Biomedical Engineering Reference
In-Depth Information
Temperature, and the type of precursor powder, the amount of
precursor powder, and processing agents control the time selected
for manufacturing the carrier. The manufacturing of the carrier
can be done completely before or during loading of the drug. This
renders a controlled release time to be selected, from a few hours to
days and months.
The drug is introduced in the carrier by mixing the drug into the
precursor powder or the hydrated CBCs or other porous phases.
The material can be formed into a paste by mixing it with a water-
based hydration liquid. The powder can also be pressed into pellets,
which thereafter are soaked in the liquid. The paste or the soaked
pellets start to develop the microstructure, which to a great extent
will contribute to the controlled release of the drug. The time and
temperature after the mixing will determine the degree of hydration,
that is, the porosity obtained. The porosity can be controlled within
a broad interval of open porosity.
The drugs can be loaded in the water-liquid, in the pore system
of inert filler particles, and in processing agents (accelerators,
retarders, viscosity controlling agents, and other rheological
agents). Thus drugs can be loaded both during formation of hydrates
or after hydration by infiltration. The infiltration comprises water
penetration of precursor materials or hydrated materials using
wetting at normal pressure, during vacuum, or at overpressure.
For hydrophobic medical agents, the agent can be easily mixed into
the precursor powder or together with the ceramic or other filler
materials.
The amount of drug loaded in the carrier is determined by the
content of the drug in the dry powder and the hydration liquid.
The liquids involved in the introduction of the drug into either
the dry powder or the hydration liquid are easily controlled in
charged amounts of liquids. The reaction takes preferentially place
in high humidity, where no liquid in the carrier is vanished into the
environment.
Optionally, the carrier powder may comprise inert oxides of Ti,
Si, Ba, or Zr to increase strength or radio-opacity. The oxides may
take the form of porous and/or dense particles. The incorporation
of the drug or medical agent into the carrier material in the porous
inert ceramic material may be performed by filling the pores of
the inert ceramic with the drug, mixing it with the powder prior to
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