POD 3 Liposomes micelles

PF1012

Surfactants are \___

amphiphilic

Many surfactants with pharmaceutical applications have a \___ chain and a \___ or \___ head

single hydrophobic
simple ionic
large non-ionic

The head group of surfactant are classified as \___

Anionic
Cationic
Zwitterionic
Non-ionic

Example of non-ionic surfactants?

sorbitan esters - Spans
polysorbates - Tweens

Pharmaceutical Applications of Surfactants?

Solubilisation (Solubilize poorly water-soluble drugs)
Detergency (Eg cleaning skin)
Wetting agent (Lower contact angle between surface and wetting liquid)

What's the difference below and above CMC?

What's the main reason for micelle formation?

To minimize free energy

Micelles continually form and don't break down in solution T/F

False they do break down

List some factors affecting CMC & micellar size?

Structure of the hydrophobic group (↑ chain length \= ↓ CMC)
Nature of hydrophilic group (non-ionic generally ↓ CMC)
Electrolyte addition ↓ CMC and ↑ the micellar size

Micelles are used to formulate \___ drugs in colloidal solutions

low solubility

At what critical packing parameter (CPP) can surfactants form spherical micelles?

< 1/3

Other than spherical micelles, what can surfactants can also form?

Cylindrical Micelles 1/3 < CPP < 1/2
Flexible Bilayers or Vesicles 1/2 < CPP

What determines the type of micelle formed?

Dispersed medium

Drug molecules are located differently in solution due to

polarity

Drug molecules can be located

In the core
On the surface
Palisade layer (in between core and the outside)
An intermediate position (dunno what the hell this is but amphiphilic drug can basically exist like picture b)

What is the main pharmaceutical interest in micelles?

Solubilization influenced by

Nature of solubilisate (what u need to solubilize)
Surfactant chain length
Temp

What is Maximum additive concentration (MAC)?

Max amount of drug that can be incorporated into a micellar system (at fixed surfactants conc and temperature)

Micelle instability can result due to

Change in temp, pH, addition of additives at change Hydrophilic-lipophilic balance of surfactant

What happens if the concentration of surfactant drops below CMC?

precipitation of the drug

List some application of Micelles

administration of steroids (where oily solution or suspension not suitable)
Dettol - Solution of Chloroxylenol B.P.
Aqueous injections of water insoluble vitamins (A, D, E, K)
Anti-cancer drug Paclitaxel

What are Polymeric Micelles?

Micelles formed from block copolymers

Diameter of polymeric micelles

10-80 nm

Polymeric micelles compare to surfactant micelles?

more stable, lower CMC

Application of polymeric micelles in drug delivery

Solubilised (poorly soluble drugs) in hydrophobic micelle core
Conjugation to micelle polymer (drug stick to polymers)

Polymeric micelles also serve as ligands (sometimes)

I can’t make a question out of this one

Polymeric micelles shell is

hydrophilic

Polymeric micelles shell forms barrier which

Reduce aggregation and protein binding

main component of liposomes?

phospholipids (amphiphilic -\> exhibit surfactant behaviour)

In liposomal system, drug can dissolve in

Within the aqueous core
Within bilayer
Adsorbed on surface

Types of liposomes?

Multilamellar vesicle (MLV) ⦾
Large unilamellar vesicle (LUV) O
Small unilamellar vesicle (SLV) o
Oligolamellar vesicles (OLV) ⦾ (2-5 bilayers)

In an aqueous medium, the phospholipid molecules self-assemble into

bilayer sheets

Liposome formation does not require energy T/F

False

Liposome typically size

20 nm to 10µm

Liposome stability and surface charge can be influenced by

Phospholipid composition
Addition of cholesterol

What charge is on surface of liposome?

negative, positive or neutral

What influences the distribution of liposomes?

Modifying the size, lamellarity (how many layers), charge or surface FGs

Why are drugs encapsulated in liposome?

Prolong drug activity, protect drug from enzyme

What does similarity with the cell membrane mean for liposomes?

They can interact with cells

Liposome can be designed to \___ the encapsulated drug to \___

direct/ specific biological targets

Liposomes can be used for which ROA?

orally, topically, transdermally and parenterally

What can happen to Liposomes after IV administration?

Disintegrate in the circulation
Cleared by macrophages
Escape from the circulation via leaky blood vessels

The leaking of liposomes from the systemic circulation to sites of inflammation and tumour can be \___ for the delivery

advantageous

What is AmBisome®?

Amphotericin B (single bilayer) liposome for infection

Where is Amphotericin B in AmBisome®?

Within the membrane