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 Absorbable
Monofilament Surgical Sutures
Temporary
Skin Substitutes for Wound Dressings
Absorbable
Nerve Guides
Chitosan-based
Products
Synthetic
Lung Surfactant
Ring-Opening
Polymerisation of Cyclic Esters
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| Small-scale melt spinning apparatus |
The main objective here is to develop a new absorbable monofilament surgical
suture with properties comparable with current commercial materials but
lower in cost. A range of new biodegradable polyesters have been structurally
designed, synthesized and characterized. Of these, co- and terpolyesters
of L-lactide-caprolactone-glycolide show the most potential. Advanced melt
spinning trials are now in progress in an attempt to build into the monofilament
fibres the polymer morphology needed to give the required mechanical properties.
Here the main aim is to develop a polymer film covering for use as a wound
dressing which does not need to be changed every day. The initial target
is that it can be left in place on the wound surface for a period of up
to 1 week. Results have shown that synthetic hydrogels for use in wound
dressings are better prepared from water-soluble monomers in aqueous solution
rather than from non-water-soluble monomers in bulk. In this way, the hydrogel
forms in its more natural hydrated state rather than in the dry state. A
new-generation, speciality water-soluble monomer which falls into this category
is 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) with which methylene
bis-acrylamide is commonly employed as the crosslinking agent.
Absorbable nerve guides are already in use in hospitals abroad but not yet
in Thailand where nerve grafting from donor sites is still the common procedure.
However, orthopaedic surgeons in Thailand are well aware of the development
of absorbable nerve guides and are very keen to try them out. Since these
materials are not far removed from our absorbable sutures in terms of their
chemical composition, this project draws heavily on the knowledge and experience
which has already been built up from the suture project in the tailor-making
of biodegradable polyesters.
In this project, our main interest lies in the wet spinning of drug-containing
chitosan fibres, and chitosan fibres for making non-woven cloths. In addition,
we are also doing some work on the solution blending of chitosan with other
polymers in an attempt to produce fibres with better mechanical properties
than straight chitosan which is inherently stiff and rather brittle.
This line of research is being carried out in collaboration with the Polymer
and Biomaterials Group at Aston University, UK. The objective is to synthesize
a polymer which, through an appropriate balance of hydrophilic and hydrophobic
interactions, can mimic the lipid-apoprotein assemblies in the human body's
own natural lung surfactant. If successful, this could provide a cure for
respiratory distress syndrome (RDS) in prematurely born babies.
Fundamental research increases our understanding of the kinetics and mechanisms
of cyclic ester ring-opening polymerisation and, in the case of copolymerisation,
the ways in which the monomer sequencing can be controlled. This work underpins
all of our projects in which these polyesters are designed and synthesized.
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