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Liposomes for drug delivery Flashcards

(54 cards)

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1
Q

Phospholipids organise themselves into spherical structure known as liposomes. TRUE OR FALSE?

A

TRUE

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2
Q

Phospholids are derived from eggs or soya. TRUE OR FALSE?

A

TRUE

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3
Q

what happends to surfactants when they are dispersed in water?

A
  • They form micelles

- The hydrophobic tails are inside the structure

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4
Q

No all surfactnat form micelles when dispersed in water. TRUE OR FLASE?

A

TRUE

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5
Q

Phospholipids are surfactants but they do not normally form micelles. TRUE OR FALSE?

A

TRUE

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6
Q

what is the thermodanymic stable state of phospholipids in water?

A
  • A bilayer
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7
Q

Shacking phospholipids with water forms large liposomes in a onion like layer called multilamellar vesicles also known as MLV’s. TRUE OR FALSE?

A

TRUE

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8
Q

Passing the MLV’s through a high shear mixer breaks these down into Unilamellar vesicles. TRUE OR FLASE?

A

TRUE

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9
Q

The bilayer formed by the phospholipid in water is temperature sensitive. TRUE OR FALSE?

A

TRUE

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10
Q

The lipid bilayer has a melting transition and temperature depending on specific phospholipid. TRUE OR FALSE?

A

TRUE

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11
Q

The properties of a bilayer change considerably on melting e.g order and permeability. TRUE OR FLASE?

A

TRUE

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12
Q

In a solif membrane things do not diffuse laterally. TRUE OR FALSE?

A

TRUE

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13
Q

In a liquid membrane things can diffuse laterally. TRUE OR FALSE?

A

TRUE

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14
Q

What influences bilayer melting?

A
  • Properties of the fatty acid chain of the phospholipid
  • Chain length
  • Chain saturation
  • Inclusion of other lipophilic molecules e.g cholesterol
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15
Q

Naturally phospholoids are unsaturated. TRUE OR FLASE?

A

TRUE

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16
Q

Unrefined grades of naturally occuring phospholipids are called lecithin. TRUE OR FALSE?

A

TRUE

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17
Q

Saturated or pure lipids are made by enzymatic transesterification. TRUE OR FALSE?

A

TRUE

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18
Q

What is enzymatic transesterification?

A
  • When a bunch of enzymes snip off phospholilid and add different groups
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19
Q

Liposomes are colloidal systems that are charge stabilised. TRUE OR FALSE?

A

TRUE

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20
Q

If the phospholipid is uncharged then the emulsifion would not be stable. TRUE OR FALSE?

A

TRUE

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21
Q

Phsopholipid ionsation is comples and depends on the headgroup. TRUE OR FALSE?

A

TRUE

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22
Q

The ionisation properties of phospholipids is dependent upon the zeta potential measurements. TRUE OR FALSE?

23
Q

Sometimes phospholipids can be psotively or negatively charged or sometimes they can have zwitterions. TRUE OR FLASE?

24
Q

When the phospholipid head group has positive and negative charge, the overall net charge is usually neutral. TRUE OR FLASE?

25
The phospholipid can have 2 negative charge and one positive charge which will lead to there being an overall negative charge. TRUE OR FLASE?
TRUE
26
Why use liposome for drug delivery?
- The idea is to use the liposome as a drug carrier - The drug in solution is encapsulated into the liposome - This protects the drug from the blood stream/ the drug is carried around the blood stream without being noticed - Once the durg has reached its target, it is released from the liposome
27
What is the first problem with liposomes as drug delivery system?
- It is getting the drug inside the liposome
28
If the liposomes gets formed in the solution of the drug, parts of the drug becomes entrapped. TRUE OR FLASE?
TRUE
29
Liposomes have very few effeciency, only a small percentage of the drug is in the internal phase. TRUE OR FALSE?
TRUE
30
Because the drug leaks out slowly, the system must then be freeze dried without damaging the liposome. TRUE OR FALSE?
-TRUE
31
What molecules are used to help the vesicles stay intact when freeze drying the liposomes to prevent leakage?
- Cryoprotectants
32
What are common cryoprotectants?
- Dissacharides e.g sucrose
33
Monosaccharides are relatively poor cryoprotectants. TRUE OR FALSE?
TRUE
34
What do the cryoprotectants do?
- They promote the formation of glass during the freeze drying and hence prevents the formation of ice crystals
35
The hydroxyl group on the cryoprotectant can form hydrogen bond with phospholipid when water is removed during freeze drying. TRUE OR FALSE?
TRUE
36
What is reffered to as the replacement theory?
- The bilayer previously supported by water is now supported by the cryoprotectant
37
describe unsaturated phospholipids?
- Low melting point - Mobile so contents can leak out easily - easy to pack liposomes
38
what is the purpose of cholesterol?
- It is added to improve rigidity and stability
39
Describe saturated phopholipids?
- They stay in liposome (encapsulated material stays in the liposome) - But processing is very difficult
40
A small amount of charged phospholipid is needed to make liposomes (1-5%). TRUE OR FALSE?
TRUE
41
What is the typical manufacturing sequence of liposomes as drug delivery system?
- The phospholipids are dissolved in a solution usually ethanol - Slowly inject into water (also known as ethanol injection method) - Liquid becomes cloudy as a result - Sepearte the liposomes from the undtrapped drug using gel chromatography - Freeze dry the resulting suspension of the liposome
42
Ho ware liposomes removed when in the blood?
- Removed by the liver
43
The body can recognise the phospholipids as foreign. TRUE OR FALSE?
TRUE
44
How does an immune response begin with liposomes in the blood?
- It begins by the recognition of proteins adsorbing to the liposomes surface
45
Hydrophilic polymers are known to stop the adsorption of proteins. TRUE OR FALSE?
TRUE
46
Polyoxyethylene forms the coating on the surface of the liposome. TRUE OR FALSE?
TRUE
47
What are ghost cells?
- They have similar function to liposomes as they encapsulate drugs
48
Ghost cells uses patients own cells to prevent an immune response (red blood cells mostly used). TRUE OR FLASE?
TRUE
49
What are niosomes?
- they are non-ionic surfactants that form hollow vesicles
50
If pH lower than pka then the liposome becomes unionised and unstable. TRUE OR FLASE?
TRUE
51
What are the 4 factors that can affect stability of freeze dried product?
- Size (larger vesicles are unstable) - Charge (a small negative charge helps stabilise the liposome) - Sugar - depends on the size of the vesicle - Dry-mass ratio
52
what physical changes can happen to liposomes?
- Change in charge - Change in stability of membrane e.g lack of cholesterol - Change in permeability (temperature)
53
Explain why a cryoprotectant is needed for the freeze-drying of liposomes? Explain the possible mechanismsof cryoprotection
- Protects liposomes from damage | - Promotes glass formation instead of ice crystal
54
what are bilayer defects?
- They are defects is the loss of lipid molecules from the bilayer

Jihong Han's lectures (11 decks)

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