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Jihong Han's lectures > Liposomes for drug delivery > Flashcards

Liposomes for drug delivery Flashcards

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?

A

TRUE

23
Q

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

A

TRUE

24
Q

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

A

TRUE

25
Q

The phospholipid can have 2 negative charge and one positive charge which will lead to there being an overall negative charge. TRUE OR FLASE?

A

TRUE

26
Q

Why use liposome for drug delivery?

A
  • 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
Q

What is the first problem with liposomes as drug delivery system?

A
  • It is getting the drug inside the liposome
28
Q

If the liposomes gets formed in the solution of the drug, parts of the drug becomes entrapped. TRUE OR FLASE?

A

TRUE

29
Q

Liposomes have very few effeciency, only a small percentage of the drug is in the internal phase. TRUE OR FALSE?

A

TRUE

30
Q

Because the drug leaks out slowly, the system must then be freeze dried without damaging the liposome. TRUE OR FALSE?

A

-TRUE

31
Q

What molecules are used to help the vesicles stay intact when freeze drying the liposomes to prevent leakage?

A
  • Cryoprotectants
32
Q

What are common cryoprotectants?

A
  • Dissacharides e.g sucrose
33
Q

Monosaccharides are relatively poor cryoprotectants. TRUE OR FALSE?

A

TRUE

34
Q

What do the cryoprotectants do?

A
  • They promote the formation of glass during the freeze drying and hence prevents the formation of ice crystals
35
Q

The hydroxyl group on the cryoprotectant can form hydrogen bond with phospholipid when water is removed during freeze drying. TRUE OR FALSE?

A

TRUE

36
Q

What is reffered to as the replacement theory?

A
  • The bilayer previously supported by water is now supported by the cryoprotectant
37
Q

describe unsaturated phospholipids?

A
  • Low melting point
  • Mobile so contents can leak out easily
  • easy to pack liposomes
38
Q

what is the purpose of cholesterol?

A
  • It is added to improve rigidity and stability
39
Q

Describe saturated phopholipids?

A
  • They stay in liposome (encapsulated material stays in the liposome)
  • But processing is very difficult
40
Q

A small amount of charged phospholipid is needed to make liposomes (1-5%). TRUE OR FALSE?

A

TRUE

41
Q

What is the typical manufacturing sequence of liposomes as drug delivery system?

A
  • 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
Q

Ho ware liposomes removed when in the blood?

A
  • Removed by the liver
43
Q

The body can recognise the phospholipids as foreign. TRUE OR FALSE?

A

TRUE

44
Q

How does an immune response begin with liposomes in the blood?

A
  • It begins by the recognition of proteins adsorbing to the liposomes surface
45
Q

Hydrophilic polymers are known to stop the adsorption of proteins. TRUE OR FALSE?

A

TRUE

46
Q

Polyoxyethylene forms the coating on the surface of the liposome. TRUE OR FALSE?

A

TRUE

47
Q

What are ghost cells?

A
  • They have similar function to liposomes as they encapsulate drugs
48
Q

Ghost cells uses patients own cells to prevent an immune response (red blood cells mostly used). TRUE OR FLASE?

A

TRUE

49
Q

What are niosomes?

A
  • they are non-ionic surfactants that form hollow vesicles
50
Q

If pH lower than pka then the liposome becomes unionised and unstable. TRUE OR FLASE?

A

TRUE

51
Q

What are the 4 factors that can affect stability of freeze dried product?

A
  • 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
Q

what physical changes can happen to liposomes?

A
  • Change in charge
  • Change in stability of membrane e.g lack of cholesterol
  • Change in permeability (temperature)
53
Q

Explain why a cryoprotectant is needed for the freeze-drying of liposomes? Explain the possible mechanismsof cryoprotection

A
  • Protects liposomes from damage

- Promotes glass formation instead of ice crystal

54
Q

what are bilayer defects?

A
  • They are defects is the loss of lipid molecules from the bilayer

Jihong Han's lectures (11 decks)

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