5.3 Biodegradable and bioresorbable materials
5 min read•july 30, 2024
Biodegradable and bioresorbable materials are game-changers in regenerative medicine. They break down in the body, with bioresorbable materials completely absorbed. These materials can be tailored for various applications, from tissue to .
Controlling degradation is key for optimal performance. Factors like chemical composition and surface area influence breakdown rates. By fine-tuning these properties, we can create materials that support tissue growth, deliver drugs, or provide temporary implants, revolutionizing medical treatments.
Biodegradable vs Bioresorbable Materials
Definitions and Distinctions
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- Biodegradable materials can be broken down by biological processes into smaller components that can be metabolized or excreted by the body (enzymes, cellular activity)
- Bioresorbable materials are a subset of biodegradable materials that degrade and dissolve, being absorbed by the body with no residual substance left behind
- The key distinction is that bioresorbable materials are completely absorbed, while biodegradable materials may leave some residual components after degradation
Degradation Mechanisms and Influencing Factors
- Degradation mechanisms for biodegradable materials include:
- : breaking down the material's chemical structure through reaction with water
- : breaking down the material through reaction with oxygen
- : enzymes catalyzing the breakdown of the material's chemical bonds
- Bioresorbable materials typically degrade through a combination of hydrolysis and cellular activity, such as phagocytosis by macrophages, leading to complete resorption
- Factors influencing the degradation rate of biodegradable and bioresorbable materials:
- Chemical composition: the types of chemical bonds and functional groups present in the material
- Molecular weight: higher molecular weight generally leads to slower degradation
- Crystallinity: higher crystallinity generally leads to slower degradation due to reduced accessibility for degradation processes
- Surface area: larger surface area exposes more of the material to degradation processes, leading to faster degradation
- Byproducts of the degradation process can include monomers, oligomers, and other small molecules, which may have varying levels of and potential toxicity
Design Considerations for Biomaterials
Degradation Rate and Byproduct Toxicity
- The degradation rate should be tailored to match the desired application and the rate of tissue regeneration or drug release
- Rapid degradation may lead to premature loss of mechanical support or burst release of drugs
- Slow degradation may hinder tissue regeneration or result in a prolonged inflammatory response
- Byproducts of the degradation process should be non-toxic and readily metabolized or excreted by the body to minimize adverse reactions
- Example: (PLA) degrades into lactic acid, which is a naturally occurring metabolite in the body
- Example: (PGA) degrades into glycolic acid, which is also a naturally occurring metabolite
Mechanical Properties and Surface Characteristics
- The mechanical properties should be sufficient to support the intended application (temporary structural support, withstanding physiological loads)
- The degradation process should not significantly compromise the material's mechanical properties until the regenerated tissue can assume its functional role
- The initial mechanical properties and degradation kinetics should be carefully balanced to ensure optimal performance throughout the regeneration process
- The material's surface properties can influence:
- Cell attachment, proliferation, and differentiation (hydrophilicity, roughness)
- Degradation rate (hydrophilicity, surface area)
- Example: increasing surface roughness of a biodegradable polymer scaffold can enhance cell attachment and proliferation
Applications of Biodegradable Materials
Tissue Engineering Scaffolds
- Biodegradable and bioresorbable materials are widely used in tissue engineering scaffolds to provide temporary structural support and guide the regeneration of tissues (bone, cartilage, skin)
- These materials can be engineered to mimic the extracellular matrix's structure and composition, promoting cell adhesion, proliferation, and differentiation
- Example: collagen scaffolds for skin tissue engineering, as collagen is a major component of the skin's extracellular matrix
- Biodegradable and bioresorbable materials can be used to fabricate porous scaffolds with interconnected networks that facilitate cell infiltration, nutrient transport, and waste removal
- Example: 3D-printed (PCL) scaffolds with interconnected pores for bone tissue engineering
Drug Delivery Systems and Temporary Implants
- In drug delivery systems, biodegradable and bioresorbable materials can be used to encapsulate and release drugs in a controlled manner, improving therapeutic efficacy and minimizing side effects
- The degradation rate of the material can be tuned to achieve desired drug release profiles (sustained release, pulsatile release)
- Example: (PLGA) microspheres for sustained release of growth factors in tissue engineering applications
- Biodegradable and bioresorbable materials are used in temporary implants, such as sutures, staples, and bone fixation devices, which provide mechanical support during the healing process and then degrade, eliminating the need for a second surgery for removal
- Example: biodegradable sutures made from PLA or PGA, which degrade over several weeks to months, depending on the specific composition and processing
Degradation Kinetics in Regenerative Medicine
Challenges in Controlling Degradation Kinetics
- Controlling the degradation kinetics and resorption of biomaterials is crucial for ensuring optimal performance in regenerative medicine applications
