Biomedical Engineering Reference
In-Depth Information
Close-up:
SC-preexisting pore
R
p
Z
R
eff
Z
SC-lipid melting
FIGURE 9.5
Thermal destruction of lipid architecture in the vicinity of preexisting
pathway.
site transport and pulse protocol was made by Vanbever et al. (1999). Here
the excised skin is placed between two reservoirs (donor and receptor) during
electroporation, and using fluorescence microscopy relations between several
pulse parameters and size and number of the LTRs are recorded. No regions
were recorded for 20 pulses at 100 V and of duration 100 msec, although by
tripling the duration to 300 msec large, rare regions up to 0.8 mm in diameter
are found. A train of 20 pulses at 200 V and 100 ms (doubling the voltage)
results in a few pores of diameter between 0.4 and 0.8 mm. Increasing both the
voltage and duration to 300 V and 300 msec results in 0.2-0.6 mm diameter
pores occurring more often at about 6 per 0.1 cm
2
.
9.6.4 Lipid Thermal Phase Transitions
One of the most important characteristic phenomena of longer-pulse-type skin
electroporation are the microscale thermal effects that also help change the
structure of the lipid sheets. While in pure diffusion models of transdermal
transport these thermal effects are not really considered, these influences are
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