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Saaliha Part 4 – PM4B > Advanced Drug Delivery 6 - Microparticles and Nanoparticles > Flashcards

Advanced Drug Delivery 6 - Microparticles and Nanoparticles Flashcards

1
Q

What are Microparticles

A
  • Particles in the micro size range, normally between 3-800 µm
  • Two types: microcapsules, microspheres
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2
Q

What is a microsphere

A
  • No distinct region
  • Matrix system
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3
Q

What is a microcapsules

A
  • Two distinct regions: external wall and central core
  • A reservoir system since they consist of two parts
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4
Q
A

Microcapsule: has distinct regions
Technically a polynuclear microcapsule because it has multiple nuclei

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5
Q

Which one is which: microcapsule, microsphere

A

Top: microcapsule - distinct regions (external wall, central core), reservoir system
Bottom: microsphere - no distinct region, matrix system

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6
Q

Administration routes of Microparticles

A
  • IV
  • directly to specific compartment (e.g. inhalation, local injection, SC)
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7
Q

What does body distribution of Microparticles depend on

A
  • Size
  • Shape
  • Surface charge
  • Surface tension
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8
Q

5 requirements of materials used to make Microparticles

A
  1. Chemically inert
  2. Non-toxic
  3. Biocompatible
  4. Biodegradable if necessary
  5. Easy to sterilise - esp for injections
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9
Q

Examples of materials used to make Microparticles

A
  • Proteins (e.g. albumin, gelatin)
  • Polysaccharides (e.g. starch, cellulose, chitosan)
  • Polyesters (PLA, PGA, PLGA)
  • Polyanhydrides
  • Polyvinyl derivatives
  • Polyacrylates
  • Others e.g. waxes
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10
Q

5 applications of Microparticles

A
  1. MR
  2. Conversion of liquids into pseudo solids
  3. Protection from external environment
  4. Mask flavour and odour - organoleptic properties
  5. Reduce gastric irritation
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11
Q

How to convert liquids into pseudo solids using Microparticles

A

Encapsulate the liquid API to form a microcapsule, this makes it become a pseudo solid

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12
Q

3 Steps to prepare Microparticles

A
  1. Disperse drug in the polymer (constituent) solution
  2. Coacervation (or phase separation)
  3. Hardening of coating
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13
Q

Coacervation

A

The process by which a polymer solution separates into two phases

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14
Q

4 factors of coacervation

A
  1. Changing temperature of polymer solution
  2. Salting out
  3. Adding non solvent
  4. Inducing a polymer-polymer interacition
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15
Q

Ways to harden coating

A

Promote cross linking or cool the system down

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16
Q

Coacervation: changing temperature of polymer solution

A
  • Materials have different solubilities at different temperatures
  • There is a dispersion of the drug in the polymer solution - polymer is dissolved
  • Change to a temperature at which polymer is no longer soluble so that it precipitates out and you form microparticles
17
Q

Coacervation: salting out

A
  • Drug dispersed in polymer solution
  • Add an inorganic salt (contains anions + cations)
  • Water molecules will preferentially interact with the charged ions
  • Polymer will precipitate out
  • Microparticles will form
18
Q

Coacervation: adding a non solvent

A
  • Polymer is solubilised in solvent A
  • Add non-solvent
  • Will cause polymer to become less soluble and associate with each other
  • Forms a dense liquid phase (coacervate) and a dilute liquid phase (supernatant)
  • Polymer will precipitate out
  • Microparticles will form
19
Q

Coacervation: inducing polymer-polymer interaction

A
  • Add a second polymer to the solution that interacts with the first polymer and makes it precipitate out
  • Formation of Microparticles
20
Q

Preparation of Microparticles via interfacial polymerisation

A
  1. Start with a monomer and make the polymerisation in situ
  2. Polymer is formed at the interface between two immiscible liquids: organic phase and aqueous phase + dissolved drug
  3. By addition, you can obtain microspheres
  4. By condensation, you can form microcapsules
21
Q

Preparation of microspheres by heat or chemical denaturation

A

Good way to make Microparticles when material is protein

  1. Oil phase, add an aqueous solution of protein + drug
  2. Mix the two to form emulsion: water in oil
  3. Need a trigger to denature protein so that Microparticles can form
  4. Chemical: add glutharaldehyde or butadiene which cross links protein and it will precipitate out
  5. Physical: heat system 100-170C to denature and precipitate protein out
22
Q

Spray drying to form Microparticles

A
  1. Atomisation of liquid feed (also containing drug) into fine droplets
  2. These are dried using heated gas system
  3. Liquid evaporates to form dry particles
  4. Dried particles separated from gas stream and collected
23
Q

5 advantages of spray drying to form Microparticles

A
  1. quick and reproducible
  2. control of particle size
  3. low cost
  4. good yield
  5. applicable to heat sensitive materials
24
Q

limitations of spray drying to form Microparticles

A
  • need polymers that give low viscosity - solutions
  • need small droplets
  • water soluble compounds have poor encapsulation
25
Q

5 ways that drug is released from microspheres

A
  1. Erosion
  2. Disintegration of microsphere in body to release API
  3. Swelling of microsphere, and API diffuses out
  4. Desorption and diffusion
  5. Ionic exchange
26
Q

Drug release from microspheres: desorption & diffusion

A
  • In the microsphere, some of the drug could be inside and some could be adsorbed on surface via interactions
  • Once administered, there is a change in environment
  • Adsorbed drug may come off and diffuse into the body fluids
27
Q

Drug release from microspheres: ionic exchange

A
  • Adsorbed drug is an ion - a charged drug
  • Administer microsphere
  • Many ions present tin body that can interact and swap with the drug
28
Q

What are nanoparticles

A

Particles in the nano size range: nm
Two types: nano capsules and nanospheres

29
Q

Nanocapsules

A
  • 2 distinct regions so are a reservoir system
  • External wall and central core
30
Q

Nanospheres

A

Matrix system as they only have a single region

31
Q

Location of API in nanoparticles

A

API can be:

  • Dissolved
  • encapsulated
  • adsorbed on the surface

No covalent bonds - just interactions

32
Q

3 ways to make nanoparticles

A
  1. Some scientists make PDG and from them they make nanoparticles (hybrid system)
  2. Using ready made polymers
  3. Methods that require polymerisation
33
Q

2 polymers most commonly used for nanoparticles

A

PLA and PLGA

34
Q

Preparation of nanoparticles using solvent evaporation

A
  1. Two beakers: polymer + drug and water +emulsifying agent
  2. Mix the two to form an oil water emulsion
  3. Droplets of solvent contain the polymer + drug
  4. Solvent evaporation to form nanoparticles
  5. Nanoparticles will precipitate and can be collected
35
Q

Toxicity of Microparticles and nanoparticles

A
  • Generally acute toxicity is low as it depends on materials used and they are not toxic
  • Toxicity depends on size and number of particles injected

Longer term toxicity:

  • consider possibility of material starting to accumulate in body
  • need to ensure material is being eliminated from body e.g. by biodegradation and bioerosion
36
Q

Problems with IV injections of nanoparticles and a solution

A
  • Nanoparticles can be endocytosed by macrophages of the reticular endoplasmic system (RES)
  • This is good if we are targeting the liver or spleen
  • This is bad if it reaches other tissues because it won’t be effective
  • Strategy: PEG-coated nanoparticles to mask them from macrophages
37
Q

What is ABRAXANE

A
  • Nanoparticle on the market
  • contains palictaxel
  • used in cancer therapy for advanced metastatic breast, pancreatic and NSCLC

Saaliha Part 4 – PM4B (73 decks)

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