- Challenges in controlling degradation kinetics include:
- Complex interplay of material properties (molecular weight, crystallinity, surface area)
- Variability in the biological environment (pH, enzymatic activity, cellular response)
- Inconsistent degradation rates can lead to:
- Premature loss of mechanical support
- Uncontrolled release of bioactive factors
- Prolonged inflammatory responses
- Compromised regeneration process
Opportunities for Advanced Control Strategies
- Advanced material processing techniques can be used to fine-tune the material's properties and control degradation kinetics:
- : combining different monomers to create copolymers with tailored degradation properties
- : mixing different polymers to achieve desired degradation characteristics
- : altering the surface chemistry or topography to influence degradation rate and cellular interactions
- Incorporation of stimuli-responsive elements can enable the material to respond to specific biological cues and regulate its degradation rate:
- pH-sensitive moieties: material degradation rate changes based on local pH changes in the biological environment
- Enzyme-cleavable moieties: material degradation is triggered by the presence of specific enzymes in the tissue
- Mathematical modeling and computational simulations can aid in predicting and optimizing the degradation behavior of biomaterials, reducing the need for extensive experimental testing
- Development of novel biodegradable and bioresorbable materials with precisely controlled degradation kinetics and resorption profiles can lead to improved regenerative medicine outcomes:
- Enhanced tissue regeneration
- Reduced inflammation
- Minimized side effects
Key Terms to Review (24)
3D printing: 3D printing, also known as additive manufacturing, is a process that creates three-dimensional objects layer by layer from digital models. This technology allows for the precise fabrication of complex geometries, making it particularly useful in the development of customized medical devices and scaffolds using both natural and synthetic biomaterials.
Biocompatibility: Biocompatibility refers to the ability of a material to perform with an appropriate host response when implanted or used within a biological environment. This means that the material should not elicit a harmful reaction and should ideally promote tissue integration, making it crucial for successful biomedical applications.
Blending: Blending refers to the process of combining two or more materials to create a composite that possesses enhanced properties compared to the individual components. In the context of biodegradable and bioresorbable materials, blending can help improve mechanical strength, degradation rates, and biocompatibility, making these materials more suitable for various medical applications.
Co-polymerization: Co-polymerization is a chemical process where two or more different monomers are combined to create a copolymer, which exhibits properties distinct from those of the individual homopolymers. This technique allows for the customization of material properties, such as mechanical strength, biodegradability, and thermal stability, making it especially important in the development of biodegradable and bioresorbable materials for medical applications.
Drug Delivery Systems: Drug delivery systems are technologies designed to transport pharmaceutical compounds to targeted sites in the body effectively and safely. These systems enhance the therapeutic effects of drugs while minimizing side effects, utilizing various materials and methods that can be tailored to specific medical needs.
Electrospinning: Electrospinning is a process used to create nanofibers by applying a high voltage to a polymer solution, which draws out fibers from a charged droplet. This technique allows for the fabrication of scaffolds that can mimic the extracellular matrix, providing a suitable environment for cell growth and tissue development.
Enzymatic cleavage: Enzymatic cleavage refers to the process by which enzymes catalyze the breaking of chemical bonds within biomolecules, leading to the decomposition or modification of those molecules. This mechanism is crucial in the context of biodegradable and bioresorbable materials, as it influences how these materials break down in biological environments and their interaction with living tissues.
FDA Approval: FDA approval is the process by which the U.S. Food and Drug Administration evaluates and authorizes medical products, including drugs, biological products, and medical devices, ensuring they are safe and effective for public use. This process is crucial in various fields, as it directly impacts the translation of scientific advancements into practical applications, determining how therapies and materials can be used in clinical settings.
Hydrolysis: Hydrolysis is a chemical reaction that involves the breakdown of a compound due to its interaction with water. In the context of biodegradable and bioresorbable materials, hydrolysis is crucial because it facilitates the degradation of these materials in biological environments, allowing for their safe absorption and elimination from the body over time. This process is essential in designing materials that can effectively support tissue regeneration while eventually being replaced by natural tissue.
In vitro testing: In vitro testing refers to the process of conducting experiments in a controlled environment outside of a living organism, typically using cells or tissues in a laboratory setting. This method is essential for evaluating the biological properties of materials, especially in regenerative medicine, where it helps assess scaffold performance, material biodegradability, and functionalization before in vivo application. It allows researchers to gather crucial data on cellular responses and interactions, which can be pivotal in developing effective medical treatments.
