Biomedical Engineering Reference
In-Depth Information
5.
D
EVICES
U
SED IN
T
RANSDERMAL
D
RUG
D
ELIVERY
Transdermal drug delivery or drug delivery through the skin is another
non-invasive means of drug delivery which offers avoidance of first pass
hepatic effects as well as many problems associated with oral drug
administration. The stratum corneum of the skin is a barrier to absorption of
hydrophilic molecules and macromolecules. Thus, devices developed for
transdermal delivery depend on having special features to overcome this
barrier. These devices include thermo-ablating microchannel generators,
microneedles and jet injectors.
5.1. Thermo-Ablating Microchannel Generators
Thermo-ablating microchannel generators employ heat to create
micropores in the skin's stratum corneum through which water-soluble
compounds and macromolecules (e.g. gene, protein) are possibly able to be
transported (Arora et al., 2008). The heat can be generated by means of
radiofrequency energy or electrical energy. Microelectrodes may consist of an
array of electrodes which apply radiofrequency current (100-500 kHz) onto the
surface of skin to create microchannels which permit drug penetration when
drug-containing patches are applied to the affected area (Sintov et al., 2003;
Levin et al., 2005; Birchall et al., 2006; Arora et al., 2008). The microchannels
formed using the radiofrequency technology has been reported to be amenable
for delivery of nanoparticles (100 nm) (Birchall et al., 2006). Figure 18 shows
an SEM micrograph of a microchannel formed as a result of applying
radiofrequency currents on human skin (Birchall et al., 2006).
Another thermoablation technology is that represented by the PassPort
®
system (Althea Therapeutics, USA) which consists of a hand-held unit and a
―porator‖ unit comprising a disposable patch that stores the drug and
incorporates an array of metallic filaments. The hand-held unit produces a
brief pulse of electrical energy to the ―porator‖ which converts the electrical
current into painless and shortly existing heat to create microchannels in the
stratum corneum of the skin, permitting the drug (e.g. peptide) to pass through
(Banga, 2006; Arora et al., 2008).
