PH2107 - suspension, colloids & nanoparticles 1 Flashcards
Describe a solution
A dispersion of individual molecules dissolved in a solvent
Contains NO BITS
Monophasic (homeogenous)
Give three examples of a disperse system
Colloids
Nanoparticles
Suspensions
What are disperse systems considered to contain?
Bits
What are disperse systems made of?
Undissolved particles (solid) or droplet (liquid) in nanometer or micrometer range
Describe a disperse system
Biphasic (except emulsions, which are liquid/liquid)
What is the difference between the two biphasic disperse systems?
The particles in a coarse dispersion/suspension are greater than 1000nm in diameter
The particles in a colloid are less than 1000nm in diameter
What is the difference between a suspension, a colloid and an emulsion?
Suspensions and colloids are biphasic
Emulsions are monophasic (immiscible liquid globules)
What are the two possible states of disperse systems?
Lyophilic
Lyophobic
What is lyophilic?
Solvent attracting, solvent loving, well solvated Water as dispersant, hydrosol Readily solvated, stable Increased viscosity Easy to prepare, difficult to separate
What is lyophobic?
Solvent repelling, solvent hating, poorly solvated
Difficult to prepare, unstable
Viscosity same as continuous phase
Give an example of a lyophobic system
Metal in water, colloidal gold
Describe a colloid or nanoparticle
Particle size between 1nm - 100nm
Particles not resolved by ordinary microscope (electron microscope)
Disperse phase does not settle on standing - particles separable by ultracentrifugation (very high g) but not centrifugation
Particles pass through filter paper but not through semipermeable membrane
Diffuse very slowly
Can be drug or excipient, or drug-excipient complex
Describe a coarse dispersion or suspension
Particle size 0.5um - 500nm
Particles are visible under ordinary microscope (electron microscope)
Particles settle under gravity, by gravity
Do not pass through filter paper or semipermeable membrane
Do not diffuse
poorly water soluble drug in solution, and
excess drug as particulates (cannot dissolve)
Drug in solution at low concentration
(low solubility) but at saturation, so high
chemical potential
Susceptible to settling, therefore ‘thickening agent’ added
Give three examples of a coarse dispersion or suspension
Emulsion
Suspension
Red blood cells
Give examples of an association colloid
Vesicle
Micelle
Liposome
How are association colloids made?
Usually formed from surfactants and lipids
Give examples of colloidal nanoparticles
Polymers (e.g. PLGA, PNIPAM)
Metallic (e.g. gold or silver)
Carbon nanotubes
Dendrimers
What are the four uses/decorations for liposomes?
Conventional liposome
PEGylated liposome
Ligand targeted liposome
Multifunctional liposome
What is the function of a conventional liposome?
Hydrophobic drug carried within the membrane
Genetic material carried within the core
Hydrophilic drug carried within the core
Phospholipid membrane (e.g. anionic, cationic or neutral)
What is the structure of a PEGylated liposome?
Polyethylene glycol (PEG) bound to phosphate head in membrane
Which ligands can be used to produce a ligand targeted liposome?
- aptamer
- antibody
- protein
- peptide
- small molecules
- carbohydrates
Which ligands can be used to produce a multifunctional liposome (theranostic liposome)?
Imaging agent (e.g. Gd-DOTA-DSPE for MRI) Targeting ligand (e.g. antibody)
What is the size range of a nanoparticle?
1nm to 100nm
What are the shapes of nanoparticles?
- sphere
- cube
- rod
- plate
- star
What can be on the surface of nanoparticles?
- PEGylation or other coatings
- surface functional group (e.g. -SH, -NH2, -COOH)
- surface change (+ -> - or - -> +)
- targeting ligand (e.g. antibody, peptide, aptamer)
What materials can nanoparticles be?
- carbon nanotubes
- metal particles
- dendrimer
- polymer particle
- hydrogel particle
- protein-drug conjugate
- liposome
- solid-lipid hybrid particle
what is poly(lactic-co-glycolic acid), PLGA ?
A material commonly used to make nano particles
approved by federal drug administration
What are two major processes used in drug release from PGLA nanoparticles ?
bulk erosion/ fragmentation
where nanoparticle disintegrates based off environment & drug released
surface erosion/ dissolution
Nanoparticle is dissolving liberating drug molecules from surface
What is PNIPAM. Poly(N-isopropylacrylamide)
Poly(N-isopropylacrylamide) is a temperature-responsive single unit polymer.
