Biomedical Engineering Reference
In-Depth Information
Outer phase
Nylon
membrane
Inner phase
Lipid multi-bilayer
Nylon capsule
FIGURE 12.2
Lipid-bilayer-corked capsule.
(A)
(B)
Fluorescent
probe
Porous
glass
plate
FIGURE 12.3
(A) A Langmuir monolayer of dialkylorganosilane. (B) Permeation control of fl uorescence
molecular probe through the monolayer-immobilized porous glass plate.
shown in Figure 12.2, in which a lipid-bilayer-corked capsule is illustrated [10]. As reported by Oka-
hata and coworkers, nylon capsules with diameter of 2 mm and membrane thickness of 1 µm were
prepared by interfacial polycondensation using ethylenediamine and 1,10-
bis
(chlorocarbonyl)decane.
Surface membranes of the capsules have porous structures and are capable of stable accommodation
of multibilayer structures of lipids, as illustrated in Figure 12.2. Target drug molecules were dis-
solved in inner water pool, from where permeation of the entrapped drugs was monitored. Systematic
measurement by changing ambient temperatures revealed that the permeation coeffi cient of the drug
through the multibilayer membranes could be discontinuously altered around phase transition tem-
perature of the lipid membrane. Such controls of drug release can be successfully driven by the other
stimuli such as application of external electric fi elds [11].
The same research group also demonstrated permeation control through a much thinner supra-
molecular fi lm, that is, they realized permeation control through a single monolayer of amphiphile
(Figure 12.3) [12,13]. A monolayer of dialkylorganosilane was prepared at the air-water interface
and transferred onto a porous glass plate through Langmuir-Blodgett (LB) technique. By using this
hybrid nanostructure, material permeation through the monolayer on glass was successfully regu-
lated. The dialkylorganosilane compounds were polymerized through the formation of Si-O-Si
linkages on the acidic aqueous surface, and covalently immobilized on glass surface by reaction
