Bioabsorbable Polymers Quiz
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Questions and Answers

The degradation rate of bioabsorbable polymers is consistent across all individuals.

False (B)

Hydrophobic materials generally have a longer degradation time compared to hydrophilic materials.

True (A)

Enzymatic degradation involves enzymes having no affinity for specific chemical groups in polymers.

False (B)

The thickness of the covering soft tissue layer influences the degradation time of bioabsorbable polymers.

<p>True (A)</p> Signup and view all the answers

The testing methods for bioabsorbable polymers' degradation behavior require a combination of different methods.

<p>True (A)</p> Signup and view all the answers

Bioabsorbable materials can be metabolized within an organism.

<p>True (A)</p> Signup and view all the answers

Hydrolytic and enzymatic degradation produce high-molecular weight products.

<p>False (B)</p> Signup and view all the answers

There is no risk of long-term implant palpability with bioabsorbable materials.

<p>True (A)</p> Signup and view all the answers

Microplastics are generated from bioabsorbable polymers.

<p>False (B)</p> Signup and view all the answers

Stress shielding is a concern with bioabsorbable materials.

<p>False (B)</p> Signup and view all the answers

Enzymatic degradation does not play a role in the biodegradation of some materials.

<p>False (B)</p> Signup and view all the answers

Patient satisfaction can increase due to less pain and avoiding operations with bioabsorbable materials.

<p>True (A)</p> Signup and view all the answers

Biostable polymers are completely harmless even when dissolved into microparticles.

<p>False (B)</p> Signup and view all the answers

Chitosan is a polysaccharide derived from chitin through deacetylation.

<p>True (A)</p> Signup and view all the answers

Silk fibroin is primarily a protein produced by bacteria.

<p>False (B)</p> Signup and view all the answers

All natural polymers exist in nature as ready-for-use materials.

<p>False (B)</p> Signup and view all the answers

Bulk PGA degrades and gets absorbed in approximately 3 – 6 months.

<p>True (A)</p> Signup and view all the answers

Collagen is considered the main protein of the extracellular matrix (ECM).

<p>True (A)</p> Signup and view all the answers

Poly(lactide) has a faster degradation rate than poly(-caprolactone).

<p>True (A)</p> Signup and view all the answers

The degradation product of PLA is lactic acid, which is beneficial in the human body.

<p>True (A)</p> Signup and view all the answers

Enzymatic degradation is an ineffective method for biodegradation in tissue engineering.

<p>False (B)</p> Signup and view all the answers

Copolymers of PGA and lactide result in a limited range of polymer properties.

<p>False (B)</p> Signup and view all the answers

Polyesters generally have a high degradation rate, producing non-inflammatory products.

<p>False (B)</p> Signup and view all the answers

Suturing materials can be made from PLA.

<p>True (A)</p> Signup and view all the answers

Hydrolysis of PLA occurs without any enzymatic degradation.

<p>False (B)</p> Signup and view all the answers

The copolymerization of different lactides can improve bioactivity and cell adhesion.

<p>True (A)</p> Signup and view all the answers

Hydrogels are hydrophilic polymeric networks that can swell in water without dissolving.

<p>True (A)</p> Signup and view all the answers

Composite materials can only be created using Poly(glycolic acid) and collagen type I.

<p>False (B)</p> Signup and view all the answers

Tissue engineering scaffolds are designed to support the regeneration of tissues such as cartilage and blood vessels.

<p>True (A)</p> Signup and view all the answers

PLGA fiber/collagen composites cannot be used for engineering articular cartilage tissue.

<p>False (B)</p> Signup and view all the answers

Sutures are not classified under wound covers or biomaterials.

<p>False (B)</p> Signup and view all the answers

Natural polymers often exhibit poor mechanical properties.

<p>True (A)</p> Signup and view all the answers

Hydrogels are primarily composed of metallic components.

<p>False (B)</p> Signup and view all the answers

Hyaluronic acid is a type of natural polymer used in hydrogels.

<p>True (A)</p> Signup and view all the answers

A high swelling ratio in hydrogels indicates they contain very little water.

<p>False (B)</p> Signup and view all the answers

The primary application of hydrogels is in the construction of buildings.

<p>False (B)</p> Signup and view all the answers

Injectable hydrogels can be used as drug carriers.

<p>True (A)</p> Signup and view all the answers

The degree of cross-linking in hydrogels does not affect their properties.

<p>False (B)</p> Signup and view all the answers

Adipose stem cells are used in the repair of corneal defects.

