Biomedical Engineering Reference
In-Depth Information
very large research area investigating mesoporous silica particles as drug
delivery agents [9]. Mesoporous silica particles are also being designed
to kill cancerous tumours [10]. The idea is that the particles, containing
payloads that can kill tumour cells, are injected into the patient and the
particles arrive at the tumour, using blood transport, where they are
taken up by the cells. When the particles are inside the cells, they release
their deadly payload. The aim is that the particles will target tumours so
that they are not taken up by other (healthy) cells. This requires careful
design of functional groups on the surface of the particles, so that they
are attracted to the correct cells, and the use of other molecules that
block the premature release of the payload before the particles reach
the tumour.
For optimal control of drug loading, the porosity of the particles is
often made to have an order to it (Figure 3.6). Ordered pores are made
by adding a surfactant template to the sol. Surfactants, or 'surface-
active agents', are short molecules with one end that is hydrophilic and
the other hydrophobic. They are usually used to reduce the surface
tension of a liquid, for example in detergents or to disperse particles in
solution. When someone uses soap to wash their hands, bubbles form
as air is entrapped in the water and the bubbles are stabilised by the
surfactant. The hydrophilic end of the surfactant molecule attaches to
water and the other end is in the air. Surfactant templates work slightly
Figure 3.6
Transmission electron microscope image of a silica particle containing
ordered mesopores. (Image provided courtesy of Lijun Ji, College of Chemistry and
Chemical Engineering, Yangzhou University, China.)
