Nano-technology Flashcards
How does nanoparticle size affect surface area? How does surface area affect drug distribution?
increase SA by decreasing particle size
increased SA = increased dissolution rate = increased bioavailability
increased SA = increased contact and surface activities = increased Van der Waals attraction = increased strong bio-adhesion and uptake
How do nanoparticles affect suspensions and settling?
reducing particle size improves suspension/emulsion stability
- allows maintenance of dispersion
- reduces rate and likelihood of sedimentation
How does nanoparticles affect magnetic and optical properties?
the smaller the particle size, the greater the optical and magnetic properties
useful for cancer targeted delivery of drugs via applying an external magnetic field
- local heating by pulsed electromagnetic radiation leads to cancer cell death
How can nanoparticles be transported to the site of action?
to deliver API specifically to the therapeutic site, the drug delivery system should accompany the API beyond the absorption site
- nanoparticles display new pharmacokinetics (half life, distribution, absorption)
How can nanoparticles travel to therapeutic site?
transcellular - transport through the cell
paracellular - transport through junctions
extent of absorption and penetration of nano-systems depends on their size
What are the two methods of manufacturing nanoparticles?
top down - bigger particles (bulk materials) are broken down into nano sized particles
= milling
bottom up - nanoparticles are built up from molecules (molecules and atoms)
= controlled polymerisation, nano-precipitation, self assembly
What is the top down method used for?
produces a nano-sized drug substance
- not a drug delivery system
used mainly to enhance the drug dissolution rate and bioavailability
What is the bottom up approach used for?
produces drug delivery system (API and excipients)
- most often are polymeric excipients
- the API is entrapped or absorbed in the nanoparticles
Why is precipitation method used more than polymerisation in the bottom up approach?
polymerisation
- higher toxicity
- polymers can react with the API
How does emulsion-solvent evaporation work?
the polymer is dissolved in a volatile organic solvent into which the drug is dissolved
the resultant solution is then added to the aqueous phase containing surfactant under high homogenization to form an emulsion
after the formation of stable emulsion, the organic solvent is evaporated either by using high temperature, vacuum, or by continuous stirring
then undergoes centrifugation and washing (to remove residual stabiliser)
method results in NANO-SPHERES
How does solvent diffusion (nanoprecipitation) work?
drug and polymer are dissolved in organic solvent that is miscible with water (acetone)
the resultant solution is then added to the aqueous phase containing surfactant (via injection)
due to miscibility of solvent, it immediately forms nano spheres
- desolvation/precipitation
= the speed of solvent removal is key to obtain nanoparticles
What is salting out?
drug and polymer are dissolved in acetone (miscible with water)
this solution is emulsified under in water containing the salting out agents (electrolytes)
= such as magnesium acetate and magnesium chloride
the presence of salts in water prevent the miscible organic solvent forming diffusion into water
- forms oil in water emulsion
water dilution (distilled water) allow the solvent diffusion and thus the precipitation of nanoparticles
