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Encapsulation & Controlled Release Background Information Version 032517

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Overview

What is encapsulation?

What is self-assembly and what are the forces behind it?

What is micro and nanoencapsulation?

What types of capsules can be made?

Why is encapsulation important?

How are sodium-alginate macrocapsules formed?

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What is encapsulation?

  • Encapsulation, the process of enclosing something in a capsule, occurs naturally

Example: the formation of liposomes via the process of self-assembly

  • Liposomes

Are small, spherical vesicles made up of at least one lipid bilayer

Diameter range: a few tens of nanometers to a few tens of micrometers

    • The Core

May be various substances dependent upon the surrounding environment, liposome size, and other natural processes (ex: diffusion/osmosis)

    • The Shell

May be a hydrophilic or hydrophobic membrane surrounding the core depending on surroundings

Core

Shell

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Figure 1: The cross-section of a liposome showing phospholipid bilayer surrounding an aqueous interior and excluding an aqueous exterior environment (en.wikipedia.org/wiki/Liposome)

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What is self-assembly

  • Lipid bilayers are formed via self-assembly
  • Self-assembly
    • The formation of an organized structure within a disordered system due to various physical, chemical, electrical, and other environmental forces

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Self-assembly Example

  • Imagine a bottle of your favorite oil-based salad dressing
  • Shake the bottle vigorously and the contents become well mixed (i.e. disordered)
  • Put the bottle down and over time the oil separates from the rest of the ingredients forming a single layer at the top of the bottle
  • The oil molecules (hydrophobic lipids) have self-assembled excluding all the other (hydrophilic) ingredients
  • There is order amongst the ingredients once again

Organized oil-based salad dressing

Hydrophobic oil molecules

Hydrophilic ingredients

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Disorganized oil-based salad dressing

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What are the forces behind Self-assembly?

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  • Several forces play a crucial role in self-assembly and the formation of liposomes
    • Brownian motion
    • Random motion of particles suspended in a fluid or gas as a result of colliding with quick moving atoms or molecules (left image)

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    • Electrostatic forces that drive the hydrophobic effect
    • The tendency of hydrophobic molecules to aggregate in an aqueous (hydrophilic) environment (right image)
    • Example: when a drop of oil in a pot of water remains as one drop even after turbulent mixing

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What is micro & nanoencapsulation?�What types of capsules can be formed?

  • Both processes take advantage of self-assembly
  • Microencapsulation
    • The process of enclosing an active ingredient (food ingredients, enzymes, drugs) with a coating resulting in a capsule 1 – 1000 microns in diameter. (1, 2, 3)
  • Nanoencapsulation
    • The production of small particles that are less than one micron in diameter and contain a core material surrounded by a capsule. (3)

Micro/Nano Domains

Non Solid Domains

Non Solid Core

Solid Core

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Why is encapsulation important?

  • Active ingredients are encapsulated for intended release
  • Encapsulation of a substance is important when it is necessary to
    • Entrap it within a shell (permanently or temporarily)
    • Extend its life and stability
    • Control its release under specific environmental conditions
      • pH, salinity, temperature, etc.

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Applications of micro/nanocapsules

  • Agriculture
  • Biomedical
  • Consumer Products
  • Drug Delivery/ Pharmaceutical
  • Food Technology
  • Industrial
  • Tracers/Tagging
  • Environmental

Biomedical

Consumer Products(9)

Environmental (11)

Carbon capture

Food Technology(10)

Drug Delivery Delivery/Detection

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How are alginate macrocapsules formed?

  • Alginate is derived from giant kelp (brown seaweed)
  • Alginate is an organic polymer used in the food industry
  • Alginate reacts with calcium chloride ions to form a gel-like bead

education.mrsec.wisc.edu/

youtube.com/watch?v=afIT1vZMivM

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Formation of alginate macrocapsule beads in a calcium chloride bath

Picture Credits: Kyle Forgette

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Some alginate beads are coated with a layer of chitosan

  • What is chitosan?
    • Derived from the polysaccharide chitin found in exoskeletons (ex: crustaceans)
    • Chitin is deacetylated into �chitosan

aic.stanford.edu

MDPI.com

researchgate.net

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References

  1. http://www.academia.edu/16290403/A_SEMINAR_ON_MICROENCAPSULATION_FOR_CORROSION_DETECTION_AND_CONTROL_WRITTEN_BY_ENWENYEOKWU_GENESIS_NNEJI
  2. file:///C:/Users/jq6246vh/Downloads/50406777-MIT.pdf
  3. http://site.thebiotransportlab.com/whatIsMicroencapsulation.htm
  4. http://www.sciencefriday.com/educational-resources/salad-dressing-science-emulsions/
  5. http://webspace.clarkson.edu/projects/crcd/me537/notes/aerosols/aerosols_page19.html
  6. http://oregonstate.edu/instruct/bb450/450material/lecture/introductionoutline.html
  7. http://pubs.rsc.org/-/content/articlelanding/2015/ra/c5ra01629k#!divAbstract
  8. https://www.slideshare.net/srinivasnaik52643/controlled-release-formulations-as-a-smart-delivery-system-for-eco-friendly-pesticides-ssnaik-tnau
  9. http://www.nanowhite.com.my/index2.html
  10. http://munews.missouri.edu/news-releases/2011/0909-the-next-generation-of-ice-cream-one-bite-two-flavors/
  11. http://www.nature.com/articles/ncomms7124
  12. arthropods-grade7.wikispaces.com/Crustaceans