Polymer Drug Delivery Systems Quiz
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What is the degradation time of PLGA polymer with a 75:25 L:G ratio under aqueous conditions?

  • 1–2 months
  • 5–6 months
  • 4–5 months (correct)
  • 3–4 months

    • PLGA can be effectively used for the entrapment of therapeutics with a limited range of molecular weights.

    False

    What is the main benefit of PEGylating NPs in vivo?

    To prolong circulation and minimize bioadhesion and immunological response.

    PLGA copolymers are developed along with __________ to improve biocompatibility.

    <p>polyethylene glycol (PEG)</p> Signup and view all the answers

    Match the following PLGA characteristics with their descriptions:

    <p>50:50 L:G ratio = Degrades in 1–2 months 75:25 L:G ratio = Degrades in 4–5 months 85:15 L:G ratio = Degrades in 5–6 months PEGylated NPs = Prolonged circulation and minimized bioadhesion</p> Signup and view all the answers

    What defines surface erosion in polymers?

    <p>Degradation starts at the matrix surface.</p> Signup and view all the answers

    Bulk erosion occurs when the rate of erosion is greater than the rate of water penetration in the bulk polymer.

    <p>False</p> Signup and view all the answers

    What profile describes the most common drug release from polymeric drug delivery systems?

    <p>Triphasic profile</p> Signup and view all the answers

    Hydrophobic drugs produce a ________-order release rate.

    <p>zero</p> Signup and view all the answers

    Match the following drug release mechanisms to their descriptions:

    <p>Diffusion through water filled pores = Drug molecules move through spaces filled with water Diffusion through the polymer matrix = Drug molecules move through the polymer material Osmotic pumping = Drug release is facilitated by osmotic pressure Erosion = Degradation of the polymer matrix leads to drug release</p> Signup and view all the answers

    What is passive targeting in nanosphere drug delivery systems primarily related to?

    <p>Biophysicochemical properties of the nanoparticles</p> Signup and view all the answers

    Active targeting involves the preferential accumulation of nanoparticles at active sites without modifying their surface.

    <p>False</p> Signup and view all the answers

    What effect allows passive targeting of nanoparticles to accumulate in tumors?

    <p>Enhanced permeability and retention (EPR) effect</p> Signup and view all the answers

    Polymeric micelles are formed when amphiphilic block copolymers self-assemble in __________ media.

    <p>aqueous</p> Signup and view all the answers

    Which of the following is NOT an advantage of polymeric micelles?

    <p>High critical micelle concentration (CMC)</p> Signup and view all the answers

    Match the following features of polymeric micelles to their descriptions:

    <p>Hydrophilic head groups = Prevents recognition by the immune system Size &lt; 200 nm = Allows passive accumulation at tumors Core-shell architecture = Stability and drug encapsulation Low CMC = Greater stability and lesser dissociation</p> Signup and view all the answers

    Polymeric micelles have a narrow size distribution and typically range in size from 10–100 nm.

    <p>True</p> Signup and view all the answers

    What type of polymeric micelle is used as a doxorubicin-entrapping system?

    <p>Pluronic polymeric micelle</p> Signup and view all the answers

    What is the primary component of the Ocusert implant?

    <p>Polyethylene Vinyl Acetate (PEVA)</p> Signup and view all the answers

    The Geomatrix drug delivery system uses a combination of different polymer layers to control drug release.

    <p>True</p> Signup and view all the answers

    What type of delivery system is Risperdal Consta?

    <p>Long acting PLGA microsphere</p> Signup and view all the answers

    The __________ is a pulsatile-release oral capsule that regulates drug delivery through osmotic pressure.

    <p>OROS</p> Signup and view all the answers

    What key factor affects the diffusivity of polymers in drug delivery systems?

    <p>Crystallinity</p> Signup and view all the answers

    Silicone capsules used in drug delivery systems are biodegradable.

    <p>False</p> Signup and view all the answers

    What is the primary function of PEGylation in nanoparticle drug delivery systems?

    <p>To modify the surface of nanoparticles for improved in vivo use</p> Signup and view all the answers

    Transderm Scop uses PEVA as a rate-controlling membrane to deliver __________ for motion sickness.

