Biosystems
The electronic properties and interactions of matter at an atomic level
in biological environments is very much unknown. Yet the detailed understanding
of these systems is crucial to the successful development of many new technologies
that have direct impact on biosystems. These include medical implants, delivery
systems such as those required for radiopharmaceuticals, bio-sensors and chips
for diagnostics, biomimetic materials such as the construction of artificial skin and
organs, and novel photosynthetic devices.
Vacuum ultraviolet spectroscopy (VUV) is able to probe the valence and
low-lying core states of many elements in the periodic table. The interaction of such states
ultimately controls the complex interactions and properties observed in biological systems.
The high flux and small spot size produced by VUV synchrotron light sources will allow for many
ground-breaking expeiments and studies to be performed on biosystems from a sub-angstrom to micron scale.
Studies will initially focus on more traditional, but still poorly understood, systems such as
the electronic properties of amino acids on various surfaces. A significant new direction would be
the in situ study of liquid-solid interfaces and sandwiches. As most biosystems are made of
several functioning parts, small spot microscopy on objects as tiny as only a few nanometre to as
large as a few micron in size would be of tremendous impotrance in order to determine accurately
the electronic state of each component part of the system.
Surface science, which is supported by soft x-ray,
vacuum ultraviolet and
vibrational spectroscopy techniques, has recently been increasing
in prominence in the biomedical area, based on the fact that many biological reactions occur at
surfaces. Any fundamental understanding of the biocompatibility of a medical device must take
into account the properties of proteins and cells at interfaces, and the characteristics of
local biological reactions. Principles worked out in surface science laboratories are likely to
become the basis for ways of improving the function and durability of materials featured in
a wide range of medical products.
As an example, the hemocompatibility of synthetic surfaces can be improved by various
biologically active substances, of which heparin is perhaps the most promising. To immobilize heparin
onto biomaterial surfaces, its physicochemical properties are modified by incorporation of a specific binding
agent onto the heparin molecules. The resulting modified-heparin coating material has a high affinity for a variety
of synthetic surfaces, and retains all biological properties of the unmodified heparin.
This offers the prospect, for example, of heparin-coated bypass circuits for use in open-heart surgery.