made to mimic the natural mineral phase of bone. They are mostly used in bone repair.
Calcium Phosphates
This includes hydroxyapatite (HAp), tricalcium phosphate (TCP), and dicalcium phosphate dihydrate (DCPD). These materials are biocompatible and encourage bone growth by bonding directly to bone tissue.
- Uses: Bone defect fillers, fracture repair, and bone tissue engineering scaffolds.
- Limitation: Ceramics are brittle, so they are often combined with polymers for flexibility.
Why Material Choice Matters?
The selection of material depends on:
- Degradation Rate: It must match the tissue healing process so the implant supports healing before disappearing.
- Mechanical Strength: Some implants need to withstand stress (e.g., bone plates), while others need flexibility (e.g., vascular scaffolds).
- Biocompatibility: Minimizing immune reactions and ensuring safe absorption.
- Application: Different medical areas (orthopedics, cardiovascular, maxillofacial) have specific material needs.
Interesting Facts and Data
- According to studies, the degradation time for PLA implants can range from months to years, allowing its use in a broad range of applications.
- Magnesium-based stents have shown promise to reduce long-term complications linked to permanent metallic stents common in cardiovascular treatments.
- The global market for bioresorbable polymers in medical applications continues to grow rapidly, expected to reach several billion USD by the late 2020s due to increased adoption in minimally invasive surgeries.