    <p>scopolamine</p> Signup and view all the answers

    Match each drug delivery system with its specific drug released:

    <p>Ocusert = Pilocarpine Progestesert = Progesterone Transderm Scop = Scopolamine Lupron Depot = Luteinizing hormone-releasing hormone (LHRH)</p> Signup and view all the answers

    PLGA microparticles were developed to treat breast cancer.

    <p>False</p> Signup and view all the answers

    Which of the following is NOT an advantage of controlled drug delivery systems?

    <p>Increased toxic side effects</p> Signup and view all the answers

    Biodegradable polymers can break down into toxic byproducts.

    <p>False</p> Signup and view all the answers

    Name one synthetic biodegradable polymer that is FDA-approved.

    <p>Poly(lactic acid) or Poly(glycolic acid) or Poly(D,L-lactic-co glycolic acid)</p> Signup and view all the answers

    The breakdown of polymers due to biological actions is known as __________.

    <p>biodegradation</p> Signup and view all the answers

    Match the following polymers with their description:

    <p>PGA = Biodegradable suture material PLA = FDA-approved synthetic polymer PLGA = Microsphere drug delivery system PCL = Used in tissue engineering</p> Signup and view all the answers

    What is one factor that affects drug release from polymeric systems?

    <p>Polymer crystallinity</p> Signup and view all the answers

    Natural degradable polymers typically have less batch-to-batch variability compared to synthetic polymers.

    <p>False</p> Signup and view all the answers

    What are the two classifications of degradable polymers?

    <p>Natural and synthetic</p> Signup and view all the answers

    Controlled drug delivery can lead to improved patient __________ and clinical outcomes.

    <p>compliance</p> Signup and view all the answers

    What is the primary purpose of incorporating labile bonds in degradable polymers?

    <p>To enhance degradation through hydrolysis or enzymatic cleavage</p> Signup and view all the answers

    What is the main property of PLGA-PEG-PLGA copolymers at physiological temperatures?

    <p>They form highly viscous gels</p> Signup and view all the answers

    Polycaprolactones (PCL) have a high glass transition temperature (Tg) of +60°C.

    <p>False</p> Signup and view all the answers

    What are poly(amino acids) commonly utilized for?

    <p>Drug delivery of low-MW drugs</p> Signup and view all the answers

    Pluronic is also known by the trade name ______.

    <p>Poloxamers</p> Signup and view all the answers

    Match the following naturally occurring biodegradable polymers with their sources:

    <p>Collagen = Animal connective tissue Chitosan = Crustacean exoskeleton Gelatin = Animal collagen Alginate = Brown algae</p> Signup and view all the answers

    What is a major application of chitosan?

    <p>Wound dressing and healing</p> Signup and view all the answers

    Hyaluronic acid (HA) is characterized as a toxic polymer.

    <p>False</p> Signup and view all the answers

    What are the two main components of hyaluronic acid?

    <p>D-glucuronic acid and N-acetyl-D-glucosamine</p> Signup and view all the answers

    The glass transition temperature (Tg) of polycaprolactones (PCL) is approximately ______ °C.

    <p>-60</p> Signup and view all the answers

    What enhances chitosan's degradation rate?

    <p>Bulky side groups</p> Signup and view all the answers

    Alginate's solubility is affected by environmental pH.

    <p>True</p> Signup and view all the answers

    What is the degree of deacetylation related to in chitosan?

    <p>Crystallinity and degradation rates</p> Signup and view all the answers

    Pluronic copolymers are composed of ______ and poly(propylene oxide) (PPO).

    <p>polyethylene oxide (PEO)</p> Signup and view all the answers

    Which characteristic of HA makes it suitable for hydrogel formulations?

    <p>High hydrophilicity</p> Signup and view all the answers

    Study Notes

    Introduction

    • Drug concentration in the blood plasma does not remain constant; it fluctuates between the maximum therapeutic concentration (MTC) and minimum effective concentration (MEC).
    • This fluctuation can lead to either toxic side effects from excessively high drug levels or lack of efficacy from insufficient levels.
    • Frequent dosing is required to maintain therapeutic plasma levels for drugs with short half-lives, leading to poor patient compliance and unwanted side effects.
    • Controlled drug delivery aims to deliver the drug at a predetermined rate, either locally or systemically.

    Polymer Crystallinity

    • Polymer crystallinity refers to the degree of ordered crystalline regions within a polymer.
    • Polymers rarely achieve 100% crystallinity; they are typically semi-crystalline.
    • Only amorphous regions are permeable to water molecules and other substances.
    • Crystallinity affects a polymer's mechanical strength, swelling, and rates of hydrolysis and biodegradation.
    • A lower degree of crystallinity corresponds with higher macromolecular chain mobility, leading to faster drug release.

