Liposomes Flashcards
what are liposomes used for in pharmacy?
drug deliver systems
act as a vehicle/carrier component of nanomedicines
what type of material are liposomes?
natural or synthetic materials – polymers, proteins, lipid
in the nm range
what are the physical properties of liposomes?
hollow, or have a porous or solid interior
Closed, spherical vesicles of single or multiple lipid bilayers (lamellae), enclosing an internal aqueous core
how can liposomes be used to deliver drugs?
incorporated inside particles (encapsulation, entrapment)
on particle surfaces (adsorption, attachment)
why are drug delivery systems used?
improve drug potency and efficacy by…
* Improving drug solubility and dissolution - Small carrier size, high surface area:volume ratio
* Providing a sustained/controlled drug release
* Prolonging drug residence time in the systemic circulation
* Protecting drug from harsh in vivo conditions - Most effective if drug is encapsulate
* Improving drug transport across biological barriers
* Facilitating targeted drug delivery- Enhanced delivery to particular/specific cells or tissues
how does sa:volume ratio affect degradation?
as its easier for aqueous fluid (e.g. GI fluid) to penetrate the particle via the polymer = faster drug release due to the molecule being subjected to degradation
why is targeted drug delivery useful?
increased delivery efficacy and decreases the drug toxicity/side effects
why is chitosan nanoparticles important?
increase adhesion to mucosa and as a result, increase the retention time.
this allows drug transport across biological barriers (e.g. chitosan nanoparticles nasally)
what is preferred natural or synthetic liposomes?
synthetic as we can control the structure and purity
what are some examples of synthetic lipids?
phospholipids
what does it mean by phospholipid molecules are amphiphilic?
They contain a hydrophobic and a hydrophilic component
what can happen to hydrophobic heads in phospholipids?
they can have a surface charge
what happens to phospholipids in aq environments?
arrange themselves into bilayer structures → liposome formation (with energy input)
how can we classify liposomes?
size or by surface charge (cationic/anionic/neutral)
what size classification of liposomes are used the most? and why?
SUV - due to mainly being reproducible in manufactoring
how are liposomes prepared?
Lipid film hydration – very popular for lab-scale production (MAIN WAY)
* Solvent injection
* Reverse phase evaporation
* Microfluidic techniques
what organic solvents are used in lipid film hydration?
chloroform/methanol
explain lipid film hydration
- lipid is dissolved in an organic solvent
- flask is shaken/rotated in an rotary evaporation set up
- the organic solvent evaporates
- aqueous solution (buffer) added for hydration allowing the film to swell and form a bilayer
- stirring (T° > Tm)
- size reduction
why is the solvent and liposomes shaken/rotated during the heating phase?
due to the solvent being volatile
what are the different size reduction techniques?
- extrusion (mainly used)
- probe sonication
- bath sonication
explain the extrusion process
filtered unit with an ideal pore size chosen
pressure and heat used to force the solution through the filter = uniform size
what is phase transition temperature ?
Tm or Tc
Temperature at which lipids undergo a change in physical state from ordered gel phase to disordered liquid crystalline phase
what happens to the liposomes if T° < Tm
they will be ordered
in a gel phase
what happens to the liposomes if T° > Tm
they will be disordered
in a liquid crystalline phase
