Video summary

Week 01: Lecture 05: Commonly used Polymers in DDS

Main summary

Key takeaways

Educational

Main ideas / lessons from the lecture

Purpose of the lecture

The lecture introduced and explained commonly used polymers in novel drug delivery systems (DDS), with emphasis on:

  • Their nature (natural vs. synthetic; block/triblock; cationic, nonionic, etc.)
  • How they respond in the body, including:
    • Release behavior
    • Responsiveness to triggers such as temperature
  • How they degrade, including biodegradation pathways
  • Example polymers and their typical DDS roles, such as:
    • Implants
    • Nanoparticles
    • Hydrogels
    • Films

General ways polymers are used in DDS

Polymers can be used to:

  • Form implants/devices where drug release occurs as the polymer degrades, via:

    • Dissolution
    • Diffusion-controlled release
    • Swelling-controlled release

  • Form colloidal carriers, especially polymeric nanoparticles/nanocarriers (noted size range: ~1 to 1000 nm), which can support different administration routes, including oral routes depending on particle size.

  • Create advanced architectures/formulations such as:

    • Microspheres / nanospheres
    • Microparticles / nanoparticles
    • Dendrimers
    • Polymer–drug conjugates
    • Polymer-conjugated lipids / responsive liposomes
    • Hydrogels
    • Nanofibers
    • Oral thin films (rapidly disintegrate in the mouth to help mask the taste of bitter drugs)

  • Influence drug behavior through polymer–drug conjugation: conjugated drugs may show different ADME, efficacy, and safety compared with the free drug.

Polymer examples and key concepts

1) Natural polymers (biodegradable; used in drug delivery / tissue engineering)

Examples mentioned

  • Chitosan
  • Alginate
  • Hyaluronic acid
  • Dextran
  • Gelatin

Chitosan-specific points

  • Biodegradable and biocompatible
  • Antimicrobial action
  • Exhibits positive charge, pH-responsiveness, temperature-responsiveness, and biodegradability/biocompatibility
  • Used for:
    • Absorption enhancement
    • Controlled release
    • Bioadhesion / mucoadhesion (mucus interaction)
    • Permeability enhancement

Degree of deacetylation and derivatization

  • The degree of deacetylation alters:
    • Solubility
    • Properties
    • Molecular weight
  • Derivatization / conjugation can convert chitosan into stimuli-responsive polymers, such as:
    • pH-sensitive
    • temperature-sensitive
    • or other trigger-responsive variants

2) Synthetic polymers (examples listed)

  • PLGA
  • Polycaprolactone
  • Polyvinyl acrylate (spelled variably in subtitles)
  • Polyamino acids
  • Pluronics / Pluronic F127

3) PLGA (poly(lactic-co-glycolic acid)) — “most commonly used”

Type

  • Biodegradable and biocompatible copolymer
  • Comprised of lactic acid + glycolic acid monomers

Why the monomer ratio matters

  • PLGA properties—and thus drug loading and release—depend strongly on the lactic:glycolic molar ratio
  • Glycolic acid is more water soluble than lactic acid

Composition vs. degradation/release

  • 50/50 lactic:glycolic
    • Higher copolymer hydrophilicity
    • Leads to faster degradation → faster release
  • More lactic-rich (e.g., ~75:25 to 85:15 lactic:glycolic)
    • Polymer becomes more hydrophobic
    • Results in slower degradation → slower drug release

Biodegradation pathway

  • PLGA degrades via hydrolysis
  • Breaks down into lactic acid and glycolic acid
  • Further metabolized and excreted → complete biodegradation

Typical uses

  • Used in many DDS systems, including implants and tissue engineering

Design implication

  • Optimize the lactic:glycolic ratio to achieve the desired control-release profile for the active molecule

4) Poly(N-isopropyl acrylamide) — thermoresponsive polymer

Type and purpose

  • Thermoresponsive polymer used for active targeting, especially cancer targeting
  • Rationale: the cancer microenvironment has higher temperature due to increased metabolism (linked to hyperthermia)

LCST behavior (mechanism)

  • Response occurs at a characteristic threshold called LCST
  • Provided threshold: below ~32°C
  • When temperature rises above LCST:
    • Polymer shifts from soluble to insoluble/aggregated state

Illustrative observation

  • Around 25°C: solution appears clear (soluble)
  • Around 45°C: visible physical change (consistent with temperature-triggered response)

DDS uses

  • Hydrogels
  • Tissue engineering
  • Smart coatings
  • Temperature-triggered in-target release

5) Polyamidoamine — dendrimer-focused polymer

Primary use

  • Dendrimer applications

Dendrimer description

  • “Tree-like” 3D network structures featuring:
    • Internal core
    • Interior architecture
    • Terminal groups
    • Generational/branching layers with exponentially more branching points

Functional groups and charge behavior

  • Contains amide and amine functionalities
  • Described as cationic (positive charge)

Complexation / stabilization role

  • Positive charge helps complex with negatively charged molecules, such as:
    • Nucleic acids
    • Proteins / peptides
    • sRNA

Cell interaction

  • Positive charge improves interaction with negatively charged cell membranes via electrostatics, supporting selectivity

Conjugation

  • Surface functional groups enable conjugation of drug molecules

6) Polymeric triblock: Pluronics / Pluronic F127

Also known as

  • Pluronics
  • Specific example: Pluronic F127

Structure

  • Triblock copolymer composed of:
    • Polyethylene oxide (PEO)
    • Polypropylene oxide (PPO)
  • Repeating unit includes PEO segments, supporting amphiphilicity

Charge/property

  • Nonionic (no charge observed in water dispersion)

Hydrophilic–hydrophobic balance (amphiphilicity)

  • PEO = hydrophilic (“water-loving”)
  • PPO = hydrophobic (“water-ripping,” as phrased)
  • Net result: amphiphilic, enabling:
    • Micelles and other carriers for water-insoluble drugs

Other roles

  • Acts as a stabilizer (lecture noted help from relatively low molecular weight)
  • Used for temperature-sensitive in situ gels, where it undergoes a phase transition from solution to gel under biological conditions—especially with temperature change

Sources / speakers featured

  • Dr. Dr. Satish Davanapelli Assistant Professor, Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Mumbai

Original video