fuels to function efficiently, and would not contribute
net CO 2 to the atmosphere nor produce toxic waste as
with conventional batteries.
Another area of intense study is the development
of renewable biofuels with much focus being given to
developing terrestrial plant species to produce the
precursors to biodiesel. Microalgae present a potential alternative source of hydrocarbons for the generation of biofuels as some species naturally produce
significantly more oil (per year per unit area of land)
than terrestrial oil seed crops. Several marine species
such as Porphyridiuim, Chlorella, and Tetraselmis
are currently under investigation as sources rich in
hydrocarbons suitable for biofuel production.
Biomaterials
Another area of interest is the development of novel
biomaterials inspired by marine organisms. Areas of
particular interest are the mechanism of calcium- and
silica-based structure formation which is found in
many phytoplankton, formation of hard chitinous
shells in many larger marine organisms such as oysters
and crabs, as well as the very powerful bioadhesives
produced by mussels and barnacles. Proteins form the
basis of a number of naturally occurring adhesive
molecules which display a number of attractive features, particularly for clinical and other specialist applications. These features include the ability to adhere
strongly to both smooth and uneven surfaces with a
high degree of bonding strength and the ability to
form and maintain bonds in very humid and wet
conditions. This bonding ability seems to be strongly
linked to the presence of hydroxylated tyrosine residues (L-dopa; L-3,4-dihydroxyphenylalanine) in such
proteins and it is thought that adhesion involves
interactions between the hydroxyl groups and the
target surface. The development of powerful adhesives
which can cure rapidly under wet conditions and are
nontoxic would be of particular value in the clinic. At
present there is considerable interest in using bioadhesives in the field of ophthalmology where the use of
alternatives to sutures in, for example, corneal grafts is
desired in order to reduce the risks of irritation and
scarring to the eye following surgery. Another area
where the use of bioadhesives is being actively researched is in drug delivery where the ability to attach
naturally occurring polymers which can slowly release
a drug over time would be useful. This is particularly
relevant for poorly soluble biological drugs based on
antibodies and other large proteins which can be difficult to administer. The potential contribution that
marine-derived biomaterials and bioadhesives could
make to such fields is enormous.
Chitin is the second most abundant natural
polysaccharide after cellulose and is found in the
exoskeletons of crustaceans such as crabs and shrimp
as well as in the cell walls of fungi and cuticles of
insects. The deacetylation of chitin produces chitosan, a biopolymer with great potential in medicine. Chitosan and its derivatives possess numerous
applications due to their properties which include
reactive functional groups, gel-forming capability,
low toxicity, and high adsorption capacity, as
well as complete biodegradability and antibacterial
and antifungal activities. These properties make
chitosan particularly attractive in areas of research
such as drug delivery and tissue engineering where a
nontoxic, biodegradable scaffold with antimicrobial
activity would be particularly attractive. Both
chitin and chitosan can influence the immune system
and are being studied extensively as biomaterials in
the development of supports for accelerated wound
healing. These chitosan-based materials are also
being modified to improve adhesion to wound
sites and for the incorporation of antimicrobial
agents to minimize the risk of infection. Chitosan
and its derivatives are also being used to develop
scaffolds for applications in tissue engineering to
grow cells to form complex structures which could
ultimately be used to replace damaged tissues and
organs.
The elaborate silica-based structures (frustules)
which are exhibited by many diatoms have been of
interest to materials scientists for many years and
recent studies have begun to reveal some of the
characteristics that are present in these silica shells,
including an understanding of the proteins and other
molecules involved in structure formation (Figure 4).
The highly precise nature of the structures has led to
suggestions that the silica structures can be used
directly as either templates for microfabrication or as
materials for use in microprocesses such as filters in
microfluidics. By understanding and manipulating
the growth environment of any given diatom it may
be possible to modify the precise geometry of the
natural silica shells it produces and the resultant
frustules could then be modified using standard
microengineering techniques to create new nanostructures with potential applications in the development of medical devices. The glass-like properties
of diatom frustules, the remains of which form
diatomite (diatomaceous earth), have over 300 recorded commercial applications. The fine pores present in the frustules make them especially useful in
filtration processes and the bulk of diatomite is used
for this purpose. It has also been suggested that
frustules might have applications in the development
of new optical devices.