    Polymer Glass Transition

    • Tg is the temperature at which a polymer transitions from a glassy state to a rubbery state.
    • Tg is typically determined using differential scanning calorimetry (DSC).
    • Below Tg, the polymer is glassy with limited mobility and slow diffusion rates.
    • Above Tg, the polymer is rubbery, enabling improved water penetration and drug diffusion.
    • A balance between amorphous and crystalline regions is essential for drug delivery applications.

    Polymer Hydrophilicity/Hydrophobicity

    • Solubility is a critical factor in drug delivery system design.
    • Solubility depends on the chemical nature, structure, and crystallinity of the polymer.
    • Hydrophobic polymers exhibit drug release controlled by surface erosion.
    • Hydrophilic polymers may degrade via bulk erosion.
    • Mixing hydrophilic and hydrophobic polymers can increase pore formation, accelerating polymer degradation and drug release.

    Biodegradable Polymers

    • Biodegradation is the breakdown of polymers by cellular or in vivo biological processes into nontoxic byproducts, like water and carbon dioxide.
    • Most biodegradable polymers used in drug delivery applications utilize hydrolysable ester bonds.
    • Biodegradable polymers have advanced drug delivery, medical devices, tissue engineering, and biomaterials.

    Biocompatibility

    • Biocompatibility means a material does not produce toxic or harmful effects on biological systems.
    • Good biocompatibility does not automatically ensure good biodegradability.

    Commonly Used Biodegradable Polymers

    • Poly(glycolic acid) (PGA), Poly(lactic acid) (PLA), and Poly(lactic-co-glycolic acid) (PLGA) were among the earliest synthetic biodegradable polymers, used as sutures.
    • Poly(ε-caprolactone) (PCL) is another well-known FDA-approved material, noted for its slow degradation rates.
    • Other polymers include Poly(ortho esters) (POE), Poly(anhydrides), Poly(amides), and various copolymers.

    Polymer Molecular Weight

    • Low molecular weight (MW) polymers degrade more rapidly.
    • MW significantly impacts drug release profiles and biological properties of polymeric drug delivery systems.
    • Lower MW leads to smaller nanoparticles, influencing drug release kinetics, circulation, and accumulation in organs.

    PLGA Polymers

    • PLGA is a polyester with linkages in its carbon backbone, commonly employed due to its prolonged degradation.
    • It's prepared via ring-opening polymerization of cyclic lactide and glycolide monomers.
    • Variables like MW and the ratio of lactide-to-glycolide (L/G) affect its degradation rate.

    PLGA Copolymers/PEGylation

    • PEGylated PLGA (PLGA-PEG) copolymers enhance circulation times and biocompatibility by creating a steric barrier.
    • Triblock PLGA-PEG-PLGA copolymers form viscous gels at physiological temperatures, offering temperature-sensitive drug delivery.

    Polycaprolactones (PCL)

    • PCL is an aliphatic polyester made from ε-caprolactone, used as a slow-release scaffold in tissue engineering.
    • Having a low glass transition temperature (Tg), it remains semi-rigid at room temperature.
    • Modifications of PCL with other polymers improve degradation and reactivity.

    Polyamides

    • Poly(amino acids) deliver low-molecular-weight drugs, are relatively nontoxic, and generally degraded by enzymes.
    • Degradation rate is influenced by the hydrophilicity of the contained amino acids.
    • Examples include poly(γ-glutamic acid) and poly(L-lysine).

    Polymeric Micelles

    • Formed when amphiphilic block copolymers self-assemble in aqueous media.
    • Characterized by a core-shell structure and narrow size distribution (10-100nm).
    • Lower critical micelle concentration (CMC) value contributes to greater stability and reduced dissociation in the bloodstream.

    Advantages of Polymeric Micelles

    • Enhancing solubility for hydrophobic drugs.
    • Prolonged circulation times due to a hydrated "stealth" polymer surface.
    • Minimizing renal excretion due to large size.
    • Active and passive targeting capabilities.

    Fabrication Techniques

    • Several methods for encapsulating therapies in polymeric nanoparticles (NPs).
    • Methods depend on drug and polymer properties and desired NP characteristics.
    • Some fabrication techniques include bottom-up (emulsion, polymerization, precipitation) and top-down (nanoprecipitation, emulsification).

