T HER MORESPONSIVE
DELIVERY
Thermoresponsive Drug Delivery Systems:
Fiction or Reality?
By: Akm Khairuzzaman, PhD
INTRODUCTION
Drug Delivery Technology Jun e 2009 Vol 9 No 6
The pharmaceutical world is getting
more complicated, diversified, and
expensive in modern times. Successful
efforts have been made with commercially
available controlled-release devices to
deliver drugs to a specific site, but there
still exists insufficiencies in certain clinical
situations, such as the delivery of insulin,
arrhythmia, chemotherapy, hormonal
therapy, and many others.1-4 Therefore,
diseases are now very often looked at from
a genetic perspective, and a molecular
level of treatment is increasingly being
considered as the therapeutic future. To
achieve such an objective, several
environmentally responsive polymers have
been used that are commonly known as
Smart Materials. 5 They react to an external
applied force, ie, electrical, chemical,
stress/strain, light, and magnetic field.
Using these concepts, some researchers
actually have been able to control drug
release in connection with several
physiological stimuli. Prof. Robert Langer
at the Massachusetts Institute of
Technology is the pioneer who has
successfully designed numerous smart
materials for drug and DNA/RNA delivery
platforms for many therapeutic areas. 6 He
has used almost all sorts of stimuli, such
as oscillating magnetic fields, thermal,
chemical, ultrasound, light, and electrical,
to modulate the drug release from such
smart materials. Similarly, many other
research articles have been published in
the past decade, but yet the possibility of
commercialization of these concept-based
dosage forms is indeed fiction.
This article reviews one such
interesting smart drug delivery system
(thermoresponsive) in which the drug
molecule is physically attached to or
entrapped in a polymer that is capable of
conformational or phase changes under
different regimes of temperature. 7 Such
polymers are called thermosensitive
polymers. These are potential candidates
for a targeted drug delivery system,
especially for anti-cancer drugs. However,
the concern here is the human body’s
capability to maintain a controlled body
temperature (except in the case of fever)
unless there is a significant temperature
change in the target organ. One such
clinical situation is very common in cancer
treatment, where there is a bimodality
approach of combining localized
FIGURE 1