Expanded structure at higher temperature
- load drug
Collapses structure at lower temperature
- drug expelled
Co polymer with acrylic acid provides temperature and pH response
What are decorated liposomes
Liposomes in which groups have been added to it.
What are some advantages of suspensions?
Limits degradation
Particles undergo dissolution in stomach
Higher bioavailability than tablet, capsule (but not solution)
Taste masking properties
why are suspensions able to mask taste ?
Only individual drug molecules can
interact with gustatory cells, to elicit
taste reponse
Particles > 10 μm cannot even enter
taste bud pore
Therefore, particles in suspension
have little taste
What is the effect on light by colloidal particles?
Although colloidal particles are often too small to be visible individually, they are large enough to interfere with the path of light travelling through
When light enters a dispersion, some goes straight through but some is scattered by particles, the degree of light scattering depends on particle size: small particles “bend” light more than big particles
What are the differences between suspensions and oral solutions?
Suspensions:
- contain poorly water soluble drugs in solution
- have excess drug as particulates (cannot dissolve)
How are suspensions made?
Drug in solution at low concentration (low solubility) but at saturation (high chemical potential)
Why is a thickening agent added to a suspension?
Suspensions are susceptible to settling
What is light scattering influenced by?
- particle size
- particle population
- wavelength of incident light
Which colour of light is scattered more easily?
Blue light has a short wavelength, which is scattered more than red light as it has a higher wavelength
What is the Tyndall effect?
when light is shone through colloidal sol, scattering causes the beam path becomes illuminated
light shone through:
Solution has no effect
colloid creates visible beam
suspension creates visible beam but also has visible particles
What can be used to optimise the biodistribution of drugs to diseased organs, tissues or cells in order to improve and target drug delivery?
Gold lyophobic nanoparticles
Gold lyophobic nanoparticles can be used to optimize the biodistribution of drugs to diseased organs, tissues or cells, in order to improve and target drug delivery.
What is turbidity?
Cloudiness of a dispersion due to light scattering
What effect does concentration of dispersed particles have on the turbidity of a dispersion?
The greater the concentration of dispersed particles, the more light is scattered and the more turbid (milky white) the dispersion appears
What is Gaussian distribution?
A symmetrical bell shaped curve found when plotting size against intensity - the peak being the average particle size
What is dispersity?
A measure of the homogeneity/heterogeneity of the disperse phase
What is meant by polydisperse?
Irregular, wide particle size range, size, shape and mass
Can be due to aggregation / agglomeration but also simply by different primary size
What is meant by monodisperse?
Narrow particle size range, shape and mass
What is polydispersity now known as?
Uniform
What is monodispersity now known as?
Non-uniform
What is the Polydispersity index
A measure of distribution of mass or size in a population of particles/globules
Why is the Polydispersity Index important?
Polydisperse systems have a greater tendency to flocculate and sediment than monodisperse systems
How is the Polydispersity Index calculated?
(Standard deviation / average NP size) x 100
What should the Polydispersity Index ideally be?
Less than 0.5
What does a PDI of 1 indicate?
The sample has a very broad size distribution and may contain large particles or aggregates that could be slowly sedimenting
What is the size range for droplets in nanoemulsions?
20 - 500nm
What does a Polydispersity index of 1 in a nanoemulsion?
Means the emulsion is high polydisperse i.e. droplet sizes are highly varied
What is the Encapsulation Efficiency?
The percentage of a drug that is successfully entrapped into a micelle or nanoparticle
How is the Encapsulation Efficiency calculated?
(Total drug added - free non-entrapped drug) /
total drug added
What is the Loading Capacity?
The amount of drug loaded per unit weight of the nanoparticle, indicating the percentage of mass of the nanoparticle that is due to the encapsulated drug
How is Loading Capacity calculated?
The amount of total entrapped drug /
total nanoparticle weight
What is yield, in terms of drug delivery?
A reflection of the amount of drug delivered per amount encapsulated, given as a percent
What is ultracentrifugation?
A centrifuge capable of generating acceleration as high as 1,000,000g. Sufficient to cause sedimentation
What is used to separate colloidal particles from smaller contaminants, using a semi-permeable membrane?
Dialysis or electro-dialysis
Give an example of a colloid that can be treated using dialysis
Blood, in renal failure