<p>True (A)</p> Signup and view all the answers

Flashcards

Biodegradation

The breakdown of a material by a biological system, often leading to simpler products.

Bioabsorbable / Bioresorbable

Materials that can be broken down and absorbed by the body, eventually being metabolized and eliminated.

Hydrolytic Degradation

A type of biodegradation where water molecules directly break down the material.

Enzymatic Degradation

A type of biodegradation where enzymes produced by the body break down the material.

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Biodegradation Products

The ultimate goal of both Hydrolytic and Enzymatic degradation is to break down materials into small, water-soluble molecules.

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Bioresorbable Polymers and Plastics

Polymers are often considered plastics, but bioresorbable polymers are designed to break down safely within the body.

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Metabolism of Bioresorbable Polymers

The process by which bioresorbable polymers are broken down and absorbed by the body.

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Microplastics and Bioresorbable Polymers

Microplastics are a concern for non-biodegradable plastics, but bioresorbable polymers are designed to break down before reaching microplastic size.

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Biodegradation Rate

The speed at which a bioabsorbable polymer breaks down in the body. This rate can be influenced by factors like the material's properties, the manufacturing process, and the implantation site.

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Bioabsorbable Polymer

A material that is designed to break down and be absorbed by your body, often used in medical implants.

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Biocompatibility Testing

Bioabsorbable polymers need to be very safe and not cause any harm to your body. This includes testing how the material breaks down, how it interacts with your body, and any potential toxic effects.

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Natural Polymers

Natural polymers are derived from living organisms and consist of long chains of repeating units.

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Collagen

Collagen, a main component of connective tissues, provides strength and structure.

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Gelatin

Gelatin, a derivative of collagen, is a soluble protein used in food and pharmaceuticals.

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Fibrin

Fibrin, formed during blood clotting, is a fibrous protein that helps stop bleeding.

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Hyaluronic acid

Hyaluronic acid, a glycosaminoglycan, is found in connective tissues and helps retain water.

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Why does PGA degrade faster than PLA?

Polyglycolic acid (PGA) is a biodegradable polymer that breaks down faster than polylactic acid (PLA). This is because PGA is more attracted to water (hydrophilic) compared to PLA.

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What's the benefit of copolymerizing glycolide and lactide?

By changing the ratio of glycolide and lactide in a copolymer, we can adjust the properties of the resulting polymer. This allows us to create different polymer compositions for specific applications.

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What is PLA?

Polylactic acid (PLA) is a biodegradable polymer made from lactic acid. It's a natural byproduct of the body.

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How does PLA degrade?

PLA degrades by breaking down the ester bonds within its structure. The process is called hydrolysis, where water molecules react with the polymer.

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How long does PLA degradation take?

PLA takes a long time to degrade completely, typically 3 to 5 years. This is much longer than PGA which degrades in a few months.

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What is PCL?

Poly-ε-caprolactone (PCL) is a biodegradable polymer that degrades slowly. This is because it's not as easily broken down by water, making it more resistant to degradation.

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How does PCL degrade?

PCL degrades through a process called hydrolysis, where water molecules break down the polymer bonds. However, at later stages, enzymes can also break down PCL.

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How can PCL be modified?

PCL can be combined with other monomers like lactide and glycolide to create copolymers. This allows us to tune the properties of the material for specific applications.

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Bioabsorbable Materials

Materials that can be broken down by the body, and eventually absorbed and eliminated. Useful for biocompatible implants and drug delivery.

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Bioresorbable Polymers

Materials that are designed to break down into harmless products within the body, usually within a specific timeframe.

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Hydrogel

A type of material that is composed mainly of water and can swell significantly.

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Synthetic Polymer

A polymer that is created synthetically, not found in nature.

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Injectable Hydrogel

A type of hydrogel that can be injected into the body, often used for drug delivery or tissue regeneration.

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Biocompatibility

The ability of a material to be tolerated by the body without causing harmful reactions.

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Study Notes

Polymers as Biomaterials

  • Polymers are used as biomaterials for their variety in composition, properties, and available forms (e.g., solid, elastic, hydrogel)
  • They are easy to manufacture into complex shapes (sheets, fibers, powders, films)
  • Biodegradable polymers have reasonable costs, and are used in load-bearing applications
  • Biostable polymers have a more complex structure, with mechanical properties and thermal resistance, and have higher prices.

