Stimuli responsive polymers Flashcards
Name 4 pH sensitive polymer blocks
Poly(acrylic acid)
Poly(methacrylic acid)
Poly(2-ethyl acrylic acid)
Poly(2-propyl acrylic acid)
Name 2 temperature sensitive polymer blocks
N-isopropylacrylamide
Poly(organophospazenes)
What is Eudragit E
Cationic copolymer
What is Eudragit L
Anionic copolymer
What is cellulose acetate phthalate
pH responsive system
Explain how cellulose acetate phthalate works in the context of vaginal drug delivery
At lower pH, it is insoluble and remains as a gel.
At higher pH, it dissolves allowing drug release.
Vaginal pH is normally acidic, and drug remains trapped, allowing for sustained release.
Semen has a higher pH, increasing drug solubility, triggering rapid drug release.
Active ingredient in Timoptic XE
Timolol maleate
What is gellan gum
Polysaccharide which remains liquid in a bottle but gels upon contact with tear film
Explain how gellan gum is used in Timoptic XE
It is a negatively charged polysaccharide.
It is installed into the eye as eye drops.
Ca2+ ions in the tear film neutralise the gellan gum, making it less soluble.
Ca2+ ions cross-link polymer chains, forming a structured gel network
The gel holds the drug in place, allowing slow sustained release
Indication of Timoptic XE
Beta blocker for glaucoma. To be applied once daily
Positive thermosensitive hydrogels
Contain mostly hydrophilic monomers.
Experience an increase in swelling with an increase in temperature.
Negative thermosensitive hydrogels
Contain some hydrophobic monomers.
Experience a decease in swelling with an increase in temperature
What is PNIPAAm
Poly(N-isopropylacrylamide)
Temperature sensitive polymer
What is LCST
Lower critical solution temperature
What happens <LCST
Polymer chains are well hydrated and have a random coil configuration.
They are swollen.
What happens >LCST
They take on a much more compact configuration by sudden dehydration and increased hydrophobic interactions.
Collapsed
What is the LCST of PNIPAAm
~33
What is PAAm often used in?
Antigen responsive hydrogel swelling systems
3 classes of light sensitive release systems
UV sensitive
Visible light sensitive hydrogels
Near-infrared radiation sources
Name 4 photoactive groups which undergo reversible structural changes under UV light
Azobenzene
Cinnamoyl
Spirobenzopyran
Triphenylmethane
