Stimuli-Responsive Lipid -Based Self-Assembled Systems - Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals - page 264

TABLE 9.2 Means of Inducing Hyperthermic Condition in Tissues for
Activation of Thermally Sensitive Drug Delivery Systems

Lipid System and Route of
Administration Heat Source Activation Site

Laser: NIR lasers
can penetrate to
depths of 50 mm
though the skin.

Liposome, systemic Subcutaneous

(Mackanos et al., 2009 )

Liposome, systemic Tumor (Gaber, 2002 ; Gaber,

et al., 1996; Ponce et al.,
2006 ; Weinstein et al., 1979 )

Liposome, intravenous (IV) Ocular (Desmettre et al., 1999 )

Liposome, systemic Liver (Mordon et al., 1996 )

Electromagnetic
fi eld (EMF)

Liposome incorporating
dextran magnetite or
colloid; iron oxide;
systemic

Site accessed by EMF
(Babincová et al., 2002;
Viroonchatapan et al., 1997;
Zhu et al., 2009)

Ultrasound
Microwave Liposome incorporating

dextran magnetite or
colloid; iron oxide;
systemic

Site accessed by EMF
(Babincová , 1993 )

Heat/cool pack Bulk liquid crystal;

subcutaneous

Subcutaneous
(Fong et al., 2009)

Figure 9.3 Schematic showing the formation of a pore by pore-forming amphiphiles
above the melting transition temperature of the lipids comprising the liposome, result-
ing in drug release. [Adapted from Petrov et al. (2009) with permission from the
American Chemical Society © 2009.]

the literature compared to other self-assembled structures. The application of
hyperthermia takes advantage of the acyl-chain melting phase transition in
phospholipids, which results in an increase in permeability across the lipid
bilayer, and consequent drug release (as illustrated in Fig. 9.3). The transition
temperature of the lipids and the heat applied is tuned to be just above
physiological temperature but low enough so as to not perturb cell function
in surrounding tissues. The fi rst systems were reported by Yatvin and co-
workers (Weinstein et al., 1979; Yatvin et al., 1978), who designed liposomes