Biodegradation Mechanisms

  • Hydrolytic degradation is a chemical reaction where water breaks up bonds in a material
  • Chain scission is when water molecules separate certain bonds in the material
  • Enzymatic degradation is when enzymes (proteins in tissues) catalyze biochemical reactions like hydrolysis or oxidation
  • Both hydrolyitic and enzymatic degradation produce low molecular weight products that are soluble and metabolized by the body

Classification of Polymers

  • Biostable polymers
  • Bioabsorbable polymers
  • Natural polymers, including modified natural polymers
  • Synthetic polymers

Classification of Biostable Polymers

  • Mass production of biostable polymers lead to technical/engineering specialty polymers, increasing in use and cost as the structure becomes more complex

Why Polymers in Medicine?

  • Variety of compositions and properties
  • Easy to fabricate complex forms (sheets, fibers)
  • Reasonable costs
  • Biodegradable
  • Lower strength and moduli than metals and ceramics (usually not suited for load-bearing applications)

Bioabsorbable Implants

  • Implants avoiding removal surgery
  • No long-term implant complications, palpability, or temperature sensitivity
  • No risk for children’s growth disturbance or stress shielding
  • Avoiding trauma from traditional implant removal
  • Patient satisfaction due to less pain

Definitions

  • Biodegradation: breakdown of a material by a biological system
  • Bioabsorbable/bioresorbable: capable of degradation/dissolving and metabolized within an organism

A Couple of Minutes to Discuss

  • Many polymers are considered plastics that can degrade in the body without causing reactions, but some are not truly metabolized
  • Microplastics in the body may be relevant only for biostable polymers dissolved into microparticles

How Long Is The Degradation Time?

  • The length depends on the characteristics of the material, including
    • Material properties (hydrophobic vs hydrophilic, polymer structure/morphology)
    • Molecular weight
    • Manufacturing process (parameters, sterilization)
    • Implantation site (inside vs. outside bone, tissue layer thickness, and vascularity/blood circulation)
  • Individual differences in metabolism and/or local vascularity/blood circulation affect degradation

How the Degradation Behavior is Tested?

  • A combination of methods is required
  • Measure and analyze different properties along the degradation process, including mass loss, molecular weight, crystallinity, etc.

Enzymatic Degradation

  • Enzymes (proteins in tissues) have a particular affinity for certain chemical groups present in polymers
  • They catalyze biochemical reactions like hydrolysis and oxidation in the body
  • (May occur at a later stage in degradation of materials that degrade via hydrolysis, when the initial stages have already already happened)

Hydrolytic and Enzymatic Degradation

  • Both mechanisms produce low molecular weight, water-soluble products that the body metabolizes
  • The mechanisms can exist in combination

Common Synthetic, Bioabsorbable Polymers

  • Synthetic polymers include hydroxy acids, vinylic polymers, polyesters, and their copolymers
  • Various types of polymers are used:
    • Poly(glycolic acid) (PGA) (homopolymer)
    • Poly(lactic acid) (PLA) (homopolymer)
    • Poly(ε-caprolactone) (PCL) (homopolymer)
    • Poly(butylene succinate) (PBS) (copolymer)
    • Poly(lactic-co-glycolic acid) (PLGA) (copolymer)
    • Others copolymers

Bioabsorbable Synthetic Polymers

  • Polyesters including PGA, PLA, PCL, PBS, PLGA, and others

Polyglycolide (PGA)

  • Highly crystalline
  • High melting point
  • Low solubility in organic solvents
  • Used early development of totally synthetic, bioabsorbable sutures (Dexon)

Polyglycolide(PGA) for Degradation

  • Degradation involves hydrolysis and enzymatic degradation
  • The degradation products (glycolic acid) are eliminated through the metabolic pathway as CO2 and H2O
  • Bulk PGA degrades and is absorbed relatively quickly compared to PLA
  • Copolymerization with more hydrophobic lactide can provide a wider range of polymer properties

Biodegradable Synthetic Polymers - Polylactides

  • Polymers obtained from different isomers (PLLA, PDLA, PDLLA) and copolymers, which have different properties
  • Different degradation rates, physical, and chemical characteristics (can be adjusted) can be processed in different ways
  • Polyesters have a slow degradation rate
  • Significantly hydrophobic

Polylactide (PLA)

  • PLA degrades by bulk hydrolysis of ester bonds to lactic acid
  • Lactic acid is a byproduct of anaerobic metabolism in the human body
  • The complete degradation takes 3-5 years for some forms (longer than PGA)

