SUPPORTED CELL MIMETIC MONOLAYERS AND THEIR COMPATIBILITY - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 655

to loss of intermolecular interactions within the membrane 14 . The molecules are
laterally mobile within the monolayer. This lateral mobility and expansion gives
a time-dependent renewability of the surfaces under water. Sackman et al. has
immobilized proteins into these monolayers and attempted to evaluate the adhe-
sion induced receptor aggregation and adhesion plaque formation 15 .
20.3.2 Optimization of Heterogeneous Phospholipids/
Glycolipid/Cholesterol Ternary Lipid Composition, Lateral Stability
Improvement, and Preliminary Blood Compatibility Studies
The authors attempted to immobilize these monolayers over polymeric sub-
strates. The cell membrane components of the endothelial cell membrane, phos-
phatidylcholine (PTC) for phospholipid, Galactocerebroside (GalC) for
glycolipid and cholesterol (Chol) based on the head group structure to represent
the major lipid components of the endothelial luminal cell membrane. Further,
macromolecules such as protein (albumin), polysaccharide (heparin) and polymer
(Polyethylene glycol), and so on, were incorporated into these lipid monolayers.
The interfacial behavior of various combinations of lipids as well as the lipid mac-
romolecular combinations have been studied at the air/water interface and depos-
ited on hydrophobic polymer substrates like polycarbonate (PC) and poly methyl
methacrylate (PMMA) with the help of the Langmuir-Blodgett (LB) trough. The
packing and orientation of the supported monolayers have been varied by means
of changing the lipid composition rather than the deposition parameters. This
approach seems to be more similar to the in vivo conditions. The different
supported monolayer surfaces prepared accordingly are: closely-packed
ordered hydrophobic surface—polymer (PC) modifi ed with the combination
(PTC : Chol : GalC) (1 : 0.35 : 0.125); loosely - packed ordered hydrophobic sur-
face — PC modifi ed with the combination (PTC : Chol) (1 : 0.35); closely packed
ordered hydrophilic surface— PC modifi ed with the combination (PTC : Chol)
(1 : 0.7). Such an optimized surface (PTC : Chol : GalC) (1 : 0.35 : 0.125) has been
identifi ed based on maximum transfer ratio from the air/water interface and char-
acterized by using atomic force microscope (AFM). The concentration of choles-
terol has been found to be an important parameter that infl uences the transfer
ratio. The GalC improves the monolayer integrity under reduced Chol concen-
tration. The blood compatibility of these supported monolayers was studied by
protein adsorption, blood cell adhesion, and calcifi cation.
The authors have optimized an outer cell mimetic lipid composition (OCMC)
containing (OCMC) (PTC : Chol : GalC) (1 : 0.35 : 0.125) based on the air/water
interfacial studies. Further macromolecular anchors such as albumin (OCMC-A)
(PTC : Chol : GalC : Alb) (1 : 0.35 : 0.125 : 0.008), albumin and heparin (OCMC -
AH) (PTC : Chol : GalC : Alb : Hep) (1 : 0.35 : 0.125 : 0.008 : 0.052), as well as albumin,
heparin and polyethylene glycol (OCMC - AHP) (PTC : Chol : GalC : Alb : Hep :
PEG) (1 : 0.35 : 0.125 : 0.008 : 0.052 : 0.15) were incorporated into the lipid layers.
The albumin is treated with organic solvents to do phase inversion and incor-
porated into the lipid solution to get stabilized itself. The air/water interfacial