P9: Nanocarrier Systems

Question 1

what is the stratum corneum

Answer 1

the outermost layer of the epidermis
the location of barrier within the skin largely resided in the stratum corneum, prevents the entry of both toxic and topical agents

Question 2

what are nanoparticles

Answer 2

solid colloidal particles ranging from 1-1000nm; consists of macromolecular materials, can be used as drug carriers in which the active principle is dissolved, entrapped or encapsulated, or to which the active principle is absorbed or attached

Question 3

what is nanomedicine

Answer 3

application of technologies on the scale of 1-500nm to diagnose and treat diseases; increases drug penetration and stability, too small to be detected by immune system, deliver the drug in the target organ using lower doses to reduce side effects

Question 4

what are vesicle based lisosomes

Answer 4

lipid bilyer structures made of phospholipids and cholesterol
hydrophilic drugs are entrapped in the aqueous layer of the liposomes, while hydrophobic drugs are incorporated in the lipid bilayers

Question 5

what are the advantages of liposomes

Answer 5

biocompatibility, low toxicity, targeted delivery of drugs to the site of action

Question 6

what are the limitations of topical drug delivery

Answer 6

limited penetrating ability (confined to upper layers of stratum corneum), chemically and physically unstable

Question 7

what are transfersomes

Answer 7

ultra-deformable liposomes composed of phospholipids and additional surfactant/emulsifier
edge activators that destabalise the lipid bilayers of the stratum corneum and increase in deformability by lowering interfacial tension of lipid bilayers

Question 8

what are the advantages of transfersomes

Answer 8

elastic vesicles capeable of permeating intact skin, by squeezing themselves along the intracellular sealing lipid of the stratum corneum, the drug penetrating ability increases; localised at higher concentration in the deep layers of the skin than liposomes

Question 9

what are the disadvantages of transfersomes

Answer 9

edge activators must be highly pure to avoid skin irritation and toxicity

Question 10

what are ethosomes

Answer 10

soft lipid vesicles composed of phospholipids, water and ethanol in relatively high concentrations

Question 11

what are the advantages of ethosomes

Answer 11

more effective transdermal delivery than classic liposomes, smaller and higher entrapment efficiency liposomes, interferes with lipid bilayers of the stratum corneum due to fluidising effect of alcohol, shows better skin permeation and stability than classical liposomes, alcohol also enhances deformability of vesicles

Question 12

what are the disadvantages of ethosomes

Answer 12

skin irritation due to high concentration of alcohol

Question 13

what are binary ethosomes

Answer 13

developed by adding another type of alcohol to the classical ethosomes, most commonly used alcohols are propylene glycol and isopropyl alcohol

Question 14

what are transethosomes

Answer 14

new generation of ethosomal systems
contains basic components of classical ethosomes and an additional surfactant
developed in an attempt to combine the advantages of classical ethosomes and deformable liposomes
entrap drugs with MW ranging from 130Da to 200-325Da

Question 15

what is celecoxib

Answer 15

NSAID COX-2 inhibitor

prevents skin cancer development and increases effectiveness of anticancer drugs

Question 16

what does SLN stand for

Answer 16

solid lipid nanoparticles

Question 17

what does NLC stand for

Answer 17

nanostructured lipid carriers

Question 18

what are the three SLN types

Answer 18

1. homogenous matrix model (release from 1-14 days)
2. drug-enriched shell model (fast compound delivery)
3. drug-enriched core model (slow controlled release of the active)

Question 19

what are the disadvantages of SLN

Answer 19

decreased loading capacity, expulsion of drug during storage

Question 20

what are some advantages of NLC

Answer 20

overcome the limits of SLN, different matrix structure

Question 21

what are the three types of NLC

Answer 21

1. imperfect type (blend of solid lipids and liquid lipids with different molecular structures)
2. amorphous type (lipid solid matrix in the amorphous state)
3. multiple type or O/F/W (drug solubility in oils is higher than in solid lipids)

Question 22

what are the shared characteristics of SLN and NLC

Answer 22

adhesive films formed on the skin -> occlusive effect -> increased skin hydration

Question 23

what are the advantages of lipid nanoparticle carriers

Answer 23

low toxicity, small particle size, increased skin hydration -> occlusive effect, enhance the stability of liable compounds, physical sunscreen on their own, reduce skin irritation

Question 24

what are niosomes

Answer 24

surfactant/vesicle based

bilayered structures made of non-ionic surfactant and cholesterol

Question 25

what are the advantages of niosomes

Answer 25

able to entrap wide range of chemicals (both hydrophilic and hydrophobic), less toxic than carriers with ionic surfactant

Question 26

what are the disadvantages of niosomes

Answer 26

limited shelf-life, time-consuming and specialised required for the preparation process

Question 27

what is 5-FU (5-fluorouracil)

Answer 27

first topical therapy for the treatment of superficial basal cell carcinoma approved by the FDA
topical administration, poor percutaneous permeation due to its hydrophilic properties

Question 28

what are nanoemulsions

Answer 28

isotropic dispersed systems of two immiscible liquids (o/w or w/o)

Question 29

what are the advantages of nanoemulsions

Answer 29

both hydrophilic and hydrophobic drugs can be applied
solubilisation/extraction of stratum corneum lipids, thereby decreasing resistance for drug transport
greater and extended cellular penetration
raised efficacy due to increasing surface-to-folume ratios
non-toxic and non-irritant
kinetically stable

Question 30

what are the disadvantages of nanoemulsions

Answer 30

stability problems