Oral Delivery of Proteins and Peptides: Concepts and Applications - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 496

Bioadhesive Materials Properties Characteristics

l MW 2.2  10 5
l  2000-22,500 cps
(1% aqueous solution)
l  15-35 ml/g in acidic media (pH 1-3) 100 ml/g
in neutral and basic media
l  viscous colloid in cold water
l Insoluble in water, but swells to varying degrees
in common organic solvents, strong mineral
acids, and bases

Polycarbophil (polyacrylic acid
crosslinked with divinyl glycol)

l Synthesized by lightly crosslinking of 0.5-1% w/w
divinyl glycol
l Swellable depending on pH and ionic strength
l Swelling increases as pH increases.
l At pH 1-3, absorbs 15-35 ml of water per gram but
absorbs 100 ml per gram at neutral and alkaline pH
l Entangles the polymer with mucus on the surface of
the tissue
l Hydrogen bonding between the nonionized
carboxylic acid and mucin

Carbopol/carbomer (carboxy
polymethylene) empirical formula:
(C 3 H 4 O 2 ) x (C 3 H 5 -Sucrose) y

l Pharmaceutical grades: 934 P, 940 P, 971 P, and
974 P
l MW 1  10 6 -4  10 6
l  29,400-39,400 cps at 25°C with 0.5%
neutralized aqueous solution
l  5 g/cm 3 in bulk, 1.4 g/cm 3 tapped
l pH 2.5-3.0
l  water, alcohol, glycerin
l White, fluffy, acidic, hygroscopic powder with a
slight characteristic odor

l Synthesized by a crosslinker of allyl sucrose or allyl
pentaerythritol
l Excellent thickening, emulsifying, suspending,
gelling agent
l Common component in bioadhesive dosage forms
l Gel loses viscosity on exposure to sunlight.
l Unaffected by temperature variations, hydrolysis,
and oxidation, and resistant to bacterial growth
l Contributes no off-taste and may mask the
undesirable taste of the formulation
l Incompatible with phenols, cationic polymers, high
concentrations of electrolytes, and resorcinol

Sodium carboxymethyl
cellulose—SCMC (cellulose
carboxymethyl ether sodium salt)
empirical formula: [C 6 H 7 O 2 (OH) 3 x
(OCH 2 -COONa) x ] n

l An anionic polymer made by swelling
cellulose with NaOH and then reacting it with
monochloroacetic acid
l Grades H, M, and L
l MW 9  10 4 -7  10 5

l Emulsifying, gelling, binding agent
l Sterilization in dry and solution form, irradiation of
solution loses the viscosity
l Stable on storage
l Incompatible with strongly acidic solutions