Biomedical Engineering Reference
In-Depth Information
class of smart polymers that can be ef ectively used for pulsatile/controlled
drug delivery applications are responsive hydrogels. h e ability of hydro-
gels to respond reversibly to variations in their environment makes them
viable for widespread applications in the medical i eld [76]. Microl uidic
actuating systems have lithographically fabricated, in which the hydro-
gel present at the junction of themicrochannel actuates in response to the
changes in environmental conditions, thereby gating the microchannel
accordingly [77, 78]. Micropumps and microvalves have synthesized using
a micro-structured silicon membrane with entrapped hydrogels for envi-
ronmentally sensitive l uid gating [79].
A responsive controlled-drug-release system has been prepared where
the controlled release is achieved by actuating a polymeric valve system
also called an artii cial muscle [80]. In addition, some polymeric matri-
ces have been modii ed with gamma radiation in order to obtain stimuli-
responsive polymers which could have potential to be used as biomaterials
in the fabrication of medical devices. Polypropylene (PP) i lms have been
grat ed with thermo-pH responsive polymers in order to improve loading
of vancomycin [81]. Vancomycin is one of the most frequently chosen anti-
biotics for the treatment of infections associated with the use of catheters.
PP is widely used as component of meshes for abdominal hernias, sutures
and catheters, and it can be colonized with bacteria. Grat ing of acrylic acid
(AA) enhanced the vancomycin loading and modii ed PP i lms reduced
bioi lm formation by methicillin-resistant
Staphylococcus aureus
[82].
PP has been modii ed with PNIPAAm and N-(3-aminopropyl) meth-
acrylamide hydrochloride (APMA) as a suitable monomer able to electro-
statically interact with anionic drugs, such as nalidixic acid. Copolymer
exhibited the temperature responsiveness of PNIPAAm, while the grat ing
with a greater content in APMA led to load a higher amount of nalidixic
acid [83]. In addition to microbial agents, these kind of stimuli-responsive
polymers have been loaded with other drugs such as non-steroidal anti-
inl ammatory drugs (NSAIDs) [84]. Other authors have fabricated micro
devices with pH responsive hydrogels encompassing enzyme glucose oxi-
dase for insulin delivery applications [10, 85].
2.6.1
Advancements in Design of Medical Device
Advancements in micro- and nano-fabrication technologies have enhanced
the ability to create successful implantable and oral drug delivery systems
composed of silicon, glass, silicone elastomers and other polymers [86-88].
h e two most used conventional drug administration methods are oral and
parenteral delivery systems, however, the rate of drug delivery or the target
