Define hydrogel and make a list of most common polymers utilized to make hydroge

Question

Define hydrogel and make a list of most common polymers utilized to make hydrogels. Why are hydrogels used so often in tissue engineering? Compare and contrast hydrogels with other non-hydrogel based biomaterial. How can hydrogels be made with excellent mechanical properties? What are the different classes of hydrogels and the advantages/disadvantages of each? Define stimuli-responsive hydrogels. How would you identify pH and thermal responsive structures? Why are these hydrogels popular in biomedical applications?

Explanation / Answer

a) Hydrogels are three-dimensional, cross-linked networks of water-soluble polymers. Hydrogels can be made from virtually any water-soluble polymer, encompassing a wide range of chemical compositions and bulk physical properties

PEG, poly(ethylene glycol)PEO, poly(ethylene oxide)PPO, poly(propylene oxide)PDMAEMA, poly(dimethylaminoethyl methacrylate)PLGA, poly(lactide-co-glycolic acid)PNIPAM, poly(N-isopropylacrylamide)PPF, poly(propylene fumarate)PCL, poly(caprolactone)PU, poly(urethane) are some of polymers used to make hydrodels.

b) The unique physical properties of hydrogels have sparked particular interest in their use in drug delivery applications. Their highly porous structure can easily be tuned by controlling the density of cross-links in the gel matrix and the affinity of the hydrogels for the aqueous environment in which they are swollen. Their porosity also permits loading of drugs into the gel matrix and subsequent drug release at a rate dependent on the diffusion coefficient of the small molecule or macromolecule through the gel network.

c)Superabsorbent hydrogels with excellent mechanical properties are fabricated by introducing organic montmorillonite (OMMT) into poly(acrylic acid) (PAA) hydrogels via simple UV irradiation polymerization.

d)

Hydrogels may be categorized into four groups on the basis of presence or absence of electrical charge located on the cross-linked chains:

1) . Nonionic (neutral).

2) Ionic (including anionic or cationic).
3) Amphoteric electrolyte (ampholytic) containing both acidic and basic groups.

4) Zwitterionic (polybetaines) containing both anionic and cationic groups in each structural repeating unit.

ADVANTAGES:

#The highest absorption capacity (maximum equilibrium swelling) in saline.
# Desired rate of absorption (preferred particle size and porosity) depending on the application requirement.
# The highest absorbency under load (AUL).
# The lowest soluble content and residual monomer.

DISADVANTAGES :

#High cost

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