16-04-2012, 03:29 PM
Characterization of Microchannels Created by Metal Microneedles: Formation and Closure
[attachment=20165]
INTRODUCTION
Stratum corneum (SC), the outermost layer of the skin,
obstructs foreign particles as well as hydrophilic compounds
from entering the body. Several enhancement methods such
as intraepidermal administration, iontophoresis, ultrasound,
electroporation, chemical enhancers, and microneedles (MN)
have been employed to overcome this barrier (1–10) and new
minimally invasive techniques are continually being investigated.
While chemical enhancers have been widely investigated
for enhancing drug permeation levels, they tend to disrupt
the lipid bilayers of the stratum corneum. Alternatively, physical
enhancement methods have been used.
RESULTS AND DISCUSSION
Traditionally, chemical agents such as esters, azones,
cyclodextrins, etc. have been employed in formulations as a
means to alter the barrier properties of the stratum corneum
layer of skin and aid in better permeation of the active agent.
These permeation enhancers tend to disrupt the lipid
structure of the SC layer, thereby causing damage which
takes a long recovery time (22). Physical enhancement
techniques like iontophoresis, sonophoresis, and microdermabrasion
overcome the stratum corneum barrier effectively.
However, they have their own set of limitations. Application
of iontophoresis for drug delivery is limited by the restriction
on the size of the drug molecule can be administered by this
technique (∼12 kDa).
CONCLUSIONS
Our pursuit for simple and effective treatments and devices
for several cosmetic and therapeutic applications has been a
continual process. Microneedles offer a simple, reproducible,
and effective means for breaching the stratum corneum barrier
which allows for topical and transdermal delivery of hydrophilic
molecules. The DermaRoller® device with metal microneedles
is an easy to use handheld device which effectively creates
microchannels and may provide an alternate means for skin
microporation. The created microchannels are reversible in
nature and close within a few hours of microporation; the time
frame being dependent on the length of microneedles.
[attachment=20165]
INTRODUCTION
Stratum corneum (SC), the outermost layer of the skin,
obstructs foreign particles as well as hydrophilic compounds
from entering the body. Several enhancement methods such
as intraepidermal administration, iontophoresis, ultrasound,
electroporation, chemical enhancers, and microneedles (MN)
have been employed to overcome this barrier (1–10) and new
minimally invasive techniques are continually being investigated.
While chemical enhancers have been widely investigated
for enhancing drug permeation levels, they tend to disrupt
the lipid bilayers of the stratum corneum. Alternatively, physical
enhancement methods have been used.
RESULTS AND DISCUSSION
Traditionally, chemical agents such as esters, azones,
cyclodextrins, etc. have been employed in formulations as a
means to alter the barrier properties of the stratum corneum
layer of skin and aid in better permeation of the active agent.
These permeation enhancers tend to disrupt the lipid
structure of the SC layer, thereby causing damage which
takes a long recovery time (22). Physical enhancement
techniques like iontophoresis, sonophoresis, and microdermabrasion
overcome the stratum corneum barrier effectively.
However, they have their own set of limitations. Application
of iontophoresis for drug delivery is limited by the restriction
on the size of the drug molecule can be administered by this
technique (∼12 kDa).
CONCLUSIONS
Our pursuit for simple and effective treatments and devices
for several cosmetic and therapeutic applications has been a
continual process. Microneedles offer a simple, reproducible,
and effective means for breaching the stratum corneum barrier
which allows for topical and transdermal delivery of hydrophilic
molecules. The DermaRoller® device with metal microneedles
is an easy to use handheld device which effectively creates
microchannels and may provide an alternate means for skin
microporation. The created microchannels are reversible in
nature and close within a few hours of microporation; the time
frame being dependent on the length of microneedles.