In vivo evaluation: In vivo evaluation refers to the assessment of biological materials, devices, or therapies within a living organism, providing insights into their safety, effectiveness, and biocompatibility. This type of evaluation is crucial for understanding how biodegradable and bioresorbable materials interact with biological systems in real-time, leading to informed decisions about their applications in regenerative medicine.
ISO Standards: ISO standards are internationally recognized guidelines and specifications that ensure the quality, safety, efficiency, and interoperability of products and services. These standards play a crucial role in various fields, including biomaterials, as they help establish benchmarks for material safety, performance, and compatibility within biomedical applications.
Mechanical Strength: Mechanical strength refers to the ability of a material to withstand an applied force without failure, deformation, or fracture. This property is crucial for ensuring that biodegradable and bioresorbable materials can support biological structures during healing and that engineered blood vessels and vascular grafts maintain their shape and function under physiological conditions. The interplay between mechanical strength and other properties such as biocompatibility and degradation rate is essential in designing effective medical devices.
Osseointegration: Osseointegration is the process through which a dental implant or orthopedic implant becomes firmly anchored to the bone through direct structural and functional connection. This biological phenomenon is crucial for the stability and longevity of implants, making it essential for successful rehabilitation in regenerative medicine. The quality of osseointegration can be influenced by various factors, including the material properties of the implant, surface treatments, and the biological response of the host tissue.
Oxidation: Oxidation is a chemical process involving the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. In the context of biodegradable and bioresorbable materials, oxidation can play a critical role in the degradation and breakdown of these materials within biological environments. This process can influence the mechanical properties, biocompatibility, and overall performance of such materials in regenerative medicine applications.
Poly(lactic-co-glycolic acid): Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable and biocompatible copolymer made from lactic acid and glycolic acid, widely used in biomedical applications such as drug delivery and tissue engineering. Its unique properties, such as tunable degradation rates and excellent mechanical strength, make it suitable for various applications, particularly in regenerative medicine where it can be used to create scaffolds for tissue repair and regeneration.
Polycaprolactone: Polycaprolactone (PCL) is a biodegradable polyester with a low melting point and good mechanical properties, widely used in various biomedical applications such as drug delivery and tissue engineering. Its biodegradability and bioresorbability make it an excellent choice for creating scaffolds that can support cell growth while gradually breaking down in the body.
Polyglycolic Acid: Polyglycolic acid (PGA) is a biodegradable polymer that is derived from glycolic acid and is commonly used in medical applications such as sutures, drug delivery systems, and tissue engineering scaffolds. Its biodegradability allows it to break down in the body over time, making it a suitable choice for temporary implants and devices that support healing processes without the need for surgical removal.
Polylactic acid: Polylactic acid (PLA) is a biodegradable and bioresorbable polymer derived from renewable resources, such as corn starch or sugarcane. It has gained significant attention in the field of regenerative medicine and tissue engineering due to its favorable mechanical properties, biocompatibility, and ability to degrade into non-toxic byproducts in the body. This makes PLA a valuable material for creating scaffolds and drug delivery systems that can safely dissolve in the body over time.
Scaffolds: Scaffolds are three-dimensional structures designed to support cell attachment and growth in tissue engineering, providing a temporary framework for cells to form new tissues. These structures play a crucial role in regenerative medicine by facilitating cellular interactions and guiding tissue development.
Self-healing materials: Self-healing materials are innovative substances designed to automatically repair themselves after damage, mimicking biological healing processes. This property is particularly valuable in various applications, including biodegradable and bioresorbable materials, where maintaining functionality and integrity over time is essential, especially in medical devices and implants that need to degrade safely in the body while still providing therapeutic support.
Smart biomaterials: Smart biomaterials are advanced materials designed to respond dynamically to environmental stimuli, such as temperature, pH, or biochemical signals. These materials can adapt their properties in real-time, making them particularly useful in medical applications where they can enhance the performance of implants and tissue engineering constructs. Their ability to interact with biological systems in a controlled manner allows for improved healing and integration into the body.
Surface modification: Surface modification refers to the intentional alteration of a material's surface properties to improve its compatibility with biological systems or to achieve desired functionalities. This technique is crucial for enhancing the performance of biomaterials, as it can influence factors like biodegradability, cell adhesion, and bioactivity, making it integral to various applications in regenerative medicine and tissue engineering.
Tissue Ingrowth: Tissue ingrowth refers to the process by which living tissues grow into a biomaterial or scaffold, integrating with it to support regeneration and healing. This phenomenon is crucial in regenerative medicine, particularly when using biodegradable and bioresorbable materials that are designed to be replaced by natural tissue over time. Effective tissue ingrowth can enhance the functionality of implants and support the body’s healing processes.