Biomedical Engineering Reference
In-Depth Information
(Source: Birchall et al., 2006).
Figure 18. An SEM micrograph showing a channel that opened after applying
radiofrequency current to the skin.
5.2. Microneedles
Microneedles are micro-sized needles fitted on a base used for transdermal
delivery of drugs and vaccines (Henry et al., 1998; Prausnitz, 2004). There are
many types of microneedles depending on their structure and design.
Microneedles are generally divided into solid and hollow microneedles
(Prausnitz, 2004).
Solid microneedles create micro scale holes in the skin to enhance the
transportation of various therapeutic materials, followed by applying a topical
formulation or a patch that contains the drug. Solid microneedles can be made
from metals such as stainless steel or titanium, or biodegradable polymers such
as polylactic co-glycolic acid (Arora et al., 2008). Treatment of skin with solid
microneedles has been reported to enhance the transport of a range of
molecules including the small molecule calcein (Henry et al., 1998) and
macromolecules such as insulin and albumin as well as larger nanoparticles
having diameters of up to 100nm (McAllister et al., 2003). A commercial
example of solid microneedles is the Solid Microstructured Transdermal
System
(sMTs)
(3M,
USA)
comprising
biocompatible
polymeric
microneedles designed for delivery of vaccine, peptide and protein.
