Biomedical Engineering Reference
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Figure 32.5.
Microsphere images taken under an optical microscope,
showingtheformationofbubbles.Thebubblesizeincreaseswithtime,indi-
cating the continuous release of oxygen. Bubbles are seen as white cycles,
and the microbeads are the opaque spheres.
microscope. In this study, the ORMs were sandwiched between
two glass slides, and after that, water was carefully introduced
through the edge. During this process, entrapment of air bubbles
was avoided. As the oxygen was produced, bubble formation was
observed on the microspheres' surface, and when images were
taken under a periodic period, the growing size of the bubbles
entrapped between the slides indicated the continuous release of
oxygen. An example of such images observed is shown in Fig. 32.5.
Although this method provides no concrete data on the concen-
tration and rate of oxygen production, direct observation can give
very convincing evidence in proving ORMs are releasing oxygen, as
intended.
32.3.4.2 Quantitative analytical approach
Besides qualitative observation, systematic and precise analyti-
cal measurements are required in evaluating the release pro-
files of oxygen from the microspheres. This approach generates
quantitative concrete values that are used directly to analyze and
compare the performance of microsphere batches prepared either
using the same or different materials, methods, or production set-
tings. In addition, the microspheres can be categorized accord-
ing to the oxygen-releasing amount and rate, which is a useful
guideline for assigning or predicting their suitability for some
applications, as some require more concentration than others.
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