    Mechanisms of Drug Release

    • Mechanisms of drug release from polymeric systems include diffusion through water-filled pores, diffusion through the polymer matrix, and erosion.
    • These mechanisms may be surface or bulk dependent.

    Drug Release Profiles

    • Drug release from polymeric NPs commonly follows a triphasic pattern consisting of a burst release phase, a slow release phase, and a faster release phase as degradation proceeds.

    Macromolecular Drug Delivery Systems

    • Generally use nondegradable (silicone, polyurethanes) for initial delivery systems.
    • Macromolecular systems often rely on diffusion and degradation of the matrix.

    Norplant I/II

    • Norplant I, an example, used six silicone capsules implanted in the upper arm for progestin delivery (hormonal birth control).
    • Later versions (Norplant II) used improvements to control the release using slightly different polymers.

    Ocusert, Progesterone, and Transderm Scop

    • Ocusert is an ocular implant delivering pilocarpine, a drug for glaucoma.
    • The sustained release was achieved using PEVA.
    • Progesterone IUD (Intrauterine Device) and Transderm Scop (the first skin-patch for scopolamine, an anti-nausea drug) are examples of macroscopic polymeric drug delivery devices.

    OROS

    • OROS is an oral polymeric system for sustained drug delivery.
    • Water absorption creates osmotic pressure for drug release.

    Geomatrix

    • Geomatrix is a controlled drug delivery system formed from hydroxylpropyl methylcellulose (HPMC), used to tailor drug release via layered swelling, gelling, and erosion rate control.

    Microscale Polymeric Drug Delivery Systems

    • Examples include PLGA microparticles used to treat prostate cancer by delivering luteinizing hormone-releasing hormone (LHRH).
    • This system resulted in slower drug release and an overall extended therapeutic effect despite the shorter half-life of LHRH.
    • Another example is Risperdal Consta, which improves the effectiveness for patients with schizophrenia while using long-acting PLGA microspheres.

    Nanoscale Polymeric Drug Delivery Systems

    • Nanoparticles (NPs) facilitate advancements in nanomedicine, enabling targeted therapy.
    • PEGylation modifies the NP surface for enhanced in vivo circulation and reduced immunogenicity.
    • Targeted drug delivery is key to limiting off-target effects and maximizing treatment efficacy.
    • Passive targeting, based on tumor-associated permeability and retention (EPR), and active targeting (ligands on surface of NPs) are specific strategies employed in this field.

    Polymer Micelles

    • Pluronic (poloxamers) micelles are nonionic triblock copolymers (PEO–PPO–PEO) exhibiting surfactant functionality.
    • They encapsulate hydrophobic drugs in their core, creating robust drug delivery vehicles.

    Naturally Occurring Biodegradable Polymers

    • Materials include proteins (collagen, albumin, gelatin), and polysaccharides (agarose, alginate, carrageenan, hyaluronic acid, chitosan, cyclodextrins).
    • These materials, although potentially useful, typically exhibit lower reproducibility and versatility compared to synthetic counterparts.
    • Chitosan is often used as a drug delivery matrix, benefiting from an ability to remain in vivo for an extended time and interact with mucin.
    • Alginate and hyaluronic acid (HA) also demonstrate diverse applications in tissue engineering and drug delivery due to their biocompatibility.

    Chitosan

    • Derived from crustacean exoskeletons, chitosan acts as a biodegradable matrix for drug delivery.
    • Its deacetylation status influences its crystallinity and degradation rates, impacting in vivo behavior.
    • The insolubility of chitosan in water necessitates prior solubilization (with dilute acid) before use.

    Hyaluronic Acid (HA)

    • HA is a naturally occurring polysaccharide involved in tissue engineering and drug delivery.
    • Its hydrophilic nature and high water absorption capacity allow for expansion and potential drug delivery.
    • The presence of carboxyl groups leads to its anionic character, crucial for localized targeting.

    Alginate

    • Derived from brown algae, alginate is a naturally occurring anionic polysaccharide.
    • Its variable molecular weight and composition affect its physicochemical properties, including viscosity and water uptake.
    • Alginate's potential as a drug delivery system arises from its mucoadhesive character, enabled by the presence of free carboxyl groups interacting with mucin.

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