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Synthetic
Polymeric wound dressings such as silicons, polyurethanes, polyvinyl chloride
or polyethylene have made their appearance in the market recently. They are
generally thin layer films which have a synthetic adhesive as a coating on the
inner surface that adheres well to dry skin at the wound margins but does not
adhere to the wound site. Recently natural polymers such as collagen, fibrin,
fibronectin, alginate and hyaluronic acid have been studied as dressings for
dermal wounds.
Innovative
polymer applications will contribute significantly to the rapid development of
future medical technology. Key drivers will be microsystem technology,
minimally invasive surgical procedures and also dispersing and packaging
systems, which thanks to their easy handling, help the patient comply with the
physicians prescription. This scenario requires the development of
problem-solving products that can only be realised with high-performance
polymers. Present advances in materials science and biotechnology and rapidly
blurring the line between the worlds of synthetic and biological polymers and
their applications. Furthermore, synthetic polymers are being designed to
minic, either structurally or functionally as biological polymers.
Some
of the recent developments in polymers as materials for biomedical devices
include:
Drug
Delivery Systems: Controlled drug delivery occurs
when a polymer whether natural or synthetic is judiciously combined with a
drug or other active agent in such a way that the active agent is released
from the material in a predesigned manner. The release of the active agent may
be constant or cyclic over a long period of time or it may be triggered by the
environment or other external events. Recent advances have made these systems
capable of responding to changes in the biological environment in such a
manner that they can deliver or cease to deliver the drugs based on these
changes . Other systems have been developed which lead to the delivery of a
drug to the specific targeted cell, tissue, or site. Some of the polymers
being used for drug delivery system include: Poly (2-hydroxy ethyl
methacrylate), poly (N-vinyl pyrolidone), poly (vinyl alcohol). etc.
Insulin
Metering Devices: The various designs of insulin
metering devices that are now available make diabetics more independent and
improve their quality of life. Using Opti Pen 2 developed by Hoechst Marion
Roussel the patients can inject the requisite amount of insulin into their
bodies themselves. The metering device administers exactly the stipulated
amount of insulin, releasing it on rotation. Acetal copolymers having good
mechanical properties, good mouldability and good slip properties are the best
materials for such devices.
Needlefree
Injector: A needlefree disposable injector has been
introduced which is meant to be used by the manufacturers in the development
of products that can be self-administered by patients. About half the size of
a fountain pen, the inexpensive disposable device is fast and easy to use and
causes virtually no pain. The patient simply removes the safety seal and
presses the injector against an arm or thigh . A precise dosage of medicine is
automatically injected through the skin within a fraction of a second as
compressed nitrogen expands to activate the system. The functional parts of
this device are made of injection moulded liquid crystal polymers because of
the requirement of very high strength at a low wall thickness.
Medicine
Inhaler Systems: Many medicines must be inhaled
directly for rapid and maximum effect. 3M Health care has come up with a
development which ensures very good relationship between metering and inhaling
processes. Further developments is such systems are proceeding in the
direction of metering and atomization devices that atomize the requisite
amount of any medicine such that in one inhalation, as much as possible
reaches the bronchi.
Implantable
Pumps: The latest developments of miniature
implantable pumps have targeted two specific areas - cardiac support and drug
delivery. Devices for both applications are undergoing clinical trials and in
some cases are already available in Europe. One of the most attractive
applications for implantable pumps is insulin delivery . The diabetic patients
are the one which will thus benefit most directly from this new technology. In
cardiac field, these miniature pumps are saving lives by replacing and
restoring heart function by left ventricular assist devices (LVADS) which take
over the job of pumping blood for the heart.
However
these implantable pumps being mostly in the clinical trials have reached to a
remarkable level of accuracy but still have not overcome a number of critical
design and performance obstacles. There is a need of further refinements in
biomaterials which will help in advancement of the technology through greater
miniaturization of a complete closed-loop implantable pump system.
Blood
Oxygenators: During open-heart surgery, blood
circulation is maintained via a heart-lung machine. The heart of this system
is the oxygenator which enriches the blood with oxygen and removes carbon
dioxide. Polycarbonate is used for the sturdy of oxygenators because its high
transparency permits rapid and accurate visual inspection, while high fracture
resistance guarantees reliability in use. Among others Bayer is supplying
polycarbonate in the name of Makrolon which offers a unique combination of
strength, hardness and rigidity with toughness and fracture resistance.
Macromolecular
Hydrogel: A combination of a three-dimensional
polymer matrix consisting of acrylics with solvent components present in a
polymer network, produces a highly safe hydrogel with high electric
conductivity, low skin irritation, and tackiness controllable over a wide
range. Sekisui Plastics Co. ltd. japan has developed a hydrogel in the name of
Technogel which has got numerous applications. The solid like elasticity of
this material is actualized with a liquid like softness that promises to serve
many applications in various fields.
Microporous
Membranes: A microporous membrane is a thin, flat
sheet of polymeric material, superficially resembling paper, that contains
billions of microscopic pores. Depending on the membrane, these pores can
range in size from 0.01 to more than 10am. Numerous polymers can be used to
produce hydrophilic or hydropropylene, PVDF and acrylic copolymers. All these
polymers are treatable to obtain specific surface characteristics that can be
both hydrophilic and hydrophobic (repelling liquids with low surface tensions
such as multivitamin infusious, lipids, surfactants, oils and organic
solvents).
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