| Summary: | Drug delivery systems (DDS) are essentially pharmaceutical products for human
therapy, typically involving a mixture of active ingredients and excipients. Based
upon quantitative characterization of structure, the thesis introduces the concept
of classifying the architecture of DDS into four levels by their spatial scale and
the life time period. The primary level is recognised as the static structure of the
whole dosage form with a size from μm to cm with the final structure generated
by formulation design. The secondary level categorises the structures of particles
or sub-units to form a DDS with sizes from nm to mm as key units in processing
such as mixing, grinding, granulation and packing; The tertiary level represents
the dynamic structures of DDS during the drug release phase in vitro or in vivo
incorporating the structure size range from nm to mm, which undergo changes
during dissolution, swelling, erosion or diffusion. The spatial scale for the
quaternary level is defined as the meso or micro scale architecture of active and
non-active molecules within a DDS with sizes from Å to μm for the molecular
structure of drug and excipients.
Methods combining X-ray tomography, image processing, and 3D
reconstructions have been devised and evaluated to study systematically
pharmaceutical structures and correlate them with drug release kinetics of DDS.
Based on the quantitative structural information of pharmaceutical intermediates
and dosage forms, it is possible now to correlate structures with production
processing, behaviour and function, and the static and dynamic structures of DDS
with the release kinetics. Thus, a structure-guided methodology has been
established for the research of DDS. === Chinese Academy of Sciences
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