118 MARINE CHEMICAL AND MEDICINE RESOURCES
net CO 2 to the atmosphere nor produce toxic waste as
with conventional batteries.
Another area of intense study is the development
of renewable biofuels with much focus being given to
developing terrestrial plant species to produce the
precursors to biodiesel. Microalgae present a potential alternative source of hydrocarbons for the generation of biofuels as some species naturally produce
significantly more oil (per year per unit area of land)
than terrestrial oil seed crops. Several marine species
such as Porphyridiuim, Chlorella, and Tetraselmis
are currently under investigation as sources rich in
hydrocarbons suitable for biofuel production.
Biomaterials
Another area of interest is the development of novel
biomaterials inspired by marine organisms. Areas of
particular interest are the mechanism of calcium- and
silica-based structure formation which is found in
many phytoplankton, formation of hard chitinous
shells in many larger marine organisms such as oysters
and crabs, as well as the very powerful bioadhesives
produced by mussels and barnacles. Proteins form the
basis of a number of naturally occurring adhesive
molecules which display a number of attractive features, particularly for clinical and other specialist applications. These features include the ability to adhere
strongly to both smooth and uneven surfaces with a
high degree of bonding strength and the ability to
form and maintain bonds in very humid and wet
conditions. This bonding ability seems to be strongly
linked to the presence of hydroxylated tyrosine residues (L-dopa; L-3,4-dihydroxyphenylalanine) in such
proteins and it is thought that adhesion involves
interactions between the hydroxyl groups and the
target surface. The development of powerful adhesives
which can cure rapidly under wet conditions and are
nontoxic would be of particular value in the clinic. At
present there is considerable interest in using bioadhesives in the field of ophthalmology where the use of
alternatives to sutures in, for example, corneal grafts is
desired in order to reduce the risks of irritation and
scarring to the eye following surgery. Another area
where the use of bioadhesives is being actively researched is in drug delivery where the ability to attach
naturally occurring polymers which can slowly release
a drug over time would be useful. This is particularly
relevant for poorly soluble biological drugs based on
antibodies and other large proteins which can be difficult to administer. The potential contribution that
marine-derived biomaterials and bioadhesives could
make to such fields is enormous.
Chitin is the second most abundant natural
polysaccharide after cellulose and is found in the
exoskeletons of crustaceans such as crabs and shrimp
as well as in the cell walls of fungi and cuticles of
insects. The deacetylation of chitin produces chitosan, a biopolymer with great potential in medicine. Chitosan and its derivatives possess numerous
applications due to their properties which include
reactive functional groups, gel-forming capability,
low toxicity, and high adsorption capacity, as
well as complete biodegradability and antibacterial
and antifungal activities. These properties make
chitosan particularly attractive in areas of research
such as drug delivery and tissue engineering where a
nontoxic, biodegradable scaffold with antimicrobial
activity would be particularly attractive. Both
chitin and chitosan can influence the immune system
and are being studied extensively as biomaterials in
the development of supports for accelerated wound
healing. These chitosan-based materials are also
being modified to improve adhesion to wound
sites and for the incorporation of antimicrobial
agents to minimize the risk of infection. Chitosan
and its derivatives are also being used to develop
scaffolds for applications in tissue engineering to
grow cells to form complex structures which could
ultimately be used to replace damaged tissues and
organs.
The elaborate silica-based structures (frustules)
which are exhibited by many diatoms have been of
interest to materials scientists for many years and
recent studies have begun to reveal some of the
characteristics that are present in these silica shells,
including an understanding of the proteins and other
molecules involved in structure formation (Figure 4).
The highly precise nature of the structures has led to
suggestions that the silica structures can be used
directly as either templates for microfabrication or as
materials for use in microprocesses such as filters in
microfluidics. By understanding and manipulating
the growth environment of any given diatom it may
be possible to modify the precise geometry of the
natural silica shells it produces and the resultant
frustules could then be modified using standard
microengineering techniques to create new nanostructures with potential applications in the development of medical devices. The glass-like properties
of diatom frustules, the remains of which form
diatomite (diatomaceous earth), have over 300 recorded commercial applications. The fine pores present in the frustules make them especially useful in
filtration processes and the bulk of diatomite is used
for this purpose. It has also been suggested that
frustules might have applications in the development
of new optical devices.
118 MARINE CHEMICAL AND MEDICINE RESOURCES