90
Transmembrane potential (V)
8
7
6
5
Outer membrane with electroporation.
4
Outer membrane without electroporation.
Inner membrane with electroporation.
3
Inner membrane without electroporation.
2
1
0
−1 0
4
8
12
16
20
Time (ns)
Electromagnetic Fields in Biological Systems
Figure 2.8 Simulation results for a double-shelled prolate spheroidal cell (a 1 :b 1 = 3:5) with
b 1 = 5 μm and b 3 = 4 μm. A 100 kV/cm, trapezoidal external pulse with rise, fall, and ON times
of 1.5, 1.5, and 10 ns, respectively, was used. (After Hu, Q., and R. P. Johsi. 2009. IEEE Trans
Biomedical Eng 56:1617–26.)
2.3.3 Models of Electric Field Interactions
in Tissues and Nerves
Some work has been reported in quantifying electric fields in tissues, particularly the
skin (Weaver 2000; Weaver, Vaughan, and Chizmadzhev 1999). Human skin provides
a formidable barrier against dessication, mechanical injury, and the entry of infectious
microorganisms and toxic chemicals. The stratum corneum (SC) is the skin’s outermost
∼20-μm-thick layer and responsible for the barrier function (Elias and Menon 1991). It
provides an effective “brick wall” (Michaels, Chasekaran, and Shaw 1975) with multilamellar lipid bilayer (“mortar”) surrounding keratin-filled corneocytes (“bricks”) that
present a large barrier to ionic and molecular transport. A simplified brick wall model
was used to probe skin site electroporation (Weaver 2000) and the creation of microconduits. For example, the dark, solid lines in Figure 2.9 represent five to six lipid bilayer
membranes between corneocytes, with aqueous pathways (light regions in center and
right parts) created by electrical pulses. The hatched regions indicate keratin matrix
within corneocytes. A single, local transport region is depicted, showing only one-third
of the 15–16 corneocyte layers of the SC. Experiments (Ilic et al. 1999) using an electrically insulating mask with a 200-μm diameter hole have demonstrated the creation of a
single microconduit of about the same size.
Electric field calculations for cylindrical geometries are quite important from the
standpoint of analyzing field penetration and bioeffects in nerves. Most reports on
nerve stimulation (McNeal 1976; Rattay 1990; Reilly 1998) have focused on other issues
such as plasma membrane potentials, nerve excitation thresholds, influence of different
Transmembrane potential (V)
8
7
6
5
Outer membrane with electroporation.
4
Outer membrane without electroporation.
Inner membrane with electroporation.
3
Inner membrane without electroporation.
2
1
0
−1 0
4
8
12
16
20
Time (ns)
Electromagnetic Fields in Biological Systems
Figure 2.8 Simulation results for a double-shelled prolate spheroidal cell (a 1 :b 1 = 3:5) with
b 1 = 5 μm and b 3 = 4 μm. A 100 kV/cm, trapezoidal external pulse with rise, fall, and ON times
of 1.5, 1.5, and 10 ns, respectively, was used. (After Hu, Q., and R. P. Johsi. 2009. IEEE Trans
Biomedical Eng 56:1617–26.)
2.3.3 Models of Electric Field Interactions
in Tissues and Nerves
Some work has been reported in quantifying electric fields in tissues, particularly the
skin (Weaver 2000; Weaver, Vaughan, and Chizmadzhev 1999). Human skin provides
a formidable barrier against dessication, mechanical injury, and the entry of infectious
microorganisms and toxic chemicals. The stratum corneum (SC) is the skin’s outermost
∼20-μm-thick layer and responsible for the barrier function (Elias and Menon 1991). It
provides an effective “brick wall” (Michaels, Chasekaran, and Shaw 1975) with multilamellar lipid bilayer (“mortar”) surrounding keratin-filled corneocytes (“bricks”) that
present a large barrier to ionic and molecular transport. A simplified brick wall model
was used to probe skin site electroporation (Weaver 2000) and the creation of microconduits. For example, the dark, solid lines in Figure 2.9 represent five to six lipid bilayer
membranes between corneocytes, with aqueous pathways (light regions in center and
right parts) created by electrical pulses. The hatched regions indicate keratin matrix
within corneocytes. A single, local transport region is depicted, showing only one-third
of the 15–16 corneocyte layers of the SC. Experiments (Ilic et al. 1999) using an electrically insulating mask with a 200-μm diameter hole have demonstrated the creation of a
single microconduit of about the same size.
Electric field calculations for cylindrical geometries are quite important from the
standpoint of analyzing field penetration and bioeffects in nerves. Most reports on
nerve stimulation (McNeal 1976; Rattay 1990; Reilly 1998) have focused on other issues
such as plasma membrane potentials, nerve excitation thresholds, influence of different