Poly-ɛ-caprolactone (PCL)

  • Degrades relatively slowly compared to PLA
  • Accompanied by enzymatic degradation at a later stage
  • Slower degradation and mass absorption
  • Copolymerized with lactide, glycolide, etc.
  • Mixed with other polymers well

Copolymers

  • Homopolymer properties may not be sufficient for medical applications
  • Copolymerization can modify properties such as mechanical properties, degradation, and crystallinity

Copolymers for Medical Uses

  • Polymer response to stress/strain depends on variables like strain rate, temperature, and time
  • This viscoelastic behavior can be modified via copolymers (blending of polymers or copolymerization of different monomers)
  • Typical copolymer materials for lactides are glycolide and trimethylene carbonate

What's Wrong with the Early Generation Biodegradables?

  • PGA (semi-crystalline, hydrophilic, fast degradation, rapid strength loss) lead to higher risk of inflammation in adult patients
  • PLLA (high crystallinity, hydrophobic, very slow, unpredictable degradation) lead to late inflammatory response
  • Crystalline residue also results in a longer degradation period

Poly(lactide-co-glycolide) (PLGA)

  • Is amongst the most studied bioabsorbable polymers
  • Well-known properties
  • Biocompatible
  • Simple processing
  • Degrades to lactic acid and glycolic acid
  • Possible modification

Poly(lactide-co-caprolactone) (PLCL)

  • Flexible
  • Good drug release properties
  • Tailorable properties dependent on ratio of monomers
  • Degrades faster than their respective homopolymers

Materials Selection

  • Selection of materials based on factors like strength, flexibility, and degradation characteristics for various application needs, like implants, screws, plates, and nails

Summary of Synthetic, Bioabsorbable Polymers

  • Bioabsorbable polymers are used temporary function/support
  • Hydrolytic degradation with synthetic biopolymers (BPs)
  • Processing similar to stable polymers (mostly melt processing)
  • Variety in shapes and geometries (often without solvents)

(Modified) Natural Bioabsorbable Polymers

  • Derived from nature (animals and plants)
  • Can be modified
  • Offer good biocompatibility and degradability, but have disadvantages
  • Poor mechanical properties
  • Batch-to-batch variations
  • Difficulty processing

Future of Bioabsorbable Polymers

  • Metal-based implants may be replaced by biocompatible, sustainable polymers, and/or tissues

General Announcements

  • Visit schedule, lectures, and hands-on sessions
  • Exam schedule and details
  • Enrolment information

Hydrogels

  • Hydrophilic polymeric network that swells in water without dissolving
  • Soft and rubbery, containing large amounts of water

Hydrogel Applications

  • Carriers for drug delivery, wound dressings, contact lenses, and tissue engineering scaffolds

Injectable Hydrogels

  • Formulation, methods of chemical/physical crosslinking, and applications relating to polymers

Summary of (Modified) Natural Polymers

  • Polymers are derived from nature (animals and plants)
  • Natural polymers often have good biocompatibility and degradability
  • The main disadvantages are poor mechanical properties and batch-to-batch variation, as well as difficulty in processing

Why growing interest in Natural polymers?

  • Growth of tissue engineering
  • Continuous search for better implant material
  • Increased biocompatibility
  • Increased cell adhesion, migration, and proliferation
  • Enzymatic degradation
  • Everyday uses: starch-based bags, paper coating

Natural Polymers (main proteins of the ECM)

  • Collagen: Main protein in the ECM
  • Gelatin: Low MW derivative of collagen
  • Fibrin: Insoluble network of polymerized blood proteins
  • Elastin: Highly elastic protein in connective tissue
  • Hyaluronic acid: Important polysaccharide of the ECM
  • Chitosan: Polysaccharide derived from chitin (deacetylation)
  • Alginate: Polysaccharide obtained from cell walls
  • Silk fibroin: Fibrous protein from silkworms

How To Obtain Natural Polymers?

  • Natural polymers are not always ready-for-use: extraction, purification, and often modification are needed
  • Series of treatments (chemical and heat), and recombination of proteins, may be needed to make the polymer suitable for use.

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Polymers as Biomaterials PDF

Description

Test your knowledge about bioabsorbable polymers and their degradation processes. Explore key concepts such as hydrophilic vs hydrophobic materials, enzymatic degradation, and the impact of tissue covering on degradation time. This quiz covers important factors that influence the behavior of bioabsorbable materials in medical applications.

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