Technology
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POTENTIAL
OF PLASTICS IN MEDICINE
Dr.
V. Kalliyana Krishnan, Scientist, Sree Chitra Tirunal Institute for
Medical Sciences & Technology
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Emerging Trends for the new millennium
Many of the polymers and the existing processing techniques have to undergo
considerable improvement in order to produce polymers which can perform better
in biological environment. What happens at the polymer-living system interface
at the moment of implantation and the subsequent happenings within the body
system is yet to be clearly understood in spite of lots of existing theories
and hypotheses. For a better understanding of the interfacial phenomena, new
analytical methods such as
imaging and assaying techniques are needed to analyse the polymer at the
molecular level both at static and dynamic phases and observe the behavior of
the biological entities both at the surface as well as the bulk.
Biological modification of polymers is one of the new trends adopted to
improve biocompatibility by adding biofunctionality to the polymer surfaces.
Biological entities such as heparin and heparin fragments, heparinase,
urikinase, streptokinase, albumin and endothelial cell seeding onto polymer
surfaces is expected to improve blood material interactions considerably.
Development of stimuli responsible polymers is another emerging trend.
Polymers with ability to respond to physical, chemical or biological signals
such as temperature of pH changes, electrical or optical signals in the
biological environment have been synthesised. Table 4 lists some of the
emerging trends of synthetic plastics in the area of medicine.
Status of Biomedical Technology in India
Sree Chitra Tirunal Institute for Medical Sciences & Technology at
Trivandrum pioneered the development of medical device technology in India.
Government of India declared it as an Institute of national importance in
1980. Work in inter-disciplinary areas of biomedical technology such as
biomaterial development, processing, characterization, testing and evaluation
of medical devices are being carried out here. A technoprove facility exists
for the pilot production of medical devices and it helps to serve as a link
between Institute and industry. Table 5 lists the devices commercialized,
products ready for commercialisation and products under development at SCTIMST
during the last 20 years.
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Table 1a: Nondegradable polymers used
for drug delivery systems
| Hydrophilic
polymers |
Hydrophobic
polymers |
|
Poly
(HEMA)
Polythylene
oxide
Polyvinyl
pyrrolidone
Polyvinyl
alcohol
Polyacrylamide |
Silicones
Ethylene-vinyl
acetate
Polyurethane
elastomers |
|
Table 1b: Biodegradable Polymeric
Materials used for drug delivery
|
Natural
Polymers |
Synthetic
Polymers |
|
Albumin
Collagen
& Gelatin
Chitin
and chitosan
Fibrinogen
Antibodies
Dextran
Alginate,
Casein
Cellulose,
Starch |
Poly
(a-hydroxy acids)
Poly
(a-amino acids)
Poly(e-caprolactone)
Poly
(orthoesters)
Poly
(anhydrides)
Poly(alkyl
2-cyanoacrylates) |
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Table 2: Commercially available wound dressing
materials
| Type |
Name/Manufacturer |
Description |
| Adherent, Absorbent, |
|
Many absorbent woven and nonwovengauze products |
| Nonocclusive |
Adaptic |
Knitted
cellulose acetate impregnated with petrolactum |
| Adherent, |
Johnson & Johnson Inc |
emulsion |
| Nonabsorbent, |
N-Terface/Winfield |
|
| Nonocclusive |
Melonin/ |
Nonadherent
perforated PET film backed by absorbent |
| Nonadherent, |
Smith & Nephew |
cellulosic
acrylic layer |
| Nonabsorbent, |
Silicone NA
Johnson & Johnson Inc
Sorbsan / Steriseal Telfa/Kendal |
Knitted
cellulose acetate fabric with silicone coating
Calcium alginate
Cotton sandwich between perforated
nonadherent |
| Noncclusive |
|
PETF sheets. |
| Absorbent, Occlusive, |
|
|
| Nonadherent, |
|
|
| Semiocclusive |
|
|
| Hydrocolloid |
Comfeel
Ulcus/ |
Absorbent
carboxymethyl cellulose adhesive layer backed by |
| Dressing |
Coloplast |
a
polyurethane film. |
| Composite dressing |
Viasorb/Sherwood |
Cotton
polyester pad contained within a polyurethane sleeve |
| Hydrogel dressing |
Vigilon/Bard |
Crosslinked
PEO hydrogel between two PE films. |
| Semiocclusive, |
Bioocclusive |
Transparent
polyurethane film with acrylic adhesive |
| Occlusive, |
Johnson &
Johnson Inc |
|
| Nonabsorbent |
|
|
| Biological dressing |
Biobrane
Woodtreat Laboratories |
Silicone/Nylon
collagen bilayer composite |
| Medicated dressing |
Bactigras,
Smith & Nephew |
Chlorhexidine
tulle gras |
|
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Table 3: Dental applications of various polymers
| Application |
Polymer used |
| Denture base
polymers |
Natural rubber,
Polym ethyl methacrylate, Polycarobonates, Nylon |
| Soft denture liners |
Silicone rubber,
silicone-acrylic, Hydrogels |
| Maxillofacial
surgery |
Silicone rubber,
silicone acrylic |
| Artificial treeth
Restorative materials |
Crosslinked PMMA
Filled BIS-GMA, Urethane dimethacrylates |
| Crown and
Bridgeterials |
Polyethyl methacry
malate, Poly isobutyl methacrylate, Epimine |
| Root canal fillers
rubber |
Hydrogels, Silicone |
| Impression
materials sodium alginate + |
RTV silicone
rubber, filler |
|
Table 4: Emerging trends of plastics in medicine
| Polymers
with improved biocompatibility |
Bioresponsive
and biofunctional polymers |
- Studies for better understanding of the phenomena at the
polymer-living system interface.
- Development of new analytical methods, imaging and assaying
techniques.
- Biological modification of polymer surfaces.
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- Preparation of polymeric matrices which would respond physical,
chemical or biological stimuli.
- Polymeric carriers with ligands which would have specific biological
recognition abilities.
|
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Table 5: Biomedical products developed at BMT Wing,
SCTIMST (1979-1999)
| Products
commercialised |
Products
ready for tech. transfer |
Products
under development |
| Blood Bag |
Dental Composite |
Coating on
urinary catheter |
| Bubble
Oxygenator |
Vascular graft |
Membrane
Oxygenator |
| Cardiotomy
Reservoir |
Hydrogel
microspheres |
Surface
modification of PVC |
| Hydrocephalus
Shunt |
New born calf
serum |
Coating on
urinary catheter |
| Mechanical Heart
Valve |
Fibrin glue |
Diagnostic kits |
| Opthalmic Sponge |
Sceleral
buckling device |
|
| Concentric
needle electrode |
|
|
| Bone Wax |
|
|
| Hydroxyapatite
powder |
|
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|
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